The role of index humeral stem length and convertibility in outcomes after revision to reverse shoulder arthroplasty

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Abstract
Background: The development of modular platform humeral stems has introduced multiple variables to consider during revision of a failed anatomic shoulder arthroplasty to reverse (RTSA). While studies have demonstrated that retention of a well-fixed and well-positioned stem is associated with less blood loss, faster surgical time, and lower complication rates, stratification based on stem length has been limited. This study investigates clinical outcomes after revision RTSA in relation to humeral component conversion versus explantation. Methods: This was a retrospective case series of consecutive patients from 2014 to 2021 who underwent revision from anatomic shoulder arthroplasty or hemiarthroplasty to RTSA. Variables included indication for revision, estimated blood loss (EBL), changes in hemoglobin/hematocrit, operative time, need for osteotomy or cortical window, intraoperative/postoperative complications, and reoperations. Outcomes were also compiled for forward elevation, external rotation, visual analog scale pain, American Shoulder and Elbow Surgeons standardized assessment, and Single Assessment Numeric Evaluation scores. Patient-reported outcome measures were collected at 1 year and at >2 years. The cohort was divided into three categories, (1) stem retention, (2) short-stem explant, and (3) standard stem explant. Results: Final analysis included 72 patients. Time from index to revision surgery was significantly longer in the standard explant group (2.2 vs. 2.5 vs. 4.5 years, p = 0.02). A cortical window or osteotomy was performed in 11 of 31 (35.5%) standard length explants and none of the conversions or short stems (p = 0.001). EBL was higher among standard explants (150 vs. 150 vs. 200 mL, p = 0.003). There was a similar trend in operative time (125 vs. 108 vs. 154 min, p = 0.02). Postoperative patient-reported outcome measures were not significantly different among groups. There was, however, a significant decrease in forward elevation (134 vs. 126 vs. 112 degrees, p = 0.03) and external rotation (31 vs. 35 vs. 24 degrees, p = 0.02) among the standard explants. There were no differences among groups with regard to rates of intraoperative or postoperative complications or reoperations. Conclusion: In this review of patients undergoing revision RTSA, there was a clinically relevant increase in blood loss, surgical time, and a decrease in ultimate range of motion when explanting standard length stems as compared to short-stem or convertible implants. While there are continued trends towards short-stem and canal-sparing implants for anatomic shoulder arthroplasty, the relative benefit of convertibility in the revision setting warrants continued evaluation. Level of Evidence: III – retrospective cohort design.

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