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Rotator cuff: failure and treatment

Ahmad, C. S., A. M. Stewart, et al. (2005). "Tendon-bone interface motion in transosseous suture and suture anchor rotator cuff repair techniques." Am J Sports Med 33(11): 1667-71. BACKGROUND: Although many studies involving rotator cuff repair fixation have focused on ultimate fixation strength and ability to restore the tendon's native footprint, no studies have characterized the stability of the repair with regard to motion between the tendon and repair site footprint. HYPOTHESIS: Suture anchor fixation for rotator cuff repair has greater interface motion between tendon and bone than does transosseous suture fixation. STUDY DESIGN: Controlled laboratory study. METHODS: Twelve fresh-frozen human cadaveric shoulders were tested in a custom device to position the shoulder in internal and external rotations with simulated supraspinatus muscle loading. Tendon motion relative to the insertional footprint on the greater tuberosity was determined optically using a digital camera rigidly connected to the humerus, with the humerus positioned at 60 degrees of internal rotation and 60 degrees of external rotation. Testing was performed for the intact tendon, a complete supraspinatus tear, a suture anchor repair, and a transosseous tunnel repair. RESULTS: Difference in tendon-bone interface motion when compared with the intact tendon was 7.14 +/- 3.72 mm for the torn rotator cuff condition, 2.35 +/- 1.26 mm for the suture anchor repair, and 0.02 +/- 1.18 mm for the transosseous suture repair. The transosseous suture repair demonstrated significantly less motion when compared with the torn rotator cuff and suture anchor repair conditions (P <.05). CONCLUSION: Transosseous suture repair compared with suture anchor repair demonstrated superior tendon fixation with reduced motion at the tendon-to-tuberosity interface. CLINICAL RELEVANCE: Development of new fixation techniques for arthroscopic and open rotator cuff repairs should attempt to minimize interface motion of the tendon relative to the tuberosity.

Aoki, M., H. Oguma, et al. (2001). "Fibrous connection to bone after immediate repair of the canine infraspinatus: the most effective bony surface for tendon attachment." J Shoulder Elbow Surg 10(2): 123-8. The purpose of this histologic study was to identify the most effective bony surface for fibrous connection to bone after immediate repair of the canine infraspinatus. Light microscopic views were used to evaluate collagen fiber development. The left infraspinatus tendon of 15 dogs was transected and repaired to 3 different bone surfaces: a tendon end adjacent to the tendon insertion (group 1, n = 5), a calcified fibrocartilage layer (group 2, n = 5), and a cancellous surface (group 3, n = 5). Tendon repair to distal tendon ends restored the 4-layered enthesis in the healing period, whereas tendon repair to the calcified fibrocartilage layer considerably delayed fiber development into bone. Fiber connection to cancellous surface developed according to the remodeling of trabecular bone. Secure fiber connection into the thickened trabecular bone developed by 16 postoperative weeks. On the basis of these results, in clinical settings, ruptured tendon ends should be attached to the remaining distal tendon end or to a cancellous surface; they should not be attached to a calcified fibrocartilage layer.

Barton, E. R., J. A. Gimbel, et al. (2005). "Rat supraspinatus muscle atrophy after tendon detachment." J Orthop Res 23(2): 259-65. Rotator cuff tears are one of the most common tendon disorders found in the healthy population. Tendon tears not only affect the biomechanical properties of the tendon, but can also lead to debilitation of the muscles attached to the damaged tendons. The changes that occur in the muscle after tendon detachment are not well understood. A rat rotator cuff model was utilized to determine the time course of changes that occur in the supraspinatus muscle after tendon detachment. It was hypothesized that the lack of load on the supraspinatus muscle would cause a significant decrease in muscle mass and a conversion of muscle fiber properties toward those of fast fiber types. Tendons were detached at the insertion on the humerus without repair. Muscle mass, morphology and fiber properties were measured at one, two, four, eight, and 16 weeks after detachment. Tendon detachment resulted in a rapid loss of muscle mass, an increase in the proportion of fast muscle fibers, and an increase in the fibrotic content of the muscle bed, concomitant with the appearance of adhesions of the tendon to surrounding surfaces. At 16 weeks post-detachment, muscle mass and the fiber properties in the deep muscle layers returned to normal levels. However, the fiber shifts observed in the superficial layers persisted throughout the experiment. These results suggest that load returned to the muscle via adhesions to surrounding surfaces, which may be sufficient to reverse changes in muscle mass.

Berg, E. E., M. E. Pollard, et al. (2001). "Interarticular bone tunnel healing." Arthroscopy 17(2): 189-95. PURPOSE: To evaluate the healing behavior of an interarticular bone tunnel exposed continuously to a synovial environment. TYPE OF STUDY: Experimental in vivo animal model. METHODS: Twenty-six adult rabbits had 3.2-mm diameter tunnels drilled in the femur and tibia of both hind-limb stifle joints parallel to but without violation of the native anterior cruciate ligament (ACL). The animals were euthanized at 1, 2, 4, and 12 weeks postoperatively. Decalcified sections were made of the bone tunnels and new bone formation was computer quantified using histomorphometric methods at each time interval. RESULTS: In this model, bone tunnel healing velocity was most rapid between 1 and 2 weeks after surgery. Both femoral and tibial interosseous tunnels showed substantial bone ingrowth (71% of bone tunnel volume) by 2 weeks postoperatively. The peripheral tunnel segment, that third of the tunnel furthest from the joint surface, healed rapidly and was 99% occluded with bone (99% confidence interval, 93.7% to 100%) at 2 weeks. Tunnel ingrowth was delayed and incomplete in the articular third of the tunnel, especially the femoral side. At 12 weeks, by volume, only 69.1% (99% confidence interval, 52.3% to 85.7%) of the interarticular third of the femoral tunnel was ingrown with new bone. Peripheral third bone tunnel healing was significantly greater than articular third tunnel healing at all time intervals; P <. 005 for the femoral and P <. 05 for the tibial tunnel. CONCLUSIONS: Interarticular bone tunnels heal from the outside in. At 12 weeks, bone healing was slower and incomplete in the articular segment of the tunnel, closest to the joint surface. The same biologic factors that impede intersubstance ACL healing may interfere with bone tunnel healing and be another cause of bone tunnel enlargement after ACL reconstruction.

Biberthaler, P., E. Wiedemann, et al. (2003). "Microcirculation associated with degenerative rotator cuff lesions. In vivo assessment with orthogonal polarization spectral imaging during arthroscopy of the shoulder." J Bone Joint Surg Am 85-A(3): 475-80. BACKGROUND: Diminished vascular supply is associated with degenerative rotator cuff lesions. Orthogonal polarization spectral imaging allows noninvasive assessment of microcirculation without application of fluorescent contrast medium. The aim of our study was to visualize and quantify in vivo the microcirculation of the rotator cuff during arthroscopic surgery and to compare the results with the number of microvessels identified in vitro by immunostaining of biopsy specimens taken from the scanned areas. METHODS: Eleven patients with clinical signs of a degenerative rotator cuff lesion were studied. Prior to arthroscopic subacromial decompression, the superficial part of the supraspinatus tendon at the edge of the lesion as well as the unaffected tendon insertion was examined. Microvascular parameters established for the description of tissue perfusion with use of conventional intravital fluorescence microscopy (functional capillary density and capillary diameter) were assessed in vivo. Biopsy specimens were taken from the scanned areas, and the microvessels were localized by immunostaining for the endothelial surface marker CD31. RESULTS: In the region of the unaffected tendon insertion, the mean baseline functional capillary density (and standard deviation) was 106 +/- 13 cm/cm(2) and the mean capillary diameter was 10 +/- 0.7 microm. In contrast, at the edge of the lesion, the functional capillary density was significantly reduced to 20 +/- 14 cm/cm(2), whereas the diameter of the vessels that were present did not differ. The total number of vessels stained in vitro was also significantly reduced at the edge of the lesion compared with the number of vessels in the tendon insertion zone. CONCLUSIONS: Quantitative in vivo analysis of human microcirculation during arthroscopy demonstrated that the functional capillary density at the edge of a degenerative rotator cuff lesion was significantly reduced compared with that in the control tissue. The capacity to assess microcirculatory flow in vivo may help to identify specific repair strategies based on knowledge of individual perfusion patterns.

Bicknell, R. T., C. Harwood, et al. (2005). "Cyclic loading of rotator cuff repairs: an in vitro biomechanical comparison of bioabsorbable tacks with transosseous sutures." Arthroscopy 21(7): 875-80. PURPOSE: This study compares rotator cuff repair strength after cyclic loading of bioabsorbable tacks and traditional transosseous sutures, and correlates the results with bone density, age, and gender. The hypotheses were that tack repair strength would be inferior to transosseous sutures and that repair strength would be directly related to bone quality. TYPE OF STUDY: In vitro randomized biomechanical study. METHODS: Eight paired cadaveric shoulders with a standardized supraspinatus defect were randomized to tack or suture repair and subjected to step-wise cyclic loading. Repair migration was measured by quantifying the motion of markers affixed to tendon and bone using a digital camera. Failure mode, cycles, and load were measured for 50% and 100% loss of repair. Results were correlated with bone density, age, and gender. RESULTS: Tack repairs failed at the tack-tendon interface, whereas suture rupture was the mode of failure for the suture repairs. Mean values for 50% loss of repair were 206 +/- 88 cycles and 44 +/- 15 N for the sutures, and 1,193 +/- 252 cycles and 156 +/- 20 N for the tacks (P <.05). The corresponding values for 100% loss of repair were 2,458 +/- 379 cycles and 294 +/- 27 N for the sutures, and 2,292 +/- 333 cycles and 263 +/- 28 N for the tacks (P >.05). These results did not correlate with bone density, age, or gender. CONCLUSIONS: This study has shown that bioabsorbable tacks provide improved repair strength in comparison with traditional suture techniques. Repair strength did not correlate with bone quality, and this may be attributed to failure primarily through the repair construct or at the tack-tendon interface and not through bone. This report describes a new high-resolution optical method of measuring tendon repair strength that should be a useful model for future studies. CLINICAL RELEVANCE: This study demonstrates the biomechanical advantages of a sutureless tack device for rotator cuff repair compared with a traditional augmented suture repair technique.

Boileau, P., N. Brassart, et al. (2005). "Arthroscopic repair of full-thickness tears of the supraspinatus: does the tendon really heal?" J Bone Joint Surg Am 87(6): 1229-40. BACKGROUND: Good functional results have been reported for arthroscopic repair of rotator cuff tears, but the rate of tendon-to-bone healing is still unknown. Our hypothesis was that arthroscopic repair of full-thickness supraspinatus tears achieves a rate of complete tendon healing equivalent to those reported in the literature with open or mini-open techniques. METHODS: Sixty-five consecutive shoulders with a chronic full-thickness supraspinatus tear were repaired arthroscopically in sixty-five patients with use of a tension-band suture technique. Patients ranged in age from twenty-nine to seventy-nine years. The average duration of follow-up was twenty-nine months. Fifty-one patients (fifty-one shoulders) had a computed tomographic arthrogram, and fourteen had a magnetic resonance imaging scan, performed between six months and three years after surgery. All patients were assessed with regard to function and the strength of the shoulder elevation. RESULTS: The rotator cuff was completely healed and watertight in forty-six (71%) of the sixty-five patients and was partially healed in three. Although the supraspinatus tendon did not heal to the tuberosity in sixteen shoulders, the size of the persistent defect was smaller than the initial tear in fifteen. Sixty-two of the sixty-five patients were satisfied with the result. The Constant score improved from an average (and standard deviation) of 51.6 +/- 10.6 points preoperatively to 83.8 +/- 10.3 points at the time of the last follow-up evaluation (p < 0.001), and the average University of California at Los Angeles score improved from 11.5 +/- 1.1 to 32.3 +/- 1.3 (p < 0.001). The average strength of the shoulder elevation was significantly better (p = 0.001) when the tendon had healed (7.3 +/- 2.9 kg) than when it had not (4.7 +/- 1.9 kg). Factors that were negatively associated with tendon healing were increasing age and associated delamination of the subscapularis or infraspinatus tendon. Only ten (43%) of twenty-three patients over the age of sixty-five years had completely healed tendons (p < 0.001). CONCLUSIONS: Arthroscopic repair of an isolated supraspinatus detachment commonly leads to complete tendon healing. The absence of healing of the repaired rotator cuff is associated with inferior strength. Patients over the age of sixty-five years (p = 0.001) and patients with associated delamination of the subscapularis and/or the infraspinatus (p = 0.02) have significantly lower rates of healing.

