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Motion Deficits of Thumb Opposition and Circumduction Due to Carpal Tunnel Syndrome
Tamara L. Marquardt1; Raviraj Nataraj, PhD1; Peter J. Evans, MD, PhD2; William H. Seitz Jr, MD2; Zong-Ming Li, PhD1
1Biomedical Engineering, Cleveland Clinic, Cleveland, OH; 2Orthopaedic Surgery, Cleveland Clinic, Cleveland, OH
Introduction: Carpal tunnel syndrome (CTS) is associated with sensory and motor impairments resulting from the compressed and malfunctioning median nerve. These impairments affect the thumb which is indispensable to hand function and is required to move in multiple directions through coordinated articulations at its three joints. CTS sufferers often experience clumsiness while performing daily tasks, but the pathokinematics of the thumb associated with CTS remain unclear. The purpose of this study was to evaluate thumb motion abnormities associated with CTS. It was hypothesized that CTS would result in translational and angular motion deficits during thumb opposition and circumduction.
Methods: Eleven patients with CTS (49.5 ± 9.6 years) and 11 age- and gender-matched healthy controls (48.9 ± 7.6 years) participated in this study. Translational and angular motion of the thumb was obtained using marker-based video motion analysis during thumb opposition and circumduction tasks. Translational metrics included thumb tip path length and thumb tip position, normalized according to subject specific palm width (PW); angular kinematics were quantified by examining 6 angular degrees of freedom.
Results: Analyses revealed translational and angular motion deficits for patients with CTS. In comparison to control subjects, the path length traveled by the thumb tip for CTS patients was approximately 30% less during opposition and 25% less during circumduction (p < 0.001). Specifically, CTS patients were unable to reach a similar maximum ulnar position of their thumb tip during opposition, with an ulnar deficit of 0.3 PW (p < 0.05). The angular range of motion for the CTS group was 36-41% less for the metacarpophalangeal and interphalangeal joints in extension/flexion compared to the control group across both opposition and circumduction (p < 0.05). These kinematics abnormalities were present even though there was no difference in pinch strength between the two groups (53.1±18.1 N for patients with CTS and 57.2±18.1 N for controls, p = 0.56).
Conclusions: Motion deficits of the thumb are present for CTS patients while completing tasks of opposition and circumduction. Improving the understanding of thumb pathokinematics associated with CTS may help clarify the clumsiness in hand function related to CTS given the critical role of the thumb in dexterous manipulation. Furthermore, such advanced kinematic analyses may be used to assess functional improvement following median nerve decompression.
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