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 field. 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.