Boon, J. M., M. A. de Beer, et al. (2004). "The anatomy of the subscapularis tendon insertion as applied to rotator cuff repair." J Shoulder Elbow Surg 13(2): 165-9. The tendons constituting the rotator cuff (RC) are often torn, and several techniques for their repair have been established. The existence of an extension of the supraspinatus tendon into that of the subscapularis has often been overlooked. The purpose of this study was to study this extension in human dissections. The possible posterolateral extension of the subscapularis tendon and the interdigitating of this extension with the supraspinatus tendon were addressed. A horizontal band of tissue 1 cm below the superior ridge of the greater tuberosity of the humerus was harvested from 43 cadavers and thus included tissue constituting the greater tuberosity, bicipital groove, and lesser tuberosity. The sample extended 2 cm medially along the lesser tuberosity and 1 cm laterally along the greater tuberosity. Macroscopic findings suggest a continuous band of tissue extending across the bicipital groove. High collagen content was microscopically confirmed at different sections, and the collagen was densely distributed along the horizontal axis of the tissue samples.

Boyer, M. I., F. Harwood, et al. (2003). "Two-portal repair of canine flexor tendon insertion site injuries: histologic and immunohistochemical characterization of healing during the early postoperative period." J Hand Surg [Am] 28(3): 469-74. PURPOSE: In vivo animal studies have indicated that the complex structure of the tendon-bone interface may not be restored after repair even under optimal conditions. Controversy exists about the histologic findings in the early postoperative period after tendon reattachment to bone; this may have impact on biomechanical properties. The objective was to study the histologic structure and immunohistochemical staining of the tendon-bone interface in a large model of digital flexor tendon-bone repair. The hypothesis was that the tendon-bone interface matures and assumes a progressively more anatomic histologic and immunohistochemical appearance during the first 6 weeks after repair. METHODS: Twenty-four canine flexor digitorum profundus tendons were released from their insertion by sharp dissection and repaired to bone. The forelimb was immobilized after surgery and 10 minutes of daily passive motion rehabilitation was performed. Dogs were killed at 10, 21, and 42 days after surgery. Hematoxylin-eosin and immunohistochemical staining for types I, II, and II collagen were performed. RESULTS: Although at both 10 and 21 days after surgery substantial inflammation was seen at the tendon-bone repair site, this had decreased markedly by 42 days. Although direct apposition of tendon to bone was seen at 42 days, the mature tendon-bone insertion site was not recreated by this time. Staining for types I and III collagen was diffuse throughout the tendon-bone insertion throughout the interval examined. CONCLUSION: These findings suggest that at 6 weeks after surgery the intact tendon-bone repair site shows minimal histologic and molecular similarity when compared with unoperated specimens.

Chambler, A., S. Rawlinson, et al. (2004). "Quantitative cytochemical evidence for local increases in bone turnover at the acromial enthesis of the human coracoacromial ligament." J Rheumatol 31(11): 2216-25. OBJECTIVE: Enthesophytic bone outgrowths are found at many ligament attachment sites, and while their incidence is associated with many pathologies, the mechanism by which they form remains controversial. We hypothesized that changes in local cell behavior, provoked by mechanical alterations within the coracoacromial ligament (CAL), lead to acromial enthesophyte formation. We investigated whether cell behavior at acromial entheses is consistent with this. METHODS: We used quantitative enzyme cytochemistry to measure glucose 6-phosphate dehydrogenase (G6PD), alkaline phosphatase (ALP; osteoblastic activity), and tartrate-resistant acid phosphatase (TRAP; osteoclastic phenotype) activities in cells of the acromial attachment into the CAL in patients with rotator cuff tears. RESULTS: (1) Resident osteoblasts on the acromion's inferior aspect express elevated activity of G6PD and ALP, indicative of increases in osteogenic potential. (2) These activities are selectively raised at the "leading edge" of acromial bone CAL enthesis. (3) In contrast, distribution of TRAP-positive cells does not exhibit a spatial correlation with enthesis architecture. We also found that cells situated close to the CAL attachment into the acromion exhibited elevated levels of G6PD and ALP activity, but intriguingly, also showed higher TRAP activity than neighboring cells distant from entheses. CONCLUSION: These results suggest that the acromion in these patients undergoes bone accretion at the inferior attachment of the CAL, and that enthesial ligament cells close to the bone express characteristics consistent with enthesophyte formation at the leading edge of this bony spur's extension into the ligament.

Chambler, A. F., A. M. Bull, et al. (2003). "Coracoacromial ligament tension in vivo." J Shoulder Elbow Surg 12(4): 365-7. Tension in the coracoacromial (CA) ligament has been postulated as the mechanism of acromial spur formation. Five patients (mean age, 58 years) undergoing open rotator cuff repair were recruited. A differential variable reluctance transducer (DVRT) was inserted into the CA ligament parallel to the fiber orientation. The DVRT measured linear displacement as the glenohumeral joint was moved through 90 degrees of abduction and full internal/external rotation. The CA ligament was then removed with the DVRT in situ. The specimen was mounted on a material-testing machine. Load was applied in the line of the CA ligament fibers, and the DVRT output recorded. The CA ligament was found to be under tension, which was lowest with the arm adducted (mean, 8.9 N; range, 3.7-22 N) and highest in abduction (mean, 15.7 N; range, 6.5-38 N). This study confirms CA ligament tension in vivo as a possible stimulus for acromial spur formation.

Chambler, A. F., A. A. Pitsillides, et al. (2003). "Acromial spur formation in patients with rotator cuff tears." J Shoulder Elbow Surg 12(4): 314-21. In this study we analyzed the acromial spurs of 15 patients with impingement syndrome undergoing open rotator cuff repair. Mineral apposition analysis and quantitative cytochemical techniques for glucose-6-phosphate dehydrogenase (G6PD) activity (pentose phosphate pathway), alkaline phosphatase (ALP) activity (osteoblast activity), and tartrate-resistant acid phosphatase (TRAP) activity (osteoclast phenotype) were used to examine the distribution and level of activity of selected marker enzymes within the acromial spur insertion into the coracoacromial ligament in order to establish whether local behavior of bone cells is consistent with the proposed secondary development of the acromial spur. Our results indicate that G6PD and ALP activity was higher in osteoblasts on the inferior surface compared with the superior surface of the acromial spur in all patients (P <.001). This area correlated to the most intense area of mineral apposition shown by dual tetracycline labeling. TRAP activity revealed a heterogeneous distribution within the samples. A greater G6PD activity per cell (mean increase of 87%) was seen at the tip compared with that in post- and pre-tip zones within the coronal plane (P <.0002). The qualitative and quantitative enzyme analyses show that the acromial insertion of the coracoacromial ligament is actively involved in bone turnover. The spatial distribution patterns of metabolically active bone-forming osteoblastic cells compared with a heterogeneous distribution of TRAP-positive osteoclasts provide evidence of bone remodeling consistent with the morphologic contours of the acromial enthesis. The sites of oxytetracycline labeling appear to correlate with the sites of high ALP and G6PD activity, which supports the concept of spur formation being a secondary phenomenon in the presence of established rotator cuff tears. Chbinou, N. and J. Frenette (2004). "Insulin-dependent diabetes impairs the inflammatory response and delays angiogenesis following Achilles tendon injury." Am J Physiol Regul Integr Comp Physiol 286(5): R952-7. Although impaired wound healing associated with type 1 diabetes mellitus has been well studied in skin tissue, the influence of this metabolic disorder on tendon healing and recovery has not been extensively investigated. Because tendons are known to have limited repair potential, we studied the tendon-healing process by using a diabetic rat tendonitis model. We tested the hypothesis that diabetes influences the inflammatory response, cell proliferation, and angiogenesis in injured Achilles tendons. Diabetes was induced by injecting streptozotocin at 45 mg/kg body wt. Non-diabetic rats as well as diabetic and insulin-treated diabetic animals were then injected with collagenase. The accumulation of inflammatory cells was quantified in transversal sections of Achilles tendon by using immunohistochemical staining at days 0, 1, 3, 7, 14, and 28 posttrauma. The number of proliferative cells and the extent of neovascularization was also quantified in the paratenon and the core of the tendon at days 0, 3, 7, 14, and 28 posttrauma. Relative to nondiabetic and insulin-treated diabetic animals, the numbers of accumulated neutrophils and ED1(+) and ED2(+) macrophages in diabetic rats decreased by 46, 43, and 52%, respectively, in the first 3 days after injury compared with levels in nondiabetic and insulin-treated diabetic animals. The density of newly formed blood vessels decreased by 35 and 29% in the paratenon and the core of tendon, respectively, at days 3 and 7 after injury. Lastly, the concentration of proliferative cells decreased by 34% in the paratenon at day 7 posttrauma in injured tendons from diabetic rats relative to nondiabetic rats. These results indicate that alterations in inflammatory, angiogenic, and proliferative processes occurred in the diabetic state that might eventually perturb tendon healing and remodeling.

Clark, J., J. A. Sidles, et al. (1990). "The relationship of the glenohumeral joint capsule to the rotator cuff." Clin Orthop Relat Res(254): 29-34. The glenohumeral joint capsules of 23 shoulders in which the rotator cuff was not torn were studied by gross dissection and histologic methods. The cuff tendons were resected, leaving the intact capsule attached to the bones. This dissection method provided a unique overview of the capsule in situ and allowed the areas of cuff tendon and muscle attachment to be mapped. The capsule was found to be a continuous cylinder between humerus and glenoid. On approximately one-third of the capsule (the portion adjacent to the humeral tuberosities), tight insertions of cuff tendons were noted. The superior segment between subscapularis and supraspinatus contained the coracohumeral ligament. This segment appeared to reinforce the cuff through a transversely oriented band similar to the glenohumeral ligaments. Clark, J. M. and D. T. Harryman, 2nd (1992). "Tendons, ligaments, and capsule of the rotator cuff. Gross and microscopic anatomy." J Bone Joint Surg Am 74(5): 713-25. We investigated the structure of the myotendinous rotator cuff in thirty-two grossly intact cuffs from thirty fresh cadavera of subjects who had been seventeen to seventy-two years old at the time of death. We studied the gross anatomy of the capsule and ligaments of the cuff, as well as histological sections of the tendons of the subscapularis, supraspinatus, and infraspinatus muscles. The tendons were found to splay out and interdigitate to form a common, continuous insertion on the humerus. The biceps tendon was ensheathed by interwoven fibers derived from the subscapularis and supraspinatus tendons. The anterior margin and bursal surface of the supraspinatus tendon were enveloped by a thick sheet of fibrous tissue derived from the coracohumeral ligament. Fibers from the coracohumeral and glenohumeral ligaments were found concentrated in a plane between the capsule and the tendons of the cuff. Microscopically, in the region of the supraspinatus and infraspinatus tendons, the cuff was composed of five layers defined by the attachments and orientations of the fibrous elements in each of these layers.

Cohen, D. B., S. Kawamura, et al. (2005). "Indomethacin and Celecoxib Impair Rotator Cuff Tendon-to-Bone Healing." Am J Sports Med. BACKGROUND: Nonsteroidal anti-inflammatory drugs are commonly prescribed after rotator cuff repair. These agents can impair bone formation, but no studies have evaluated their impact on tendon-to-bone healing. HYPOTHESIS: Traditional nonselective nonsteroidal anti-inflammatory drugs and cyclooxygenase-2--specific nonsteroidal anti-inflammatory drugs interfere with tendon-to-bone healing. STUDY DESIGN: Controlled laboratory study. METHODS: One hundred eighty Sprague-Dawley rats underwent acute rotator cuff repairs. Postoperatively, 60 rats received 14 days of celecoxib, a cyclooxygenase-2--specific nonsteroidal anti-inflammatory drug; 60 received indomethacin, a traditional nonselective nonsteroidal anti-inflammatory drug; and 60 received standard rat chow. Animals were sacrificed at 2, 4, and 8 weeks and evaluated by gross inspection, biomechanical testing, histologic analysis, and polarized light microscopy to quantify collagen formation and maturation. RESULTS: Five tendons completely failed to heal (4 celecoxib, 1 indomethacin). There were significantly lower failure loads in the celecoxib and indomethacin groups compared with the control groups at 2, 4, and 8 weeks (P <.001), with no significant difference between nonsteroidal anti-inflammatory drug groups. There were significant differences in collagen organization and maturation between the controls and both nonsteroidal anti-inflammatory drug groups at 4 and 8 weeks (P <.001). Controls demonstrated progressively increasing collagen organization during the course of the study (P <.001), whereas the nonsteroidal anti-inflammatory drug groups did not. CONCLUSION: Traditional and cyclooxygenase-2--specific nonsteroidal anti-inflammatory drugs significantly inhibited tendon-to-bone healing. This inhibition appears linked to cyclooxygenase-2. CLINICAL RELEVANCE: If the results of this study are verified in a larger animal model, the common practice of administering nonsteroidal anti-inflammatory drugs after rotator cuff repair should be reconsidered. Dahners, L. E. and B. H. Mullis (2004). "Effects of nonsteroidal anti-inflammatory drugs on bone formation and soft-tissue healing." J Am Acad Orthop Surg 12(3): 139-43. Nonsteroidal anti-inflammatory drugs continue to be prescribed as analgesics for patients with healing fractures even though these drugs diminish bone formation, healing, and remodeling. Inhibition of bone formation can be clinically useful in preventing heterotopic ossification in selected clinical situations. In this regard, naproxen may be more efficacious than the traditional indomethacin, and short-term administration is as effective as long-term. When fracture healing or spine fusion is desired, nonsteroidal anti-inflammatory drugs should be avoided. Some nonsteroidal anti-inflammatory drugs have a positive effect on soft-tissue healing; they stimulate collagen synthesis and can increase strength in the early phases of repair during skin and ligament healing. Cyclooxygenase-2 inhibitors have an adverse effect on bone healing and may have an adverse effect on ligament healing. Therefore, further investigation is necessary to confirm that traditional nonsteroidal anti-inflammatory drugs may be preferable for the healing of collagenous tissues.

