Purpose: Scapular stress fracture (sSF) is a difficult complication to treat after reverse total shoulder arthroplasty (RSA). The aim of this study was to identify the prevalence and possible risk factors in a large population.
Methods: A total of 2165 RSAs that were implanted between January 2006 and October 2017 in five hospitals were evaluated. Within this cohort, sSF was radiologically confirmed. Age, gender, surgical indication and hospital of treatment were determined for the entire cohort. A matched 3:1 case-control study was then performed to investigate several clinical and surgical variables.
Results: sSF occurred in 3.1% (63 patients), with a median time interval of five months post-operative [IQR = 9, range: (1-79)]. Within the entire cohort, females (OR = 2.99) and rotator cuff arthropathy (RCA) (OR = 2.79) were more prone to this complication. Age had little influence (OR = 1.03). After exclusion, fifty-five eligible cases were matched to 165 controls based on hospital, gender, age and surgical indication. After univariable analysis, significance was obtained for osteopenia (P = 0.037), osteoporosis (P = 0.032), surgical approach (P = 0.002) and peri-operative acromioclavicular (AC) joint surgery (P = 0.035). Multivariate analysis demonstrated that osteopenia (OR = 3.94), osteoporosis (OR = 2.85) and a deltopectoral approach (OR = 3.70) were independent risk factors.
Conclusion: According to our findings, older women with poor bone quality and a history of RCA suffered more frequently from sSF. Anterolateral approach during surgery was a surgical protective factor, possibly due to the mobilization of the acromioclavicular joint. Although this study indicates who is at risk for sSF, further investigation for prevention of sSF in these patients is necessary.
Keywords: Acromion; Complication; Reverse shoulder arthroplasty; Risk factors; Scapula; Stress fracture.