Gait Biomechanics of Individuals with Transtibial Amputation: Effect of Suspension System

Prosthetic suspension system is an important component of lower limb prostheses. Suspension efficiency can be best evaluated during one of the vital activities of daily living, i.e. walking. A new magnetic prosthetic suspension system has been developed, but its effects on gait biomechanics have not been studied. This study aimed to explore the effect of suspension type on kinetic and kinematic gait parameters during level walking with the new suspension system as well as two other commonly used systems (the Seal-In and pin/lock). Thirteen persons with transtibial amputation participated in this study. A Vicon motion system (six cameras, two force platforms) was utilized to obtain gait kinetic and kinematic variables, as well as pistoning within the prosthetic socket. The gait deviation index was also calculated based on the kinematic data. The findings indicated significant difference in the pistoning values among the three suspension systems. The Seal-In system resulted in the least pistoning compared with the other two systems. Several kinetic and kinematic variables were also affected by the suspension type. The ground reaction force data showed that lower load was applied to the limb joints with the magnetic suspension system compared with the pin/lock suspension. The gait deviation index showed significant deviation from the normal with all the systems, but the systems did not differ significantly. Main significant effects of the suspension type were seen in the GRF (vertical and fore-aft), knee and ankle angles. The new magnetic suspension system showed comparable effects in the remaining kinetic and kinematic gait parameters to the other studied systems. This study may have implications on the selection of suspension systems for transtibial prostheses. Trial Registration Iranian Registry of Clinical Trials IRCT2013061813706N1.

choose which system is appropriate for which patient [4]. Clinicians, administrators, medical researchers, and third-party payers are required to make decisions about the quality of care and the effectiveness of the prosthesis. The use of silicone liners in prosthetics is not new. It has two main functions, namely, protection of the amputation stump and suspension of the prosthesis [5,6]. Suspension in silicone suction socket can be achieved in different ways, such as shuttle lock, sleeve, or a Hypobaric Sealing Membrane (HSM) around the liner (a new technology in silicone liners).
On the basis of the researcher's experience, available suspension systems for lower limb amputations have not yet fully addressed the patients' needs. A great number of amputees have some problems in their stump, like contracture, diabetic, or skin problem and they complain about the suspension system in terms of donning and doffing, gait and pain.
It was the starting point to deal with this topic in general and invent a new suspension system which can cover some of the shortcomings of the existing suspension systems for lower limb amputees.

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To obtain kinematics and kinetics of trans-tibial and trans-femoral amputees gait using the new suspension system and compare that to the locking liner and Seal-in liner by using motion analysis approach.

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To evaluate the biomechanical characteristics of each of the suspension systems (new system, locking or seal-in) in terms of comfort, function and satisfaction in amputees.

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To evaluate prosthesis users' satisfaction and perceived problems with the three suspension systems, including the new system.
The project will result in the development of a new prosthetic suspension system which is expected to be cheaper, result in low levels of pistoning, improve the amputee's satisfaction, and cause less pressure at the stump-linersocket interface.
The new prosthetic suspension system has the potential to be used as suspension system for both transtibial and transfemoral prostheses. Following a review of literature, a new magnetic suspension system will be designed, fabricated and fine-tuned. The prototype will be tested mechanically under loading. The finite element analysis is then performed to study the possible loading behaviors of the system during ambulation.
The result of the finite element analysis and mechanical testing will be used to modify and enhance the model. Next, a pilot study will be conducted on transtibial and trasfemoral amputees. The demographic and physical data will be collected following informed consent. Stump characteristics will be recorded as well.
Three pair of prostheses will be fabricated for each subject using: new prototype, pin & lock system, and seal-in liner.
All prostheses will be made by the researcher herself to ensure consistent manufacture, fit and alignment.
Each prosthesis consists of a total surface weight bearing socket, silicone liner, shuttle lock, valve or new magnetic system, tube adaptor, clamp adaptor, and foot. The components would be as follows (in addition to the new running. Next, they will wear each pair of prostheses for one month and a modified PEQ questionnaire will be employed to assess the user's satisfaction. Gait analysis will be performed by a Vicon motion capture system (seven MX-F20 cameras, 50HZ) synchronized with two Kistler and two AMTI force plates integrated into Vicon Nexus 1.4 software to record the data. Helen Hayes marker set will be used. The positions of most of the anatomical landmarks will be assumed to coincide with the center of the marker used. The force platform signals are filtered with a Butterworth low pass filter at 10Hz. For each trial, angular displacements, internal joint moments, joint powers, and the force applied on the limb will be plotted over one gait cycle.
Each subject will complete five successful trials using each of the suspension systems randomly. Pistoning movements inside the prosthetic socket will be measured for each subject during walking, stair and ramp negotiation. The data will be used to study the shear and stress forces at the socket-liner-limb interface by finite element analysis (FEA).
Socket-liner interface pressure will be determined by F-scan socket sensors (Tekscan).
All the above mentioned experiments will be done by 2 conventional and our new suspension systems.