Ditsios, K., M. I. Boyer, et al. (2003). "Bone loss following tendon laceration, repair and passive mobilization." J Orthop Res 21(6): 990-6. Little is known about the localized changes in bone mass that occur following tendon or ligament injury. Interruption of normal load transfer at the insertion site will presumably lead to a localized loss of bone, although few data exist to support this claim. To test this hypothesis, we transected the canine flexor digitorum profundus (FDP) tendon from its insertion, and either repaired it using a trans-osseous suture technique or left it unrepaired (laceration only). Post-operatively, forelimbs in the repair group were cast immobilized except for 10 min of daily passive mobilization rehabilitation, whereas in the laceration only group dogs were allowed full weight bearing. At 5-42 days post-injury, we assessed bone mineral density (BMD) using pQCT and osteoclast surface by histomorphometry. We measured significant bone loss in the distal phalanx after combined FDP tendon laceration, repair, and post-operative passive mobilization, with BMD decreases of 20%, 40%, and 41% at 10, 21, and 42 days (p<0.01). Moreover, we observed that passive mobilization and tendon laceration each contributed independently to the observed bone loss. At 42 days, BMD was reduced by 21% in bones that were not injured but were subjected to the post-operative passive mobilization protocol, while BMD was reduced by 28% in bones subjected to tendon laceration and full weight bearing (p<0.01). In both the passive mobilization and laceration specimens, we counted significantly increased osteoclasts after only 7-10 days, and these increases persisted through 42 days (p<0.05). We conclude that rapid and sustained bone resorption leads to significant bone loss in the 6-week period following flexor tendon injury and repair. This bone loss may impact healing by impeding the restoration of a strong tendon-bone interface.

Duckworth, D. G., K. L. Smith, et al. (1999). "Self-assessment questionnaires document substantial variability in the clinical expression of rotator cuff tears." J Shoulder Elbow Surg 8(4): 330-3. The goal of this investigation was to document the variability in the clinical expression of full-thickness rotator cuff tears with practical and standardized patient self-assessment tools. One-hundred twenty-three consecutive patients with full-thickness cuff tears diagnosed by standard cuff-imaging methods (sonography, arthrography, or magnetic resonance imagery) assessed their own shoulder function and health status with the Simple Shoulder Test and the Short Form 36, respectively. As a group, these patients were substantially compromised in their ability to perform the functions of the Simple Shoulder Test and in the Short Form 36 scales of physical role, physical function, and comfort. As individuals, however, their self-assessments varied widely. The standard deviations were often greater than 50% of the mean and the range of responses often covered the entire scale from the minimum possible score to the maximum possible score. These results show the importance of documenting the clinical expression of cuff tears in patients at initial evaluation and when treatment is being considered. The results also show the practicality of standardized self-assessment questionnaires in such documentation.

Fealy, S., R. S. Adler, et al. (2006). "Patterns of vascular and anatomical response after rotator cuff repair." Am J Sports Med 34(1): 120-7. BACKGROUND: It has been assumed that a robust vascular response at the tendon to bone interface during rotator cuff repairs is an integral part to the healing process. There are few studies that have explored this in an in-vivo prospective fashion. PURPOSE: To prospectively characterize vascular and anatomical patterns in repaired rotator cuff tendons using Power Doppler sonography in a double-blinded fashion. STUDY DESIGN: Case control study; Level of evidence, 3. METHODS: Fifty patients undergoing rotator cuff repair were enrolled: 28 mini-open, 14 open, and 8 arthroscopic repairs; 20 patients were controls. Patients underwent Power Doppler sonography at 6 weeks, 3 months, and 6 months postoperatively. Power Doppler sonography analysis examined 6 areas of the rotator cuff repair: discretely marginated intrasubstance, partial-thickness defects, full-thickness defects, focal thinning of repair, presence of bursal or joint fluid, and location of anchors. A subjective scoring system assessed blood flow in each region. RESULTS: There was a predictable, significant decrease in vascular scores after rotator cuff repair over time. The mean vascular score was 11.6 at 6 weeks, 8.3 at 3 months, 7.0 at 6 months, and 2.4 for controls. There was a significant difference (P <.05) in vascular recruitment scores between each time period, with the most robust flow at the peritendinous region. The lowest vascular score was at the anchor site or cancellous trough. Forty-eight percent of the patients had a rotator cuff repair defect postoperatively. These findings did not correlate with functional assessment and outcome at 6 months. There was no significant difference in vascular scores between the defect and no-defect groups. Mean University of California, Los Angeles; L'Insalata; and American Shoulder and Elbow Surgeons scores at 6 months were 28.6, 86.3, and 81.5, respectively. Thirty-three percent of asymptomatic controls had a rotator cuff tear that averaged 7.6 x 7.1 mm. CONCLUSION: The robust vascular response dropped with time, which is not seen in asymptomatic shoulders. Nearly half of the patients demonstrated persistent rotator cuff defects after rotator cuff repair that did not correlate with functional outcome and physical findings at 6 months.

Fealy, S., E. W. April, et al. (2005). "The coracoacromial ligament: morphology and study of acromial enthesopathy." J Shoulder Elbow Surg 14(5): 542-8. The coracoacromial ligament (CAL), normally a superior restraint against humeral translation, is frequently involved in rotator cuff impingement pathology. However, surgical excision of the CAL is not always clinically successful. Little anatomic information exists about the morphology and function of this ligament. The CAL and glenohumeral joint in 56 cadaveric shoulders were examined in 31 cadavers. Nineteen dimensional parameters were obtained by direct measurement. In 16 shoulders, specific attention was directed at the anterior band of the CAL. Variation exists in the morphology of the CAL. The most common configuration of the CAL was two distinct ligamentous bands that could be classified anatomically as an anterolateral band (ALB) and posteromedial band (PMB). The ALB commonly extended to the posterolateral aspect of the acromion. Furthermore, it frequently extended anterolaterally to the acromion, ending in a coracoacromial falx. Spur formation had occurred in 10 of 16 shoulders evaluated and always appeared in the ALB. Spur formation in the ALB correlated with a focal CAL that was narrower, less divergent, shorter, and thicker than a diffuse CAL that did not have a spur. The mean angle of diversion between the ALB and PMB, when a spur was present, was 31 degrees compared with 45 degrees when no spur was present. CAL band thickness varied, with the ALB being thicker at the acromion than at the coracoid and the PMB being thicker at the coracoid than at the acromion. During arthroscopic subacromial decompression, failure to visualize the anterolateral corner of the acromion adequately may result in incomplete resection of the CAL, especially if the PMB is mistaken to be the entire ligament. Incomplete removal of the CAL may be a factor in clinical failures of arthroscopic subacromial decompression. The preferential location of spurs in the ALB suggests that it is a major load-bearing structure. Furthermore, the ALB is thicker at the acromion, suggesting increased strain. Our data suggest that a possible function of the CAL is to dampen stress on the acromion from muscle activity.

Fuchs, B., M. K. Gilbart, et al. (2006). "Clinical and structural results of open repair of an isolated one-tendon tear of the rotator cuff." J Bone Joint Surg Am 88(2): 309-16. BACKGROUND: The clinical outcomes of open rotator cuff repair are well established, but the structural results and their effect on clinical outcome are poorly known. We assessed the structural changes in the musculotendinous units after open rotator cuff repair and correlated these findings with the clinical outcome to establish a benchmark for future series. METHODS: Thirty-two consecutive standardized open repairs of a single tendon tear of the rotator cuff were analyzed in twenty-one men and eleven women with an average age of 59.0 years. The supraspinatus tendon was involved in twenty-two patients and the subscapularis tendon, in ten. The clinical outcome, including the Constant score, was assessed prospectively for all patients at an average of thirty-eight months postoperatively. The structural outcome was assessed on standardized magnetic resonance imaging scans. RESULTS: The mean overall subjective shoulder value was 82.8% of the value for a normal shoulder. On the average, the age and gender-adjusted Constant score increased from 63.9% preoperatively to 94.5% postoperatively (p < 0.0001); the score for pain, from 6.8 points to 13.2 points (p < 0.0001); and the score for activities of daily living, from 11.2 points to 17.9 points (p < 0.0001). The overall rerupture rate was 13% (four of the thirty-two shoulders). All reruptures were distinctly smaller than the original tear. Muscular atrophy or fatty infiltration did not significantly decrease after the tendon repair. In fact, fatty infiltration in the supraspinatus (p < 0.0053) and infraspinatus (p < 0.003) muscles increased significantly. CONCLUSIONS: Direct open repair of a complete, isolated tear of one tendon of the rotator cuff resulted in significant subjective and objective improvement and very high patient satisfaction. Successful direct repair was not associated with a decrease in preoperative muscular atrophy and was associated with increased fatty infiltration of the muscle.

Galatz, L. M., C. M. Ball, et al. (2004). "The outcome and repair integrity of completely arthroscopically repaired large and massive rotator cuff tears." J Bone Joint Surg Am 86-A(2): 219-24. BACKGROUND: The impact of a recurrent defect on the outcome after rotator cuff repair has been controversial. The purpose of this study was to evaluate the functional and anatomic results after arthroscopic repair of large and massive rotator cuff tears with use of ultrasound as an imaging modality to determine the postoperative integrity of the repair. METHODS: Eighteen patients who had complete arthroscopic repair of a tear measuring >2 cm in the transverse dimension were evaluated at a minimum of twelve months after surgery and again at two years after surgery. The evaluation consisted of a standardized history and physical examination as well as calculation of the preoperative and postoperative shoulder scores according to the system of the American Shoulder and Elbow Surgeons. The strength of both shoulders was quantitated postoperatively with use of a portable dynamometer. Ultrasound studies were performed with use of an established and validated protocol at a minimum of twelve months after surgery. RESULTS: Recurrent tears were seen in seventeen of the eighteen patients. Despite the absence of healing at twelve months after surgery, thirteen patients had an American Shoulder and Elbow Surgeons score of >/=90 points. Sixteen patients had an improvement in the functional outcome score, which increased from an average of 48.3 to 84.6 points. Sixteen patients had a decrease in pain, and twelve had no pain. Although eight patients had preoperative forward elevation to <95 degrees, all eighteen regained motion above shoulder level and had an average of 152 degrees of elevation. At the second evaluation, a minimum of twenty-four months after surgery, the average score, according to the system of the American Shoulder and Elbow Surgeons, had decreased to 79.9 points; only nine patients had a score of >/=90 points, and six patients had a score of </=79 points. The average forward elevation decreased to 142 degrees. CONCLUSIONS: Arthroscopic repair of large and massive rotator cuff tears led to a high percentage of recurrent defects. The minimum twelve-month evaluation showed excellent pain relief and improvement in the ability to perform activities of daily living despite the high rate of recurrent defects; however, at a minimum follow-up of two years, the results deteriorated with only twelve patients who had an American Shoulder and Elbow Surgeons score of >/=80.

Galatz, L. M., S. Y. Rothermich, et al. (2005). "Delayed repair of tendon to bone injuries leads to decreased biomechanical properties and bone loss." J Orthop Res 23(6): 1441-7. INTRODUCTION: Repair of the torn rotator cuff tendon is a common procedure performed in the shoulder. In the clinical setting, a significant delay between rotator cuff tear and subsequent repair often exists. The purpose of this study was to investigate the biomechanical properties and bone density of the tendon to bone repair site after acute and delayed repair. METHODS: The supraspinatus tendons in bilateral shoulders of 60 rats were transected from the bone. In the acute group, the tendons were immediately repaired with suture. In the delayed group, the tendons were allowed to retract and repaired in a second procedure after a 3-week delay. Cross sectional area and biomechanical properties were evaluated. Bone density of the humeral head was assessed using peripheral quantitative computed tomography. Histologic sections were obtained and examined. RESULTS: At 10 days the repair tissue displayed vascular and fibroblast proliferation accompanied by predominantly mononuclear infiltrate. At 28 days the inflammatory process gradually decreased. No significant histologic differences were noted between the acute and delayed repair specimens. Cross-sectional area was higher in the delayed group at the early time points (44% at 10 days and 31% at 28 days). Viscoelastic properties were greater in the acute group at the early time points and significantly less at the latest time point, compared to the delayed group. Bone density was markedly decreased (8% and 12%, 28 and 56 days respectively) in the delay group. DISCUSSION: Inferior rotator cuff healing was demonstrated when there was a delay between injury and repair. Viscoelastic properties of the acute repairs were increased compared to the delayed group at 10 days, indicating tendon stiffening during the 3-week delay before repair. Viscoelastic properties of the acute repairs were decreased compared to the delayed group at 56 days indicating deterioration of properties over time in the delayed group. The deterioration in properties in the delayed group coincide with bone density decreases in the greater tuberosity. These results indicate that bone loss may a significant factor in poor healing.

