The pattern of idiopathic isolated teres minor atrophy with regard to its two-bundle anatomy.

OBJECTIVE: We aimed to analyze the pattern of teres minor atrophy with regard to its two-bundle anatomy and to assess its association with clinical factors. MATERIALS AND METHODS: Shoulder MRIs performed between January and December 2016 were retrospectively reviewed. Images were evaluated for the presence and pattern of isolated teres minor atrophy. Isolated teres minor atrophy was categorized into complete or partial pattern, and partial pattern was further classified according to the portion of the muscle that was predominantly affected. The medical records were reviewed to identify clinical factors associated with teres minor atrophy. RESULTS: Seventy-eight shoulders out of 1,264 (6.2%) showed isolated teres minor atrophy; complete pattern in 41.0%, and partial pattern in 59.0%. Most cases of partial pattern had predominant involvement of the medial-dorsal component (82.6%). There was no significant association between teres minor atrophy and previous trauma, shoulder instability, osteoarthritis, and previous operation. The history of shoulder instability was more frequently found in patients with isolated teres minor atrophy (6.4%), compared with the control group (2.6%), although the difference was not statistically significant. CONCLUSION: Isolated teres minor atrophy may be either complete or partial, and the partial pattern may involve either the medial-dorsal or the lateral-ventral component of the muscle. The imaging findings of partial pattern teres minor atrophy indicate that the two muscle components may have separate innervation.

Clinical outcomes after decompression of the nerve to the teres minor in patients with idiopathic isolated teres minor fatty atrophy.

BACKGROUND: The purpose of this manuscript is to describe what we believe to be the first series of patients surgically treated for idiopathic isolated teres minor atrophy and to present the results of surgical decompression of the nerve to the teres minor. METHODS: This is a retrospective cohort of 22 patients who underwent decompression of the nerve to the teres minor for isolated teres minor atrophy. Clinical data including duration of symptoms, additional diagnoses, concurrent procedures, preoperative physical examination findings, imaging data, and preoperative visual analog scale (VAS), Simple Shoulder Test (SST), and American Shoulder and Elbow Surgeons (ASES) scores were collected from the medical record. Postoperative patient-based clinical outcome measures including VAS, SST, and ASES scores were obtained during clinical examination or by telephone interview. RESULTS: Average length of follow-up was 26 months. Nine patients had concurrent procedures performed. Preoperatively, 12 of 14 (86%) had external rotation weakness in Hornblower's position. Postoperatively, pain scores decreased an average of 4 points; ASES scores increased 31.7 ± 20.2 points; SST scores increased 3.1 ± 2.3 points. No external rotation weakness was noted postoperatively in any tested patient. Two patients developed adhesive capsulitis. No other complications occurred. CONCLUSIONS: Isolated compression of the nerve to the teres minor is a rare and novel clinical entity. In properly selected cases, open release of the fascial sling enveloping the nerve branches to the teres minor can provide relief of symptoms and clinical improvement.