A comparison of revision rates for stemmed and stemless primary anatomic shoulder arthroplasty with all polyethylene glenoid components. Analysis from the Australian Orthopaedic Association National Joint Replacement Registry.

BACKGROUND: We compared the rate of all cause revision of two classes of primary anatomic shoulder arthroplasty, stemmed (stTSA) and stemless (slTSA) undertaken with cemented all polyethylene glenoid components. METHODS: A large national arthroplasty registry identified two cohort groups for comparison, stTSA and l undertaken for all diagnoses between 1st January 2011 and 31st December 2021. A sub-analysis from 1 January 2017 allowed capturing of additional patient demographics including ASA score, BMI and glenoid morphology. The cumulative percent revision (CPR) was determined using Kaplan-Meier estimates of survivorship and hazard ratios (HR) from Cox proportional hazard models adjusted for age and gender. RESULTS: Of the 7,995 stTSA procedures, the CPR at 9 years was 5.6% (95% confidence interval (CI) 5.0, 6.4) and for 3,156 slTSA procedures was 4.4% (95% CI 3.6, 5.5). There was no significant difference in the rate of revision between study groups (HR=0.76 (95% CI 0.51, 1.14),p=0.189, adjusted for age, gender, humeral head size, humeral fixation, bearing surface, glenoid design and mean surgeon volume). There was an increased rate of revision for stTSA and slTSA undertaken with humeral head sizes <44mm (stTSA <44mm vs 44-50mm HR=1.56(1.18, 2.08),p=0.001; slTSA <44mm vs 44-50mm HR=2.08(1.32, 3.33),p=0.001). Mean surgeon volume (MSV) as a continuous predictor was not a revision risk to stTSA vs slTSA, but categorically a low MSV (<10 stTSA + slTSA cases per annum) was associated with a higher revision rate for stTSA (10-20 cases/year vs <10 cases/year HR=0.72(0.55, 0.95),p=0.019), but was not in slTSA. Revision rates were increased for stTSA with non-XLPE polyethylene glenoids vs XPLE after 2 years (HR= 2.20(1.57, 3.08), p<0.001), but did not significantly differ for slTSA. Metal/XPLE (humeral/glenoid) bearing surface of stTSA rate of revision was not different to each combination of slTSA bearing surface. Instability/Dislocation was a revision risk for slTSA vs stTSA (HR=1.93(1.28, 2.91),p=0.001), but from 2017, neither ASA, BMI nor glenoid morphology changed the rate of revision. CONCLUSION: Revision rates of stTSA and slTSA did not significantly differ and were associated with humeral head size but not patient characteristics. Surgeon inexperience of anatomic shoulder arthroplasty and non XLPE glenoids were risk factors for stTSA revision, but not slTSA. Metal/XLPE stTSA rate of revision was not found to differ significantly from slTSA regardless of polyethylene or humeral head bearing type. Revision for instability/dislocation was more common for slTSA.