Identifying surgeon-controlled factors associated with acromial fractures after reverse total shoulder arthroplasty:...

Patient characteristics are the major determinants of acromial stress fracture risk after reverse total shoulder arthroplasty; the contribution of surgeon-controlled arthroplasty geometry is less certain. This study presents a method by which an individual surgeon can analyze their own fracture cases by comparing the geometry of each case with matched non-fracture controls from the same practice.

Four cases of acromial stress fracture after primary reverse total shoulder arthroplasty by an individual surgeon were analyzed. Two were Levy Type IIB fractures that displaced despite immobilization; two were Levy Type I fractures that healed without displacement. Each case was matched by age, sex, follow-up and surgical date to four controls. Fourteen geometric measurements were obtained on standardized Grashey radiographs.

In both displaced Levy Type IIB fractures, the distance from the glenosphere centre of rotation to the acromion (AC) was equal to or less than the distance from the centre of rotation to the greater tuberosity (CT), indicating potential tuberosity-acromion impingement with arm elevation. This relationship was not seen in the controls or in the Levy Type I fractures. Humeral distalization was associated with the Levy Type I, but not the Levy Type IIB, fractures.

This method offers a practical framework by which an individual surgeon can analyze their own acromial fracture cases to identify modifiable surgeon-controlled factors. In this surgeon's practice, selecting and placing implants to avoid AC ≤ CT may reduce the risk of displacing Levy Type IIB acromial fractures.