Osseointegrated prostheses reduce reactive stability demands during walking in Service members with unilateral transfemoral amputation

Background: Heightened fall risk following lower limb amputation can lead to adaptations during walking that increase proactive stability (e.g., a wider base of support). However, such compensations also reduce maneuverability, increasing reactive stability demands (e.g., corrective steps) as more lateral foot placement necessitates greater lateral impulses. By improving prosthetic control, osseointegration (OI) may mitigate fall risk and reduce the need for proactive stability compensations. Thus, this work aims to characterize proactive stability compensations, via mediolateral margins of stability (MOS_ML) as well as reactive stability demands, via absolute and net integrated whole-body angular momentum (iWBAM), and variability in net iWBAM. Methods: Eight Service members (SMs) with unilateral transfemoral amputation completed biomechanical gait evaluations before, and 12- and 24-months after OI. We hypothesized minimum MOS_ML would decrease as would absolute tri-planar integrated WBAM (iWBAM) and net iWBAM variability following OI, indicative of decreased reliance on proactive stability compensations and reduced reactive stability demands, respectively. Results: Relative to pre-OI, minimum MOS_ML did not decrease at either post-OI evaluation, sagittal absolute iWBAM were 8.8 % and 7.0 % less at 12-months and 24-months post-OI, respectively. Additionally, sagittal net iWBAM variability decreased by 32.1 % at 24-months post-OI versus pre-OI. No other differences were observed in pre- versus post-OI measures. Significance: These findings suggest that, unlike civilian populations, OI does not decrease passive stability compensations among SMs; however, OI may reduce reactive stability demands relative to socket-suspended prostheses among SMs. Future work should evaluate whether these differences extend to decreased fall risk in daily life.