Galatz, L. M., L. J. Sandell, et al. (2006). "Characteristics of the rat supraspinatus tendon during tendon-to-bone healing after acute injury." J Orthop Res 24(3): 541-550. Rotator cuff repair is known to have a high failure rate. Little is known about the natural healing process of the rotator cuff repair site, hence little can be done to improve the tendon's ability to heal. The purpose of this study was to investigate the collagen formation at the early repair site and to localize TGFbeta-1 and 3 during early healing and compare their levels to cell proliferation and histological changes. Bilateral supraspinatus tendons were transected and repaired in 60 rats. Specimens were harvested and evaluated at 0, 1, 3, 7, 10, 28, and 56 days. Histological sections were evaluated for cell morphology. Immunohistochemistry and in situ hybridization was performed to localize protein and mRNA for collagen types I and III and TGFbeta-1 and 3. Proliferating cell nuclear antigen (PCNA) assay was performed to measure cell proliferation, and cells were counted to determine cell density. Biomechanical properties were evaluated. Repair tissue demonstrated an initial inflammatory response with multinucleated cells present at 1 and 3 days, and lymphocytes and plasma cells presents at 7 and 10 days. Capillary proliferation began at 3 days and peaked at 10 days. Ultimate force increased significantly over the time period studied. Collagen I protein and mRNA significantly increased at 10 days, and reached a plateau by 28 and 56 days. Collagen III showed a similar trend, with an early increase, and remained high until 56 days. TGFbeta-1 was localized to the forming scar tissue and showed a distinct peak at 10 days. TGFbeta-3 was not seen at the healing insertion site. Cell proliferation and density followed the same trend as TGFbeta-1. A wound healing response does occur at the healing rotator cuff insertion site, however, the characteristics of the tendon after healing differ significantly from the uninjured tendon insertion site at the longest time-point studied. A distinctive collagen remodeling process occurred with an initial increase in the formation of collagen types I and III followed by a decrease toward baseline levels seen at time 0. Growth factor TGFbeta-1 was localized to repair tissue and coincided with a peak in cell proliferation and cellularity. Repair sites remained unorganized histologically and biomechanically inferior in comparison to previously described uninjured insertion sites. (c) 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:541-550, 2006.

Gazielly, D. F., P. Gleyze, et al. (1994). "Functional and anatomical results after rotator cuff repair." Clin Orthop Relat Res(304): 43-53. The anatomic condition of the rotator cuff and the functional results obtained were studied in a homogeneous series of 100 full thickness cuff tears in 98 patients with an average followup of 4 years. Constant's functional score, used by the European Society for Shoulder and Elbow Surgery, was done preoperatively and postoperatively in each patient, in addition to ultrasonography at followup. There was a close correlation between the anatomic condition of the cuff and Constant's functional score before surgery (p = 0.0063) and after repair, irrespective of the type of tear repaired (p = 0.0012) or the sonographic appearance of the cuff at followup (p = 0.0001). Ultrasonography showed 65% intact cuffs, 11% intact but thinned cuffs, and 24% recurrent defects. Three predisposing factors for recurrence were noted: size of tear to be repaired (p = 0.0001) accounted for 57%, age (p = 0.063) for 25%, and degree of occupational use for 18%. The functional results obtained were more related to the anatomic condition of the repaired cuff at followup than to the tear size at surgery. Predictive clinical factors for recurrence included overall Constant's functional score, reduced ability to perform daily activities, reduced active flexion, abduction and external rotation, and loss of muscular strength. Constant's functional score reflected the functional results with accuracy, reliability, and reproducibility. Additional ultrasonography appears necessary to specify the exact size of the recurrent defect and to distinguish between certain anatomic types, such as thinned cuffs, which can give rise to difficult problems in manual workers after defect repair.

Gazielly, D. F., P. Gleyze, et al. (1995). "[Functional and anatomical results after surgical treatment of ruptures of the rotator cuff. 1: Preoperative functional and anatomical evaluation of ruptures of the rotator cuff]." Rev Chir Orthop Reparatrice Appar Mot 81(1): 8-16. PURPOSE OF THE STUDY: In a consecutive series of 98 patients presenting 100 full thickness cuff tears and managed by the same medico-surgical team, the authors studied the correlation between preoperative shoulder function values and the anatomic lesions found at surgery. Predictive factors of tear size were evaluated and any elements that were likely to improve preoperative function were determined so that patients could be best prepared for surgery. The validity of preoperative radiographic assessment of lesions was examined. MATERIAL AND METHODS: Prior to surgery, each patient was given the same rehabilitation program, the same arthrotomographic assessment of lesions and each was rated functionally using Constant's scoring method. Preoperative radiographic assessment of lesions showed supra-spinatus tears in 69 per cent, combined supraspinatus and infraspinatus tears in 22 per cent, and tears involving the supraspinatus, infraspinatus and subscapularis in 9 per cent. RESULTS: The preoperative Constant score averaged 46/100 points. The score was higher when patients had been prepared by preoperative rehabilitation to overcome stiffness. The optimum duration of rehabilitation was found to be 3 months (p < 0.05). Active range of motion was 90 per cent of normal in 84 per cent of cases. The patients in this series therefore underwent surgery more for continuing severe pain (25 per cent) and muscle weakness (86 per cent) than for reduced active motion. DISCUSSION: Examination of the correlations existing between an anatomic lesion and the preoperative rating of shoulder function shows that the Constant preoperative score provides a good prediction of the size of the tear to be repaired (p = 0.0063). The greater the tear size, the lower the preoperative Constant sore is. Active range of motion (especially in abduction and external rotation) and muscular strength are factors with the most predictive value contrary to pain and discomfort which are influenced by tear size. CONCLUSION: Preparing patients suffering full thickness cuff defects through preoperative rehabilitation to overcome stiffness provides the best conditions for surgery. Constant's functional scoring method gives a reproducible and reliable reflection of the anatomic rotator cuff lesion to be repaired. Its use for preoperative rating is useful for determining a reference value for function prior to surgery.

Gerber, C., B. Fuchs, et al. (2000). "The results of repair of massive tears of the rotator cuff." J Bone Joint Surg Am 82(4): 505-15. BACKGROUND: Massive tears of the tendons of the rotator cuff cause atrophy and fatty degeneration of the rotator cuff muscles and painful loss of function of the shoulder. Repair of massive rotator cuff tears is often followed by retears of the tendons, additional muscular degeneration, and a poor clinical outcome. The purposes of this study were to determine whether a new method of repair of rotator cuff tendons can yield a lower retear rate and a better clinical outcome than previously reported methods, to assess the muscular changes following repair of massive tears of the musculotendinous units, and to correlate findings on magnetic resonance imaging with the clinical results. METHODS: Twenty-nine massive rotator cuff tears involving complete detachment of at least two tendons were repaired operatively with use of a new laboratory-tested technique in a prospective study. At least two years (average, thirty-seven months; range, twenty-four to sixty-one months) postoperatively, twenty-seven patients were evaluated clinically and with magnetic resonance imaging to determine the clinical outcome, the integrity of the repair, and the condition of the rotator cuff muscles. RESULTS: The age and gender-adjusted Constant score improved from an average of 49 percent preoperatively to an average of 85 percent postoperatively, corresponding to a subjective shoulder value of 78 percent of that of a normal shoulder. Pain-free flexion improved from an average of 92 degrees to an average of 142 degrees, and abduction improved from an average of 82 degrees to an average of 137 degrees. Pain decreased and performance of activities of daily living improved significantly (p < 0.05). The seventeen patients who had a structurally successful repair all had an excellent clinical outcome. Muscle atrophy could not be reversed except in successfully repaired supraspinatus musculotendinous units. Fatty degeneration increased in all muscles. CONCLUSIONS: The method of repair of massive rotator cuff tears that was used in this study yielded a comparatively low retear rate and good-to-excellent clinical results; however, the repair did not result in substantial reversal of muscular atrophy and fatty degeneration. Retears occurred more often in patients who had had a shorter interval between the onset of the symptoms and the operation (p < 0.05). Patients who had a retear had improvement of the shoulder compared with the preoperative state, but they had less improvement than did those who had a successful repair.

Gerber, C., D. C. Meyer, et al. (2004). "Effect of tendon release and delayed repair on the structure of the muscles of the rotator cuff: an experimental study in sheep." J Bone Joint Surg Am 86-A(9): 1973-82. BACKGROUND: Ruptures of the tendons of the rotator cuff lead to profound and possibly irreversible changes in the structure and physiological properties of the rotator cuff muscles. Muscle atrophy and fatty infiltration are important prognostic factors that affect the natural history and outcome of treatment. The purpose of this study was to examine the amount of muscle atrophy and fatty infiltration in an animal model and to determine whether the repair of a long-standing tendon tear can reverse these changes. METHODS: The infraspinatus tendon in six sheep was released and encased in a silicone tube to prevent spontaneous healing. The musculotendinous unit was allowed to retract for forty weeks. Throughout this period, the muscular changes were studied with use of computed tomography, histological analysis, and electron microscopy. At forty weeks, the elasticity, intramuscular pressure, and perfusion were measured intraoperatively and a tendon repair was carried out. The structural changes of the muscle were studied for thirty-five weeks after the repair. The animals were then killed, and the musculotendinous units were examined macroscopically and by computed tomography, histological analysis, and electron microscopy. RESULTS: At the time of the tendon release, the infraspinatus showed no fatty changes. The force needed to cause a tendon excursion of 1 cm was a mean (and standard deviation) of 6.8 +/- 1 N. The application of tension on the tendon did not alter the perfusion and decreased the intramuscular pressure. After the tendon release, muscular atrophy developed and there was a significant increase (p < 0.001) in interfascicular and intrafascicular fat, representing fatty infiltration rather than fatty degeneration. Furthermore, there was an increase of interstitial connective tissue. At the time of the tendon repair, between forty and forty-two weeks after the release, there was a sevenfold poorer elasticity of the musculotendinous unit but preserved muscle perfusion. The structural changes increased six weeks after the repair and then recovered partially at twelve and thirty-five weeks thereafter but only to the amount demonstrated before the repair. CONCLUSIONS: Musculotendinous retraction induced by tendon release is associated with profound changes in the structure and function of the affected muscle. Vascularization, intramuscular pressure, and individual fiber composition are not markedly affected, and muscle fibers do not appear to degenerate. However, muscle atrophy, infiltration by fat cells, and an increase of interstitial connective tissue lead to impairment of the physiological properties of the muscle. These changes were irreversible under the conditions of this experiment with the repair technique used.

