Previous Research

Advancing Computer Manufactured Sockets

The purpose of this project was to assess fabrication quality of computer-manufactured prosthetic sockets and positive models, and to determine socket size errors that negatively impact the health and quality of life of lower limb prosthesis users. We found considerable variability in the quality of computer-manufactured sockets and models made by the central fabrication industry in prosthetics. Some central fabrication facilities (~40%) consistently demonstrated very low manufacturing error while others were less consistent. These findings led us to publish an evaluation strategy for central fabrication facilities to test their equipment. The strategy may also be useful to companies who manufacture fabrication equipment as well as clinics who construct sockets in house.

We also investigated size and shaping error that caused clinically detectable changes in prosthetic fit. Our findings indicated that sockets oversized as little as 1.0% were clinically distinguishable from properly-sized sockets. Other studies indicated potential metrics for early detection of deterioration in socket fit that may be useful towards creating outcome assessment criteria for clinical care.

Publications

  1. JE Sanders, JB McLean, JC Cagle, DW Gardener, KJ Allyn, "Technical note: Computer-manufactured inserts for prosthetic sockets", Medical Engineering and Physics, vol. 38, pp. 801-806, 2016
  2. JE Sanders, MR Severance, D Swartzendruber, KJ Allyn, MA Ciol, "Influence of prior activity on residual limb volume and shape measured using plaster casting: results from individuals with trans-tibial limb loss", Journal of Rehabilitation Research and Development, vol. 50, no. 7, pp. 1007-1016, 2013 PMID: 4435802
  3. JE Sanders, MR Severance, KJ Allyn, "Computer-socket manufacturing error: How much before it is clinically apparent?", Journal of Rehabilitation Research and Development, vol. 49, no. 4, pp. 567-582, 2012 PMID: 22773260
  4. JE Sanders, MR Severance, TR Myers MA Ciol, "Central fabrication: carved positive assessment", Prosthetics and Orthotics International, vol. 35, no. 1, pp. 81-89, 2011
  5. JE Sanders, MR Severance, "Measuring foam model shapes with a contact digitizer", Prosthetics and Orthotics International, vol. 35, no. 2, pp. 243-245, 2011
  6. JE Sanders, EL Rogers, EA Sorenson, GS Lee, DC Abrahamson, "CAD/CAM transtibial prosthetic sockets from central fabrication facilities: How accurate are they?", Journal of Rehabilitation Research and Development, vol. 44, no. 3, pp. 395-405, 2007 PMID: 18247236
  7. JE Sanders, SB Mitchell, SG Zachariah, K Wu, "A digitizer with exceptional accuracy for use in prosthetics research: a technical note", Journal of Rehabilitation Research and Development, vol. 40, no. 2, pp. 191-196, 2003 PMID: 15077643

Biomaterials and Tissue Engineering

In this work, we developed and tested novel materials for use in a variety of tissue engineering applications. One area we focused on was improving the biocompatibility of implantable materials with the ultimate goal being long-term improvements in tissue health. We focused on finely tuning the material properties of implants to more closely match those of the host tissue, more specifically by tuning fiber diameters in fibro-porous implants so that they were not encapsulated by host tissue. We also focused on tissue engineering methods to enhance vascularity to promote blood flow through a porous implant material. Enhancing blood flow through implantable materials is a key strategy to improve their integration into host tissue and to increase the likelihood of long-term tissue health.

Publications

  1. JE Sanders, CE Stiles, CL Hayes, "Tissue Response to Single Polymer Fibers of Varying diameters: Evaluation of Fibrous Encapsulation and Macrophage Density", Journal of Biomedical Material Research, vol. 52, no. 1, pp. 231-237, 2000 PMID: 10906696
  2. JE Sanders, ST Bishop, CE Stile, PK Schuessler, "Fibroin and Polymer-Based Fibroporous Biomaterials: Candidate Materials for Biomechanical Implants", ASME Symposium on Porous, Cellular and Microcellular Materials, 1998
  3. JE Sanders, SG Zachariah, "Mechanical Characterization of Biomaterials", Annals of the New York Academy of Sciences, vol. 831, pp. 232-243, 1997 PMID: 9616715

Interface Pressure and Shear Stress Management

In prosthetics, it is important to attain an appropriate distribution of pressure and shear stress at the limb-socket interface to maximize stability without overloading the soft tissues of the residual limb. In the lower-limb prosthesis these mechanical stresses can be very large and potentially dangerous, as the soft tissues of the residual limb are often expected to bear multiple times full body weight such as during walking or jogging.

