Plantar foot pressure responses to changes during dynamic trans-tibial prosthetic alignment in a clinical setting.

Abstract

Alignment of a lower limb prosthesis refers to the spatial orientation of the prosthetic components and socket with respect to one another. During the process of dynamic alignment, a prosthetist repeatedly modifies this spatial orientation and observes the amputee's resulting walking pattern, eventually arriving at an alignment that is judged to be optimal. Quantification of the effect of each alignment modification and correlation of the magnitude of modification with the changes in gait could improve understanding of the process and promote an evidential base for practice. This investigation quantified bilateral plantar foot pressures in six trans-tibial amputee subjects during the process of dynamic alignment at prosthetists' clinics during regularly scheduled appointments. Outcomes of changes in prosthetic alignment during the clinical dynamic alignment process were determined to be quantifiable via plantar pedobarography. Changes in the angle between the pylon and the socket in the frontal plane produced predictable shifts in foot pressure between medial and lateral foot regions under the prosthesis, and typically shifted pressure to the lateral region of the contralateral foot, regardless of the direction of the modification. Temporal parameters revealed that subjects initially adopt a conservative locomotor pattern after an alignment change but within a few steps begin to refine their gait and approach more symmetrical single limb support times. Plantar pedobarography provides the clinician with potentially useful information to augment dynamic alignment and provides a tangible record of the results of the process.