Trans-tibial prosthetic system design and benefits for the amputee : an evidence based clinical study

Buis, A. and Dumbleton, T. and McHugh, B.F. and McKay, G. and Murray, K. and Sexton, S. (2007) Trans-tibial prosthetic system design and benefits for the amputee : an evidence based clinical study. In: 12th World Congress of the International Society for Prosthetics and Orthotics, 2007-07-29 - 2007-08-03.

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Evidence based practice is important in the provision of the best possible care and the enhancement of quality of life for the lower limb amputee. However, there is a limited amount of evidence available about what constitutes a good socket fit. The aim of this study was to investigate and to compare the dynamic interface pressure distribution of a 'hands on' and 'hands off' type of socket design and relate this to patient feedback and activity level. Evidence gained will contribute to socket prescription and design for trans-tibial amputees. METHOD Subjects: Established (at least 1 year) unilateral trans-tibial amputees (n=50) were divided in two equal subject groups. Group 1 was fitted with a PTB style socket and group 2 was fitted with a pressure cast style socket. Groups were well matched in terms of age, gender, pathology and BMI. Apparatus: A Tekscan pressure measurement system was used to record the stump/socket interface pressure distribution of the patients own prosthesis. A Prosthesis Evaluation Questionnaire (PEQ) was used as a qualitative measure for evaluating the prosthesis and health-related quality of life. An ActivPAL activity monitor was attached to the prosthesis for one week to provided quantitative information on the use of the prosthetic limb. Data Analysis: 3 way repeated measure ANOVA used to indicate variations in interface pressure within socket and between groups throughout stance phase. Independent sample tests used to determine if differences exist between groups for PEQ and activity monitor results. RESULTS Stump/socket interface pressure distribution is similar between groups. Pressure levels were higher in pressure cast sockets. Similar responses were seen between groups when answering PEQ questions. Subjects responded with high satisfaction in all PEQ categories. Subjects walked an average of 8200 steps per day; there were no significant differences between groups. PEQ responses did not correlate with daily activity. DISCUSSION Interface pressure within the prosthetic socket can be used to evaluate socket fit. Previous studies comparing the two casting concepts have shown that significant differences exist in the distribution and magnitude of interface pressure (Convery and Buis, 1998, Goh et al., 2004). The differences in magnitude and distribution of interface pressure were not observed in this study. Both groups reported a high satisfaction in all areas of quality of life, and the activity of the subject was not influenced by the type of socket worn. The prostheses used in this investigation differed from most previous research studies investigating interface pressure as subjects own prostheses were instrumented. These had been delivered by their prosthetist and worn in daily activities for at least six months prior to this study. Over this time adjustments to walking patterns and physiological changes to the residual limb and additional stump socks worn may all have contributed in reducing initial differences seen in interface pressure between casting concepts. CONCLUSION Two different casting philosophies are used to produce the majority of trans-tibial sockets. Based on these principles and previous experimental evidence, a significant difference in loading pattern and pressure was expected within the prosthetic socket. These differences were not seen in the socket in the long term after delivery of the prosthesis. Adaptation over time may have reduced any initial differences between the two designs.