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Muscle architectural changes after massive human rotator cuff tear
Author(s) -
Gibbons Michael C.,
Sato Eugene J.,
Bachasson Damien,
Cheng Timothy,
Azimi Hassan,
Schenk Simon,
Engler Adam J.,
Singh Anshuman,
Ward Samuel R.
Publication year - 2016
Publication title -
journal of orthopaedic research®
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.23256
Subject(s) - sarcomere , muscle architecture , rotator cuff , anatomy , context (archaeology) , supraspinatus muscle , cadaveric spasm , tears , tendon , medicine , skeletal muscle , biology , surgery , myocyte , paleontology
Rotator cuff (RC) tendon tears lead to negative structural and functional changes in the associated musculature. The structural features of muscle that predict function are termed “muscle architecture.” Although the architectural features of “normal” rotator cuff muscles are known, they are poorly understood in the context of cuff pathology. The purpose of this study was to investigate the effects of tear and repair on RC muscle architecture. To this end thirty cadaveric shoulders were grouped into one of four categories based on tear magnitude: Intact, Full‐thickness tear (FTT), Massive tear (MT), or Intervention if sutures or hardware were present, and key parameters of muscle architecture were measured. We found that muscle mass and fiber length decreased proportionally with tear size, with significant differences between all groups. Conversely, sarcomere number was reduced in both FTT and MT with no significant difference between these two groups, in large part because sarcomere length was significantly reduced in MT but not FTT. The loss of muscle mass in FTT is due, in part, to subtraction of serial sarcomeres, which may help preserve sarcomere length. This indicates that function in FTT may be impaired, but there is some remaining mechanical loading to maintain “normal” sarcomere length‐tension relationships. However, the changes resulting from MT suggest more severe limitations in force‐generating capacity because sarcomere length‐tension relationships are no longer normal. The architectural deficits observed in MT muscles may indicate deeper deficiencies in muscle adaptability to length change, which could negatively impact RC function despite successful anatomical repair. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2089–2095, 2016.