title: Posterior Displacement of Supraspinatus Central Tendon Observed on Magnetic Resonance Imaging: A Useful Preoperative Indicator of Rotator Cuff Tear Characteristics.
abstract: OBJECTIVE
  To characterize the orientation of the normal supraspinatus central tendon and describe the displacement patterns of the central tendon in rotator cuff tears using a magnetic resonance imaging (MRI)-based method.
  
  
  METHODS
  We performed a retrospective MRI and chart review of 183 patients with a rotator cuff tear (cuff tear group), 52 with a labral tear but no rotator cuff tear (labral tear group), and 74 with a normal shoulder (normal group). The orientation of the supraspinatus central tendon relative to the bicipital groove was evaluated based on axial MRI and was numerically represented by the shortest distance from the lateral extension line of the central tendon to the bicipital groove. Tear size, fatty degeneration, and involvement of the anterior supraspinatus were evaluated to identify the factors associated with orientation changes.
  
  
  RESULTS
  The mean distance from the bicipital groove to the central tendon line was 0.7 mm and 1.3 mm in the normal group and labral tear group, respectively. Full-thickness cuff tears involving the anterior supraspinatus showed a significantly greater distance (17.7 mm) than those sparing the anterior supraspinatus (4.9 mm, P = .001). Fatty degeneration of the supraspinatus was significantly correlated with the distance (P = .006). Disruption of the anterior supraspinatus and fatty degeneration of the supraspinatus were independent predictors of posterior displacement.
  
  
  CONCLUSIONS
  The supraspinatus central tendon has a constant orientation toward the bicipital groove in normal shoulders, and the central tendon is frequently displaced posteriorly in full-thickness rotator cuff tears involving the anterior leading edge of the supraspinatus. The degree of posterior displacement is proportional to tear size and severity of fatty degeneration of the supraspinatus muscle. A simple and quick assessment of the central tendon orientation on preoperative MRI can be a useful indicator of tear characteristics, potentially providing insight into the intraoperative repair strategy.
  
  
  METHODS
  Level IV, diagnostic case-control study.
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State Hershey College of Medicine, Hershey, Pennsylvania, U.S.A.
authors.forename: Gary F
authors.initials: GF
authors.lastname: Updegrove
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State Hershey College of Medicine, Hershey, Pennsylvania, U.S.A.
authors.forename: April D
authors.initials: AD
authors.lastname: Armstrong
authors.affiliation: Department of Radiology, Penn State Hershey College of Medicine, Hershey, Pennsylvania, U.S.A.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Mosher
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State Hershey College of Medicine, Hershey, Pennsylvania, U.S.A.. Electronic address: hkim2@hmc.psu.edu.
authors.forename: H Mike
authors.initials: HM
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care; D012189:Retrospective Studies; D017006:Rotator Cuff / Q000473:pathology* / Q000601:surgery; D000070636:Rotator Cuff Injuries; D013708:Tendon Injuries / Q000175:diagnosis*; D055815:Young Adult