Gerber, C., A. G. Schneeberger, et al. (1999). "Experimental rotator cuff repair. A preliminary study." J Bone Joint Surg Am 81(9): 1281-90. BACKGROUND: The repair of chronic, massive rotator cuff tears is associated with a high rate of failure. Prospective studies comparing different repair techniques are difficult to design and carry out because of the many factors that influence structural and clinical outcomes. The objective of this study was to develop a suitable animal model for evaluation of the efficacy of different repair techniques for massive rotator cuff tears and to use this model to compare a new repair technique, tested in vitro, with the conventional technique. METHODS: We compared two techniques of rotator cuff repair in vivo using the left shoulders of forty-seven sheep. With the conventional technique, simple stitches were used and both suture ends were passed transosseously and tied over the greater tuberosity of the humerus. With the other technique, the modified Mason-Allen stitch was used and both suture ends were passed transosseously and tied over a cortical-bone-augmentation device. This device consisted of a poly(L/D-lactide) plate that was fifteen millimeters long, ten millimeters wide, and two millimeters thick. Number-3 braided polyester suture material was used in all of the experiments. RESULTS: In pilot studies (without prevention of full weight-bearing), most repairs failed regardless of the technique that was used. The simple stitch always failed by the suture pulling through the tendon or the bone; the suture material did not break or tear. The modified Mason-Allen stitch failed in only two of seventeen shoulders. In ten shoulders, the suture material failed even though the stitches were intact. Thus, we concluded that the modified Mason-Allen stitch is a more secure method of achieving suture purchase in the tendon. In eight of sixteen shoulders, the nonaugmented double transosseous bone-fixation technique failed by the suture pulling through the bone. The cortical-bone-augmentation technique never failed. In definite studies, prevention of full weight-bearing was achieved by fixation of a ten-centimeter-diameter ball under the hoof of the sheep. This led to healing in eight of ten shoulders repaired with the modified Mason-Allen stitch and cortical-bone augmentation. On histological analysis, both the simple-stitch and the modified Mason-Allen technique caused similar degrees of transient localized tissue damage. Mechanical pullout tests of repairs with the new technique showed a failure strength that was approximately 30 percent of that of an intact infraspinatus tendon at six weeks, 52 percent of that of an intact tendon at three months, and 81 percent of that of an intact tendon at six months. CONCLUSIONS: The repair technique with a modified Mason-Allen stitch with number-3 braided polyester suture material and cortical-bone augmentation was superior to the conventional repair technique. Use of the modified Mason-Allen stitch and the cortical-bone-augmentation device transferred the weakest point of the repair to the suture material rather than to the bone or the tendon. Failure to protect the rotator cuff post-operatively was associated with an exceedingly high rate of failure, even if optimum repair technique was used. CLINICAL RELEVANCE: Different techniques for rotator cuff repair substantially influence the rate of failure. A modified Mason-Allen stitch does not cause tendon necrosis, and use of this stitch with cortical-bone augmentation yields a repair that is biologically well tolerated and stronger in vivo than a repair with the conventional technique. Unprotected repairs, however, have an exceedingly high rate of failure even if optimum repair technique is used. Postoperative protection from tension overload, such as with an abduction splint, may be necessary for successful healing of massive rotator cuff tears.

Gigante, A., M. Marinelli, et al. (2004). "Fibrous cartilage in the rotator cuff: A pathogenetic mechanism of tendon tear?" J Shoulder Elbow Surg 13(3): 328-32. There is no consensus on the pathogenesis of rotator cuff tears. Fibrous cartilage has been hypothesized to develop in some tendons as a result of shear or compressive forces, resulting in a tissue less capable of resisting normal tensile load and more prone to tearing. To test the hypothesis that metaplastic fibrocartilage in the rotator cuff could be involved in the pathogenic mechanism of its tear, samples from 34 acute and chronic torn rotator cuffs were subjected to histologic and immunohistologic study for the presence and type of cartilage (hyaline, fibrous, or elastic) in the area of the lesion and surrounding tissues. Detection of type I and II collagen, S-100 protein, and chondroitin sulfate allowed areas of fibrous cartilage to be seen in all samples, suggesting that the characteristic of rotator cuff tendons to work both in tension and in compression may stimulate fibrocartilaginous metaplasia and lead to a complete tear.

Gimbel, J. A., S. Mehta, et al. (2004). "The tension required at repair to reappose the supraspinatus tendon to bone rapidly increases after injury." Clin Orthop Relat Res(426): 258-65. Rotator cuff tears occur frequently and can cause significant pain and reduced shoulder function. A high percentage of patients are satisfied after surgical repair of rotator cuff tears, but a smaller percentage of patients with chronic tears continue to have pain and poor shoulder function. This may be partly attributable to an increase in the repair tension, the force required at repair to reappose the tendon to its original insertion site on the humerus. Increases in repair tension have been shown to occur for long-standing ruptures of the supraspinatus tendon, but the precise tension at various times after injury are unknown. Therefore, the objective of the current study was to determine the repair tension at various times after a rotator cuff tear. This was achieved by creating a full-thickness supraspinatus tendon tear in a rat model and measuring the mechanical characteristics of the musculotendinous unit at 0, 2, 4, 9, and 16 weeks after injury. The repair tension rapidly increased initially after injury followed by a progressive, but less dramatic, increase with additional time. These findings suggest that rotator cuff tears should be repaired early in the clinical setting. Future studies will investigate the effect of repair tension on tendon to bone healing after repair.

Gimbel, J. A., J. P. Van Kleunen, et al. (2004). "Supraspinatus tendon organizational and mechanical properties in a chronic rotator cuff tear animal model." J Biomech 37(5): 739-49. Rotator cuff tears of the shoulder are a common cause of pain and disability. The successful repair of rotator cuff tendon tears depends on the time from onset of injury to the time of surgical repair. However, the effect of time from injury to repair remains poorly understood. A rat model was used to investigate the supraspinatus tendon organizational and mechanical property changes that occur with time post-injury to understand the natural injury response in the absence of repair. It was hypothesized that increased time post-injury would result in increased detrimental changes to tendon organizational and mechanical properties. Tendons were detached at the insertion on the humerus without repair and the quantitative organizational and mechanical properties were analyzed at 1, 2, 4, 8, and 16 weeks post-detachment. Tendon detachment resulted in a dramatic decrease in mechanical properties initially followed by a progressive increase with time. The quantitative collagen fiber orientation results provided corroborating support to the mechanical property data. Based on similarities in histology and mechanical properties to rotator cuff tears in humans, the animal model presented here is promising for future investigations of the tendon's natural injury response in the absence of repair.

Gleyze, P., H. Thomazeau, et al. (2000). "[Arthroscopic rotator cuff repair: a multicentric retrospective study of 87 cases with anatomical assessment]." Rev Chir Orthop Reparatrice Appar Mot 86(6): 566-74. PURPOSE OF THE STUDY: The aim of this study was to evaluate the anatomical and technical limits of endoscopic rotator cuff repair. Anatomical results were also compared with functional assessment of the shoulder. MATERIAL AND METHODS: A multicentric series of 87 patients presenting a full thickness rotator cuff tear repaired endoscopically was retrospectively reviewed at 25.4 months (mean) post surgery. Limits of the surgical technique were studied in correlation with functional results and anatomic radiographic evaluation (arthroscans in 93 p. 100). RESULTS: Anatomical repair (normal thickness and no contrast in the subacromial space on arthroscan) was achieved in 83 p. 100 of the rotator cuffs with limited damage to the frontal part of the supra spinatus tendon. This percentage fell to 57.8 p. 100 in case of posterior extension of the tear to the supra spinatus tendon and further dropped to 40.8 p. 100 in case of retraction to the apex of the humeral head. Functional outcome evaluated with the Constant score was strongly related to the radiographic cuff condition (p <0.05). For distal and anterior tears of the supra spinatus tendon, the Constant score at revision was 89.8 points in cases with anatomic repair at revision. This score fell to 75 when the rotator cuff tear was evidenced radiographically (p <0.0001). For tears involving the entire supra spinatus tendon repaired by arthroscopy, the functional difference at revision was 8 points on the Constant scale. Objective and subjective analysis of the surgical procedure identified significant peroperative elements predictive of clinical and anatomical outcome (difficult reduction, p <0.05; subjective degree of solidity, p <0.0001; anatomical aspect of the repaired cuff, p <0.05). DISCUSSION: A comparison of our findings with data on equivalent lesions reported in the literature suggests that endoscopic surgery for rotator cuff tears offers both functional and anatomic results equivalent to those achieved with conventional open surgery. This assumes that the surgical procedure is carried out by surgeons experienced in shoulder arthroscopy who can precisely gauge the posterior/anterior extension of the tears and the limits of the surgical technique.

Goldberg, B. A., S. B. Lippitt, et al. (2001). "Improvement in comfort and function after cuff repair without acromioplasty." Clin Orthop Relat Res(390): 142-50. The repair of full thickness rotator cuff tears traditionally has included acromioplasty and coracoacromial ligament section. Acromioplasty can be complicated by deltoid detachment, compromise of the deltoid lever arm, anterosuperior instability, and adhesions of the rotator cuff tendons under the bleeding cancellous bone of the osteotomized acromion. This report concerns the improvement in shoulder function at a minimum of 2 years after 27 full thickness rotator cuff repairs were done without deltoid detachment, acromioplasty, or section of the coracoacromial ligament. The mean number of Simple Shoulder Test functions that the patients could do increased from six of 12 before surgery to 10 of 12 at an average followup of 4 years after surgery. Eight of 12 individual Simple Shoulder Test functions were significantly improved after the procedure. There also was a significant improvement in the Short Form-36 comfort, physical role function, and mental health scores. When done without acromioplasty, cuff repair avoids the possibility of deltoid detachment, altered deltoid mechanics, anterosuperior instability, and tendon scarring to the cancellous undersurface of the acromion.

Goldberg, B. A., R. J. Nowinski, et al. (2001). "Outcome of nonoperative management of full-thickness rotator cuff tears." Clin Orthop Relat Res(382): 99-107. The study documented the functional outcome in a consecutive series of 46 patients from an individual practice meeting the inclusion criteria of (1) a full-thickness rotator cuff tear seen by ultrasonography, arthrogram, or magnetic resonance imaging, (2) absence of a Workers' Compensation claim or previous surgery, (3) followup of at least 1 year, and (4) election of nonoperative management by the patient. Twenty-six of the tears involved only the supraspinatus, two involved the supraspinatus and infraspinatus, and two involved the supraspinatus, infraspinatus, and subscapularis (16 reports did not specify the size of the tear). Treatment consisted only of patient education and a home program of gentle stretching and strengthening. Patients completed the Simple Shoulder Test at the initial visit and sequentially at 6-month intervals thereafter. At an average followup of 2.5+/-1.6 years, 27 (59%) patients experienced improvement with nonoperative treatment, 14 (30%) patients experienced worsening, and five (11%) patients remained unchanged. The average number of Simple Shoulder Test functions the patients could perform initially was 5.6+/-3.2. At the latest followup, the average number of Simple Shoulder Test functions the patients could perform improved to 7.0 +/-3.8. The ability to sleep on the affected side and the ability to place the hand behind the head were significantly improved.

Goodmurphy, C. W., J. Osborn, et al. (2003). "An immunocytochemical analysis of torn rotator cuff tendon taken at the time of repair." J Shoulder Elbow Surg 12(4): 368-74. During rotator cuff repairs, it is recommended that the hypovascular tissue edge be resected. To investigate rotator cuff tendon histopathology, we performed immunohistochemistry on 8 surgical and 6 cadaveric specimens. Hoechst nuclear stain and standard hematoxylin-eosin were used for morphologic analysis. Antibody to human von Willebrand factor tagged with fluorescein isothiocyanate, conjugated, was used to visualize vascularity, and antibody to human procollagen type I tagged with Cy3 was used to visualize new procollagen synthesis. There were no significant differences in the vascularity of surgical specimens sectioned near the tear site (<2.5 mm from tear margin) and matched cadaveric controls. However, sections taken 2.5 to 5 mm away from the tear demonstrated more vessels than those taken from either control or surgical specimens within 2.5 mm of the tear (P <.001). There were no differences in nuclear distribution patterns or in procollagen production and distribution between surgical specimens from sites near the tear or away from the tear. On the basis of morphologic architecture, these data suggest that minimal debridement of tendon edges only is required to maximize healing of the rotator cuff tendon at the time of repair.

Goradia, V. K., M. C. Rochat, et al. (2000). "Tendon-to-bone healing of a semitendinosus tendon autograft used for ACL reconstruction in a sheep model." Am J Knee Surg 13(3): 143-51. Anterior cruciate ligament (ACL) reconstruction was performed in a single hind limb of 30 sheep using a doubled semitendinosus tendon graft. Three additional animals were used as controls. Histologic and biomechanical analysis was performed from 4-52 weeks postoperatively. Perpendicular collagen fibers were found connecting the tendon graft to the bone tunnels at 8 weeks. These fibers were seen circumferentially at 12 weeks. By 24 weeks, the bone tunnel was well-defined, and no further changes were observed at 52 weeks. Tendon incorporation within the femoral and tibial tunnels was similar at each interval. Although the small sample size did not permit statistical testing, the reconstruction strength was similar up to 12 weeks (15%-19% of controls). This increased at 24 (28%) and 52 (40%) weeks. The stiffness primarily increased from 4-8 weeks (18%-39%) and 24-52 weeks (52%-82%). Up to 12 weeks, failures occurred by graft pull-out from the bone tunnel. All 24- and 52-week specimens ruptured through the intra-articular portion of the graft, further indicating sufficient graft incorporation within the bone tunnels.

