Acromion and scapular spine fractures after reverse shoulder arthroplasty: rate of detection by computed tomography

Background

Acromion and scapular spine fractures (ASFs) after reverse total shoulder arthroplasty have been reported at a rate of 3.9 percent. Radiographs have been shown to be unreliable at identifying these fractures, with an estimated 20% false negative rate. A computed tomography (CT) scan is typically performed when initial radiographs are inconclusive and clinical suspicion for ASF remains high. However, the accuracy of identifying ASF fractures after reverse shoulder arthroplasty (RSA) with CT has not been studied. The purpose of this paper is to evaluate the ability of CT scans to detect clinically suspected ASF fractures after RSA when initial radiographs are inconclusive.

Methods

A retrospective review of our institution’s shoulder and elbow repository identified 111 patients treated with RSA from 2006 to 2022 that subsequently sustained an ASF. Upon clinical suspicion of an ASF, a 4-view radiographic series was obtained. If no fracture was clearly identified, a thin-cut CT was obtained. Additional four-view radiographic series were taken at each subsequent follow-up. Rate of detection by CT scan was defined using the number of cases with positive scans out of the number in which both a CT scan was performed, and a fracture was identified on either CT scan or other additional follow-up imaging.

Results

After inconclusive radiographs, a CT was ordered for 61 patients (55%) at a median of 1.3 weeks after the onset of signs/symptoms suspicious for ASF. Fractures were identified in 52 cases (85.2%) at a median of 1.6 weeks after the onset of sign/symptoms. The fracture was not seen on CT in 9 cases at a median of 0.9 week after the onset of sign/symptoms, representing a false negative rate of 14.8%. These fractures were later identified on radiographs at a median of 5.9 weeks following the CT scan. No statistical differences were observed in sensitivity of CT scan between fracture types. Fractures initially missed on CT scan eventually displaced and became nonunions.

Conclusion

CT scans can be helpful in identifying and characterizing ASF following RSA, with an overall rate of detection (sensitivity) of 85%. Consideration of alternative advanced imaging may be needed for patients with negative CT scans and a high index of clinical suspicion for ASF.