High Metaphyseal Filling Ratios in Humeral Stem Result in Open Reduction Internal Fixation Compared to Revision Arthroplasty for Periprosthetic Fractures

Background As shoulder arthroplasty increases, periprosthetic humeral fractures are becoming more common. However, optimal management of these fractures remains unclear. Higher stem filling ratios may contribute to stress shielding, reduced bone integrity, and fracture risk, but their influence on clinical management after fracture has not been studied. The purpose of this study is to evaluate how metaphyseal filling ratios (FRmet) and diaphyseal filling ratios (FRdia) of the implant correlate to the treatment of periprosthetic fractures. We examined whether specific filling ratios lead to performing revision arthroplasty or open reduction internal fixation (ORIF) of the humerus. Methods A retrospective case series was conducted at a single institution, including patients who underwent revision of total shoulder arthroplasty between October 2012 to August 2025. Patients were identified through electronic medical record query using Current Procedural Technology (CPT) code 23473 and Picture Archive Communication System (PACS) with search term “periprosthetic humerus fracture". Patients who had previously undergone an anatomic or reverse total shoulder arthroplasty and sustained a periprosthetic humeral fracture were included. Pre-fracture radiographs were analyzed to assess prosthesis FRmet and FRdia. Patients were divided into two groups based on treatment: revision arthroplasty and ORIF. Chi-squared and t-tests were used to assess statistical significance at p < 0.05. Results Thirty-two patients met inclusion criteria, with 17 who underwent revision arthroplasty and 15 who underwent ORIF. There were no differences in baseline demographics between the two cohorts. Patients managed with ORIF had statistically higher FRmet (0.79) compared with those treated with revision arthroplasty (0.68, p = 0.0047). FRdia and stem length did not differ statistically between cohorts. Conclusion Higher FRmet ratios were associated with an increased likelihood of undergoing ORIF compared to revision arthroplasty after periprosthetic humeral fracture. FRmet may serve as a beneficial radiographic parameter to influence surgical decision-making in the management of periprosthetic humeral fractures.