(L-456) Use of a Socket-Suspended Prosthesis Affects Upper Extremity Kinematics During Unilateral Activities of Daily Living

Introduction:: Individuals with unilateral transhumeral (TH) amputations have the highest rate of prosthesis abandonment, as high as 60% [1-3]. Common reasons for device abandonment include the weight of the device, decreased range of motion in the shoulder, and an inability to spatially control the device [2, 4]. TH prosthesis dissatisfaction and abandonment complicate the completion of many activities of daily living (ADLs) and may place excess burden on proximal joints and the contralateral, intact limb [5]. However, there is a lack of research quantifying how TH prostheses impact kinematics during ADLs. The objective of this study was to investigate the impact of conventional socket-suspension systems on body positioning and motion, comparing proximal and contralateral joint kinematics and spatial control while individuals use their intact limb and TH prosthesis to complete unilateral ADLs. We hypothesized that when using a prosthesis to complete a unilateral ADL, (1) there will be increased angular displacements in the trunk, neck, and contralateral shoulder, and (2) there will be decreased motion smoothness in the trunk, neck, and contralateral shoulder, compared to completing the same ADL with the intact limb.


Materials and Methods:: Eight male subjects with unilateral TH limb loss and socket-suspended prostheses participated in the study (median age: 58 years (range 29-77)). Four subjects used a body-powered hook, one a myoelectric hook, and three a myoelectric hand. The subjects had used their devices for a median of 5 years (range 2-12). Subjects completed three unilateral ADL tasks using their prosthetic limb and their intact limb – comb hair, underhand toss, and targeted reach. Kinematic data were collected using a 24-camera VICON motion capture system at the Veterans Affairs Salt Lake City Gait Lab. Subjects completed each ADL three times with their intact limb and three times with their prosthetic limb. A modified Plug-In Gait marker set was used to track 5 segments (trunk, head, arms, forearms, and hands). The marker trajectory data were captured at 100 Hz and synchronized using Vicon Nexus 2.9 software. Data were post-processed using Visual3D and filtered with a fourth-order, low-pass Butterworth filter with a cut-off frequency of 6 Hz [6]. Angular displacement was calculated for the trunk, neck, and shoulder for each trial. Motion smoothness for each body segment was calculated from the number of velocity peaks with magnitudes greater than 10% of the maximum velocity, where fewer velocity peaks indicated smoother motion [7]. To account for the small sample size and anticipated variability from using different prostheses, a Paired-Sample Wilcoxon Signed Ranks test was used for angular displacement and motion smoothness comparisons between completing the task with each limb. P≤0.05 was the threshold for significance.

Results, Conclusions, and Discussions:: When completing the tasks with the prosthesis compared to the intact limb, there was increased trunk angular displacement in the sagittal plane during targeted reaching trials, in the coronal plane during the underhand toss and targeted reaching trials, and in the transverse plane during targeted reaching trials. When completing the task with the prosthesis, there was increased neck flexion during targeted reaching trials, lateral flexion during the comb hair and targeted reaching trials, and rotation during underhand toss and targeted reaching trials. For all tasks, when using the prosthesis, there was significantly greater contralateral shoulder flexion, abduction, and rotation compared to the use of the intact limb. When completing the underhand toss with the prosthesis, compared to using the intact limb, overall motion smoothness was decreased in the trunk, head, and contralateral limb.


Our results identified significant impacts on proximal joints, including the ipsilateral shoulder and trunk, and contralateral limb kinematics when completing ADLs with a prosthesis. These differences in body and joint positioning and motion smoothness may affect musculoskeletal health and how individuals use their prostheses. Compensatory motions may increase neck and back pain, and reduced smoothness could result in slower, less reliable movement.

This study characterized kinematic changes from conventional socket suspension systems in individuals using TH prostheses. Individuals with TH amputation disproportionately abandon their prostheses, citing issues related to the socket-suspension system. These prosthesis abandonment rates emphasize a need for novel prosthesis attachment systems, such as the percutaneous osseointegrated (OI) endoprosthetic docking system [8, 9]. OI endoprosthetics replace the need for sockets and are expected to address most issues related to TH prostheses abandonment. These OI endoprosthetic systems have improved satisfaction and functional use in cases of transfemoral amputation. However, OI endoprosthesis use in upper extremity is underreported, and comparative studies with conventional socket prosthetics are needed to effectively evaluate the benefits of these novel docking systems. These results will provide the necessary data for future comparative studies between conventional socket systems and OI endoprostheses. These results will also improve understanding of how individuals use their current socket-suspended TH prosthetic systems.


Acknowledgements (Optional): : This work was supported by the Department of Veterans Affairs Medical Research Funds (RX003071, RX002935), resources at both the Salt Lake City VA Medical Center and the Orthopaedic Research Laboratory, University of Utah School of Medicine, Salt Lake City, Utah, and the National Science Foundation Graduate Research Fellowship under Grant No. 1747505.

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