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Comprehensive Analysis of Socket-Type and Osseointegrated Lower-Limb Prostheses-Advancing Forward to Improve Comfort, Safety and Walking Ability

Lee, Winson C.C., Frossard, Laurent A., & Zhang, Ming (2006) Comprehensive Analysis of Socket-Type and Osseointegrated Lower-Limb Prostheses-Advancing Forward to Improve Comfort, Safety and Walking Ability. In Joint Local Symposium 2006. Physical Sciences and Engineering in Medicine: The Local Scene in Queensland XVII, May, Brisbane.

Abstract

Introduction There are at least 3 million people globally who need prosthetic treatment. A lower-limb prosthesis is conventionally attached to the residual limb by a socket and/or some suspension devices. Although this approach has been used for over 50 years, previous studies have pointed the phenomena that residual limb pain, gait deviation and prosthetic structural failure are common. Poor socket fit, rigid ankle joint and improper prothesis design are the main causes of the problems. On the other hand, a few teams are developing a surgical approach for directly connecting a prosthesis into the femur using a titanium implant (osseointegration). The advantages are improved comfort and sensory feedback, and greater hip range of motion. However, occasional mechanical failure of fixation is probably one major downside aspect of this surgical procedure. There is a need for analysis and further improvement in both conventional and osseointegrated prostheses. This article presents a series of our two studies on socket-type and osseointegrated prostheses. Methods Socket-type prostheses: A step-to-step method was used to design and evaluate a particular prosthesis type- monolimb- a low-cost trans-tibial prosthesis with the socket and shank moulded into one piece of thermoplastic. Taguchi method and computational modelling were used to optimize the design of a monolimb giving appropriate overall flexibility and structural integrity. Finite element modelling was used to study the effect of flexibility on socket-limb interface stress, which is believed to be related to comfort of the use of socket-type, prostheses. Experimental fatigue test was performed upon repeated loading. Gait tests were performed comparing the optimized flexible monolimb to conventional "rigid" prostheses. Osseointegration: Load applied on the fixation was monitored by a transducer when the transfemoral amputees walked in a straight line. Twelve participants were involved, representing about 15% of the global population fitted with lower-limb osseointegrated fixations. Step-tostep and subject-to-subject variability in load were studied. Temporal gait parameters were studied from the force-time data obtained by the transducer. The temporal parameters were compared with amputees using socket-type prostheses and non-amputees. Results An optimized shank design for a monolimb was suggested. Increased overall prosthesis flexibility tends to reduce socket-limb interface stress. Fatigue test showed there is no visual necking of material after 500,000 cycles of load. Gait tests suggested the optimized monolimb gave amputees better comfort and gait performance- offering similar functional advantages to the some commercialized high-cost prosthetic components. Three-dimensional forces and moments of each participant fitted with osseointegrated prostheses during normal walking were revealed. Variations of load between steps and among subjects were quantified. Cadence of the amputees fitted with osseointegrated fixations were found lower than the nonamputees, but in the range of amputees using socket-type prostheses. Discussion and Conclusions Using appropriate computational and experimental approaches, socket-type and osseointegrated prostheses were analysed and designed. Initial success in the socket-type prosthesis design, and the collection of crucial information for osseointegrated prostheses was achieved. Further investigations, such as field test of monolimbs, study of the impact of a given parameter on loading, and mechanical design of osseointegrated fixations are necessary.

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ID Code: 4165
Item Type: Conference Paper
Additional Information: For more information contact l.frossard@qut.edu.au.
Keywords: Sockets, Osseointegrated Fixation, Lower, Limb Prostheses, Gait
Subjects: Australian and New Zealand Standard Research Classification > TECHNOLOGY (100000)
Divisions: Past > QUT Faculties & Divisions > Faculty of Built Environment and Engineering
Copyright Owner: Copyright 2006 (please consult author)
Deposited On: 17 May 2006
Last Modified: 11 Aug 2011 04:37

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