R ECOMMENDATIONS FOR FUTURE STUDY AND CONCLUDING STATEMENT

Each of the research chapters has a discussion section relevant to the findings of that study. This chapter comprises recommendations for future research and concluding statements.

8.1 R

The results and limitations of the studies in this thesis have aided in the identification of the future studies that would further inform or improve the potential for successful use of the PCAST socket in under-resourced environments.

8.1.1 Development of the PCAST technique

The PCAST socket was used with and without a Pelite liner in this research. A dedicated and controlled crossover study to assess the influence of the Pelite liner should be completed. Such a study should compare interface pressure magnitudes, locations, and loading durations of sockets cast with a thick sock (Chapter 5) and a Pelite liner (Chapter 6). The outcome of this study should lead to a definitive recommendation regarding the use of a Pelite liner with the PCAST socket. Historically, load-bearing hydrocasting techniques have been performed with the patient standing with either 50% of their body weight supported by the pressurised liquid, as performed in the studies of this thesis and previously [42, 71], or during full weight bearing [70, 72]. Intuitively, the rationale for each of these loading conditions is that the loading condition during casting reflects limb loading during stance (i.e. 50% weight bearing) and the single support phase of gait (i.e. 100% weight bearing). However, there is no empirical data to suggesting that 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 sockets manufactured using differing hydrocast loading conditions. It was hypothesised that greater loads through the socket during pressure casting results in greater pressure applied to the soft tissue and hence volumetrically smaller sockets, increased limb stability and more uniform pressure distributions. Any potential improvement in wearer outcomes with a socket cast under greater load should be considered against patient safety during casting. Adequate safety provisions should be enacted to ensure the patient is stable and supported during casting. An understanding of the influence of load during casting will inform the refinement and potentially improved consistency of hydrocasting techniques among researchers.

The adoption of direct casting and lamination techniques could allow socket production without the need for a traditional workshop and decrease manufacturing times. Assuming the socket is

121

still cast under load as described herein, direct casting should not influence wearer outcomes but improve the usability of the technique for under-resourced environments. This could be especially pertinent for rural settings and during disaster relief where infrastructure and workshops may not exist or be unusable due to damage.

8.1.2 Additional assessments

The biomechanical tests herein are limited to level walking at a self-selected pace. Future studies should quantify gait biomechanics when walking at different speeds and on non-level surfaces. Such tests may challenge stability and represent the range of walking surfaces and conditions encountered outside of the laboratory or clinic. Such tests would indicate if users of the PCAST socket experience more instability than is commonly accepted. This study should utilise motion capture techniques to quantify kinematics, kinetics and measures of stability associated with the PCAST socket. As such, this study would likely require a biomechanics laboratory and treadmill capable of inclines, declines and potentially cross-slope positions to challenge both the sagittal and coronal stability of the wearer, or wearable sensors to capture gait biomechanics as real- world obstacles are traversed. This study should also involve limb-socket interface pressure measurements to understand how loading through the limb varies with varied walking surfaces in the PCAST socket.

Comparisons of the limb-socket interface pressures of PTB and pressure-cast sockets without silicone liners exist in the literature [70, 72, 75, 76, 86]. However, due to methodological limitations or analysis methods, the anatomical loading sites, durations of loading, changing pressure profile over the whole the gait cycle, or relationship between pressure and comfort have not been adequately compared for pressure-cast and PTB sockets. A future study should compare the pressure profiles of hydrocast and PTB sockets using pressure magnitude and duration shown herein to potentially influence wearer comfort. Such a study would contribute to the literature by including comparisons of peak pressure locations, magnitudes, and loading durations between the socket types. This study should consider wearer comfort against pressures observed to confirm identified trends between the pressure parameters and resultant wearer comfort.

A study should aim to quantify the 3D geometrical differences between sockets manufactured using varied techniques, including pressure casting. Specifically, PCAST sockets cast under varied loads (e.g. 50% body weight or greater) should be compared geometrically before any participant walking trials, to identify socket shape differences, if any. Previous studies have compared socket geometries of pressure-cast and hand-cast sockets [49, 77, 78]. However, these analyses were limited to measurements at discrete points or axial slices along the length of the socket. Future

122

studies should compare the digitised 3D surfaces of the whole sockets to quantify the geometric changes to the socket shape that are responsible for any difference in wearer outcomes.

8.2 C

This thesis comprises the most comprehensive studies of wearer outcomes with pressure-cast sockets without silicone liners. This work has provided practical, methodological, and theoretical contributions to the body of knowledge through journal publications and presentations at international conferences. The data showed that the PCAST technique could create functional and satisfactory sockets against relevant baseline and gold-standard conditions. The mechanisms for this success were explored by examining the distribution, magnitude, and durations of pressures at the limb-socket interface and exploring how these pressures vary with wearer comfort. Additionally, developments to the PCAST technique were implemented and discussed. The results and limitations of the studies herein have aided in the identification of the future studies which would further inform or improve the potential for successful use of the PCAST socket in under- resourced environments.

123