INFLUENCE OF SOCKET ADDUCTION ON JOINT LOADING FOR INDIVIDUALS WITH TRANSFEMORAL AMPUTATION - By the year 2050, the number of individuals living with major lower-limb amputations in the U.S. is projected to surpass 3.5 million. These individuals often face challenges like knee osteoarthritis (OA) and hip pain due to changes in their mobility and walking patterns. Those with transfemoral amputation (TFA), where the amputation is above the knee, are particularly at a higher risk for these detrimental issues. After TFA, proper alignment of the amputated thigh bone within the socket is essential for comfort and proper function when performing activities of daily living using a prosthesis. Misalignment of the prosthesis can lead to walking problems and muscle issues. Research shows that aligning the limb in a way that keeps the amputated thigh bone in adduction (i.e., towards the body's midline) can improve stability but has mixed effects on mechanical factors in walking. Recent studies suggest that this alignment increases certain forces on the lower limbs. However, these forces are a rough estimate and cannot accurately measure the internal stresses on the lower-limb joints. Due to the difficulty of measuring joint forces experimentally without instrumented surgical interventions, musculoskeletal (MSK) modeling and simulation is a promising approach to better estimate joint forces. Providing a more accurate estimate of forces on the hip and knee joints is warranted to provide insight into lower-limb joint health in individuals with TFA who are at an elevated risk of OA.
To better understand how certain forces on the lower limb joints are influenced by prosthetic socket alignment, we propose to perform a within-subject experiment and MSK modeling and simulation with two specific aims.
Primary Aim: To examine how different socket alignments affect joint forces in both hips and non-amputated knee of individuals with TFA. We predict that more socket adduction will lead to higher joint forces, with differences depending on the activity. We propose to recruit individuals with unilateral TFA (n=8) to participate in a human subject experiment. Given that different activities affect joint forces, the experiment will involve a set of key daily activities such as walking uphill and downhill, turning, and transitioning from sitting to walking. The experimental data will be used to perform MSK modeling and simulation to estimate joint forces, accounting for forces of muscles crossing the joints, thus providing a more accurate estimation.
Secondary Aim: To investigate how socket alignment affects the external adduction moment (EAM) of the hips, which influences the compressive forces leading to hip OA. We hypothesize that greater socket adduction will lower the EAM, with variations across different activities. The experimental data will be analyzed to calculate the EAM of both hips.
The expected result of this research is to provide biomechanical evidence of the effects of socket adduction on joint loading, whose changes have been associated with OA, to guide prosthetic alignment in clinical rehabilitation practice. The primary goal is to mitigate the elevated risk of OA, especially in the intact limb, thus enhancing the functional mobility of individuals with TFA. The research aligns with the NIDILRR's mission to improve health, function, and participatory living for individuals with disabilities and fits within their research agenda in prosthetics and orthotics. The long-term goal is to optimize prosthesis function, helping individuals with TFA regain independence and improve their quality of life.
