• Vol. 40 No. 5, 252–259
  • 15 May 2011

Engineering a Trans-Tibial Prosthetic Socket for the Lower Limb Amputee



Introduction: This review addresses the different prosthetic socket designs for trans-tibial amputees, the biomechanics behind the designs and the current state of the fi eld. Of particular focus is the classic patella-tendon bearing (PTB) socket and the more recent sockets manufactured using pressure casting techniques and the theory, biomechanics and clinical implications of the two designs. Methods to examine and compare these designs are also addressed.

Materials and Methods: Journal papers by various investigators which have clinical significance/impact on the field of trans-tibial socket design were chosen for this review. Articles were chosen over a period of over 50 years to demonstrate the evolution of knowledge.

Results: The engineering of the trans-tibial socket has been largely subjected to empirical derivations and biomechanical theory that remains, for the most part, unproven. The fundamental principles of the PTB socket have been widely refuted. Hydrostatic theory based on pressure casting techniques, on the other hand, provides an optimal scenario to produce a more uniform stump/socket interface pressure.

Conclusion: Preliminary studies indicate the pressure casting technique has the potential to produce comfortable sockets, providing an alternative to the PTB design. Various studies have been attempted to quantitatively compare the 2 types of socket designs. However, further quantitative biomechanical studies are needed to explain the fundamental theory surrounding the pressure cast technique. Methods that could help further understand the pressure cast concept include amputee gait analysis, stump/socket interface pressure measurements, computer aided socket design and finite element modelling techniques.

Amputation of the lower extremities continues to be a major problem due to vascular-related diseases e.g. diabetes. It is also a prevalent occurrence in countries affected by landmines, high incidents of motor vehicle accidents and natural disasters like earthquakes. A key component of amputee rehabilitation is the engineering of devices suited to individuals in order to recover physical capabilities. A prosthesis or artificial limb is one such device that aims to substitute the loss of a limb with cosmetic and functional desirability for the amputee. Lower limb prostheses can consist of an assembly of several components such as the socket, shank, ankle and foot (Fig. 1). The socket can be considered as the most important aspect of the artificial limb, which constitutes the critical interface between the amputee’s stump and prosthesis. The design and fitting of the socket is also the most difficult procedure due to the uniqueness of each amputee’s stump. An uncomfortable socket fi t is a common complaint from lower limb amputees with surveys revealing that amputees believe comfort is the most important aspect of the prosthesis and over half of all wearers are in moderate to severe pain for most of the time whilst wearing the prosthesis.

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