Hip joint mechanics during swing limb advancement with bone-anchored limb use.

Walking swing limb advancement after transfemoral amputation relies on the hip for proper limb positioning. We compared hip mechanics and stride characteristics during swing before and after bone-anchored limb (BAL) implantation. We hypothesized swing limb advancement hip mechanics would be different and between-limb differences reduced after BAL implantation without compromising stride characteristics. Twenty participants were included in this retrospective observational investigation including overground walking motion capture before and one-year after BAL implantation. Swing was measured from contralateral foot strike to ipsilateral foot strike during four phases: (1) pre-swing, (2) initial swing, (3) mid-swing, and (4) terminal swing. Hip mechanics were quantified using hip joint angles, moments, and powers, and thigh angular velocities in the sagittal and frontal planes. Most changes with BAL use occurred in the intact limb during mid-swing and terminal swing (p ≤ 0.04) with reduced between-limb differences (p ≤ 0.05). We also observed changes in frontal plane mechanics during initial swing and mid-swing (p ≤ 0.01) suggesting decreased frontal plane deviations (e.g., less swing limb circumduction and lateral leaning) with BAL use. Gait speed and stride length were unchanged (p ≥ 0.76, g ≤ 0.07) and stride width narrowed (p < 0.01, g = 0.89). These changes in the intact limb and increased similarity between limbs suggest that BAL use might increase the contribution of the amputated limb to walking postural control and reduce long-term pain and overuse problems associated with between-limb differences without compromising stride characteristics. Additional investigations of both limbs and gait deviations associated with transfemoral amputation are needed to further understand the impact of BAL use on walking.