Isolated infraspinatus atrophy in elite volleyball player- Understanding the biomechanics, imaging and outcome

Over 800 million people worldwide play volleyball, either recreational or competitive. Even though all throwing athletes suffer from upper extremity injuries caused by overuse, volleyball additionally involves certain prototypical throwing biomechanics, not seen in other overhead sports. Complex biomechanics and the balanced interplay between the glenohumeral and scapulothoracic muscles ensure velocity and torque displacement in spike and jump-serve maneuvers (formerly known as smash) which are exclusive to volleyball. In this case report, we have described in detail the entity of isolated infraspinatus atrophy secondary to suprascapular nerve neuropathy.

Infraspinatus atrophy due to Bennett lesion causing suprascapular nerve palsy

We report the case of a 19-year-old professional volleyball player who presented with right shoulder pain exacerbated during sports activity. On physical examination, infraspinatus atrophy was evident. As the clinical setting suggested suprascapular nerve entrapment syndrome, shoulder MR and later CT were performed. The results showed radiological signs of subacute-chronic infraspinatus muscle denervation and a Bennett lesion of the shoulder, presumably due to chronic repetitive trauma during the classical overhead swing in volleyball. The patient agreed to surgical treatment, and arthroscopic decompression was achieved. After months of rehabilitation, the pain gradually subsided, the infraspinatus muscle recovered its trophism, and the patient progressively returned to her regular sports activity.

Visual Observation of Apparent Infraspinatus Muscle Atrophy in Male Professional Tennis Players

Background: Previous studies have reported visually observed apparent muscle atrophy in the infraspinous fossa of the dominant arm of overhead athletes. Several mechanisms have been proposed as etiological factors, including eccentric overload, compressive spinoglenoid notch paralabral cysts, and cumulative tensile suprascapular neurapraxia. Purpose: To report the prevalence of apparent infraspinatus atrophy in male professional tennis players and to determine whether the suspected atrophy correlates with objectively measured weakness of external rotation. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 153 male professional tennis players underwent a musculoskeletal screening examination that included visual inspection of the infraspinous fossa. Infraspinatus atrophy was defined as hollowing or loss of soft tissue bulk inferior to the scapular spine in the infraspinous fossa of one extremity that was visibly different from the contralateral extremity. This finding was observed and independently agreed upon by both an orthopaedic surgeon and a physical therapist during the examination. Also assessed were rotator cuff instrument-assisted manual muscle testing, visual observation of scapular kinesis (or motion), and glenohumeral joint range of motion for internal and external rotation and horizontal adduction. Results: In the 153 players, dominant-arm infraspinatus atrophy was observed in 92 players (60.1%), and only 1 player (0.7%) was identified with nondominant infraspinatus atrophy. A Pearson correlation showed a significant relationship between the presence of dominant-arm infraspinatus atrophy and dominant-arm external rotation strength measured in neutral abduction/adduction (at the side) ( P = .001) as well as between the presence of dominant-arm infraspinatus atrophy and bilateral external rotation strength measured at 90° of glenohumeral joint abduction ( P = .009 for dominant arm and .002 for nondominant arm). No significant correlation was found with scapular dyskinesis, glenohumeral range of motion, or instrument-assisted manual muscle testing of the supraspinatus (empty-can test). Conclusion: Visually observed infraspinatus muscle atrophy is a common finding in the dominant shoulder of asymptomatic male professional tennis players and is significantly correlated with external rotation weakness. This condition is present in uninjured players without known shoulder pathology and is not related to glenohumeral joint internal rotation, total rotation range of motion, or scapular dysfunction. Players with visually observed infraspinatus atrophy should be evaluated for external rotation strength and may require preventive strengthening.

Isolated Infraspinatus Atrophy Secondary to Suprascapular Nerve Neuropathy Results in Altered Shoulder Muscles Activity

Context: Isolated infraspinatus atrophy (IIA) is a common condition among overhead activity athletes, which affects the hitting shoulder and is caused by suprascapular nerve injury. The loss of infraspinatus function could lead to altered activity of the glenohumeral and scapulothoracic (ST) muscles and compromise the optimal shoulder function. Objective: To assess the surface electromyographic (sEMG) activity patterns, relationships, and response latencies of relevant shoulder girdle muscles in professional volleyball players with IIA and in healthy control players. Design: Cross-sectional study. Setting: Research laboratory. Patients or Other Participants: Twenty-four male professional volleyball players (12 players with diagnosed IIA and 12 healthy players) recruited from local volleyball teams. Intervention(s): sEMG activity of anterior, middle, and posterior deltoid; upper, middle, and lower trapezius; and serratus anterior (SA) was recorded and evaluated during a movement of shoulder abduction in the scapular plane, monitored with an optoelectronic motion capture system. Main Outcome Measure(s): sEMG activity, relationships, and response latencies of the selected muscles were analyzed with analysis of variance models to highlight statistical differences within and between groups. Results: Athletes with IIA demonstrated significant higher deltoid and trapezius muscles activity and lower SA activity compared with the contralateral shoulder and healthy athletes. The shoulder with IIA also showed a higher activity ratio between the upper trapezius and other ST muscles in addition to anticipated activation of the upper trapezius and delayed activation of the SA, with regard to the onset of shoulder movement. Conclusions: This study highlighted altered shoulder muscle activity levels, ST muscles imbalances, and abnormal ST recruitment patterns in the hitting shoulder of professional volleyball players with IIA, secondary to suprascapular nerve neuropathy. Such shoulder girdle muscles’ impairments may compromise the optimal scapulohumeral rhythm and function, increasing the risk of acute and overuse shoulder injuries.