Amputation due to both vascular disease and diabetes results from a combination of lack of sensory perception in the feet and a poor capacity for wounds to heal. The impaired sensory system can elicit abnormal movement biomechanics that result in an ulcer that then becomes infected and fails to heal due to poor tissue health and lack of blood flow. The care pathway of vascular and diabetic foot ulcers often starts with a minor amputation, such as a toe. However, if abnormal biomechanics persist or if wound healing does not proceed as expected, amputations can continue ultimately leading to partial foot amputations, and then eventually transtibial amputations. This process results in frequent surgery and prolonged rehabilitation for the patient, as well as high medical costs. Furthermore, this process has significant psychological effects, which can further reduce activity levels and motivation. There is a need to identify the surgical level that will be most appropriate for a patient in order to minimize rehabilitation time and give the greatest potential for long term mobility, function and quality of life.
Movement biomechanics of partial foot amputation have received limited attention in the literature compared to those after transtibial amputation. Partial foot amputation is often chosen when the location of the ulcer allows it, due to the belief that this approach is less of an insult to the musculoskeletal system and there is greater potential for symmetric biomechanics after amputation. However, prior work has suggested asymmetric walking biomechanics in people with partial foot amputation, and additional investigation is needed to establish effects of amputation level and evaluate assistive devices (Dillon et al., 2007). Much of this prior work reflects case studies or observational gait studies, and studies that compare biomechanics and health both with non-amputee control participants and with amputees at higher amputation levels are important to quantify the advantages and disadvantages of different surgical approaches. Further, biomechanics of important activities of daily living beyond gait remain unclear. Additional research is needed to understand this further and to determine the impact of such asymmetries on joint biomechanics, and indeed pressure distribution across the residual foot to ensure that we are not placing this population at greater risk of developing an ulcer due to high loading at a future date.
The proposed work will comprehensively evaluate biomechanics and function in those with partial foot amputation relative to those without an amputation and those with a transtibial amputation. Further, the pressure, ground reaction force magnitudes and ground reaction force orientations will be used to quantitatively assess the mechanics of the bottom of the foot, linking to potential long-term health and potential risk for future ulcer development and surgery. Biomechanical results will be related to quality of life measures and functional health outcomes. These results will help guide the surgical decision-making process of where to amputate and how to rehabilitate to ensure improved movement biomechanics after amputation.
Research Question: How do different foot amputations affect lower limb biomechanics and what are the implications of these differences in terms of rehabilitation, function and long-term health?
Research Objectives 1. Define the kinetic and kinematic implications of different types of foot amputation during a range of activities of daily living such as balance, straight and turning gait, and sit-to-stand in a cohort of patients with either vascular disease or diabetes. 2. Quantify the lower limb and low back kinematics and kinetics in those with different foot amputations to those with a unilateral below knee amputation in a cohort of patients with vascular disease or diabetes. 3. Evaluate the functional implications of each surgical approach defined by health and rehabilitation. 4. Determine the merits of each approach mechanically (through biomechanical analyses) and in terms of quality of life (through patient surveys and bone health).