Gotoh, M., K. Hamada, et al. (1997). "Significance of granulation tissue in torn supraspinatus insertions: an immunohistochemical study with antibodies against interleukin-1 beta, cathepsin D, and matrix metalloprotease-1." J Orthop Res 15(1): 33-9. The pathophysiology of rotator cuff tears can be elucidated by examining the tendinous insertion of the supraspinatus muscle. As seen by light microscopy, the granulation tissue around the insertion of a torn supraspinatus tendon appears to induce osteochondral destruction by means of multinucleated giant cells and chemical mediators. The purpose of this study was to examine the contribution of certain chemical mediators to osteochondral destruction using immunohistochemical analysis of interleukin-beta, cathepsin D, and matrix metalloprotease-1. Sixteen supraspinatus insertions with portions of the greater tuberosity, including eight complete-thickness tears and eight incomplete-thickness tears, were obtained during surgery. Six fresh cadaveric supraspinatus tendons without grossly evident tears served as normal controls. Strong immunoreactivity was found in all 16 torn supraspinatus insertions but not in the six insertions of apparently intact tendons. Macrophages and multinucleated giant cells, which showed immunoreactivity for all three chemical mediators, were often found at the interface between the osteochondral margin of the enthesis and the granulation tissue, suggesting that they may be involved in osteochondral destruction. We therefore concluded that, in addition to repetitive subacromial impingement, this granulation tissue may contribute to the development of rotator cuff tears by weakening the insertion.

Goutallier, D., J. M. Postel, et al. (2003). "Influence of cuff muscle fatty degeneration on anatomic and functional outcomes after simple suture of full-thickness tears." J Shoulder Elbow Surg 12(6): 550-4. Two hundred twenty shoulders with a rotator cuff tear repaired by simple tendon-to-bone suture were analyzed to determine whether the severity of presurgical fatty degeneration had an influence on their anatomic and functional outcome. Fatty degeneration was evaluated for each muscle with the 5-stage grading system developed by Goutallier et al. A global fatty degeneration index (GFDI), the mean value of the 3 muscles, was calculated for each shoulder. Cuff integrity was evaluated by magnetic resonance imaging (116 cases) or computed arthrotomography scan (104 cases) at a mean 37 months' follow-up, and functional outcomes were evaluated with the Constant score. A recurrent tear was found in 79 cases (36%) and was more frequently encountered in posterosuperior tears. The likelihood of a recurrent tear was greater for tendons whose muscle showed fatty degeneration greater than grade 1. Fatty degeneration of the infraspinatus or subscapularis muscles had an influence on supraspinatus tendon outcome. A GFDI lower than 0.5 was necessary to yield less than 25% retears. The mean global Constant score was 75 at revision, significantly lower when a retear was present (70.5 versus 77.5). In the subgroup of watertight cuffs, it was lower when GFDI was higher. Fatty degeneration is an important prognostic factor in rotator cuff surgery.

Greis, P. E., R. T. Burks, et al. (2001). "The influence of tendon length and fit on the strength of a tendon-bone tunnel complex. A biomechanical and histologic study in the dog." Am J Sports Med 29(4): 493-7. Using a dog model, we examined the influence of tendon length and fit within a bone tunnel on the pull-out strength of a tendon-bone tunnel complex at 6 weeks after fixation. Fourteen adult mongrel dogs (weight, 25 to 30 kg) underwent bilateral hindlimb surgery in which the extensor digitorum longus tendon was transplanted into an extraarticular metaphyseal bone tunnel. Our findings demonstrated that pull-out strength at 6 weeks was enhanced by increasing the length of tendon within the tunnel. The average load to failure with 1 cm of tendon within the tunnel was 153.7 +/- 78.6 N, compared with 265.5 +/- 93.3 N for the specimens with 2 cm of tendon in the tunnel. Tendon fit within the tunnel was also found to be important. The average load to failure when a tendon was placed in a 4.2-mm diameter tunnel was 301 +/- 61 N at 6 weeks. The average load to failure when the tendon was placed within a 6-mm diameter tunnel was 228 +/- 65 N. These differences were statistically different. Histologically, the interface between the tendon and bone appeared to be most mature when there was intimate bone-to-tendon contact. These data suggest that maximizing tendon length within a bone tunnel and minimizing tendon-tunnel diameter mismatch will maximize the strength of a tendon-bone tunnel complex at 6 weeks.

Haahr, J. P., S. Ostergaard, et al. (2005). "Exercises versus arthroscopic decompression in patients with subacromial impingement: a randomised, controlled study in 90 cases with a one year follow up." Ann Rheum Dis 64(5): 760-4. OBJECTIVES: To compare the effect of graded physiotherapeutic training of the rotator cuff versus arthroscopic subacromial decompression in patients with subacromial impingement. METHODS: Randomised controlled trial with 12 months' follow up in a hospital setting. Ninety consecutive patients aged 18 to 55 years were enrolled. Symptom duration was between six months and three years. All fulfilled a set of diagnostic criteria for rotator cuff disease, including a positive impingement sign. Patients were randomised either to arthroscopic subacromial decompression, or to physiotherapy with exercises aiming at strengthening the stabilisers and decompressors of the shoulder. Outcome was shoulder function as measured by the Constant score and a pain and dysfunction score. "Intention to treat" analysis was used, with comparison of means and control of confounding variables by general equation estimation analysis. RESULTS: Of 90 patients enrolled, 84 completed follow up (41 in the surgery group, 43 in the training group). The mean Constant score at baseline was 34.8 in the training group and 33.7 in the surgery group. After 12 months the mean scores improved to 57.0 and 52.7, respectively, the difference being non-significant. No group differences in mean pain and dysfunction score improvement were found. CONCLUSIONS: Surgical treatment of rotator cuff syndrome with subacromial impingement was not superior to physiotherapy with training. Further studies are needed to qualify treatment choice decisions, and it is recommended that samples are stratified according to disability level.

Hamada, K., A. Tomonaga, et al. (1997). "Intrinsic healing capacity and tearing process of torn supraspinatus tendons: in situ hybridization study of alpha 1 (I) procollagen mRNA." J Orthop Res 15(1): 24-32. To determine the healing potential and healing process of torn supraspinatus tendons, in situ hybridization was used to localize cells containing alpha 1 type-I procollagen mRNA. Biopsy specimens of torn supraspinatus tendons from 19 patients with complete-thickness tears and 13 patients with incomplete-thickness tears were obtained during surgery. Four macroscopically normal supraspinatus tendons were obtained to serve as normal controls. Specimens were fixed in 10% buffered formalin and embedded in paraffin. A 22-mer oligonucleotide probe was labeled with digoxigenin and used as an in situ marker. The labeled cells were mainly composed of tenocytes and undifferentiated mesenchymal cells. In complete-thickness-tears, the labeled cells at the proximal tendon-stumps in the specimens that were obtained less than 4 months after trauma were significantly more abundant than in the specimens obtained 4 months or more after trauma. However, the number of labeled cells was maintained at the torn portion even in long-standing incomplete-thickness tears. The labeled cells at the margins of concomitant intratendinous extensions of the tears were detected even in the long-standing tears. The intratendinous extensions exhibited more labeled cells than the bursal-side or joint-side layers of the tendon substance in the incomplete-thickness tears (p < 0.05). The torn supraspinatus tendon may possess an intrinsic healing capability in the intermediate and late phases of tendon healing. Incomplete-thickness tears and concomitant intratendinous extensions can continue to rupture after the initial injury.

Harryman, D. T., 2nd, C. M. Hettrich, et al. (2003). "A prospective multipractice investigation of patients with full-thickness rotator cuff tears: the importance of comorbidities, practice, and other covariables on self-assessed shoulder function and health status." J Bone Joint Surg Am 85-A(4): 690-6. BACKGROUND: Rotator cuff tears are among the most common conditions of the shoulder. One of the major difficulties in studying patients with rotator cuff tears is that the clinical expression of these tears varies widely and different practices may have substantially different patient populations. The goals of the present prospective multipractice study were to use patient self-assessment questionnaires (1) to identify some of the characteristics of patients with rotator cuff tears, other than the size of the cuff tear, that are correlated with shoulder function, and (2) to determine whether there are significant differences in these characteristics among patients from the practices of different surgeons. METHODS: Ten surgeons enrolled a total of 333 patients with a full-thickness tear of the supraspinatus tendon into this prospective study. Each patient completed self-assessment questionnaires that included items regarding demographic characteristics, prior treatment, medical and social comorbidities, general health status, and shoulder function. RESULTS: As expected, patients who had an infraspinatus tendon tear as well as a supraspinatus tendon tear had significantly worse ability to use the arm overhead compared with those who had a supraspinatus tear alone (p < 0.005). However, shoulder function and health status were correlated with patient characteristics other than the size of the rotator cuff tear. The number of shoulder functions that were performable was correlated with the subscales of the Short Form-36 and was inversely associated with medical and social comorbidities. The patients from the ten different surgeon practices showed significant differences in almost every parameter, including age, gender, method of tear documentation, tear size, prior treatment, medical and social comorbidities, general health status, and shoulder function. CONCLUSIONS: Clinical studies on the natural history of rotator cuff tears and the effectiveness of treatment must control for a wide range of variables, many of which do not pertain directly to the shoulder. Patients from the practices of different surgeons cannot be assumed to be similar with respect to these variables. Patient self-assessment questionnaires appear to offer a practical method of uniform assessment across different practices.

Harryman, D. T., 2nd, L. A. Mack, et al. (1991). "Repairs of the rotator cuff. Correlation of functional results with integrity of the cuff." J Bone Joint Surg Am 73(7): 982-9. We evaluated the results of 105 operative repairs of tears of the rotator cuff of the shoulder in eighty-nine patients at an average of five years postoperatively. We correlated the functional result with the integrity of the cuff, as determined by ultrasonography. Eighty per cent of the repairs of a tear involving only the supraspinatus tendon were intact at the time of the most recent follow-up, while more than 50 per cent of the repairs of a tear involving more than the supraspinatus tendon had a recurrent defect. Older patients and patients in whom a larger tear had been repaired had a greater prevalence of recurrent defects. At the time of the most recent follow-up, most of the patients were more comfortable and were satisfied with the result of the repair, even when they had sonographic evidence of a recurrent defect. The shoulders in which the repaired cuff was intact at the time of follow-up had better function during activities of daily living and a better range of active flexion (129 +/- 20 degrees compared with 71 +/- 41 degrees) compared with the shoulders that had a large recurrent defect. Similar correlations were noted for the range of active external and internal rotation and for strength of flexion, abduction, and internal rotation. In the shoulders in which the cuff was not intact, the degree of functional loss was related to the size of the recurrent defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Jiang, Y., J. Zhao, et al. (2002). "Trabecular microstructure and surface changes in the greater tuberosity in rotator cuff tears." Skeletal Radiol 31(9): 522-8. OBJECTIVE: When planning surgery in patients with rotator cuff tear, strength of bone at the tendon insertion and trabecular bone structure in the greater tuberosity are usually taken into consideration. We investigated radiographic changes in bone structure of the greater tuberosity in rotator cuff tears. DESIGN: Twenty-two human cadaveric shoulders from subjects ranging from 55 to 75 years of age were obtained. The integrity of the rotator cuff was examined by sonography to determine if it is intact without any tear, or torn partially or completely. The humeral head was sectioned in 3 mm thick coronal slab sections and microradiographed. After digitization of the microradiographs and imaging processing with in-house semi-automated image processing software tools developed using software interfaces on a Sun workstation, the trabecular histomorphometrical structural parameters and connectivity in the greater tuberosity were quantified. The degenerative changes on the surface of the greater tuberosity were interpreted blindly by 2 independent readers. RESULTS: Among the 22 shoulder specimens, the rotator cuff was found intact in 10 shoulders, partially in 7 and fully torn in 5. Statistically significant loss in apparent trabecular bone volume fraction, number of trabecular nodes, and number of trabecular branches, and a statistically significant increase in apparent trabecular separation and number of trabecular free ends were found in the greater tuberosity of the shoulders with tears. The loss was greater in association with full tear than in partial tear. Thickening of the cortical margin of the enthesis, irregularity of its surface, and calcification beyond the tidemark were observed in 2 (20%) shoulders with intact rotator cuff, in 6 (86%) shoulders with partial tear, and in 5 (100%) shoulders with full tear. CONCLUSIONS: Rotator cuff tears are associated with degenerative changes on the bone surface and with disuse osteopenia of the greater tuberosity. Aging, degenerative enthesopathy of the supraspinatus tendon, and rotator cuff tears appear closely related.

