Whole-body angular momentum is influenced by bone-anchored limb use and amputation level during walking.

Background: Bone-anchored limbs (BALs) improve mobility, physical activity, multi-joint biomechanics, and static balance measures compared to when using a socket prosthesis. However, evidence surrounding how BAL use influences dynamic balance, and whether this is dependent on amputation level, remains unknown.

Research questions: Does BAL use change dynamic balance as compared to a socket prosthesis? Do changes in dynamic balance with BAL use differ by amputation level?

Methods: Thirty-two participants with prior unilateral amputation (19 transfemoral, 13 transtibial) who underwent BAL implantation were retrospectively enrolled. Whole-body motion capture data during overground level walking was collected before (using socket prosthesis) and 12-months after BAL implantation. The range of whole-body angular momentum (WBAM) and peak external demand moment were compared across timepoints and groups using a two-way mixed model ANOVA.

Results: Frontal and transverse plane WBAM were reduced in individuals with transfemoral amputation when using a BAL as compared to a socket prosthesis (p < 0.001 and p < 0.001, respectively). Furthermore, when using a BAL or socket prosthesis, frontal plane WBAM was larger in individuals with transfemoral amputation compared to transtibial amputation (p = 0.028 and p = 0.018), which coincided with a larger peak external demand moment (p = 0.027 and p = 0.007).

Significance: Smaller ranges of WBAM and a smaller external demand moment during walking indicate improved dynamic stability when using a BAL compared to socket-type prosthesis, and thus likely suggest a reduced fall risk. As walking is most unstable in the mediolateral direction, greater ranges of frontal plane WBAM (worsened regulation) in individuals with transfemoral amputation compared to transtibial amputation may indicate more compromised balance control and greater fall risk.