BIO-RSA（骨性オフセット増加型リバース型肩関節形成術）の生存率と長期（最低10年）成績

Bony Increased Offset-Reverse Shoulder Arthroplasty (BIO-RSA) has shown promising short- to medium-term results; however, long-term outcomes are lacking. The goal of the present study was to report on survival and long-term (minimum 10-year follow-up) outcomes of BIO-RSA.

Retrospective monocentric study with prospectively collected data, including 192 patients (196 shoulders) who underwent primary BIO-RSA for the treatment of osteoarthritis with cuff deficiency between 2006 and 2014. Mean age at surgery was 73 ±7 years (70% of females). A structural bone graft, harvested from the humeral head, was fixed on the glenoid with a long post baseplate, and a Grammont-type (Aequalis Reversed II, Tornier, 155° of neck-shaft angle) prosthesis was used. At a minimum of 10 years, 55 patients died, 31 were lost to follow-up, 6 patients had dementia, leaving 100 patients (104 shoulders) to assess long-term clinical and subjective results. Graft incorporation, scapular notching and glenoid inclination correction were assessed on 41 shoulders who accepted to come back for radiographic and CT-Scan analysis. The mean follow-up was 12.7 years (10 to 18 years).

The 10-year prosthesis survival, using Kaplan-Meier method with revision as endpoint, was 98% (95% CI: 94-99%). Among the 196 BIO-RSAs performed, 4 (2%) were revised: 1 for traumatic postoperative humeral fracture and 3 for glenoid loosening. Glenoid loosening occurred in 5 cases (2.5%): 3 cases of aseptic loosening (all with superior tilt of the glenoid), 1 case of septic loosening and 1 case of traumatic glenoid mobilization; there was no glenoid failure after 5 years. On last follow-up CT-scan images, we observed full integration of the bone graft without resorption in 95% (39/41). Severe (grade 3 or 4) scapular notching occurred in 32% and was associated with superior glenoid tilt (p=0.002). At last follow-up, no prosthesis dislocation was reported, and acromial/scapular spine fractures occurred in 2%. The mean Constant score was 72 ±14 points and mean SSV 80% ±18. Overall, 93% (98/104) were satisfied and stated that they would undergo the procedure again, if needed.

The BIO-RSA is a safe and durable surgical procedure with 98% of prosthesis survival rate at mean follow-up of 12.7 years (10 to 18 years) and 95% of complete bone graft incorporation. Bony lateralization does not increase the risk of glenoid loosening or acromial/scapular spine fractures, while it protects from prosthetic instability. Superior glenoid tilt is a risk factor for scapular notching and baseplate loosening and should be corrected.