Secondary comorbidities (e.g., low back pain (LBP) or osteoarthritis (OA)) are more prevalent in individuals with unilateral transtibial amputation (TTA) using socket prostheses compared to able-bodied individuals. This is due to asymmetric joint loading that arises from compensatory movement patterns, such as increased lumbopelvic motion. Osseointegrated prostheses are an alternative to socket prostheses, yet it remains unknown how this prosthesis type influences multi-joint loading. This thesis developed a musculoskeletal model with a six degree-of-freedom residuum-socket interface and investigated the influence of osseointegrated prostheses on multi-joint biomechanics in patients with unilateral TTA;​ which provides information on how this type of prosthesis could impact the etiology of LBP and OA.

The first goal of this project was to develop a musculoskeletal model including a six degree-of-freedom residuum-socket interface and compare joint loading to a rigid connection. Five patients with unilateral TTA using socket prostheses completed a motion capture data collection which was then used to complete a musculoskeletal modeling workflow. The second goal of this project was to quantify changes in movement patterns and joint loading before and after prosthesis osseointegration for patients with TTA. Motion capture data was collected from 7 patients with unilateral TTA. Musculoskeletal models were developed for each patient, and lumbopelvic, hip, and knee kinematics, kinetics, and joint reaction forces were calculated bilaterally.

The results from this project indicate inclusion of a six degree-of-freedom residuum socket interface in the musculoskeletal model shows agreement between experimental data indicating appropriate representation of the residuum-socket interface. Furthermore, aberrant lumbopelvic ROM decreased contributing to improved hip joint loading symmetry after prosthesis osseointegration. Improved joint loading symmetry and associated compensatory movement patterns may indicate that osseointegrated prostheses have a positive impact on LBP and OA etiology.