title: Effects of glenoid inclination and acromion index on humeral head translation and glenoid articular cartilage strain.
abstract: BACKGROUND
  Previous clinical studies have reported associations between glenoid inclination (GI), the acromion index (AI), and the critical shoulder angle (CSA) on the one hand and the occurrence of glenohumeral osteoarthritis and supraspinatus tendon tears on the other hand. The objective of this work was to analyze the correlations and relative importance of these different anatomic parameters.
  
  
  METHODS
  Using a musculoskeletal shoulder model developed from magnetic resonance imaging scans of 1 healthy volunteer, we varied independently GI from 0° to 15° and AI from 0.5 to 0.8. The corresponding CSA varied from 20.9° to 44.1°. We then evaluated humeral head translation and critical strain volume in the glenoid articular cartilage at 60° of abduction in the scapular plane. These values were correlated with GI, AI, and CSA.
  
  
  RESULTS
  Humeral head translation was positively correlated with GI (R = 0.828, P < .0001), AI (R = 0.539, P < .0001), and CSA (R = 0.964, P < .0001). Glenoid articular cartilage strain was also positively correlated with GI (R = 0.489, P = .0004) but negatively with AI (R = -0.860, P < .0001) and CSA (R = -0.285, P < .0473).
  
  
  CONCLUSIONS
  The biomechanical shoulder model is consistent with clinical observations. The prediction strength of CSA is confirmed for humeral head translation and thus presumably for rotator cuff tendon tears, whereas the AI seems more appropriate to evaluate the risk of glenohumeral osteoarthritis caused by excessive articular cartilage strain. As a next step, we should corroborate these theoretical findings with clinical data.
authors: Laboratory of Biomechanical Orthopedics, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
authors: Christoph
authors: C
authors: Engelhardt
authors: Service of Orthopedics and Traumatology, Lausanne University Hospital, Lausanne, Switzerland.
authors: Alain
authors: A
authors: Farron
authors: Department of Diagnostic and Interventional Radiology, Lausanne University Hospital, Lausanne, Switzerland.
authors: Fabio
authors: F
authors: Becce
authors: Institute of Sports Sciences, Faculty of Biology Medicine, University of Lausanne, Lausanne, Switzerland; Department of Physiology, Faculty of Biology Medicine, University of Lausanne, Lausanne, Switzerland.
authors: Nicolas
authors: N
authors: Place
authors: Laboratory of Biomechanical Orthopedics, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
authors: Dominique P
authors: DP
authors: Pioletti
authors: Laboratory of Biomechanical Orthopedics, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland. Electronic address: alexandre.terrier@epfl.ch.
authors: Alexandre
authors: A
authors: Terrier
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D001837:Body Weights and Measures; D002358:Cartilage, Articular; D005260:Female; D006801:Humans; D058430:Humeral Head; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000209:etiology*; D066230:Patient-Specific Modeling; D016059:Range of Motion, Articular; D012016:Reference Values; D000070636:Rotator Cuff Injuries / Q000209:etiology*; D012540:Scapula; D012785:Shoulder Joint / Q000502:physiology*; D013314:Stress, Mechanical; D055815:Young Adult
keywords: Glenoid inclination; acromion index; critical shoulder angle; glenohumeral osteoarthritis; humeral head translation; musculoskeletal model