Full-thickness supraspinatus tears are associated with more synovial inflammation and tissue degeneration than partial-thickness tears
Shindle MK, Chen CC, Robertson C, DiTullio AE, Paulus MC, Clinton CM, Cordasco FA, Rodeo SA, Warren RF. J Shoulder Elbow Surg. 2011 Sep;20(6):917-27. Epub 2011 May 25.
https://www.ncbi.nlm.nih.gov/pubmed/21612944
Rotator cuff disease is a common cause of shoulder pain and dysfunction. A range of pathology exists, with the disease rapidly advancing in some and progressing slowly in others. Unfortunately, treatment for this disease, rotator cuff repair, is plagued with high failure rates, depending on tear severity. Specifically, partial thickness (PTh) tears have been associated with better clinical outcomes than full thickness (FTh) tears; however, the mechanism for this discrepancy remains unclear. The altered gene expression present during synovial inflammation has been implicated as a potential intrinsic factor but has not been proven. Therefore, 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. Forty patients with isolated PTh or FTh (18 to 75 years of age, symptomatic despite 6 months of conservative treatment, no NSAIDs within 3 days) supraspinatus tears underwent a biopsy of four locations: torn supraspinatus edge (most diseased portion), subacromial bursa, synovium (area of rotator interval), and intact subscapularis tendon. These tissues were extracted for histomorphologic analysis (to determine collagen organization and the distribution of cells and vasculature) and quantitative real-time PCR (to determine mRNA expression of pro-inflammatory, remodeling, and angiogenic factors). Results showed an increase in pro-inflammatory cytokines (IL-1beta, IL-6, TNF-α, COX-2, iNOS) and angiogenic (VEGF) factors in the synovium and an increase in tissue remodeling factors (MMP-13, MMP-9) in the torn supraspinatus of FTh tears. Additionally, increased tendon degeneration was present in the adjacent intact subscapularis tendon and no changes were observed in the bursal tissue.
This study demonstrates that tear severity is closely related to chronic synovial inflammation and tissue remodeling in the torn supraspinatus tendon. The increased tendon degeneration observed in the adjacent subscapularis tendon (considered to be normal) is noteworthy and the authors implicate synovial inflammation as the causative factor. However, other mechanisms should be considered including alterations in joint kinematics in the FTh group. FTh tears may disrupt the balance of forces at the shoulder, resulting in superior migration of the humeral head and subsequently abnormal joint loading. In addition, alterations in synovial gene expression with FTh tears may help explain discrepancies in shoulder pain in patients with full thickness rotator cuff tears. Specifically, the overexpression of COX-2 (enzyme responsible for production of a prostaglandin, a pain mediator) suggests a potentially more painful condition in the FTh group (inhibition of COX-2 by NSAIDs has been shown to provide pain relief). Unfortunately, the broad inclusion/exclusion criteria (including patients from a wide range of ages (18 to 75 years) and no distinction between bursal or articular sided tears) for this study do not allow us to make definitive recommendations from the results. Additionally, the causative factor (inflammation +/or altered loading) for degenerative changes in the subscapularis in the presence of full-thickness isolated supraspinatus tears has not been fully elucidated. However, it is a good starting point in understanding the mechanisms by which rotator cuff degeneration occurs. A better understanding of the role of joint inflammation in rotator cuff disease is important because clinicians can prescribe effective treatments in order to limit the progression of the tear and improve clinical outcomes. Depending on the severity of the tear, would the results of this study alter how you treat patients? What other factors should be considering before definitive recommendations could be made?
Written by: Katie Reuther
Reviewed by: Stephen Thomas
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Shindle MK, Chen CC, Robertson C, DiTullio AE, Paulus MC, Clinton CM, Cordasco FA, Rodeo SA, & Warren RF (2011). Full-thickness supraspinatus tears are associated with more synovial inflammation and tissue degeneration than partial-thickness tears. Journal of Shoulder and Elbow Surgery, 20 (6), 917-27 PMID: 21612944