Obtaining reliable measurements of pressure and shear stress at the limb-socket interface is challenging due to space constraints and the need to leave the inside surface of the socket unaltered so as not to affect the distribution of pressure and shear. Prior to this project, knowledge of interface pressure and shear was limited by a lack of reliable measurements. In this work, we developed specialized transducers that were installed onto prosthetic sockets to measure both pressure and shear stresses at the socket wall. We performed a series of studies and obtained pressure and shear measurements at several locations on multiple study participants. This work has informed several of the other projects in our research group by providing a better understanding of the mechanical stresses that are to be expected at various locations within a prosthetic socket.

Publications

  1. JE Sanders, AK Jacobsen, R Fergason, "Effects of fluid insert volume changes on socket pressures and shear stresses: Case studies from two trans-tibial amputee subjects", Prosthetics and Orthotics International, vol. 30, no. 3, pp. 257-269, 2006
  2. JE Sanders, SG Zachariah, AK Jacobsen, JR Fergason, "Changes in interface pressures and shear stresses over time on trans-tibial amputee subjects ambulating with prosthetic limbs: comparison of diurnal and six-month differences", Journal of Biomechanics, vol. 38, no. 8, pp. 1566-1573, 2005
  3. JE Sanders, JR Fergason, SG Zachariah, AK Jacobsen, "Interface pressure and shear stress changes with amputee weight loss: case studies from two trans-tibial amputee subjects", Prosthetics and Orthotics International, vol. 26, no. 3, pp. 243-250, 2002
  4. R Saxena, SG Zachariah, JE Sanders, "Processing computer tomography bone data for prosthetic finite element modeling: A technical note", Journal of Rehabilitation Research and Development, vol. 39, no. 5, pp. 609-614, 2002 PMID: 17642025
  5. SG Zachariah, JE Sanders, "Standing interface stresses as a predictor of walking interface stresses in the trans?tibial prosthesis", Prosthetics and Orthotics International, vol. 25, no. 1, 2001
  6. JE Sanders, SG Zachariah, AB Baker, JM Greve, C Clinton, "Effects of changes in cadence, prosthetic componentry, and time on interface pressures and shear stresses of three trans-tibial amputees", Clinical Biomechanics, vol. 15, no. 9, pp. 684-694, 2000
  7. SG Zachariah, JE Sanders, "Finite element estimates of interface stress in the trans-tibial prosthesis using gap elements are different from those using automated contact", Journal of Biomechanics, vol. 33, no. 7, pp. 895-899, 2000
  8. SG Zachariah, JE Sanders, "Pre-stresses due to trans-tibial socket donning: A nonlinear finite element analysis with contact", BMES/EMBS Conference, 1999, 1999
  9. JE Sanders, DM Bell, RM Okumura, AJ Dralle, "Effects of alignment changes on stance phase pressures and shear stresses on transtibial amputees: measurements from 13 transducer sites", IEEE Transactions on Rehabilitation Engineering, vol. 6, no. 1, pp. 21-31, 1998
  10. BJ Hafner, SG Zachariah, JE Sanders, "Automated alignment of contour pairs: A hybrid approach with applications to prosthetics", Proc. 1998 RESNA Annual Conference, pp. 283-285, 1998
  11. JE Sanders, D Lam, AJ Dralle, R Okumura, "Interface pressures and shear stresses at thirteen socket sites on two persons with transtibial amputation", Journal of Rehabilitation Research and Development, vol. 34, no. 1, pp. 19-43, 1997 PMID: 9021623
  12. SG Zachariah, JE Sanders, "Finite Element Modeling of Contact Stresses Between the Below-Knee Residual Limb and Prosthetic Socket", ASME, 1997
  13. SG Zachariah, JE Sanders, "Interface mechanics in lower-limb external prosthetics: A review of finite element models", IEEE Transactions on Rehabilitation Engineering, vol. 4, no. 4, pp. 288-302, 1996
  14. SG Zachariah, JE Sanders, GM Turkiyyah, "Automated hexahedral mesh generation from biomedical image data: applications in limb prosthetics", IEEE Transactions on Rehabilitation Engineering, vol. 4, no. 2, pp. 91-102, 1996
  15. JE Sanders, LM Smith, FA Spelman, DJ Warren, "A portable measurement system for prosthetic triaxial force transducers", IEEE Transactions on Rehabilitation Engineering, vol. 3, no. 4, pp. 366-372, 1995
  16. JE Sanders, AJ Dralle, R Okumura, G Turkiyyah, HD Jang, D Lam, D Berglund, R Reed, G Hwaung, R Miller, " Interface Mechanics In Prosthetics: A System For Analysis", RESNA 95, pp. 242-244, 1995
  17. LM Smith, JE Sanders, FA Spelman, "A portable signal conditioning and data acquisition system for prosthetic triaxial force transducers", Engineering in Medicine and Biology Society, 1993. Proceedings of the 15th Annual International Conference of the IEEE, 1993
  18. JE Sanders, CH Daly, "Normal and shear stresses on a residual limb in a prosthetic socket during ambulation: comparison of finite element results with experimental measurements", Journal of Rehabilitation Research and Development, vol. 30, no. 2, pp. 191-204, 1993 PMID: 8035348
  19. JE Sanders, CH Daly, EM Burgess, "Interface shear stresses during ambulation with a below-knee prosthetic limb", Journal of Rehabilitation Research and Development, vol. 29, no. 4, pp. 1-8, 1992 PMID: 4433005
  20. JE Sanders, DA Boone, CH Daly, "The residual limb/prosthetic socket interface normal stress and shear stress", Proceedings of the 13th Annual RESNA Conference, 1990
  21. JE Sanders, CH Daly, "Normal and shear interface stresses in lower-limb prosthetics", Engineering in Medicine and Biology Society, 1989. Proceedings of the 15th Annual International Conference of the IEEE, pp. 1443-1444, 1989

