title: Scapular fractures after reverse shoulder arthroplasty: evaluation of risk factors and the reliability of a proposed classification.
abstract: BACKGROUND
  The aims were to determine the sensitivity of plain radiographs to detect scapular fractures after reverse shoulder arthroplasty (RSA), to test the reliability of a proposed classification, and to evaluate risk factors.
  
  
  METHODS
  We matched 53 patients with scapular fractures after RSA to 212 control patients. Clinical risk factors were assessed by correlating comorbidities. Independent observers reviewed radiographs to assess fracture detection accuracy and test the reliability of a proposed classification. Radiographic risks were evaluated by measuring acromial thickness, acromial tilt, glenoid-to-tuberosity distance, and acromion-to-tuberosity (AT) distance.
  
  
  RESULTS
  Independent reviewers accurately diagnosed 78.8% of fractures and 97.4% of controls with good inter-rater reliability (κ = 0.782) and excellent intrarater reliability (κ = 0.862). Inter-rater reliability of the classification was moderate (κ = 0.422). Osteoporosis significantly increased the risk of fracture (odds ratio, 1.97; 95% confidence interval, 1.00-3.91); however, no difference was found for other comorbidities or between preoperative and postoperative radiographic parameters. A significant difference occurred between groups from the postoperative radiographs to the most recent radiographs for AT distance (0.4 ± 5.5 mm for control group and 8.3 ± 7.6 mm for fracture group, P < .001) and acromial tilt (1.8° ± 6.3° for control group and 14° ± 15° for fracture group, P < .001). Of 16 scapular spine fractures, 14 occurred from a screw tip; however, screw orientation and length were not different between groups.
  
  
  CONCLUSIONS
  Osteoporosis is a significant risk factor for scapular fractures after RSA. The current classification has only moderate reliability, suggesting that an alternative classification method is needed. Decreasing AT distance and increasing acromial tilt on consecutive radiographs may improve fracture detection. Advanced imaging may be needed to confirm the diagnosis. Whereas most scapular spine fractures occurred from a screw, the surgical technique did not increase the relative risk.
authors: Florida Orthopaedic Institute, Tampa, FL, USA.
authors: Randall J
authors: RJ
authors: Otto
authors: Nazeem A
authors: NA
authors: Virani
authors: Jonathan C
authors: JC
authors: Levy
authors: Phillip T
authors: PT
authors: Nigro
authors: Derek J
authors: DJ
authors: Cuff
authors: Mark A
authors: MA
authors: Frankle
mesh_terms: D000174:Acromion / Q000000981:diagnostic imaging / Q000293:injuries; D000368:Aged; D000369:Aged, 80 and over; D019643:Arthroplasty, Replacement / Q000009:adverse effects* / Q000379:methods; D005260:Female; D050723:Fractures, Bone / Q000145:classification* / Q000000981:diagnostic imaging* / Q000209:etiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011859:Radiography; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012307:Risk Factors; D012540:Scapula / Q000000981:diagnostic imaging* / Q000293:injuries; D012680:Sensitivity and Specificity; D012785:Shoulder Joint / Q000000981:diagnostic imaging / Q000601:surgery*
keywords: Acromial fractures; Case-Control Design; Crosby classification; Diagnostic Study; Level IV; interobserver reliability; intraobserver reliability; reverse shoulder arthroplasty; risk factors