A Mechanistic Classification for Superior Labral Injuries Guides Operative Management.

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Abstract

[Indexed for MEDLINE] Conflict of interest statement: Disclosures The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: D.C.T. is a board or committee member of the American Orthopaedic Society for Sports Medicine; has received other financial or material support from Arthrex, Breg, DJOrtho, Mitek, and Smith & Nephew; has received IP royalties from DePuy, A Johnson & Johnson Company; and has received research support from Smith & Nephew. B.C.L. is a board or committee member of the American Orthopaedic Society for Sports Medicine and Arthroscopy Association of North America, has received research support from Arthrex and Wright Medical Technology, and is a paid consultant for Miach and DePuy, A Johnson & Johnson Company. T.L. is a board or committee member of the Arthroscopy Association of North America, is a paid presenter or speaker for Lima, is a paid consultant for Lima and Stryker, has received other financial or material support from Lima, and has received research support from Arthrex and Wright Medical Technology. J.R.W. is a board or committee member of the American Orthopaedic Society for Sports Medicine and Arthroscopy Association of North America, is a paid presenter or speaker for Arthrex and Vericel, is a paid consultant for Geistlich, is a member of the editorial or governing board for Ortho Info, and has stock or stock options with Viewf. C.S.K. has received consultation or advisory fees from Acumed, Restore3d, and Smith & Nephew and has stock or stock options with GE Healthcare, Johnson & Johnson, Merck, and Pfizer. J.F.D. is a board member of the AAOS, American Journal of Sports Medicine, American Orthopaedic Society for Sports Medicine, Arthroscopy Association of North America, and Society of Military Orthopaedic Surgeons. A.P.T. is a board or committee member of AAOS and the American Orthopaedic Society for Sports Medicine and has received other financial or material support from Arthrex, Breg, Mitek, Smith & Nephew, and Stryker. All other authors (E.T.H., J.T-K., S.G.L., B.S.C., Z.W.H., A.M.M., J.M.L., L.E.M., T.R.D., K.E.B.) declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. 19. J Orthop Res. 2006 Aug;24(8):1737-44. doi: 10.1002/jor.20188. Variation in external rotation moment arms among subregions of supraspinatus, infraspinatus, and teres minor muscles. Langenderfer JE(1), Patthanacharoenphon C, Carpenter JE, Hughes RE. Author information: (1)Department of Biomedical Engineering, University of Michigan, 24 Frank Lloyd Wright Dr., P.O. Box 391, Ann Arbor, Michigan 48106-0391, USA. A rotator cuff tear causes morphologic changes in rotator cuff muscles and tendons and reduced shoulder strength. The mechanisms by which these changes affect joint strength are not understood. This study's purpose was to empirically determine rotation moment arms for subregions of supraspinatus, infraspinatus, and for teres minor, and to test the hypothesis that subregions of the cuff tendons increase their effective moment arms through connections to other subregions. Tendon excursions were measured for full ranges of rotation on 10 independent glenohumeral specimens with the humerus abducted in the scapular plane at 10 and 60 degrees . Supraspinatus and infraspinatus tendons were divided into equal width subregions. Two conditions were tested: tendon divided to the musculotendinous junction, and tendon divided to the insertion on the humerus. Moment arms were determined from tendon excursion via the principle of virtual work. Moment arms for the infraspinatus (p < 0.001) and supraspinatus (p < 0.001) were significantly greater when the tendon was only divided to the musculotendinous junction versus division to the humeral head. Moment arms across subregions of infraspinatus (p < 0.001) and supraspinatus (p < 0.001) were significantly different. A difference in teres minor moment arm was not found for the two cuff tendon conditions. Moment arm differences between muscle subregions and for tendon division conditions have clinical implications. Interaction between cuff regions could explain why some subjects retain strength after a small cuff tear. This finding helps explain why a partial cuff repair may be beneficial when a complete repair is not possible. Data presented here can help differentiate between cuff tear cases that would benefit from cuff repair and cases for which cuff repair might not be as favorable. DOI: 10.1002/jor.20188 PMCID: PMC1551907