Á priori alignment of transtibial prostheses: a comparison and evaluation of three methods

The objectives of this study were to compare three á priori alignment methods and evaluate them based on initial gait quality and further alignment changes required to optimize gait. Á priori alignment is requisite for monolimbs, transtibial prostheses in which the socket and pylon are made from one piece of plastic, because monolimbs have no alignment adjustability.

The three methods investigated were traditional bench alignment (TRAD), vertical alignment axis (VAA) and anatomical based alignment (ABA). Endoskeletal components were utilized for the study, rather than monolimbs, so that alignment could be experimentally manipulated. Three endoskeletal prostheses were aligned, one according to each á priori method, for each of seven subjects. Gait and alignment data were captured, dynamic alignment was performed to optimize gait, and data were captured again.

VAA and TRAD methods required less change compared to ABA in socket flexion angle. Looking at subjects individually, VAA produced a better alignment and better gait for the greatest number of subjects.

A new refined method of á priori alignment is proposed based on the results of this study, and is applicable for á priori alignment of monolimbs or any type of transtibial prosthesis.