Altered cumulative joint moments and increased joint moment symmetry during sit-to-stand transitions for transfemoral bone-anchored limb users: A case series.
Background: Sit-to-stand transitions are demanding activities for people with unilateral transfemoral amputation. Movement asymmetries during sit-to-stand place greater stresses on the intact limb joints compared to the amputated limb joints, potentially contributing to musculoskeletal overuse injury and pain. Bone-anchored limbs address socket-related prosthesis issues, but their impact on cumulative joint moments during sit-to-stand is yet to be fully understood. The purpose of this study was to investigate changes in cumulative joint moments and moment symmetry during sit-to-stand transitions among transfemoral bone-anchored limb users.
Methods: A case-series of eight participants who underwent secondary bone-anchored limb implantation surgery were included. Ten consecutive days of physical activity monitoring (daily sit-to-stand) and motion capture during a 5-times sit-to-stand task were collected preoperatively (using socket prosthesis) and 12-months postoperatively. Cumulative low back, hip, and knee joint moments ([absolute joint moment impulse] x [average daily sit-to-stand]) were calculated. Between-limb symmetry was assessed using the Normalized Symmetry Index. Longitudinal changes in cumulative joint moments and moment symmetry were estimated with Hedge's g effect sizes.
Results: Medium-to-large effects (g > 0.5) were observed for increased frontal-plane amputated-limb hip moment and increased sagittal-plane cumulative low back and intact-limb knee moments. Small-to-medium effects (g < 0.5) were observed for improved between-limb frontal-plane hip moment symmetry.
Conclusions: Despite improved between-limb symmetry, persistent overloading of the intact limb was present one-year after bone-anchored limb implantation. Changes in loading without meaningful changes in average number of daily sit-to-stands suggest potential needs for advanced prosthetic component prescription and more effective movement pattern training for bone-anchored limb users.