Clinical and radiographic results of eccentric glenoid reaming in reverse total shoulder arthroplasty

Abstract

BackgroundOne option for treating glenoid bone loss in reverse shoulder arthroplasty (RSA) is eccentric reaming of the glenoid, but the effect on clinical results is unclear. The aim of this study was to investigate the association between medialization of the bone-baseplate interface (herein, ‘medialization’) caused by eccentric reaming of the glenoid and scapular notching, baseplate loosening, and clinical outcomes after RSA. MethodsWe retrospectively reviewed data for 91 patients who underwent primary RSA between January 2014 and December 2016 with a lateralized implant and a minimum 2-year follow-up. The amount of medialization was estimated using a 3-dimensional computed tomography scan-based computer planning software. The average amount of medialization estimated by the 3-dimensional planning software was 3.4 mm (range, 0.5-10 mm). Outcomes included range of motion (ROM), American Shoulder and Elbow Surgeons (ASES) score, Simple Shoulder Test (SST) score, visual analog scale (VAS) for pain, and the rates of scapular notching and baseplate loosening. The association between the estimated medialization and the outcomes of interest was evaluated using multivariate models. ResultsAfter controlling for age, sex, diagnosis, subscapularis repair, glenosphere size, and baseline ROM, medialization was not associated with the postoperative abduction (P = .35), external rotation (ER) at 90° (P = .16), internal rotation at 90° (P = .08), and internal rotation at the back (P = .06). However, we found a significant association between medialization and postoperative ER at the side (P = .02). According to the multivariate model, for a 1-mm increase in medialization during surgery, a decrease of 1.6° in postoperative ER would be expected. We found no association between medialization and the postoperative ASES score (P = .48), SST score (P = .59), or VAS score (P = .27). At a minimum of 2 years of follow-up, we found no baseplate loosening or radiographic signs of baseplate loosening in any patient. Scapular notching of grades 1 to 2 was observed in 22 patients (24%). We were not able to detect a difference in scapular notching when medialization was > 1 mm ver when medialization ≤ 1 mm (odds ratio, 2.5; 95% confidence interval: 0.28-23). ConclusionsIncreasing medialization due to eccentric reaming after RSA with a lateralized implant was associated with a decrease in postoperative ER at the side. However, increasing medialization was not associated with worse patient-reported outcome scores or increased baseplate loosening at short-term follow-up.