Residual Limb Volume Fluctuation and Accommodation

We have developed a novel bioimpedance analysis instrument and use it regularly in studies to measure limb volume. Thin electrodes are placed on the skin with very small wires exiting at the brim and extending to a data storage unit. The instrumentation is worn by subject participants for many hours while they participate in a variety of activities. The instrument has been used to better understand how design features of the prosthesis and the activity of a prosthesis user affect changes in size of a person's residual limb over the day. Through various studies we have provided key insight to patients and practitioners treating volume management challenges. We have also worked to develop novel volume management systems to overcome the detrimental effects of limb volume change on prosthetic fit and patient quality of life.

Publications

  1. JE Sanders, TL Hartley, RH Phillips, MA Ciol, BJ Hafner, KJ Allyn, DS Harrison, "Does temporary socket removal affect residual limb fluid volume of trans-tibial amputees?", Prosthetics and Prosthetics International, vol. 40, no. 3, pp. 320-328, 2016
  2. JE Sanders, JC Cagle, KJ Allyn, DS Harrison, MC Ciol, "How do walking, standing, and resting influence transtibial amputee residual limb fluid volume?", Journal of Rehabilitation Research & Development, vol. 51, no. 2, pp. 201-212, 2014 PMID: 24933719
  3. JE Sanders, "Commentary on Troedsson's 1964 Article "Stump Arterial Circulation at its Relationship to the Prescription of a Prosthesis for the Geriatric Patient"", Journal of Rehabilitation Research and Development, vol. 50, no. 5, pp. 9-9, 2013 PMID: 26306335
  4. JE Sanders, JC Cagle, DS Harrison, KJ Allyn, "How does adding and removing liquid from socket bladders affect residual limb fluid volume?", Journal of Rehabilitation Research and Development, vol. 50, no. 6, pp. 845-860, 2013 PMID: 24203546
  5. DL Swartzendruber, MT Redfield, JE Sanders, "A novel measurement device for volume management in lower limb amputees: A technical note", Medical Measurements and Applications Proceedings (MeMeA), 2013 IEEE International Symposium, 2013
  6. JE Sanders, KJ Allyn, DS Harrison, TR Myers, MA Ciol, EC Tsai, "Preliminary investigation of residual-limb fluid volume changes within one day", Journal of Rehabilitation Research and Development, vol. 49, no. 10, pp. 1467-1478, 2012 PMID: 4423818
  7. JE Sanders, DS Harrison, JC Cagle TR Myers, MA Ciol, KJ Allyn, "Post-doffing residual limb fluid volume change in people with trans-tibial amputation", Prosthetics and Orthotics International, vol. 36, no. 4, pp. 443-449, 2012
  8. JE Sanders, DS Harrison, KJ Allyn, TR Myers, MA Ciol, EC Tsai, "How do sock ply changes affect residual limb fluid volume in people with trans-tibial amputation?", Journal of Rehabilitation Research and Development, vol. 49, no. 2, pp. 241-256, 2012 PMID: 4431546
  9. JE Sanders, DS Harrison, TR Myers, KJ Allyn, "Effects of elevated vacuum on in-socket residual limb fluid volume: Case study results using bioimpedance analysis", Journal of Rehabilitation Research and Development, vol. 48, no. 10, pp. 1231-1248, 2011 PMID: 4440224
  10. JE Sanders, S Fatone, "Residual limb volume change: Systematic review of measurement and management", Journal of Rehabilitation Research and Development, vol. 48, no. 8, pp. 949-986, 2011 PMID: 4423813
  11. JE Sanders, DS Harrison, KJ Allyn, TR Meyers, "Clinical utility of in-socket residual limb volume change measurement: Case study results", Prosthetics and Orthotics International, vol. 33, no. 4, pp. 378-390, 2009 PMID: 4435543
  12. JE Sanders, GS Lee, "A means to accommodate residual limb movement during optical scanning: A technical note", IEEE Transactions on Neural Systems and Rehabilitation Engineering, vol. 16, no. 5, pp. 505-509, 2008
  13. JE Sanders, EL Rogers, DC Abrahamson, "Assessment of residual-limb volume change using bioimpedence", Journal of Rehabilitation Research and Development, vol. 44, no. 4, pp. 525-535, 2007
  14. JE Sanders, EL Rogers, DC Abrahamson, "Assessment of residual-limb volume change using bioimpedence", Journal of Rehabilitation Research and Development, vol. 44, no. 4, pp. 525-536, 2007 PMID: 18247249
  15. JE Sanders, A Karchin, JR Fergason, EA Sorenson, "A noncontact sensor for measurement of distal residual-limb position during walking", Journal of Rehabilitation Research and Development, vol. 43, no. 4, pp. 509-516, 2006 PMID: 17123190
  16. JE Sanders, DW Cassisi, "Mechanical performance of inflatable inserts used in limb prosthetics", Journal of Rehabilitation Research and Development, vol. 38, no. 4, pp. 365-374, 2001 PMID: 11563488
  17. RE Schreiner, JE Sanders, "A silhouetting shape sensor for the residual limb of a below-knee amputee", IEEE Transactions on Rehabilitation Engineering, vol. 3, no. 3, pp. 242-253, 1995
  18. RE Schreiner, JE Sanders, "A geometric shape sensor for the residual limb of below-knee amputees", Engineering in Medicine and Biology Society, 1993. Proceedings of the 15th Annual International Conference of the IEEE, pp. 1290-1291, 1993

