Conversion of stemmed hemi- or total to reverse total shoulder arthroplasty: advantages of a modular stem design.

BACKGROUND: If revision of a failed anatomic hemiarthroplasty or total shoulder arthroplasty is uncertain to preserve or restore satisfactory rotator cuff function, conversion to a reverse total shoulder arthroplasty has become the preferred treatment, at least for elderly patients. However, revision of a well-fixed humeral stem has the potential risk of loss of humeral bone stock, nerve injury, periprosthetic fracture, and malunion or nonunion of a humeral osteotomy with later humeral component loosening. QUESTIONS/PURPOSES: The purposes of this study were to determine whether preservation of a modular stem is associated with (1) less blood loss and operative time; (2) fewer perioperative and postoperative complications, including reoperations and revisions; and/or (3) improved Constant and Murley scores and subjective shoulder values for conversion to a reverse total shoulder arthroplasty compared with stem revision.
METHODS: Between 2005 and 2011, 48 hemiarthroplasties and eight total shoulder arthroplasties (total=56 shoulders; 54 patients) were converted to an Anatomical™ reverse total shoulder arthroplasty system without (n=13) or with (n=43) stem exchange. Complications and revisions for all patients were tallied through review of medical and surgical records. The outcomes scores included the Constant and Murley score and the subjective shoulder value. Complete clinical followup was available on 80% of shoulders (43 patients; 45 of 56 procedures, 32 with and 13 without stem exchange) at a minimum of 12 months (mean, 37 months; range, 12-83 months).
RESULTS: Blood loss averaged 485 mL (range, 300-700 mL; SD, 151 mL) and surgical time averaged 118 minutes (range, 90-160 minutes; SD, 21 minutes) without stem exchange and 831 mL (range, 350-2000 mL; SD, 400 mL) and 176 minutes (range, 120-300 minutes; SD, 42 minutes) with stem exchange (p=0.001). Intraoperative complications (8% versus 30%; odds ratio [OR], 5.2) and reinterventions (8% versus 14%; OR, 1.9) were substantially fewer in patients without stem exchange. The complication rate leading to dropout from the study was substantial in the stem revision group (six patients; 43 shoulders [14%]), but there were no complication-related dropouts in the stem-retaining group. If, however, such complications could be avoided, with the numbers available we detected no difference in the functional outcome between the two groups.
CONCLUSIONS: Patients undergoing revision of stemmed hemiarthroplasty or total to reverse total shoulder arthroplasty without stem exchange had less intraoperative blood loss and operative time, fewer intraoperative complications, and fewer revisions than did patients whose index revision procedures included a full stem exchange. Therefore modularity of a shoulder arthroplasty system has substantial advantages if conversion to reverse total shoulder arthroplasty becomes necessary and should be considered as prerequisite for stemmed shoulder arthroplasty systems. LEVEL OF EVIDENCE: Level III, therapeutic study.