Eshraghi, Arezoo (2014) Design, development and clinical evaluation of a new prosthetic suspension system for lower limb amputees / Arezoo Eshraghi. PhD thesis, University of Malaya.
Abstract
Momentum, gravity, and other ambulation forces tend to displace lower limb prosthesis on residual limb. Thus, suspension systems have considerable effects on the amputee’s mobility, comfort, and satisfaction with prosthesis. Negative effects of poor suspension on rehabilitation, as well as the comfort and activity level of lower limb amputees, were previously stated. This research aimed to develop a prosthetic suspension system and to explore the biomechanics of prosthesis that incorporates the new system for transtibial amputees. A prosthetic suspension system was designed and fabricated based on magnetic field. Factors that were influenced by the prosthetic suspension were derived through an extensive literature review, and an experimental protocol was subsequently developed. The mechanical properties of the designed suspension system were tested using the universal testing machine. The magnetic suspension system (MPSS) could withstand 350.9 N of tensile loading before the coupling failed. The system was equipped with an acoustic alarm system as an added safety feature: the safety alarm system would buzz a micro-controller unit if the suspension is going to fail. For validation, the MPSS was compared with two other common suspension systems, i.e. the pin/lock and the Seal-In suspension for validation. The MPSS and pin/lock caused comparable amounts of pistoning, whereas the least pistoning resulted from the Seal-In system. Interface pressure was evaluated by the Tekscan F-Socket transducers during level walking, as well as stair and ramp negotiation. The findings indicate that the mean peak pressure (in kilopascal) was lower with the MPSS than with the pin/lock over the anterior and posterior aspects during one gait cycle (P < 0.05). Overall, the average peak pressure values were higher with the Seal-In system than the MPSS and the pin/lock system. Particularly important was that the MPSS may reduce the pain and discomfort at the distal residual limb by decreasing iv the pressure within the prosthetic socket in comparison to the pin/lock system during gait. The MPSS caused significantly different peak pressures at the anterior proximal region compared with the pin/lock (P = 0.022) and Seal-In (P = 0.001) during the stair ascent and descent, and ramp negotiation. Motion analysis showed that several kinetic and kinematic variables were affected by the suspension type. The ground reaction force data revealed that lower load was applied to the joints with the MPSS compared with the pin/lock suspension. The resulting gait deviation index was considerably different from the normal with all the systems, although the index did not significantly differ among the systems. Main significant effects of the suspension type were evident in the vertical and fore-aft ground reaction forces, knee, and ankle angles. The MPSS showed comparable effects in the remaining kinetic and kinematic gait parameters. Finally, the results of the questionnaire survey revealed significantly high satisfaction rates with the MPSS, especially for donning and doffing, walking, uneven walking, and stair negotiation (P < 0.05). The MPSS may be used as an alternative suspension system for lower limb amputees because the biomechanical findings fell within the ranges found in the literature and were comparable to two other common suspension systems.
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