Kawamura, S., L. Ying, et al. (2005). "Macrophages accumulate in the early phase of tendon-bone healing." J Orthop Res 23(6): 1425-32. A scar tissue interface forms rather than a normal ligament insertion site following attachment of a tendon graft to bone. The specific cell types that initiate the process of tendon-to-bone healing are unknown. We hypothesized that inflammatory cell accumulation following tendon-to-bone repair results in this scar interface. We used a rodent model to examine the temporal and spatial pattern of accumulation of hematopoietic lineage cells in the early phase of tendon-to-bone healing. Thirty-six Lewis rats underwent anterior cruciate ligament (ACL) reconstruction in the left knee using a flexor digitorum longus tendon graft. Six animals were sacrificed at 4, 7, 11, 14, 21, and 28 days after surgery. Serial sections were analyzed for proliferating cells (PCNA), recruited macrophages (ED1), resident macrophages (ED2), neutrophils, T-lymphocytes (CD3), mast cells, immature progenitor cells/pericytes (expressing the NG2 cell-surface chondroitin sulfate proteoglycan), and newly-formed blood vessels (Factor VIII). Neutrophils, ED1(+) and ED2(+) macrophages accumulated sequentially in the healing tendon graft, with progressive cell ingrowth from the interface towards the inner tendon. Neutrophils and ED1(+) cells were seen in the tendon-bone interface at 4 days after surgery, while ED2(+) macrophages were not identified until 11 days. These cells progressively repopulated the tendon graft. NG2-positive progenitor cells were found along the edge of the bone tunnel in the interface, but these cells did not invade the tendon. Occasional T-lymphocytes and mast cells were seen in the tendon-bone interface. There was no proliferation of intrinsic tendon cells, indicating that the tendon does not directly contribute to healing. We hypothesize that cytokines produced by infiltrating macrophages are likely to contribute to the formation of a fibrous scar tissue interface rather than a normal insertion site.

Kelly, B. T., R. J. Williams, et al. (2005). "Differential patterns of muscle activation in patients with symptomatic and asymptomatic rotator cuff tears." J Shoulder Elbow Surg 14(2): 165-71. Patients with rotator cuff tears have varying degrees of symptom expression. Our purpose was to evaluate the differential firing patterns of the rotator cuff, deltoid, and scapular stabilizer muscle groups in normal control subjects and in patients with symptomatic and asymptomatic 2-tendon rotator cuff tears. Eighteen subjects were evaluated: six normal subjects and twelve with 2-tendon cuff tears (six asymptomatic and six symptomatic). All cuff tear patients had magnetic resonance imaging (MRI) scans documenting superoposterior tear configurations involving the supraspinatus and infraspinatus tendons; all normal subjects had an ultrasound examination confirming the absence of cuff pathology. Subjects were grouped based on shoulder examination and outcomes questionnaires. Asymptomatic patients had minimal pain (<3 on the visual analog scale and no loss of active range of motion compared with the contralateral side); symptomatic patients had pain greater than 3 on the visual analog scale and decreased range of motion compared with the contralateral side (>10 degrees of motion loss). Electromyographic activity from 12 muscles and kinematic data were collected simultaneously during 10 functional tasks. Both symptomatic and asymptomatic cuff subjects demonstrated a trend toward increased muscle activation during all tasks compared with normal subjects. During the internal rotation tasks, asymptomatic patients had significantly greater (P<.05) subscapularis activity than symptomatic patients (65% maximal voluntary contraction [MVC] vs 42% MVC). During the carrying task, asymptomatic patients demonstrated significantly less (P<.03) upper trapezius muscle activation than symptomatic patients (16% MVC vs 50% MVC). During shoulder elevation tasks, symptomatic patients had significantly greater supraspinatus (52% MVC vs 28% MVC, P<.03), infraspinatus (32% MVC vs 16% MVC, P<.05), and upper trapezius (39% MVC vs 20% MVC, P<.04) muscle activation compared with asymptomatic patients. During heavy elevation (8 lb), asymptomatic patients showed a trend toward increased activation (P<.06) of the subscapularis compared with symptomatic patients (34% MVC vs 21% MVC). Differential shoulder muscle firing patterns in patients with rotator cuff pathology may play a role in the presence or absence of symptoms. Asymptomatic subjects demonstrated increased firing of the intact subscapularis, whereas symptomatic subjects continued to rely on torn rotator cuff tendons and periscapular muscle substitution, resulting in compromised function.

Kobayashi, M., N. Watanabe, et al. (2005). "The fate of host and graft cells in early healing of bone tunnel after tendon graft." Am J Sports Med 33(12): 1892-7. BACKGROUND: The behavior of host and graft cells during the healing process after autologous tendon graft has not been elucidated. HYPOTHESIS: Host cells will integrate into the bone-tendon interface and contribute to cellular repopulation of the graft. STUDY DESIGN: Controlled laboratory study. METHODS: Twelve-week-old, genetically identical, female green fluorescent protein transgenic rats (n = 20) and wild-type rats (n = 20) were used. The rats were divided into 2 experimental groups. In group A, the Achilles tendons of wild-type rats were harvested and transplanted into the transcondylar femoral bone tunnels of green fluorescent protein rats. In group B, the Achilles tendons of green fluorescent protein rats were transplanted into a transcondylar femoral bone tunnel of wild-type rats. Immediately after transplantation (time zero) and at 1, 2, and 4 weeks after the transplantation, distal femoral epiphyses were harvested and cut into 14-mum serial sagittal frozen sections. The sections were examined with a confocal laser-scanning microscope to quantify green fluorescent protein-positive cell survival. RESULTS: At time zero, only host cells in group A and only graft cells in group B demonstrated green fluorescent protein signals. At 1 week in group A, many green fluorescent protein-positive cells were found in the graft. In group B, a few green fluorescent protein-positive cells were found in the graft. At 2 and 4 weeks in group A, many green fluorescent protein-positive cells were detected in the graft, but green fluorescent protein-positive cells had disappeared completely in group B. CONCLUSION: Host cells, rather than graft cells, contribute to repair of the bone-tendon interface and the remodeling of grafts after simulated autologous tendon graft.

Koike, Y., G. Trudel, et al. (2006). "Delay of supraspinatus repair by up to 12 weeks does not impair enthesis formation: A quantitative histologic study in rabbits." J Orthop Res 24(2): 202-10. The purpose of this study was to find out whether supraspinatus repair delayed by up to12 weeks affects the formation of a new enthesis when compared to an immediate repair. In 67 rabbits, the supraspinatus fibrocartilaginous enthesis of one shoulder was resected. The tendon was attached to the greater tuberosity either immediately, after a 6-week, or after a 12-week delay. Five histologic variables were used to assess enthesis formation: number of non-chondrocytes, number of chondrocytes, alignment of chondrocytes in rows, area of metachromasia on toluidine blue (TB)-stained sections indicating proteoglycan content, and area of diffracted polarized light indicating spatial alignment of collagen fibers. For every variable, progressive enthesis formation was observed. Again, for every variable and at every time point studied, no statistically significant difference was observed between tendons repaired immediately, after 6, or after 12 weeks (all p > 0.05). Supraspinatus tendon repairs delayed by 6 and 12 weeks constituted an enthesis which proceeded identically to one immediately repaired. Formation of a fibrocartilaginous enthesis depended on the elapsed time after repair and not on the duration between detachment and repair. Despite stated limitations, these results support both a trial of conservative treatment after a rotator cuff tear and a positive outcome of rotator cuff repair even if delayed by up to 12 weeks. (c) 2005 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Koike, Y., G. Trudel, et al. (2005). "Formation of a new enthesis after attachment of the supraspinatus tendon: A quantitative histologic study in rabbits." J Orthop Res 23(6): 1433-40. PURPOSE: To quantify in a longitudinal study non-chondrocytic cells and chondrocytes, tissular architecture as well as extracellular matrix restoration during the formation of an enthesis following supraspinatus tendon attachment to the humerus. METHODS: In 89 rabbits, one supraspinatus fibrocartilaginous enthesis was resected and the tendon either attached to the greater tuberosity (n=75) or not attached (n=14). The animals were sacrificed after 2, 6, 8, 12 or 24 weeks. The operated and contralateral shoulders were processed for histologic sections. Number of non-chondrocytes, chondrocytes and alignment of chondrocytes in rows were assessed histologically. Extracellular matrix restoration was measured based on (1) area of toluidine blue metachromasia indicating proteoglycan content and (2) on area of diffracted polarized light indicating spatial collagen fiber alignment. RESULTS: In the attached tendon, the number of non-chondrocytic cells sharply increased at 2 weeks, progressively decreased thereafter but remained higher than controls at all time points. Chondrocytes appeared at 2 weeks and their number reached control levels by 6 weeks (136+/-14 vs 144+/-15 controls, p>.05). The percentage of chondrocytes aligned in rows increased from 19+/-4% at 2 weeks to reach near normal values at 24 weeks (71+/-3% vs 78+/-2% controls, p>.05). Area of metachromasia increased from 0.1+/-0.1 mm(2) at 2 weeks to 3.8+/-0.3 mm(2) at 24 weeks, still below contralateral enthesis levels (4.6+/-0.1 mm(2), p<.05). Area of diffracted polarized light enlarged from 12+/-2 x 10(3) microm(2) at 2 weeks to 151+/-19 x 10(3) microm(2) at 24 weeks, still significantly smaller than contralateral levels (177+/-13 x 10(3) microm(2), p<.05). Neither chondrocytes nor metachromasia were observed in the non-attached tendons. CONCLUSION: A new enthesis was formed after attachment of the supraspinatus tendon into bony trough. Histomorphometry allowed to document extensive non-chondrocytic proliferation that was followed by appearance of chondrocytes and their spatial organization, a process was complete by 24 weeks. Extracellular matrix formation as well as spatial alignment of collagen fibers were delayed and not complete by 24 weeks. This first longitudinal investigation on the formation of the supraspinatus enthesis using quantitative outcome measures cautions against too early and too aggressive a rehabilitation program.

Kolts, I., L. C. Busch, et al. (2002). "Macroscopical anatomy of the so-called "rotator interval". A cadaver study on 19 shoulder joints." Ann Anat 184(1): 9-14. The triangular capsular space between the insertion tendons of the Mm. supraspinatus and subscapularis--the "rotator interval", can be divided into lateral, medio-superior and medio-inferior parts. The lateral part of the capsule is strengthened by the "Lig. semicirculare humeri" and the anterior fibres of the M. supraspinatus tendon. The Ligg. coracohumerale and "coracoglenoidale" are the macroscopical elements of the medio-superior part. The medio-inferior part of the "rotator interval" is reinforced by the Ligg. glenohumeralia superius et medium. The key ligament of the "rotator interval" is the "Lig. semicirculare humeri". Laterally it ensures the insertion of the anterior fibres of the M. supraspinatus tendon above the Lig. transversum humeri and on the Tubercula majus et minus. Medially it is the place of attachment of the Lig. coracohumerale and oblique fibres of the Lig. glenohumerale superius. The "rotator interval" is not a weak capsular region but a complex network of macroscopically recognizable tendinous and ligamentous structures.

Kumagai, J., K. Sarkar, et al. (1994). "The collagen types in the attachment zone of rotator cuff tendons in the elderly: an immunohistochemical study." J Rheumatol 21(11): 2096-100. OBJECTIVE. The attachment zone of the rotator cuff tendons in the elderly was studied immunohistochemically in order to determine how degenerative changes affected the pattern of collagen fiber distribution. METHODS. Twenty-seven cuffs with their bony insertion were obtained from 22 postmortem cases of both sexes ranging in age from 52 to 90 years and without a history of shoulder ailments. In addition, 3 cuff specimens from cadavers in the 3rd and 4th decades were examined for comparison. Sections of formalin fixed tissues were stained by peroxidase antiperoxidase (PAP) technique using monoclonal antibodies against types I, II and III collagen. RESULTS. Degenerative changes affecting the fibrocartilage primarily were characterized by calcification, fibrovascular proliferation and microtears. In addition, they were found in all the cuff tendons of elderly individuals but not in those from younger subjects. Immunohistochemically, the attachment zone in areas without degenerative lesions showed collagen type I labelling strongly in bone but only moderately in the fibrocartilage. The predominant labelling in the fibrocartilage was for collagen type II, and collagen type III labelled principally in perichondrocytic areas. The tide-mark showed inconsistent labelling for any of the collagen types. In the presence of degenerative lesions, the disposition of fiber types was interrupted by calcification and microtears. Collagen type II composition of the fibrocartilage was markedly altered by the presence of fibrovascular tissue which labelled only for collagen type III. CONCLUSION. We conclude that severe degenerative changes in the cuff tendons of elderly individuals, alter the collagen characteristic of the rotator cuff and that the changes could be associated with impairment of biomechanical properties of the attachment zone, and may give rise to the clinical syndrome of enthesopathy.

Kumagai, J., K. Sarkar, et al. (1994). "Immunohistochemical distribution of type I, II and III collagens in the rabbit supraspinatus tendon insertion." J Anat 185 (Pt 2): 279-84. The collagen fibres in the area of attachment of the supraspinatus tendon to bone were studied immunohistochemically in 12 mature female New Zealand white rabbits. The labelling of type I collagen was uniformly prominent in the bone as well as in the fascicles of the tendon proper but inconspicuously scattered in the unmineralised and mineralised zones of the fibrocartilage. Type II collagen, not detected in the tendon proper, was widespread in both zones of the fibrocartilage. Type III collagen, on the other hand, appeared to be confined mainly to the zone of unmineralised fibrocartilage, in addition to its presence in the endotenon of the tendon proper. The region of the tidemark failed to show immunostaining for any of the collagen fibre types. In conclusion, this study demonstrates that, although all the principal fibrous collagen types are constituents of the supraspinatus tendon at its attachment site, the distribution pattern of immunolabelling varies from zone to zone.

