Full-thickness supraspinatus tears are associated with more synovial inflammation and tissue degeneration than partial-thickness tears

Background: The objective of this study was to determine whether the tear size of a supraspinatus tendon correlated with synovial inflammation and tendon degeneration in patients who underwent shoulder arthroscopy for rotator cuff repair. We hypothesized that increased synovial inflammation would correlate with greater tear size of the supraspinatus tendon at the time of surgery. Materials and methods: Tissue from the synovium, bursa, torn supraspinatus tendon, and subscapularis tendon was obtained from patients during shoulder arthroscopy to evaluate the messenger RNA expression of proinflammatory cytokines, tissue remodeling, and angiogenesis factors in the tendon, bursa, and synovium. Additional tissue was fixed to determine histologic changes including inflammation, vascular ingrowth, and collagen organization. Results: Increased expression of interleukin 1 beta, interleukin 6, cyclooxygenase 2, matrix metalloproteinase (MMP) 9, and vascular endothelial growth factor was found in the synovium of patients with full-thickness tears versus partial-thickness tears (P < .05). In the supraspinatus tendon, increased expression of MMP-1, MMP-9, MMP-13, and vascular endothelial growth factor was found in the full-thickness group. The upregulation of these genes in the full-thickness group was consistent with enhanced synovial inflammation, greater vascular ingrowth, and the loss of collagen organization in both supraspinatus and subscapularis tendons as determined by histology. Conclusion: Increased synovial inflammation and tissue degeneration correlate with the tear size of the supraspinatus tendon. A better understanding of the relationship between synovial inflammation and the progression of tendon degeneration can help in the design of novel and effective treatments to limit the advancement of rotator cuff disease and to improve their clinical outcomes. Level of evidence: Basic Science, Molecular and Cell Biology Study. (C) 2011 Journal of Shoulder and Elbow Surgery Board of Trustees.