title: Multivariate analyses of rotator cuff pathologies in shoulder disability.
abstract: BACKGROUND
  Disability of the shoulder joint is often caused by a tear in the rotator cuff (RC) muscles. Four RC muscles coordinate shoulder movement and stability, among them the supraspinatus and infraspinatus muscle which are predominantly torn. The contribution of each RC muscle to tear pathology is not fully understood. We hypothesized that muscle atrophy and fatty infiltration, features of RC muscle degeneration, are predictive of superior humeral head translation and shoulder functional disability.
  
  
  METHODS
  Shoulder features, including RC muscle surface area and fatty infiltration, superior humeral translation and RC tear size were obtained from a consecutive series of Magnetic Resonance Imaging with arthrography (MRA). We investigated patients with superior (supraspinatus, n = 39) and posterosuperior (supraspinatus and infraspinatus, n = 30) RC tears, and patients with an intact RC (n = 52) as controls. The individual or combinatorial contribution of RC measures to superior humeral translation, as a sign of RC dysfunction, was investigated with univariate or multivariate models, respectively.
  
  
  RESULTS
  Using the univariate model the infraspinatus surface area and fatty infiltration in both the supraspinatus and infraspinatus had a significant contribution to RC dysfunction. With the multivariate model, however, the infraspinatus surface area only affected superior humeral translation (p<0.001) and discriminated between superior and posterosuperior tears. In contrast neither tear size nor fatty infiltration of the supraspinatus or infraspinatus contributed to superior humeral translation.
  
  
  CONCLUSIONS
  Our study reveals that infraspinatus atrophy has the strongest contribution to RC tear pathologies. This suggests a pivotal role for the infraspinatus in preventing shoulder disability.
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Postzone J-11-R, PO box 9600, 2300 RC Leiden, the Netherlands.
authors.forename: Jan F
authors.initials: JF
authors.lastname: Henseler
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Postzone J-11-R, PO box 9600, 2300 RC Leiden, the Netherlands; Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Yotam
authors.initials: Y
authors.lastname: Raz
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Postzone J-11-R, PO box 9600, 2300 RC Leiden, the Netherlands.
authors.forename: Jochem
authors.initials: J
authors.lastname: Nagels
authors.affiliation: Department of Medical Statistics and Bioinformatics, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Erik W
authors.initials: EW
authors.lastname: van Zwet
authors.affiliation: Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Vered
authors.initials: V
authors.lastname: Raz
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Postzone J-11-R, PO box 9600, 2300 RC Leiden, the Netherlands.
authors.forename: Rob G H H
authors.initials: RG
authors.lastname: Nelissen
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D007592:Joint Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology*; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011859:Radiography; D017006:Rotator Cuff / Q000000981:diagnostic imaging / Q000473:pathology*; D012785:Shoulder Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*