Impact of humeral component retroversion on clinical outcomes of reverse total shoulder arthroplasty with humeral lateralization

Abstract

BackgroundThe effect of humeral component retroversion on clinical outcomes after reverse total shoulder arthroplasty (RTSA) is unclear. Intended retroversion intraoperatively may not produce the same retroversion of the humeral component postoperatively. MethodsThis retrospective study was conducted on consecutive patients who received RTSA using a single product with humeral lateralization at a targeted 25° of humeral retroversion from 2014 to 2019 with minimum 1-year clinical follow-up and postoperative computed tomography (CT). Forty-five patients were enrolled, and humeral component retroversion was measured three-dimensionally. Correlation and regression analyses were conducted between humeral retroversion and postoperative isometric strength and range of motion in forward flexion (FF), external rotation (ER), and internal rotation (IR). Group comparison between a ≤25° group and a >25° group was conducted as sub-analysis to verify possible confounders. ResultsThe actual humeral retroversion was 21.7 ± 11.9°, and it was significantly correlated with postoperative FF [Pearson's correlation coefficient (PCC) = 0.464, P= .003], ER (PCC = 0.481, P = .002), and IR (PCC = 0.471, P = .002) strengths. Multivariable regression analysis showed that humeral retroversion was significantly associated with postoperative FF (Exp(B) = 0.492, P = .003), ER (Exp(B) = 0.336, P = .002), and IR (Exp(B) = 0.578, P = .002) strengths. Two groups in sub-analysis showed no significant difference in pre- or intraoperative variables other than humeral component retroversion. Some functional outcome scores including the Constant score, American Shoulder and Elbow Surgeons score, and activity scales were significantly higher in the >25° group. ConclusionDiscrepancies between intraoperatively targeted humeral retroversion angle and actual postoperative angle after RTSA should be considered by operators and researchers. Increased humeral component retroversion than recommendation can yield acceptable outcomes and might be associated with higher postoperative strength, and possibly with better functional outcome after RTSA with humeral lateralization. Level of evidenceLevel III; Retrospective Comparative Study