title: Subscapularis release in shoulder replacement determines structural muscular changes.
abstract: BACKGROUND
  Osteotomy of the lesser tuberosity in shoulder arthroplasty allows bony healing of the subscapularis tendon but does not prevent fatty degeneration in its muscle. Occurrence or increase in fatty degeneration may depend on the surgical technique.
  
  
  OBJECTIVE
  We (1) assessed fatty degeneration in the subscapularis muscle and its cross-sectional area after a C-block osteotomy of the lesser tuberosity with minimal mobilization of the subscapularis muscle, and (2) determined whether this technique had any adverse effect on function, fatty degeneration, and cross-sectional area of the subscapularis muscle.
  
  
  METHODS
  We retrospectively examined 36 patients with shoulder replacements who had C-block osteotomies. Constant-Murley scores and clinical signs of subscapularis insufficiency were recorded. We radiographically assessed prosthetic placement. On CT scans, lesser tuberosity healing, fatty degeneration, and cross-sectional area of the subscapularis muscle were determined. The minimum followup was 13 months (mean, 18 months; range, 13-33 months).
  
  
  RESULTS
  The mean absolute Constant-Murley score was 71.2. Two patients had weakness of the subscapularis muscle without loss of active motion. All tuberosities healed anatomically. A normal glenohumeral relationship was found in all cases. Fatty degeneration was Grade 0 in 44%, Grade 1 in 39%, Grade 2 in 14%, and Grade 3 in 3%. The subscapularis muscular cross-sectional area decreased from 16.7 cm(2) preoperatively to 14.5 cm(2) postoperatively (13%).
  
  
  CONCLUSIONS
  The C-block osteotomy with minimal dissection of the subscapularis is associated with a low incidence of fatty degeneration in the subscapularis muscle after shoulder arthroplasty although the muscular cross-sectional area of the subscapularis decreased.
  
  
  METHODS
  Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, Ghent University Hospital, Ghent, Belgium.
authors.forename: Lieven Franciscus
authors.initials: LF
authors.lastname: De Wilde
authors.forename: Tineke
authors.initials: T
authors.lastname: De Coninck
authors.forename: Francis
authors.initials: F
authors.lastname: De Neve
authors.forename: Bart M
authors.initials: BM
authors.lastname: Berghs
mesh_terms: D000203:Activities of Daily Living; D000273:Adipose Tissue / Q000473:pathology; D000368:Aged; D019643:Arthroplasty, Replacement / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D009135:Muscular Diseases / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D010003:Osteoarthritis / Q000175:diagnosis / Q000601:surgery; D010027:Osteotomy / Q000009:adverse effects*; D010149:Postoperative Pain / Q000175:diagnosis / Q000503:physiopathology; D011183:Postoperative Complications / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D012785:Shoulder Joint / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D013708:Tendon Injuries / Q000209:etiology / Q000473:pathology; D013710:Tendons / Q000473:pathology / Q000503:physiopathology / Q000601:surgery