Leung, K. S., L. Qin, et al. (2002). "A comparative study of bone to bone repair and bone to tendon healing in patella-patellar tendon complex in rabbits." Clin Biomech (Bristol, Avon) 17(8): 594-602. OBJECTIVES: To study the healing quality of bone to bone and bone to tendon repair in a patella-patellar tendon complex. DESIGN: In vivo animal experiment in 60 mature 32-week-old female rabbits. BACKGROUND: Injuries of patella-patellar tendon complex are not uncommon. However, no studies are available to compare the healing quality between bone to bone and bone to tendon surgical reconstructions used for repair of patella-patellar tendon complex. METHODS: A standard transverse osteotomy was performed at the distal one-third of patella of one hindlimb. Both patellar fragments were reattached for bone to bone group while the patellar tendon was reattached to the remaining patella after removing the distal one-third of patella for bone to tendon group. Patella-patellar tendon complex was harvested at 8, 12 and 24 weeks postoperatively for biomechanical and histological evaluations, with n=8 and n=2 at each healing time points in both groups. The contralateral knee served as a control. RESULTS: No significant differences in the failure loads were found between two groups. However, greater ultimate stress was found in bone to bone group as compared with bone to tendon group at week 8 and 24 (both P<0.05). On average, the ultimate stress of the bone to tendon and bone to bone group only reached 20.6(4.2)% and 28.6(6.7)% of the control values at week 24, respectively. The discrepancy between findings in failure load and failure stress might be explained by an overall larger cross-sectional area of the healing interface in bone to tendon group as compared with bone to bone group. Histology revealed that the bone to bone healing was via endochondral ossification at the healing interface. In bone to tendon group, extensive scar tissue was formed to overbridge the healing interface and remodeled with healing over time. The structural integration at the tendon and bony healing interface was poor and no typical intermitted fibrocartilage zone as seen in normal bone to tendon junction was formed. CONCLUSION: Failure load of bone to bone and bone to tendon healing interface did not differ during repair of patella-patellar tendon complex. However, the healing interface of bone to bone repair in terms of material properties as reflected by failure stress was superior to that of the bone to tendon healing. RELEVANCE: The findings of this experimental study may suggest that the anatomical reconstruction of patella-patellar tendon complex injury may be the primary concern in decision making for selecting either bone to bone or bone to tendon repair. However whenever possible, to initial fracture (bone-to-bone) fixation for ensuring better and predictable repair at the healing interface.

MacDermid, J. C., J. Ramos, et al. (2004). "The impact of rotator cuff pathology on isometric and isokinetic strength, function, and quality of life." J Shoulder Elbow Surg 13(6): 593-8. The purposes of this study were to determine the reliability of strength and self-reporting measures, the relationship of different strength measures to function, and the impact of rotator cuff pathology on patients' quality of life. Patients with nonoperated rotator cuff pathology (n = 36) and unaffected control subjects (n = 48) were assessed by use of the LIDO dynamometer to determine isometric and isokinetic (concentric and eccentric) strength of the shoulder rotators. The Shoulder Pain and Disability Index and Short Form-36 were self-reported by patients. Intraclass correlation coefficients (ICCs) were used to assess reliability, and Pearson correlations and multiple linear regression were used to determine the relationship between strength and function. The findings of this study include the following: (1) measures of self-reported physical disability had high reliability (ICC = 0.89); (2) the LIDO dynamometer reliably measured internal and external shoulder rotation strength in both concentric and isometric modes of testing (ICC = 0.78-0.94), whereas eccentric muscle actions had lower reliability; (3) all shoulder rotation strength measures were predictive of disability, with isometric external rotation strength being the most predictive (r = 0.56); and (4) the presence of rotator cuff pathology was highly predictive of impaired physical health quality of life (R(2) = 0.71, P <.001).

Mallon, W. J., G. Misamore, et al. (2004). "The impact of preoperative smoking habits on the results of rotator cuff repair." J Shoulder Elbow Surg 13(2): 129-32. We examined the outcomes of patients who underwent surgical treatment for rotator cuff tears to test the hypothesis that patients who did not smoke would have better postoperative scores than smokers. Medical charts were reviewed for patients who underwent rotator cuff repair between 1990 and 1993. We examined age, smoking status, workers' compensation status, and the size of the rotator cuff tear to determine the effect of scores on the UCLA questionnaire and a subjective pain assessment. There were 95 smokers and 129 nonsmokers. Mean preoperative UCLA scores for smokers and nonsmokers were 15.9 and 17.6, respectively; mean postoperative scores were 25.0 and 32.0, respectively. Nonsmokers had a significantly greater increase in total UCLA scores than smokers (P <.0001) and significantly higher improvement in pain scores, and more nonsmokers were classified as having good or excellent results based on the UCLA rating. On the basis of our data, nonsmokers undergoing rotator cuff repair have greater improvement of pain and better results postoperatively than smokers.

Martinek, V., C. Latterman, et al. (2002). "Enhancement of tendon-bone integration of anterior cruciate ligament grafts with bone morphogenetic protein-2 gene transfer: a histological and biomechanical study." J Bone Joint Surg Am 84-A(7): 1123-31. BACKGROUND: The integration of tendon grafts used for replacement of the anterior cruciate ligament is still sometimes unsatisfactory and may be associated with postoperative anterior-posterior laxity. The goal of this study was to examine the capacity of bone morphogenetic protein-2 (BMP-2) gene transfer to improve the integration of semitendinosus tendon grafts at the tendon-bone interface after reconstruction of the anterior cruciate ligament in rabbits. METHODS: The anterior cruciate ligaments of adult New Zealand White rabbits were replaced with autologous double-bundle semitendinosus tendon grafts. The semitendinosus tendon grafts had been infected in vitro with adenovirus-luciferase, adenovirus-LacZ (AdLacZ), or adenovirus-BMP-2 (AdBMP-2); untreated grafts served as controls. The grafts were examined histologically at two, four, six, and eight weeks after surgery. In additional experiments, the structural properties of the femur-anterior cruciate ligament graft-tibia complexes, from animals killed eight weeks postoperatively, were determined from uniaxial tests. The stiffness (N/mm) and ultimate load to failure (N) were determined from the resulting load-elongation curves. RESULTS: Genetically engineered semitendinosus tendon grafts expressed reporter genes as well as BMP-2 in vitro. The AdLacZ-infected grafts showed two different histological patterns of transduction. Intra-articularly, infected cells were mostly aligned along the surface, and they decreased in number between two and eight weeks after surgery. In the intra-tunnel portions of the grafts, the number of infected cells did not decrease during the observation period. Moreover, a high number of transduced cells was found in the deeper layers of the tendons. In the control group, granulation-type tissue at the tendon-bone interface showed progressive reorganization into a dense connective tissue, and a later establishment of fibers resembling Sharpey fibers. In the specimens with an AdBMP-2-infected anterior cruciate ligament graft, a broad zone of newly formed matrix resembling chondro-osteoid had formed at the tendon-bone interface at four weeks after surgery. This area was increased at six weeks, showing a transition from bone to mineralized cartilage and nonmineralized fibrocartilage. In addition, in the AdBMP-2-treated specimens, the tendon-bone interface in the osseous tunnel was similar to that of a normal anterior cruciate ligament insertion. The stiffness (29.0 +/- 7.1 N/mm compared with 16.7 +/- 8.3 N/mm) and the ultimate load to failure (108.8 +/- 50.8 N compared with 45.0 +/- 18.0 N) were significantly enhanced in the specimens with an AdBMP-2-transduced graft when compared with the control values (p < 0.05). CONCLUSION: This study demonstrates that BMP-2 gene transfer significantly improves the integration of semitendinosus tendon grafts in bone tunnels after reconstruction of the anterior cruciate ligament in rabbits. Clinical Relevance: Novel technologies including gene therapy and tissue engineering, such as those described in this study, may provide useful therapeutic procedures to enhance biological healing after reconstruction of the anterior cruciate ligament.

McCallister, W. V., I. M. Parsons, et al. (2005). "Open rotator cuff repair without acromioplasty." J Bone Joint Surg Am 87(6): 1278-83. BACKGROUND: In most clinical reports on rotator cuff repair, acromioplasty was done as part of the procedure. In this prospective study, we evaluated the hypothesis that rotator cuff repair without acromioplasty would result in a substantial improvement in shoulder comfort and function. METHODS: Ninety-six consecutive primary repairs of full-thickness tears of the rotator cuff were performed through a deltoid-muscle-splitting incision that preserved the integrity of the coracoacromial arch and the deltoid insertion. All patients were invited to participate in a prospective study involving periodic self-assessment of shoulder function with the Simple Shoulder Test and general health status with the Short Form-36 (SF-36) questionnaire, both of which are validated instruments. Sixty-one patients provided follow-up information for at least two years postoperatively, and the average duration of follow-up was five years. Thirty-four of the tears involved the supraspinatus tendon alone; sixteen involved the supraspinatus and infraspinatus tendons; and eleven involved the supraspinatus, infraspinatus, and subscapularis tendons. RESULTS: The percentage of shoulders that could be used to perform each of the twelve functions on the Simple Shoulder Test was significantly increased postoperatively (p < 0.002). Men and women had different degrees of function preoperatively (p < 0.00000001) and postoperatively (p < 0.001), but the improvement in function was essentially identical for the two genders. The mean improvement in the number of shoulder tests that could be performed was best for the patients with one-tendon tears (4.9 tests), next best for those with two-tendon tears (3.6 tests), and worst for those with three-tendon tears (3.3 tests). SF-36 scores for physical role (p < 0.003) and comfort (p < 0.0001) were significantly improved postoperatively. CONCLUSIONS: Significant improvement in self-assessed shoulder comfort and in each of the twelve shoulder functions was observed after rotator cuff repairs performed without acromioplasty. The technique that we used is very similar to that described by Codman almost seventy years ago.

Meyer, D. C., S. F. Fucentese, et al. (2004). "Association of osteopenia of the humeral head with full-thickness rotator cuff tears." J Shoulder Elbow Surg 13(3): 333-7. Rotator cuff tendon repair may fail for various reasons. Although the role of repair techniques and of the musculotendinous unit has been studied, there is little information on the quality of the bone to which the tendon is to be repaired. Therefore, 14 cadaveric humeral heads, 7 specimens without and 7 with a full-thickness rotator cuff tendon tear, were quantitatively assessed by use of high-resolution micro-computed tomography. Bone density is higher below the articular surface than in the greater tuberosity (40% vs 10%-20%), and tendon tears are associated with a reduction in cancellous bone density of greater than 50%, leading to a virtually hollow greater tuberosity, with intact cortical bone. The results found suggest that in long-standing rotator cuff tears, creating a deep trough should be avoided to achieve reliable tendon-to-bone contact. For optimal suture fixation to bone, sutures or anchors should be positioned subcortically or medially under the articular surface.

Meyer, D. C., H. Hoppeler, et al. (2004). "A pathomechanical concept explains muscle loss and fatty muscular changes following surgical tendon release." J Orthop Res 22(5): 1004-7. Following tendon tear, the musculo-tendinous unit retracts permanently, looses muscle fibre volume and is infiltrated with fat. This is currently considered to be an unexplained degenerative process. In a sheep model of chronic tendon tear with delayed tendon repair (35 weeks after tendon release), we studied the nature of these muscle changes in eight experimental animals. At sacrifice (75 weeks after tendon release) the muscle had retracted by 1.7+/-0.5 cm (9% of entire length, p<0.0001), the pennation angle had increased from 22+/-2.5 degrees to 50+/-11 degrees (p<0.0001) and the mean muscle fibre length had shortened from 32+/-3 to 16+/-5 mm (50%, p<0.0001). In electron and light microscopy, we found essentially normal muscle fibres with an unaltered fibre diameter and myofibrillar structure, while interstitial fat and fibrous tissue had increased from 3.9% to 45.9% (p<0.0001) of the muscle volume. Geometric modelling showed that the increase of the pennation angle separates the muscle fibre bundles mechanically like limbs of a parallelogram. Infiltrating fat cells fill the created space between the reoriented muscle fibres which may be quantitatively calculated without affecting the structural properties of the muscle cells. Fatty infiltration is therefore not seen as a degenerative process but a necessary rearrangement of the tissue after macroarchitectural changes caused by musculo-tendinous retraction.

Meyer, D. C., C. Pirkl, et al. (2005). "Asymmetric atrophy of the supraspinatus muscle following tendon tear." J Orthop Res 23(2): 254-8. Muscle atrophy is a known consequence of muscle disuse,