title: A semi-automated quantitative CT method for measuring rotator cuff muscle degeneration in shoulders with primary osteoarthritis.
abstract: Rotator cuff muscle degeneration is an important parameter to consider when planning shoulder arthroplasty.
  
  
  
  We hypothesized that rotator cuff muscle degeneration is correlated with scapulohumeral subluxation in patients planned for anatomical total shoulder arthroplasty (TSA).
  
  
  
  We developed a semi-automated quantitative CT method to measure rotator cuff muscle degeneration, and retrospectively analyzed 107 preoperative shoulder CT scans of patients with primary osteoarthritis. On a standardized sagittal-oblique CT slice perpendicular to the scapular axis, two observers measured the cross-sectional areas of residual rotator cuff muscle tissues, normalized by the estimated area of healthy muscles. Muscle degeneration was quantified in a semi-automated manner, and divided into atrophy and fatty infiltration. Scapulohumeral subluxation was determined in 3D as the distance between the humeral head center and the glenoid surface center, projected on the same CT slice, and normalized by the humeral head radius. We tested all potential correlations between muscle degeneration and scapulohumeral subluxation.
  
  
  
  Muscle degeneration, primarily due to atrophy, predominated in the supraspinatus; it varied from 0.8% to 88.8%. Scapulohumeral subluxation varied from 2.5% to 72.9%, and was mainly in a posterior and postero-superior orientation. There was a significant but weak correlation between the amount of subluxation and both supraspinatus (R=0.207, P=0.032) and infraspinatus (R=0.225, P=0.020) degeneration. Inter- and intra-observer reproducibility of muscle degeneration measurements were both excellent (ICCs range=0.955-0.987 and 0.971-0.988, respectively).
  
  
  
  This new semi-automated CT method allows to quantitatively and reproducibly measure rotator cuff muscle degeneration in shoulders with primary osteoarthritis. Muscle degeneration is weakly correlated with scapulohumeral subluxation in patients planned for anatomical TSA.
  
  
  
  Level IV.
  
  
  
  Diagnostic retrospective study.
authors.affiliation: Laboratory of biomechanical orthopedics, école polytechnique fédérale de Lausanne, Station 19, 1015 Lausanne, Switzerland. Electronic address: alexandre.terrier@epfl.ch.
authors.forename: A
authors.initials: A
authors.lastname: Terrier
authors.affiliation: Laboratory of biomechanical orthopedics, école polytechnique fédérale de Lausanne, Station 19, 1015 Lausanne, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Ston
authors.affiliation: Laboratory of biomechanical orthopedics, école polytechnique fédérale de Lausanne, Station 19, 1015 Lausanne, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Dewarrat
authors.affiliation: Department of diagnostic and interventional radiology, Lausanne university hospital, 46, rue du Bugnon, 1011 Lausanne, Switzerland.
authors.forename: F
authors.initials: F
authors.lastname: Becce
authors.affiliation: Service of orthopedics and traumatology, Lausanne university hospital, 46, rue du Bugnon, 1011 Lausanne, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Farron
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000072228:Arthroplasty, Replacement, Shoulder; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009133:Muscular Atrophy / Q000000981:diagnostic imaging*; D015588:Observer Variation; D010003:Osteoarthritis / Q000601:surgery; D015203:Reproducibility of Results; D012189:Retrospective Studies; D017006:Rotator Cuff / Q000000981:diagnostic imaging* / Q000473:pathology; D012783:Shoulder Dislocation / Q000000981:diagnostic imaging* / Q000209:etiology / Q000601:surgery*; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Atrophy; Degeneration; Fatty infiltration; Quantitative imaging; Rotator cuff muscles; Shoulder osteoarthritis