Introduction. The pathomolecular events behind the development of tendinopathy remain unknown. Methods. Paired biopsies from human shoulder supraspinatus (tendinopathy) and subscapularis (control) tendons were obtained from patients undergoing shoulder arthroscopy, with tendinopathy confirmed using light microscopy evaluation. Differentially expressed micro-RNA were identified using RNA sequencing analysis, with target genes for the differentially expressed micro-RNA predicted using miRbase and Targetscan. The micro-RNA were secondarily screened to identify those with predicted binding to genes known be involved in tendinopathy-collagen 1A1/1A2/3A1, BMP-2/7, and IL-6-with additional cross referencing of gene/micro-RNA predicted binding performed with NetworkAnalyst. Results. Supraspinatus samples demonstrated significantly greater histologic characteristics of tendinopathy versus subscapularis samples. A total of 21 micro-RNA were differentially expressed between normal and diseased tendon, with six (let-7g, miR-7a, miR-22, miR-26a/b, and miR-29a) having predicted binding to genes known to be involved in tendinopathy. Conclusion. The identiied micro-RNAs may be involved in the development of tendon disease and represent potential therapeutic targets. Level of evidence: Basic science investigation.

Background: The teres minor is a critical component of the rotator cuff and serves as one of the few external rotators of the humerus. Information is lacking regarding the effect of teres minor atrophy in isolation and in the setting of concomitant full-thickness rotator cuff tears on outcomes in patients undergoing rotator cuff surgery. Purpose: To investigate the effect of preoperative teres minor fatty infiltration on postoperative clinical outcomes in patients with and without full-thickness rotator cuff pathology. Study Design: Cohort study; Level of evidence, 3. Methods: A retrospective review of patients undergoing primary arthroscopic shoulder surgery between 2014 and 2016 was performed. Preoperative magnetic resonance imaging was used to determine fatty infiltration for each rotator cuff muscle using the modified Goutallier classification. American Shoulder and Elbow Surgeons (ASES) as well as the shortened version of Disabilities of the Arm, Shoulder and Hand (QuickDASH) scores were obtained preoperatively and during follow-up. Exclusion criteria included prior surgery on the ipsilateral shoulder or a diagnosis of inflammatory arthropathy. For analysis, patients were dichotomized to grade 0 or grade 1-4 atrophy of the teres minor as well as to full-thickness or partial-thickness rotator cuff pathology. Results: A total of 36 of 47 (76.6%) patients (mean age, 63 years; range, 45-76 years) were available for postoperative follow-up at a mean of 40 months (range, 30-48 months). Postoperative ASES score was significantly higher and QuickDASH score was significantly lower among all patients in the grade 0 group compared with the grade 1-4 group. Postoperative ASES and QuickDASH scores were not significantly different in patients with partial-thickness rotator cuff tears at any time point. However, the postoperative ASES score was significantly higher and QuickDASH score was significantly lower in the grade 0 versus grade 1-4 group for patients with full-thickness rotator cuff pathology. Conclusion: Preoperative teres minor atrophy in patients undergoing surgery for rotator cuff pathology may impair postoperative clinical outcomes, especially in patients with full-thickness tears.