Sock Thickness and Use

Daily changes in the shape and size of the residual limb affect prosthetic socket fit. Prosthetic socks are often added or removed to manage changes in limb volume. The number and thickness of prosthetic socks required to maintain fit are highly variable. Manufacturers of prosthetic socks usually characterize the thickness of their products by a metric called sock “ply;” however, differences in materials, strain, and age of socks make the meaning of amputee sock ply confusing for both prosthesis users and prosthetists.

Using a custom research instrument, compressive stresses were applied to socks while sock thickness was measured, to reflect strain and loads experienced within the socket. We aimed to facilitate understanding of the meaning of sock ply towards clinical fit. An additional goal was to characterize how sock thickness changed under loading conditions experienced while a person with limb amputation walked in a prosthesis. Results from this investigation led us to propose a new nomenclature for sock thickness that may be more intuitive to practitioners and to the industry. We have also sought to better understand how persons with transtibial amputation use socks to manage diurnal changes in volume and comfort with a customized, self-report questionnaire. This work led to current projects involving the development of field monitoring devices to record sock changes and sock thickness during normal prosthesis use.

Adding and removing prosthetic socks is currently the most-used method for maintaining good socket fit when limb volume changes occur. Previous studies regarding sock thickness and sock use have shown that the volume accommodation provided cannot be reliably predicted by sock ply or age. Direct measurement of total sock thickness may provide more meaningful insight to quantify prosthetic users' socket fit and guide volume accommodation recommendations. We have developed a clinical tool for proper measurement of sock thickness in a clinical setting. We are designing it to be handheld and easy to use while providing accurate sock thickness measurements.

Publications

  1. JC Cagle, KJ D'Silva, BJ Hafner, DS Harrison, JE Sanders, "Amputee socks: Sock thickness changes with normal use", Prosthetics and Orthotics International, vol. 40, no. 3, pp. 329-335, 2016
  2. JC Cagle, AJ Yu, MA Ciol, JE Sanders, "Amputee socks: Thickness of multiple socks", Prosthetics and orthotics International, vol. 38, no. 5, pp. 405-412, 2014
  3. K D'Silva, BJ Hafner, KJ Ally, JE Sanders, "Self-reported prosthetic sock use among persons with transtibial amputation", Prosthetics and Orthotics International, vol. 38, no. 4, pp. 321-331, 2014
  4. JE Sanders, JC Cagle, DS Harrison, A Karchin, "Amputee socks: how does sock ply relate to sock thickness?", Prosthetics and Orthotics International, vol. 36, no. 1, pp. 77-86, 2012