Clinical and radiological outcomes between stemless and stemmed anatomic total shoulder arthroplasty : a minimum 6-year follow-up

Abstract Background Stemless anatomic total shoulder arthroplasty (aTSA) was developed to address complications associated with stemmed implants, such as bone loss, stress shielding, and difficulties in revision. However, long-term data comparing stemless and stemmed TSA remain limited. Therefore, this study was conducted to evaluate the mid-to-long term outcomes of stemless aTSA. Methods This multicenter retrospective study analyzed 42 patients who underwent aTSA between 2014 and 2019, including 22 with stemless implants and 20 with stemmed implants. Clinical outcomes, including Constant shoulder score (CSS) and Korean Shoulder Score (KSS), American Shoulder and Elbow Surgeons (ASES) scores, as well as radiographic parameters such as center of rotation (COR) deviation and radiolucent lines, were evaluated at a minimum follow-up of six years. Results At six-year follow-up, the survival rate was 95.5% for stemless TSA and 95% for stemmed TSA, with one revision in each group due to subscapularis failure or aseptic loosening. Both groups demonstrated significant improvements in CSS, and KSS, ASES scores, with no significant intergroup differences. Active range of motion (ROM) at six years was comparable between groups, and COR deviation and radiolucent lines did not significantly impact functional outcomes. Additionally, most of center of rotation showed superomedial deviation and lateral glenohumeral offset increased significantly after total shoulder arthroplasty. Formal grading of glenoid radiolucent lines revealed Lazarus Grade 2–4 lucencies around the Hybrid Glenoid without significant intergroup difference ( p = 0.797), and Franklin Grade 0–1 for the metal-backed Convertible Glenoid; no gross loosening (Grade 5) was observed in either group. Conclusions This study further confirms the results of previous studies on stemless shoulder arthroplasty, suggesting that in appropriately selected patients - without significant osteoporosis and with adequate metaphyseal bone stock - stemless implants can achieve a high survival rate and comparable complication rate with the traditional stemmed implants. Given the burden of humeral stem complications and advantages of the stemless aTSA, future longer-term follow-ups with larger samples are warranted.