Anatomic Shoulder Replacement has Superior Functional Outcomes with Equivalent Survivorship Compared with Reverse Shoulder Replacement in Patients with Inflammatory Arthritis – New Zealand Registry Results

Reverse shoulder arthroplasty (rTSA) has become increasingly common for inflammatory arthritis (IA) due to concerns regarding rotator cuff failure and glenoid loosening in anatomic total shoulder arthroplasty (aTSA). Comparative data between these procedures in IA, however, remain limited. This study aims to compare functional outcomes and revision-free survival between aTSA and rTSA in IA using data from the New Zealand Joint Registry (NZJR). All primary aTSA and rTSA procedures performed for IA between 2000 and 2022 were identified in the NZJR. Demographic data, revision events, causes of revision, and Oxford Shoulder Scores (OSS) were analysed. Revision rates were expressed per 100 component-years. Cox regression models estimated the hazard of revision, adjusted for age, sex, and ASA. A total of 714 arthroplasties were included (433 rTSA, 281 aTSA) with mean follow-up of 6.0 years for rTSA and 9.8 years for aTSA. aTSA patients were younger (65.7 vs 70.3 years, p<0.001) and had higher BMI (30.3 vs 28.2, p=0.018). aTSA demonstrated significantly higher OSS at all time points: 38.7 vs 36.4 at 6 months (p=0.012), 41.9 vs 38.0 at 5 years (p=0.002), and 41.9 vs 35.4 at 10 years (p=0.021), however this did not exceed reported minimal clinically important difference. Revision rates were equivalent: 0.92 per 100 component-years for rTSA and 0.99 for aTSA (p=0.529). Ten-year revision-free survival was 92.0% for rTSA and 90.8% for aTSA. Causes of revision differed, with infection more frequent in rTSA (33.3% vs 7.4%, p=0.02), while aTSA was more often revised for glenoid loosening and cuff failure. Compared with rTSA, aTSA was associated with statistically higher functional outcomes and equivalent revision-free survival. Inflammatory arthritis is not a contraindication to aTSA with it being a viable option for appropriately selected patients, rTSA should be consider for those with rotator cuff deficiency or severe glenoid pathology.