This study aimed to determine how ankle-foot roll-over shape during walking is affected by the inherent asymmetry of people with lower-limb amputations. The researchers analyzed roll-over shapes of participants with transtibial and transfemoral amputations as they walked at self-selected speeds. They found that participants with transtibial amputations had more symmetrical gait, while those with transfemoral amputations showed highly individual adjustments in roll-over shape on their nondisabled side. The sound limb must make all compensations due to the passive properties of the prosthetic system. Roll-over shape was reproducible within each step but unique between individuals, indicating patients develop their own adjustment strategies with implications for prosthetic design.

1. Determining asymmetry of roll-over shapes in prosthetic walking Carolin Curtze, MSc; Bert Otten, PhD; At L. Hof, PhD; Klaas Postema, MD, PhD

2. Study Aim Determine how ankle-foot roll-over shape is affected by the inherent asymmetry of the locomotor system of people with lower-limb amputations. Relevance Previous studies have not described how the roll-over shape of the prosthetic limb affects the roll-over shape of the nondisabled limb.

3. Methods While participants walked at self-selected speed, we analyzed roll-over shapes in 2 dimensions, reflecting overall walking direction: We estimated effective radius of curvature by fitting best-fit circular arc to roll-over shapes. We calculated agreement between ankle-foot roll-over shapes as root-mean-square distance of 2 curves. On basis of these measures, we determined interlimb asymmetry and intralimb reprodu-cibility of roll-over shapes.

4. Results Transformation of successive center of pressure data from (a) laboratory-based to (b) shank-based coordinate system. (c) Resampled shank-based roll-over shapes to calculate root-mean-square distance between curves. Shown: Nondisabled and prosthetic limbs of participant with trans-femoral amputation .

5. Results All participants showed some asymmetry in roll-over shape (even nondisabled controls). Participants with transtibial amputation had quite symmetrical gait, while participants with transfemoral amputation showed highly individual adjustments in roll-over shape on side of nondisabled limb. Because of passive properties of prosthetic system, sound limb must make all compensations. Intralimb reproducibility was high; i.e., roll-over was about the same in every step .

6. Conclusions Patients had their own unique individual roll-over shape, like a personal signature. Roll-over shape of nondisabled limb can deviate from circular shape as an effect of adjustments. This must be considered when calculating radius of curvature. Determining roll-over shape might help us better understand adjustment strategies in prosthetic walking and achieve an optimal compromise for each patient.