Reactive balance and stepping strategy in persons using a transfemoral prosthesis

BACKGROUND: Persons with a transfemoral amputation (TFA) have poorer balance compared to able-bodied persons (AB)[1,2]. Research shows additional contributions of the intact leg to compensate for the loss of an active ankle strategy on the prosthetic limb side[2]. Currently, it is unknown whether a) reactive balance is also affected in persons with TFA, b) whether this is influenced by the type of prosthetic suspension, and c) which leg they prefer to recover from perturbations. Insight into reactive balance may ultimately help to identify who has an increased fall risk.

AIM: Determining whether reactive balance differs between persons with TFA and AB, and between types of prosthetic suspension (i.e. socket-suspended (SSP) versus bone-anchored (BAP)); and to identify which leg is used for stepping to recover from a perturbation.

METHOD: Experienced transfemoral SSP- and BAP-users and AB were recruited. Participants stood on a platform that moved at increasing perturbation intensities in forward, backward, prosthetic/non-preferred leg and intact/preferred leg stepping directions. Participants were instructed to recover their balance with a maximum of one step. The multiple stepping threshold was recorded (i.e maximum perturbation intensity (m/s2) at which one could still recover with one step), as well as the stepping leg used.

RESULTS: We included 10 AB persons (age: 57±11years) and 20 persons with TFA; 10 BAP-users (age: 59±15years, time since amputation: 25±17years) and 10 SSP-users (age: 56±13years, time since amputation: 27±14years). Balance confidence (ABC-questionnaire) and balance capacity (Brief-BEST) were significantly lower in TFA compared to AB (90vs97% and 18vs24points, p<.001 and p<.001), with no significant differences between BAP and SSP. TFA achieved a significantly lower multiple stepping threshold in the backward direction (3.5m/s2, p=.005) and towards the prosthetic/non-preferred leg (2.5m/s2, p<.001) compared to AB (both: 4.5m/s2); no significant differences between BAP and SSP. In the backward, forward, and towards the intact side, the majority of TFA used side steps with their intact leg (90, 80, and 100%). Toward the prosthetic side, mainly the prosthetic leg was used (90%).

DISCUSSION AND CONCLUSION: Results suggest reduced reactive balance in persons with TFA, which might be a result of reduced sensory feedback and delayed responses[3]. No difference between type of prosthetic suspension were found. In contrast to the stepping strategy of stroke patients[4], people with TFA prefer using their affected leg to recover from a sideways perturbations towards the prosthetic side. These findings underpin the cautious behaviour of prosthetic-users during disturbances.