Lower body kinematics and mediolateral stability of stair tasks in individuals with a Rotationplasty about the knee.

BACKGROUND: Rotationplasty is a limb-salvage surgery that repurposes the ankle joint as the new 'knee' joint to achieve active 'knee' flexion/extension. The procedure is recommended for patients who desire a more active lifestyle. Navigating stairs is critical to functional independence but has not been examined in individuals with rotationplasty. The purpose was to examine lower-limb joint, pelvis, and trunk kinematics and mediolateral stability during stair ascents/descents in individuals with rotationplasty. METHODS: Nine male participants (15.7 ± 5.1 years) executed trials of ascending/descending three stairs leading with each limb (surgical, intact). 3D kinematics were captured via 13 infrared cameras (120 Hz). The swing phase and stance phase for the leading limb and trailing limb were analyzed separately. Excursions (°) were calculated in each plane as the active joint range of motion for the ankle, knee, hip, pelvis, and trunk during each phase. Mediolateral stability was assessed with lateral margin of stability. FINDINGS: The intact limb had greater excursion in all planes for both tasks and gait phases compared to the surgical limb. Both limbs executed steps that would be considered 'unstable' with the intact limb executing more. INTERPRETATION: Individuals with rotationplasty ascend stairs with greater intact limb motion regardless of leading limb. Regardless of condition/limb, a less stable body position was observed, with more unstable steps executed by the intact limb. This observed activity is like an adaptation for reduced motion from the surgical limb.