Displacement of the Residual Limb Within Transfemoral Sockets: A Literature Review

Introduction

According to the World Health Organization and the International Society for Prosthetics and Orthotics, between 0.5 to 0.8 percent of the global population has suffered limb amputations. In the last years, Colombia, Angola, Afghanistan, and Chechenia are the countries that have held the first places with the highest amount of landmine victims. In Colombia, this weapon has left more than 10.000 affected people, many of which have suffered traumatic lower limb amputation To recover some of the lost function, amputees are generally prescribed with a prosthesis. However, the adaptation of the user with this element depends on the comfort felt when using it and consequently, on the fit between the socket and the residual limb. The fit between these two elements is highly influenced by the relative motion between them (i.e. displacement, slip). Both excess of displacement or complete absence, have several negative consequences for the amputee. Thus, measuring displacement could be an important indicator of the quality of the socket and the suspension system, and could provide critical information to improve surgical interventions, the prescription of prosthetic elements and the design and development of new prosthetic components. Several authors have investigated this topic; however, the studies have been mostly conducted on transtibial amputees. Therefore, this review aims to summarize the gathered information about the displacement between the socket and residual limb in transfemoral amputees.

Materials and Methods

A computer-aided systematic literature search was performed by two independent reviewers using three databases. The selected papers were evaluated with regards to: sample characteristics, displacement measurement instrument, measured activity, displacement axis, surfaces in contact, type of socket and type of suspension system used.

Results

Most of the studies were performed on less than five individuals with mature residual limbs and trauma caused amputation. The most common aspects of displacement were: imaging techniques (measurement instrument), gait (measured activity), vertical direction (displacement axis), bone/socket (surfaces in contact), quadrilateral (type of socket) and suction-based (suspension system). 

Conclusions

The optimal range of motion is still unknown for transfemoral amputees. A marker-based optical tracking system is promising for research purposes, while electronic sensors would be optimal for clinical use. Volume change may be an indirect and, more straightforward option to measure displacement. Further research is needed to determine the effect of using a modified socket, to find a way to measure relative motion inside the socket using marker-based optical tracking systems and to define the influence of subject-specific characteristics in the amount of displacement. A better understanding of what happens inside the socket helps to optimize prosthetic designs and to improve the amputee’s quality of life.