Risk of humeral implant subsidence in Easytech stemless rTSA is mainly associated with surgical technique and patient activity.

Abstract

Stemless reverse shoulder arthroplasty (rTSA) has been used in Europe for over 15 years with promising clinical outcomes and low complication rates. However, concerns persist regarding humeral component subsidence due to the metaphyseal fixation. Limited data exist on this potential complication. The primary aim of this study was to identify factors associated with humeral implant subsidence in stemless rTSA. The secondary objective was to evaluate the functional impact of such subsidence. This retrospective, single-center study included a consecutive series of patients who underwent primary stemless rTSA for indications including primary osteoarthritis, cuff tear arthropathy, post-traumatic arthritis, or massive irreparable rotator cuff tears. All patients had a minimum 2-year follow-up with clinical (Constant Score, Simple Shoulder Value) and radiographic evaluation. Implant subsidence was assessed by comparing immediate postoperative and final follow-up X-Rays, and categorized as none, mild (<5°), or significant (>5°). Radiographs were reviewed independently by two observers. Associations between subsidence and demographic, surgical, and implant positioning factors were analyzed, along with clinical outcomes and complication rates. Seventy-two shoulders were analyzed (48.6% male; mean age 66.9 ±8.7 years; mean follow-up 43.3 ±9.0 months). Mild and significant humeral subsidence were observed in 12.5% (9/72) of cases each. In 94% (17/18), subsidence occurred in varus. Univariate analysis identified several factors significantly associated with humeral component subsidence: male gender (p=0.006), greater patient height (p=0.007), lower preoperative external rotation (p=0.036), a humeral cut angle <140° (p=0.009), non-parallel implant alignment relative to the humeral cut (p=0.014), and superior positioning of the glenosphere (p<0.001). Subsidence was associated with greater strength (p=0.017), higher SSV (p=0.025), and higher activity scores (p=0.022), at last follow-up. There was no significant association between subsidence and overall Constant Score (p=0.097), patient satisfaction (p=0.327), implant loosening (p=0.26), occurrence of complications (p=0.17), or revision surgery (p=0.45). At a mean follow-up of 43 months, humeral implant subsidence was observed in 25% of cases, predominantly in varus. Subsidence was linked to implant positioning and patient activity level but was not associated with poorer clinical outcomes. These findings support the importance of optimal surgical technique in stemless rTSA. Level III; Retrospective Cohort Comparison; Prognosis Study.