Scapular winging due to rhomboid muscle paralysis: clinical assessment of 4 cases and anatomic study of the dorsal scapular nerve

Background: A rare cause of scapular winging is rhomboid muscle paralysis secondary to dorsal scapular nerve (DSN) neuropathy. This paralysis causes winging of the medial border of the scapula with lateral rotation of its inferior angle. We report a series of 4 clinical cases of isolated DSN compression and the results of a specific rehabilitation protocol.

Methods: A continuous clinical series of 4 patients with isolated rhomboid muscle deficiency was analyzed. Two patients were men and 2 were women, with a mean age of 40 years (range, 33-51 years). Three patients were right-handed and 1 was left-handed. Scapular winging always affected the dominant side. Two patients had occupations involving heavy physical work. The sports practiced involved exertion of the arms (dancing, boxing, gymnastics, muscle strengthening). A specific rehabilitation protocol was offered to the patients. In addition, 6 fresh cadaver dissections were performed to reveal possible DSN compression. Potential areas of compression were identified, in particular when the arm was raised.

Results: The 4 patients presented with isolated DSN neuropathy were confirmed by electroneuromyographic testing. Total correction of scapular winging was not obtained in any patient. Three patients experienced residual pain with a neuropathic pain by the questionnaire for a Diagnosis of Neuropathic Pain (DN4) score of 2. The mean Quick-Disabilities of the Arm, Shoulder and Hand (DASH) score after treatment was 31.8 of 100. The mean ASES score was 56.2. Only 1 patient agreed to rehabilitation in a specialized center and underwent follow-up electroneuromyography. Signs of rhomboid muscle denervation were no longer present and distal motor latencies had become normal. In all cadaver dissections, the DSN originated from the C5 nerve root and did not pass through the middle scalene muscle. We identified a site of dynamic compression of the DSN by the upper part of the medial border of the scapula when the arm was raised.

Discussion: DSN compression is conventionally attributed to the middle scalene muscle, but it is noteworthy that our study reveals the possibility of dynamic compression of the nerve by the proximal part of the medial border of the scapula, which occurs when the arm elevation is above 90°.

Conclusion: Our study reveals the possibility of dynamic compression of the DSN by the proximal part of the medial border of the scapula, which occurs when the arm is raised above 90°. In the absence of a surgical solution, conservative treatment is fundamental and requires management in a rehabilitation center with intervention by a multidisciplinary team.