Objective: Both clinical and radiological reports have suggested that the subclavius, a muscle in the costoclavicular space of the thoracic outlet, participates in neurogenic thoracic outlet syndrome (NTOS) in some instances, especially during movements narrowing the costoclavicular space. Magnetic resonance imaging can identify subclavius muscles with signs of nerve impingement, yet the impact of the subclavius in such situations remains unclear. Therefore, the authors investigated whether dividing or sparing the subclavius characterized by nerve impingement on MRI would affect surgical outcomes.
Methods: In this retrospective nonrandomized study, authors analyzed all NTOS patients with a subclavius muscle characterized by nerve impingement on MRI (loss of normal fat planes surrounding the brachial plexus) in the period between March 2010 and November 2016. Patients were divided into two groups: the sparing group, in which patients had undergone conventional supraclavicular scalenectomy and first rib resection (FRR), and the dividing group, in which patients had undergone scalenectomy, FRR, and subclavius dividing using a modified supraclavicular incision. The Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire, a shoulder range of motion subscale (DASH items 6, 12-15, and 19) concerning overhead activities that can significantly narrow the costoclavicular space, postoperative MRI studies, and patient self-assessments were used to assess surgical outcomes. Univariate and multivariate analyses were conducted to identify independent factors associated with subscale scores.
Results: From a total of 261 patients screened, 71 were eligible for study inclusion. Compared with the sparing group (33 patients), the dividing group (38 patients) had similar postoperative DASH scores and self-assessments but better subscale scores (9.50 ± 2.76 vs 11.94 ± 2.87, p = 0.0005). Postoperative MRI on hyperabduction showed that the brachial plexus became surrounded by normal fat tissue in the costoclavicular space in the diving group but still had signs of impingement from the untreated subclavius muscle in the sparing group. This observation agreed with a better functional recovery in terms of overhead activities in the dividing group, which was reflected by better subscale scores. Multivariate analyses indicated that the type of treatment and symptom duration prior to surgery influenced the subscale scores independently.
Conclusions: This study revealed that an untreated radiological nerve-compressing subclavius muscle could lead to a relatively lower degree of recovery in the ability to perform overhead activities for NTOS patients postoperatively, suggesting that such subclavius muscles may participate in positional brachial plexus compression during movements narrowing the costoclavicular space. Dividing the muscles could decompress the costoclavicular space more effectively and may lead to better functional recovery.
Keywords: functional outcome; magnetic resonance imaging; neurogenic thoracic outlet syndrome; peripheral nerve; radiological signs of nerve impingement; subclavius muscle.