Quantifying Musculoskeletal and Biomechanical Symmetry to Identify Injury and Fall Risks in Individuals Who Use Unilateral Lower-Limb Prostheses

Individuals who use lower-limb prostheses have increased risks of developing overuse injuries and experiencing falls compared to the general population. This is often attributed to individuals loading, or weighting, their prosthetic limb less than their intact limb. Quantifying musculoskeletal and biomechanical symmetry between prosthetic and intact limbs could help clinicians evaluate risks of developing overuse injuries and experiencing falls. However, these relationships have not been determined. The objective of this dissertation is to quantify musculoskeletal and biomechanical symmetry and determine their relationships to overuse injuries and falls in individuals with unilateral lower-limb loss. This objective has two specific aims: 1) evaluate musculoskeletal symmetry associated with risks of developing overuse injuries, and 2) determine the relationship between wearable sensor-derived walking symmetry values and falls. Musculoskeletal symmetry was quantified in skeletal properties (e.g. fracture risk via dual x-ray absorptiometry), hip and knee joint space (e.g. osteoarthritis via x-rays), and thigh muscle architecture (e.g. atrophy via cross-sectional area) in four anatomical donors and thirty post-mortem CT scans. Biomechanical symmetry was quantified in twenty-two individuals who use unilateral lower-limb prostheses. Wearable sensors called inertial measurement units were compared to the gold standard of motion capture in the first five individuals. The relationship between number of falls, clinical outcome measures, and gait symmetry will be assessed to determine if gait symmetry could supplement clinical outcome measures to evaluate fall risk. Impaired musculoskeletal symmetry suggests amputated limbs, particularly those with diabetes, had higher indications of distal femur fracture risk and more thigh muscle atrophy compared to intact limbs. Compared to healthy and diabetic control groups, individuals with amputation had higher indications of osteoarthritis and muscle atrophy bilaterally. Biomechanical studies suggest data derived from inertial measurement units were comparable to motion capture, and the Four Square Step test was associated with 12-month retrospective falls. Findings could help clinicians proactively evaluate overuse injury and fall risks in this population.