Transducer-based Comparisons of the Prosthetic Feet Used by Transtibial Amputees for Different Walking Activities: a Pilot Study

Background: Knowledge of transtibial residual limb force and moment loading during gait can be clinically useful. The research question was whether a transducer attached between the socket and pylon can be used to detect differences in loading patterns created by prosthetic feet of different design and different walking activities in real-world environments outside the gait lab.

Objectives: To develop methods for obtaining, processing, analyzing and interpreting transducer measurements and examining their clinical usefulness.

Study Design: Case series design.

Methods: A convenience sample of four K3-K4 transtibial amputees and a wireless tri-axial transducer mounted distal to the socket. Activities included self-selected comfortable speed walking, and ascending and descending ramps and steps. Measurements taken about three orthogonal axes were processed to produce plots of normalized resultant force versus normalized resultant moment. Within-subject differences in peak resultant forces and moments were tested.

Results: Loading patterns between feet and subjects and among the activities were distinctly different. Optimal loading of peak resultant forces tentatively might occur around 25% and 69% to73% of stance during self-selected comfortable walking. Ascending and descending ramps is useful for examining heel and forefoot response.

Conclusions: Force-moment plots obtained from transducer data may assist clinical decision making.

Clinical Relevance: A pylon-mounted transducer distal to the socket reveals the moments and forces transmitted to the residual limb and can be used to evaluate the loading patterns on the residual limb associated with different foot designs and different everyday activities outside the gait lab.