Determination of dynamic prosthetic alignment using forceline visualization

Objective techniques for determining proper configuration (alignment) of lower limb prostheses can help standardize and improve the functional outcomes for amputees. We propose that a dynamic forceline visualization system can assist in the development of such techniques. The forceline is a tool that allows the visualization of the ground reaction force in real time and in a spatially accurate manner relative to the image of the person as he/she walks. We evaluated a simplified version of an alignment protocol based on the forceline and using three novice clinicians and four amputee test subjects. The goal was to determine how easily the novice clinicians could learn the technique and how well they could apply it. All three clinicians were given a group training lasting about 1.5 hrs in which they were familiarized with the forceline visualization tool and were shown how to use it for determining prosthetic alignment on subjects with lower limb amputation. Then, each clinician evaluated the same four amputees both with and without the use of the forceline. The clinicians were able to learn and incorporate the simple alignment methodology using the forceline easily-each demonstrating basic understanding and skill in applying the method on the first amputee that each one evaluated. In 36% of the cases, using the line helped to standardize the clinicians' alignments to the target alignment (the laboratory "nominal"). In 14% of the cases, using the forceline actually moved the clinicians away from the laboratory nominal. The alignment technique presented can assist clinical thinking by removing some of the guesswork and uncertainty involved during the alignment process. No objective or widely accepted standard exists for the definition of an optimal prosthetic alignment. A technique, such as that presented here, may help in defining and also subsequently in obtaining an optimal alignment.