Question

What is anatomically based alignment and how this technique may facilitate the development of simplified prosthetic alignment approaches that can impact prosthetic service provision in developing nations. ?

Answer 1

Prosthetic alignment, which is concerned with the spatial relationship between prosthetic components and an amputee’s skeleton, is an important issue for lower limb amputees. Proper alignment is necessary for ground reaction force symmetry between sound and amputated limbs, improved residual limb loading, and reduced energy expenditure. In common clinical practice, prosthetists adjust eight variables to achieve clinically acceptable alignment, namely, prosthetic height, socket anteroposterior tilt, socket mediolateral tilt, foot anteroposterior shift, foot anteroposterior tilt, foot mediolateral tilt, foot mediolateral shift, and toe in/out angle. The acceptable alignment is usually accessed in 3 steps mainly bench alignment, static alignment, and dynamic alignment. Bench alignment involves adjustments to the spatial position of prosthetic components and is conducted without having an amputee wear a prosthesis. In static alignment, amputee wears the prosthesis while assuming a static standing position and prosthetic alignment is further adjusted in relation to the skeleton. In dynamic alignment, prosthetist fine-tunes alignment on the basis of the visual analysis of amputee’s gait symmetry and the amputee’s feedback and comfort. This step is usually repeated until both the amputee and the prosthetist are satisfied with the quality of prosthetic alignment. The subjectively agreement is the only criteria that uphold final clinically acceptable alignment. Given that this process is time-consuming and dependent on user and prosthetist experiences, it lacks inter- and intra-rater reliability. The improvement of prosthetic alignment measurement systems is a key prerequisite to achieve repeatable clinically acceptable alignment.

The new prosthetic alignment on the basis of anthropometrical features of lower limbs of unilateral transtibial amputees is a feasible method. The findings could lay a foundation for development of future prosthetic alignment systems. More investigations on validity and repeatability of the new method and amputees who use transtibial socket designs other than PTB are suggested.