Is preoperative 3D planning reliable for predicting postoperative clinical differences in range of motion between two stem designs in reverse shoulder arthroplasty

Abstract

Primary gleno-humeral osteoarthritis is associated with both excessive posterior humeral subluxation (PHS) and excessive glenoid retroversion in 40% of cases. These morphometric abnormalities are a particular issue since they may be responsible for a deterioration in long term clinical and radiological outcomes. The aim of this study was to perform a CT-analysis of patients who underwent Total Shoulder Arthroplasty (TSA) for primary osteoarthritis (OA) with B2-, B3- or C-type glenoids in whom an attempt was made to correct for excessive glenoid retroversion and excessive posterior humeral subluxation intraoperatively. We performed a retrospective, single-center study including 62 TSA patients with a pre-operative PHS of the glenohumeral joint (31 men, 31 women, 70±9 years) between January 2000 and January 2014. Glenoids were classified as B2 (32 cases), B3 (13 cases) or C (17 cases). Glenoid retroversion was corrected by anterior asymmetric reaming. Patients were reviewed for clinical and CT-scan assessment with a mean follow-up of 8.3 years (minimum 5 years). At final follow-up the CT-images were reconstructed in a scapular plan. A PHS index of >65% defined persistence. The revision free rate was estimated at 93%. Correlation between PHS and retroversion was moderate preoperatively (ρ=0.58) and strong at final follow-up (ρ=0.73). Postoperative CT-scans on average showed a surgical correction of PHS compared to preoperatively (79% vs 65% respectively, p<0.05) and retroversion (20° vs 10° respectively, p<0.05). At final follow-up, 25/62 patients had a persistence in 2D model and 41/62 in 2D corrected model. Persistence of PHS had no influence on clinical outcomes but did demonstrate a significantly higher glenoid loosening rate (20% vs 59%, p<0.05). Correlation between PHS and retroversion was moderate preoperatively and strengthened at long-term follow up. Anterior asymmetric reaming allowed for a surgical improvement of both PHS and retroversion, but it was not sufficient to maintain a correction over time. Glenoid loosening was more frequent in case of PHS persistence but seemingly without clinical relevance.