(P 274) PROXIMAL HUMERAL ENDOPROSTHETIC RECONSTRUCTION: RESULTS FROM THE MUTARS ORTHOPEDIC REGISTRY EUROPE (MORE)

Objective: Tumor defects around the shoulder often need reconstruction with endoprostheses; either hemiarthroplasty (hemi), reversed (RSA), or anatomic total shoulder arthroplasty (TSA). This study evaluates the clinical outcomes of patients with MUTARS proximal humerus endoprostheses using data from MUTARS Orthopedic Registry Europe (MORE).

Methods: We evaluated 170 proximal humeral reconstructions of eight participating centers; 99 (58%) hemiarthroplasties, 65 (38%) RSA, and six (4%) TSAs were included. The median follow-up time was 5.7 years (95%CI 4.3-6.9).

Results: The study cohort had a median age of 54 years (IQR 31-68), with a median resection length of 12 cm (IQR 10-16). The axillary nerve was preserved in 90% of the patients, and the deltoid muscle was partially or totally reattached in 96% of cases, with no statistically significant differences observed among the different implant types. Consistent with clinical indications, rotator cuff refixation, whether partial or total, was performed less frequently in patients undergoing RSA (77%) compared to hemi (91%) or TSA (100%). The main complications were instability (n=17,10%) and infection (n=17,10%) and were comparable between RSA and hemiarthroplasty. Patients with previous surgery at same site had a cause-specific hazard ratio (HRcs) of 3.1 (95%CI 1.1-8.6) for implant revision due to instability, while other risk factors for instability or infection were not identified. Twenty-eight implants (16%) were revised, for mechanical complications (dislocation n=12, loosening n=3, peri-prosthetic fracture n=3), and infection (n=10). The cumulative incidence of revision for mechanical complications at 2, 5, and 10 years was 8%, 12%, and 14%. For infection, these were 5%, 7%, and 7%. Compared with hemiarthroplasty, RSA offered superior anteflexion (73°[IQR 40-91] vs 30°[5-50]), abduction (70°[38-90] vs 30°[5-49]), and external rotation (15°[0-20] vs 5°[0-19]).

Conclusion: MUTARS proximal humerus reconstruction outcomes are satisfying, particularly in terms of mechanical failure. RSA and hemi exhibit comparable revision risks, Previous surgery at same site was identified as a significant risk factor for the time to revision due to instability. Despite a lower proportion of patients with (partial or total) rotatorcuff reattachment, RSA appears to provide good functional outcomes.