Unilateral transfemoral osseointegrated prostheses improve joint loading during walking

Abstract

People with unilateral transfemoral amputation using socket prostheses are at increased risk for developing osteoarthritis in both the residual hip and intact lower-limb joints. Osseointegrated prostheses are a surgical alternative to socket prostheses that directly attach to the residual femur via a bone-anchored implant, however their multi-joint loading effect is largely unknown. Our objective was to establish how osseointegrated prostheses influence joint loading during walking. Motion capture data (kinematics, ground reaction forces) were collected from 12 participants at baseline, with socket prostheses, and 12-months after prosthesis osseointegration during overground walking at self-selected speeds. Subject-specific musculoskeletal models were developed at each timepoint relative to osseointegration. Internal joint moments were calculated using inverse dynamics, muscle and joint reaction forces (JRFs) were estimated with static optimization. Changes in internal joint moments, JRFs, and joint loading-symmetry were compared using statistical parametric mapping (p≤ 0.05) before and after osseointegration. Amputated limb hip flexion moments and anterior JRFs decreased during terminal stance (p = 0.002, <0.001; respectively), while amputated limb hip abduction moments increased during mid-stance (p < 0.001), amputated hip rotation moment changed from internal to external throughout early stance (p < 0.001). Intact limb hip extension and knee flexion moments (p = 0.028, 0.032; respectively), superior and resultant knee JRFs (p = 0.046, 0.049; respectively) decreased during the loading response following prosthesis osseointegration. These results may indicate that the direct loading transmission of these novel prostheses create a more typical mechanical environment in bilateral joints, which is comparable with loading observed in able-bodied individuals and could decrease the risk of development or progression of osteoarthritis.

Keywords: Above-knee amputation; Gait; Musculoskeletal modeling; Osseointegrated prostheses; Socket prostheses.

Figure 1.

(a) CT images and experimental motion capture data were used to modify an existing generic model. (b) Subject-specific musculoskeletal models with a simulated myodesis were created for each patient before and after osseointegration. (c) Workflow in OpenSim to determine kinetics, and joint loading.

Figure 2.

Internal joint moments during stance phases of level walking before and after osseointegration. (a) Intact limb hip, knee, and lumbar joint moments in stance phase. (b) Amputated limb hip and lumbar joint moments in stance phase. Dashed blue lines represent baseline (with socket) data and solid red lines represent data for 12 months post-osseointegration surgery. The red and blue shaded areas represent ± 1 standard deviation from the means. The gray shaded areas indicate a statistically significant difference (determined using SPM) between the mean moments at baseline and 12 months after osseointegration.

Figure 3.

Bilateral joint reaction force (JRF) components and resultant during stance phases of level walking before and after osseointegration. (a) Intact limb hip, (b) intact limb knee, (c) and amputated limb hip JRF. Dashed blue lines represent baseline (with socket) data and solid red lines represent data for 12 months post-osseointegration surgery. The red and blue shaded areas represent ± 1 standard deviation from the means. The gray shaded areas indicate a statistically significant difference (determined using SPM) between the mean JRF at baseline and 12 months after osseointegration.

Figure 4.

Waveform symmetry curves of bilateral hip joint loading during stance phases of level walking before and after prosthesis osseointegration. (a) Anterior, (b) superior, (c) medial, (d) and resultant JRF symmetry waveforms between the intact and amputated limbs. A value of zero indicates perfect symmetry while +100 and −100 indicate perfect asymmetry, overloading the intact or amputated limbs respectively. Dashed blue lines show the baseline loading symmetry trend with socket prostheses, solid red lines show the loading symmetry trend 12 months after prosthesis osseointegration. The red and blue shaded areas represent ± 1 standard deviation from the means. The gray shaded areas indicate a statistically significant difference (determined using SPM) between symmetry trends at baseline and 12 months after osseointegration.