Motion of the residual femur within the socket during gait is associated with patient-reported problems in transfemoral amputees

The purpose of this study was to provide a quantitative description of residual femur motion within the socket during gait and to explore the relationship between residual femur motion and patient-reported comfort and function. It was hypothesized that increased residual bone movement would correlate to worse patient-reported comfort and function. The secondary goals were to assess within-subject step-to-step variability and between-subject variability in residual femur motion within the socket during gait. Dynamic biplane radiography, combined with conventional motion capture, was used to measure residual femur motion within the socket during treadmill walking for 10 unilateral transfemoral amputees. The questionnaire for persons with a transfemoral amputation (Q-TFA) was administered to assess prosthetic use, mobility, health problems, and global health. Increased femur pistoning (proximal-distal translation relative to the socket) correlated with worsening Q-TFA problem and global scores (ρ = 0.741, p = 0.04 and ρ = -0.783, p = 0.02, respectively). Average residual femur rotation ROMs were 7.3°±3.7°, 10.8°±4.4°, and 7.7°±4.8° for anterior tilt, internal-external rotation, and varus-valgus, respectively. Average residual femur translation ROMs were 8.6 mm ± 3.0 mm, 28.4 mm ± 13.9 mm, and 20.4 mm ± 7.2 mm for medial–lateral, pistoning, and anterior-posterior directions, respectively. Within-subject rotational and translational variability during gait averaged 2.8° and 2.0 mm or less, whereas the between-subject variability was up to 9.4° and 18.6 mm, which demonstrates residual femur motion relative to the socket is repeatable within subjects, but inconsistent across subjects during gait. The results suggest residual bone motion within the socket is a potential mechanism behind patient-reported problems and suggests a target for intervention aimed at improving transfemoral amputee quality of life.