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Background: The purpose of this study was to compare medium-term results of inlay and onlay humeral components in reverse shoulder arthroplasty (RSA). Specifically, we report differences in revision rate and functional outcomes between the 2 designs., Methods: The 3 most used inlay (in-RSA) and onlay (on-RSA) implants by volume from the New Zealand Joint Registry were included in the study. In-RSA was defined as having a humeral tray that recessed within the metaphyseal bone, whereas on-RSA was defined as having a humeral tray that rested on the epiphyseal osteotomy surface. The primary outcome was revision up to 8 years postsurgery. Secondary outcomes included the Oxford Shoulder Score (OSS), implant survival, and revision cause for in-RSA and on-RSA as well as individual prostheses., Results: There were 6707 patients (5736 in-RSA; 971 on-RSA) included in the study. For all causes, in-RSA demonstrated a lower revision rate compared to on-RSA (revision rate/100 component years: in-RSA 0.665, 95% confidence interval [CI] 0.569-0.768; on-RSA 1.010, 95% CI 0.673-1.415). However, the mean 6-month OSS was higher for the on-RSA group (mean difference 2.20, 95% CI 1.37-3.03; P < .001). However, this was not clinically significant. At 5 years, there were no statistically or clinically significant differences between the 2 groups with respect to the OSS., Conclusion: The medium-term survival of in-RSA was higher than that of on-RSA. However, functional outcomes at 6 months were better for on-RSA compared to in-RSA. Further follow-up is required to understand the long-term survivorship and functional outcomes between these designs., (Copyright © 2023 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved.)

Background: Implant survival in total shoulder arthroplasty (TSA) is currently defined with reference to a set time period (eg, 5-year implant survival). This is a difficult concept for patients to understand, especially for younger patients who have more years of life remaining. Our study aims to calculate a patient's lifetime revision risk after primary anatomic (aTSA) and reverse (rTSA) total shoulder arthroplasty-a more meaningful projection of revision risk over a patient's remaining lifetime., Methods: The New Zealand Joint Registry (NZJR) and national death data was used to calculate the incidence of revision and mortality in all patients who underwent primary aTSA and rTSA in New Zealand between 1999 and 2021. Lifetime revision risk was calculated using previously described methods, and this risk was stratified by age (46-90 years, 5-year bins), sex, and procedure type (aTSA and rTSA)., Results: In total, there were 4346 patients in the aTSA cohort and 7384 patients in the rTSA cohort. Lifetime revision risk was highest in the youngest age group (46-50 years) at 35.8% (95% CI 34.5%-37.0%) for aTSA and 30.9% (95% CI 29.9%-32.0%) for rTSA, with risk decreasing with increasing age. Across all age groups, the lifetime revision risk was higher for aTSA compared to rTSA. By sex, females reported higher lifetime revision risk for each age group in the aTSA cohort whereas males reported higher lifetime revision risk for each group in the rTSA cohort., Conclusions: Our study demonstrates that younger patients have higher lifetime revision risk after total shoulder arthroplasty. Our results highlight the long-term revision risks associated with the trend of offering shoulder arthroplasty to younger patients. The data may be used among various health care stakeholders to inform the surgical decision-making process and plan for future health care resource use., (Copyright © 2023 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: The purpose of this study was to compare the medium-term results for anatomic total shoulder arthroplasty by humeral component stem length. We hypothesize that the newer stemless implants may have comparable results to short-stem and conventional stemmed implants., Methods: The 12 most used anatomic total shoulder arthroplasty implants on the New Zealand Joint Registry were included in the study. Implants were categorized by stem length-conventional, short, and stemless. The primary outcome was revision up to 7 years postsurgery. Secondary outcomes included revision cause, implant survival, and early functional outcomes as evaluated by the Oxford Shoulder Score. Analysis was stratified by age and surgeon volume to control for potential confounding., Results: A total of 3952 patients (conventional, 3114; short, 360; stemless, 478) were included in the study. No significant difference in revision rate per 100 component-years was found between stemless, short-stem, and conventional stemmed implants (revision rate per 100 component-years: conventional, 1.01 [95% confidence interval (CI) 0.89-1.14]; short, 0.54 [95% CI 0.25-1.03]; stemless, 0.99 [95% CI 0.51-1.74]). This finding was irrespective of patient age or surgeon volume. There were no cases of humeral loosening up to 7 years' follow-up and no cases of intraoperative humeral fracture in the stemless group. Functional outcomes at 6 months postsurgery suggested better outcomes in the stemless group compared with the conventional stem group (mean Oxford Shoulder Score: conventional, 39.4; stemless, 40.7; P value = .023)., Conclusion: The medium-term survival of stemless implants for anatomic total shoulder arthroplasty appears comparable to short-stem and conventional stemmed implants. Further follow-up is required to understand the long-term survivorship and functional outcomes between these groups., (Copyright © 2022 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)