University of Washington
Applied Biomechanics Laboratory
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Research Interests
Our current research interests primarily involve the examination of the adult and pediatric spine from both clinical and injury biomechanics perspectives.  These research projects have led to improved clinical treatment and age-related biomechanical response data for the child cervical spine.  We've also investigated the biomechanics of the hip and the foot and ankle with projects seeking to optimize the surgical placement of hip implants and evaluate the design of total ankle joint replacement systems.  These efforts, both experimental and computational, are briefly described in the following five sections:

Adult Spine Biomechanics
Our adult spine research efforts have been largely focused on characterizing the mechanics of the spinal column in response to various external loads at both quasi-static and dynamic loading rates.  In addition to obtaining the more traditional load-displacement metrics, we have developed novel transducers to monitor the integrity of the spaces (foramen) available to the neurologic tissues for documenting the potential for neurologic injury both during and after spinal column injury events.  Motivating this research is need for injury tolerance criteria which assimilates both the structural and neuroprotective roles of the spine. Various modes (directions) of loading, as well as a broad spectrum of loading rates which typify the dynamic rates at which spinal injuries occur, are being investigated using our custom high-speed MTS test frame and bench-top acceleration sled.

Materials Testing System (Impact Loading) High-Rate
System (up to 10-m/s); MTS Corp., Eden Prarie, MN

Linear Motor Sled Apparatus (Inertial Loading) Dynamic Linear System (up to 15-g acceleration); Trilogy Systems, TX

Biomechanics of the Developing Spine
The effects of natural aging on the mechanics of the spine are far better understood for the mature adult spine than for the developing (immature) spine.  Beginning in 1999, our research team has been committed to measuring and documenting the mechanical properties and injury tolerance of the cervical spine and as a function of developmental age.  Foundational research studies have been completed establishing fundamental relationships between neck mechanics and developmental age both under quasi-static and dynamic loading rates.  Significant gender, spinal level and loading rate effects have been found to be associated with spinal development.  Although structural properties were strongly correlated with maturation (indicating that tissue size may be predictive), size alone cannot fully prognosticate developmental spinal mechanics since the material properties were also observed to increase with age.  These data will help to establish biomechanical response corridors for the development of child crash test dummies and injury criteria for crash test dummy assessment. 

Family of crash test dummies (courtesy of NHTSA)

Joint Replacement Biomechanics

Understanding the effect of component design and placement on the range of motion for total hip replacement (THR) was pursued using three-dimensional computer models.  Three-dimensional anatomic models were generated using CT scans and imported into a CAD modeling environment to assess joint range of motion based on object interference.  From a design perspective, femoral component head/neck ratio and liner edge shape were examined for their effect of range of motion.  In addition, the surgical placement (positioning) of both the acetabular and femoral components were studied for their effect on range of motion.

More recently, we have been actively involved in the testing of "motion preserving" spinal implants including prosthetic total disc and nucleus replacement systems, and a total facet arthroplasty system (Archus Orthopedics, Inc.).  A custom 3-D spine simulator has been developed to accommodate any combination of pure bending moments (flexion/extension, lateral bending, and axial rotation) up to a maximum of 65 N-m which may also be combinbed with a compressive follower load up to 1000 N.  A 4-camera Vicon motion capture system is used in conjunction with the simulator to accurately acquire the 3-D segmental (vertebral) kinematics.

Spine motion simulator

Biomechanics of the Foot and Ankle

Biomechanically, the foot is the primary load-bearing interface between the human body and the environment during locomotion and stance.  Working in close collaboration with the Puget Sound VA Center for Limb Loss Prevention and Prosthetic Engineering [link], our laboratory has been actively studying the biomechanics of the foot and ankle complex to characterize its mechanical (material and structural) properties and investigate the normal, pathologic, and reconstructed response to physiologic loading.  Both experimental (cadaver) and computational (finite element) models have been developed to facilitate our research aims.  Our current focus is on the continued development of a finite element (FE) model of the human foot.  As part of this focus, we have been characterizing the non-linear viscoelastic properties of the ligaments of the foot and ankle to provide accurate material models of our finite element model.

(Image courtesty of Puget Sound VA*)

We have also begun to evaluate the clinical outcomes and biomechanical effectiveness of total ankle replacement systems being surgically implanted at the University of Washington.  An ultrasound vibrometry technique has been developed to assess the status of osteointegration of the talar component of the implant.