A research team characterized the consistency of patients’ preferences in prosthetic ankle-foot alignment. The researchers analyzed alignment preferences during level-ground walking and the patient-preferred ankle angle for ascent and descent of a 10-degree ramp, with implications for the design and control of robotic prostheses.
Seven participants with transtibial amputations walked over level ground and ascended and descended a 10-degree ramp on a semi-active prosthetic ankle capable of unweighted repositioning in dorsiflexion and plantarflexion.
Preferred ankle angle was measured as subjects walked on a randomized static ankle angle and reported whether they would prefer the ankle to be dorsiflexed or plantarflexed. Subjects had reliable (consistent) preferences for alignment during level-ground walking, with deviations of 1.5 degrees from preference, resulting in an 84 percent response rate preferring changes toward the preference.
Relative to level walking, subjects preferred 7.8 degrees of dorsiflexion during ramp ascent, and 5.3 degrees plantarflexion during ramp descent. As the ankle angle better matched the ramp angle, socket pressures and tibial progression (shank pitch) both more closely mirrored those during level walking.
The study’s authors concluded that the findings provide baseline behaviors for prosthetic ankles capable of adapting to slopes based on patient preference and provide strong evidence that people with transtibial amputations can finely perceive ankle alignment.
The study, “Patient-Preferred Prosthetic Ankle-Foot Alignment for Ramps and Level-Ground Walking,” was published in IEEE Transactions in Neural Systems and Rehabilitation Engineering.
