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Abstract
Purpose
When repairing retracted rotator cuff tears, the tear pattern (eg, crescent-shaped, L-shaped) is best determined intraoperatively by evaluating the mobility of the tendon in multiple directions. The purpose of our study was to evaluate the location of the supraspinatus (SSP) muscle belly on magnetic resonance imaging (MRI) in patients undergoing arthroscopic repair of retracted rotator cuff tears. We hypothesized that the location of the rotator cuff muscle would move after tendon repair, and that the perioperative change in muscle position would correlate with the tear pattern.
Methods
A series of primary arthroscopic repairs for rotator cuff tears with >3 cm of medial retraction from 2015 to 2016 was reviewed. MRIs were performed preoperatively and within 10 days postoperatively. The SSP muscle was assessed on sagittal MRI and evaluated for the “occupation ratio”, “tangent sign”, and the “location index” proposed in this study. Pre and postoperative MRIs were compared, and correlated with intraoperatively determined tear patterns. Fifty shoulders without rotator cuff pathology were also assessed for the “location index” as control.
Results
Fifty-nine shoulders (mean age 65.0 years) were included, among which five reverse L-shaped tears were identified. The occupation ratio and tangent sign improved postoperatively. Preoperatively, in the majority of tears, the SSP muscle was located more posteriorly in the SSP fossa, compared to the control group, and shifted anteriorly after repair. However, in reverse L-shaped tears the SSP muscle was located more centrally in the fossa, and shifted posteriorly following repair.
Conclusion
Rotator cuff tearing and arthroscopic rotator cuff repair change the location of the SSP muscle. Although repair usually results in shifting of the muscle belly from posterior to anterior, reverse L-shaped tears demonstrated an opposite pattern. The location of the SSP muscle belly may be useful in predicting tear patterns of retracted rotator cuff tears.
Level of evidence
Level IV (case series).
Acknowledgments
The authors acknowledge research assistant Ms Yukiko Tago and Ms Wakako Morimoto for assisting with patient followup and data collection.
Author contributions
YO contributed to the conception and design of the study; data acquisition, analysis, and interpretation; and drafting and revising the work critically for important intellectual content. TM contributed to data acquisition, analysis, and interpretation; and drafting and revising the manuscript. SY contributed to data analysis and interpretation, and revising the manuscript. KKWT, NK, and AK contributed to the data interpretation, and revising the manuscript. IKYL contributed to the study design, data interpretation, and drafting and revising the manuscript. All authors contributed to data analysis, drafting and revising the article, gave final approval of the version to be published, and agree to be accountable for all aspects of the work.
Disclosure
YO has received a manuscript fee from Smith & Nephew for work outside the submitted study. The other authors report no conflicts of interest in this work.