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

PURPOSE: 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).

METHODS

Group A included ten cases of MB glenoid and Group B included ten cases of cemented PE that were revised to RSA. Reasons for revision included prosthesis instability, n = 6; rupture or non-functional posterosuperior rotator cuff (PS RC), n = 2; mechanical dissociation of the PE insert, n = 1; subscapularis (SSC) rupture, n = 1 for group A, and glenoid loosening, n = 6; PS RC rupture, n = 2; dislocation, n = 1 (bad quality SSC); painful stiffness, n = 1 for group B. Active motion, Constant-Murley 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 was set at α = 0.05.

RESULTS

Incidence of revision was 20% for group A versus 6.3% for group B and time to revision mean 28.3 months after primary ATSA for group A vs. 72.7 months for group B. 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 compared to Group B (VAS 0.1vs1.9; p=0.004). No other differences were detected between the two groups(p>0.05).

CONCLUSIONS

There was a higher incidence and earlier occurrence of MB glenoid implants revision compared to PE cemented glenoid implants. ATSA to RSA conversion resulted in improved functional outcomes. Post RSA motion and functional outcomes did not differ between convertible MB ATSA or cemented PE TSA implants with exception of reduced pain levels for patients treated with a convertible MB ATSA system.

LEVEL OF EVIDENCE III: Retrospective comparative study treatment study.