Targeting movement strategies to reduce impingement of the rotator cuff during overhead reaching in individuals with spinal cord injury
Cloud B, Madansingh S, Fortune E, Morrow M, Zhao K
Mayo Clinic, Rochester, Minnesota, USA
Objective: Musculoskeletal disorders of the upper extremity (UE) are common in individuals with spinal cord injury (SCI). Many cases of shoulder pain in this population are thought to result from repetitive use of the UE which damages the rotator cuff. It may be beneficial to determine movement strategies for commonly performed activities which decrease this risk. This abstract presents preliminary data evaluating differences in movement strategies (i.e. glenohumeral and scapulothoracic kinematics) between individuals with SCI who exhibit low versus high risk of impingement to the supraspinatus (SS) and infraspinatus (IS) during a unilateral overhead reaching task.
Design/Methods: Manual wheelchair users with SCI were recruited to this IRB-approved study. Participants performed a unilateral reaching task to retrieve a ~1lb aluminum can placed in front of them at midline on a surface located 54" above the ground (typical high kitchen cabinet height). Each participant completed five cycles of the reaching motion, defined from the initiation of UE elevation away from the thorax until movement terminated in a resting position at his/her side. Kinematic data were captured at 120 Hz with electromagnetic sensors (Liberty, Polhemus) placed on the thorax, scapula, and humerus. Glenohumeral (GH), scapulothoracic (ST), and thoracic (THOR) kinematics were each defined about 3 axes. The mean trajectories of each joint's motion were determined for the middle 3 reach cycles. The proximity of the SS and IS attachment sites on the humerus to the underside of the coracoacromial (CA) arch (i.e. the acromion, CA ligament, and coracoid) was estimated using proximity modelling techniques. Impingement risk was defined as proximity estimates <5mm, corresponding to distances less than the typical tendon thickness of the SS. Duration of impingement risk (percentage of cycle under 5mm) was calculated for the 3 reach cycles and averaged.
Results: Four individuals with SCI participated (26.8±4.9yr, 3 male, injury levels T3-T6). During analysis, the participants were stratified into two groups: those with prolonged impingement risk during the reaching cycle (65.0% & 76.7% SS at risk and 45.3% & 65.3% IS at risk) and those with reduced risk (37.7% & 26.0% SS at risk and 0% & 0% IS at risk). All participants demonstrated a similar mean magnitude of GH elevation during the reach. However, those who had low risk demonstrated greater mean GH external rotation (53.8° & 54.7° vs. 23.8° & 17.4°) and relatively more ST anterior tilt (18.0° & 7.8° anterior tilt vs. 5.8° & 4.7° posterior tilt) during the movement cycle.
Conclusion: The reaching task under study can be performed with reduced risk to the rotator cuff, as demonstrated by two of our participants. The reduced risk trials were characterized by greater GH external rotation and ST anterior tilt. Thus, these values could be altered during biofeedback to reduce risk in other patients with SCI.
Support: Mayo Clinic Rehabilitation Medicine Research Center, on behalf of the Craig H. Neilsen Fund for Spinal Cord Injury Care and Research Honoring Robert D. Brown Jr., M.D.
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