|Title:||Biomechanical study of foot and ankle surgery for surgical intervention|
|Advisors:||Zhang, Ming (BME)|
|Subject:||Foot -- Surgery.|
Ankle -- Surgery.
Hong Kong Polytechnic University -- Dissertations
|Department:||Interdisciplinary Division of Biomedical Engineering|
|Pages:||xxvi, 292 pages : color illustrations|
|Abstract:||Foot and ankle complex is an integral part of the locomotion system, and susceptible to injuries and diseases, because it has to sustain impact and loading that are sometimes several times of body weight during different activities. Severe disorders of the musculoskeletal structures of the foot and ankle are often alleviated using surgical treatments. Surgical treatments are expected to promptly retrieve normal functions. As the foot-ankle complex is an intricate mechanism and each segment interacts with others interdependently, any clinical interventions may result in function alterations, not only at the modified site but also over the adjacent regions even on the entire foot. Evaluation of possible biomechanical functional alterations due to surgery could provide baselines for determination and optimization of surgery protocols, and predict iatrogenic complications. Experimental studies in the biomechanical behavior of the foot and ankle have been conducted and provided valuable information. Due to the limitations in the measurement techniques and ethical issue, the rationale that is directly related to injuries is lack of evaluation, which could be well settled using computational simulations. In order to investigate the biomechanical effects of surgeries, including tarsometatarsal joint fusion, ankle arthrodesis, and total ankle arthroplasty (TAA), on the entire foot, and to predict potential complications, computational simulations of biomechanical behaviors during gait were conducted in this study. A three dimensional comprehensive finite element (FE) model of foot-ankle complex has been developed. Based on modification of this model, three surgical treatments were simulated. Gait analysis was carried out to obtain boundary and loading conditions. The model was validated through comparison of plantar pressure and joint contact pressure between the FE prediction and experimental measurement. Three featured gait instants, namely first-peak, mid-stance, and second-peak were selected for analysis. The biomechanical performances in the surgical foot models were compared to the normal foot model for identification of biomechanical effects of surgeries.|
The results show that tarsometatarsal joint fusion raised less effect on the foot and ankle biomechanics than the ankle arthrodesis and TAA surgeries, because of the relatively smaller range of motion at the tarsometatarsal joints than the ankle joint. The biomechanics of the TAA model was very close to the normal foot at the first half of stance phase, but substantially variation was induced around the second-peak instant. Different from TAA, ankle arthrodesis had more effects at the first half of the stance phase, and provided a relatively stable condition at the second-peak instant. Both ankle surgeries reduced the dorsiflexion range, with the smallest range of dorsiflexion happened in ankle arthrodesis model. TAA produced a plantar pressure distribution closer to the normal foot than ankle arthrodesis throughout the gait. It did not increase the peak pressure and did not change the location of center of pressure a lot, while ankle arthrodesis increased the peak pressure and forwarded the center of pressure anteriorly. The contact pressure at the talonavicular joint was substantially increased in the ankle arthrodesis model, and that at the medial cuneonavicular joint was obviously affected in the TAA model. The stress in the second and third metatarsals was increased in both ankle surgeries. These variations were potentially causation of complications, such as joint arthritis and bone fracture. Ankle arthrodesis is a better choice than TAA when the two surgeries are both practicable, due to the design limitation of ankle prosthesis. In case of patients with potential risk of diabetic and plantar foot problems, hallux valgus, and flexible flatfoot, total ankle arthroplasty should be avoided. This computational platform developed in this study can be further used for the optimal design of the ankle prostheses and surgical protocols.
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