Transfemoral bone-anchored limbs alter joint-load-line offset during walking

Individuals with transfemoral amputation are at a heightened risk of musculoskeletal overuse injuries and reduced stability, largely due to altered joint biomechanics. The position of the ground reaction force (GRF) relative to hip and knee joints directly influences both joint biomechanics and dynamic stability and is influenced both by both movement patterns and prosthetic alignment. However, it is unknown if it is influenced by prosthetic suspension type. Our objective was to determine how the position of the GRF relative to hip and knee joint centers during walking differs between individuals with transfemoral amputation using either a socket prosthesis or bone-anchored limb (BAL). Motion capture data was collected from a convenience sample of 17 participants with unilateral transfemoral amputation during overground walking at two timepoints: before and 12-months following BAL implantation. The distances between the GRF line of action and the hip and knee joints in the sagittal and frontal planes were calculated and compared across timepoints (α = 0.05). The distance between the GRF and hip joint center was less medial (p < 0.001) on the amputated limb and more lateral (p < 0.001) on the intact limb during stance period when using a BAL compared to a socket prosthesis. Closer positioning of the GRF relative to the hip joint may reduce frontal plane compensatory strategies required for hip stabilization, potentially reflecting a biomechanical stable gait pattern when using a BAL.