Upper extremity neuromuscular function can distinguish between individuals with and without glenohumeral labral repair

Abstract

The purpose of this study was to determine whether common measures of neuromuscular function could distinguish injury status indicated by group membership (glenohumeral labral repair, uninjured controls). 16 individuals with glenohumeral labral repair (24.1 ± 5.0 years, 36.7 ± 33.3 months after surgery) and 14 uninjured controls (23.8 ± 2.7 years) volunteered. We measured mass-normalized shoulder abduction and wrist flexion maximal voluntary isometric contraction torque (Nm/kg), motoneuron pool excitability of the flexor carpi radialis (Hoffmann reflex), corticospinal excitability of the upper trapezius, middle deltoid, and flexor carpi radialis (active motor threshold [%]) bilaterally. Receiver operator characteristic curve analyses were performed to determine if each outcome could distinguish injury status along with their outcome thresholds. Binary logistic regression was used to determine the accuracy of classification for each outcome. Our results suggest shoulder abduction torque symmetry (≤95.5 %) and corticospinal excitability for the upper trapezius (≥41.0 %) demonstrated excellent diagnostic utility. Shoulder abduction torque (≤0.71 Nm/kg) and motoneuron pool excitability (≤0.23) demonstrated acceptable diagnostic utility. Shoulder abduction torque symmetry alone was the strongest indicator, and classified injury status with 90.0 % accuracy (p < 0.01). Overall, symmetric shoulder abduction strength most accurately distinguished individuals’ injury status, suggesting the utility of bilateral assessment in this population.