Shape Analysis of Prosthetic Socket Rectification Procedure for Transtibial Amputees

Abstract

Achieving a comfortable socket residual limb interface is crucial for effective prosthetic rehabilitation, depending on the precise characterisation and fluctuations in the shape and volume of residual limbs. Clinicians rely on subjective and iterative methods for shaping sockets, often involving a trial-and-error approach. This study introduces a framework for measuring, analysing, and comparing residual limb shape and volume using scanned data to facilitate more informed clinical decision-making. Surface scans of 44 transtibial residual limb casts of various sizes and lengths were examined. All scans were spatially aligned to a mid-patella and subjected to analysis using a shape analysis toolbox. Geometric measurements were extracted, with particular attention to significant rectified regions during the cast rectification process. Following PTB guidelines, our analysis revealed substantial alterations, primarily in the mid-patella region, followed by the patellar tendon area. Notably, there was a significant volume change of 6.02% in the region spanning from mid-patella to 25% of the cast length. Beyond this point, linear cast modifications were observed for most amputees up to 60% of the cast length, followed by individual-specific deviations beyond this region. Regardless of residual limb size and length, the modifications applied to positive casts suggested categorising patients into five major groups. This study employs the AmpScan shape analysis tool, to comprehend the cast rectification process used for capturing and assessing the extent of rectification on patients’ residual limb casts. The clinical implications of our research are threefold: (a) the comparison data can serve as training resources for junior prosthetists; (b) this will aid prosthetists in identifying specific regions for rectification and assessing socket fit; (c) it will help in determining optimal timing for prosthetic fitting or replacement.

Keywords

• transtibial amputees
• prosthetic socket
• 3D scanning
• AmpScan
• cast rectification procedure