Outcomes after revision of anatomic total shoulder arthroplasty to reverse shoulder arthroplasty and comparison between cemented or metal-backed glenoid in platform systems.

Abstract

Background The objective of this study is to report the outcomes after revision of anatomical total shoulder arthroplasty (ATSA) to reverse shoulder arthroplasty (RSA) and to compare between groups depending on the primary ATSA glenoid implant type, cemented polyethylene (PE) versus a convertible metal-backed (MB). The hypothesis was that the outcomes would differ between patients treated with ATSA with PE and MB implants in favor of the platform system. Methods Group A included ten cases of convertible MB glenoid that were revised due to instability (six cases), posterosuperior rotator cuff tear (RCT) (two cases), subscapularis rupture (one case) and polyethylene dissociation (one case); Group B included ten cases of cemented PE that were revised due to glenoid loosening (six cases), RCT (two cases), dislocation (one case), and painful stiffness (one case). Active motion, Constant score, subjective shoulder value, Simple Shoulder Test and pain (VAS) were evaluated at minimum follow-up of two years. Student’s t test and Mann-Whitney tests were used for statistical analysis. Level of significance α=0.05. Results For the entire study cohort, postoperative results were improved compared to the preoperative state (p<0.05) at mean follow-up 60 months (24-188). Group A demonstrated improved postoperative pain levels compared to Group B (VAS 0.1 vs 1.9; p=0.004). No other differences were detected between the two groups (p>0.05). One complication occurred in Group B where one patient was re-operated for RSA instability with a good final functional outcome. Conclusions ATSA to RSA conversion resulted in improved functional outcomes. Post RSA motion and functional outcomes did not differ between the two groups with exception of reduced pain levels for patients treated with a convertible MB ATSA system. Level of evidence: III; retrospective comparative study; treatment study