Cement-within-cement technique in revision reverse shoulder arthroplasty: A systematic review of biomechanical data, and clinical outcomes

Background: The purpose of this research was to systematically review and summarize the existent literature on the use of the cement-within-cement technique for revision reverse shoulder arthroplasty (RSA). Methods: We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The PubMed/Medline, Scopus, and EMBASE databases were searched for relevant studies. We included clinical studies in which patients underwent RSA revision using the cement-within-cement method for the humeral component, and studies that evaluated the biomechanical performance or described the surgical technique. The methodological risk of bias was assessed using the methodological index for non-randomized studies scale. Results: The search yielded 516 records, of which two clinical and one biomechanical study met the inclusion criteria, involving 133 patients and 20 synthetic humeri. The intraoperative complication rate was 18%, all of which involved humeral fractures. The postoperative complication rate was 18% among 35 patients. The combined re-revision rate was 9%, with a reported humeral component survival rate of 100% at 2 years and 96% at 5 years. Periprosthetic fractures (1.5%) and humeral stem loosening (1.5%) led to re-revision surgeries in all cases. All studies reported improved patient-reported outcomes and range of motion. The biomechanical study demonstrated increased rotational stability in models that used larger humeral stems. Conclusions: The cement-within-cement method is a viable option for revision RSA, showing positive outcomes in terms of stability, range of motion, and clinical functional scores. The complication rate is similar to that of other revision strategies; however, the prevalence of intraoperative humeral fractures may be higher. Nevertheless, future studies with larger sample sizes and longer follow-up periods are needed to refine patient selection, determine the efficacy of long-term use, and identify factors that may influence outcomes after the cement-within-cement revision technique. Further research on an optimized stem fixation strategy is needed to improve outcomes and reduce avoidable complications. Level of evidence: Level IV, Systematic reviews.