Understanding the biomechanics of below the knee prosthetic socket fit: comparing pressure cast and traditional patella tendon bearing techniques

None listed

Conventional PTB transtibial prosthetic sockets are widely-used throughout the developing world, however, the manufacture of PTB sockets is still highly dependent on the skill and experience of the attending prosthetist. A PCAST technique for the manufacture of transtibial sockets has been shown to be a potential alternative to PTB sockets, with similar initial patient outcomes recorded for the two sockets. The PTB socket is formed by deliberately creating regions of loading corresponding with the perceived pressure tolerant and intolerant areas of the residual limb. Although, pressure cast sockets aim to load the residual limb more uniformly, eliminating regions of high pressure; previous studies have shown this does not occur. In the PTB socket, the anterior aspect of the socket is shaped closely around either side of the tibial ridge providing rotational stability of the limb. Given the PCAST does not feature this shaping, it is hypothesised that the wearer makes a number of musculo-skeletal adaptations in order to walk stably. Previous comparisons of the PCAST and PTB sockets have explored the space and time characteristics of gait and subjective comfort levels of the wearers. All previously performed tests have involved level walking at self-selected comfortable or fast pace. No studies to date have examined the musculoskeletal gait adaptations of wearers of pressure-cast sockets, or the relationships between the gait biomechanics and the resultant loading patterns in the socket. Thus, further research is required to investigate through what mechanisms or biomechanical adaptations these fundamentally different sockets achieve similar patient outcomes, and how these adaptations change when walking on a non-level surface. Historically, load bearing hydrocasting techniques have been performed with the patient standing with either with 50% of their body weight supported by the pressurised liquid, or during full weight bearing. Intuitively, the rationale for each of these loading conditions is that the loading condition during casting reflects the limb loading during stance and the single support phase of gait respectively. However, there is no empirical data to suggest the either method leads to superior fit, gait biomechanics or comfort. Nor is there any data to quantify the volume, geometry or alignment requirements of the sockets manufactured using the differing hydrocast loading conditions. An understanding of the aforementioned will allow the refinement and potentially improved consistency of hydrocasting techniques among researchers.

No related papers found yet.