Shoulder position sense in volleyball players with infraspinatus atrophy secondary to suprascapular nerve neuropathy

Isolated infraspinatus atrophy (IIA) is a common condition among overhead-activity athletes, which affects the hitting shoulder and is caused by suprascapular nerve injury. As the suprascapular nerve is a mixed nerve, such damage could lead to reduced afferent proprioceptive information and impaired shoulder sensorimotor control. This study aimed to evaluate the proprioception of the shoulder with IIA, through the assessment of shoulder position sense. The shoulder position sense was assessed in 24 professional volleyball players (12 players with IIA and 12 healthy players) with a blind dynamic shoulder repositioning test (all participants were blindfolded during the test). Three functional glenohumeral movements were tested as follows: abduction, forward flexion, and a combination of abduction and external rotation. In all three tested movements, the affected shoulder of players with isolated infraspinatus atrophy showed significantly higher hand position error than the healthy contralateral (P<10(-3), for all movements) and the healthy control group hitting shoulder (P<10(-3), for abduction and flexion; P=.02, for combined movement of abduction and external rotation). The study highlights a reduced sense of position of the hitting shoulder in professional volleyball players with IIA secondary to suprascapular nerve palsy. The higher hand position error of the pathologic shoulder suggests an impairment of the shoulder sensorimotor control system, which likely results from reduced afferent proprioceptive information. Deficient afferent proprioceptive information may result in poor accuracy in descending motor commands and impairment of the shoulder neuromuscular function, leading to reduced shoulder functional stability and increased risk of injury.