Periprosthetic Humeral Fractures After Short-Stem Reverse Shoulder Arthroplasty: Treatment Patterns, Classification, and Clinical Outcomes

<b>Background/Objectives:</b> Periprosthetic humeral fractures (PF) after reverse total shoulder arthroplasty (RSA) are expected to increase. This study investigated PF after RSA with short stems and reported outcomes. <b>Methods:</b> A total of 165 patients underwent short-stem RSAs between 2014 and 2023. Among them, patients who developed postoperative PFs were identified and classified by fracture location and stem loosening. Operative data, complications, and bone union time were analyzed. Clinical outcomes before injury and at final follow-up were evaluated. <b>Results:</b> PF occurred in 5/165 patients (3.0%). Based on our classification, four had type B1 fractures and one had a type B3 fracture. All underwent revision RSA (Re-RSA) with conversion to long-stem implants. Bone union was achieved in four patients, while one patient experienced infection without union. Among the four patients without complications, mean shoulder flexion declined from 138° pre-injury to 103°, abduction from 118° to 95°, external rotation from 37° to 31°, the American Shoulder and Elbow Surgeons (ASES) score from 82.0 to 68.7, Constant Score from 67 to 43, while the Visual Analog Scale (VAS) pain score increased from 1.7 to 2.6. <b>Conclusions:</b> All five cases of PF following short-stem RSA were stem-level (type B) fractures. All patients underwent Re-RSA using long-stem conversion. Four patients had bone union. Clinical outcomes at one year postoperatively had deteriorated mildly compared to pre-fracture. However, this change was not statistically significant. One patient had a postoperative infection, and bone union was not observed. This study indicates the need for caution regarding postoperative infections after RSA.