Surgical Approach for RSA has Little or no Influence on Scapular Inclination and Glenoid Baseplate Tilt Relative to the Horizontal

Abstract

Purpose Determine whether reverse shoulder arthroplasty (RSA) glenoid baseplate tilt is influenced by surgical approach and/or associated with functional scores. Methods In total, 501 shoulders (483 patients) who underwent RSA, by anterosuperior (AS, n = 88) or deltopectoral (DP, n = 413) approach. Preoperative and immediate postoperative anteroposterior and scapular Y-view radiographs were used to measure: Inclination of the supraspinatus fossa's floor relative to the horizontal (Sigma angle), inclination of the glenoid fossa line (or glenoid baseplate surface) relative to the horizontal (beta-h angle) or to the supraspinatus fossa's floor (beta-s angle). Results Sigma and beta-h were significantly greater for shoulders operated by DP approach, both preoperatively ( P < .001, P = .002) and postoperatively ( P = .004, P < .001), but net change was not significantly different ( P = .501, P = .742). Conversely, beta-s was significantly greater for shoulders operated by DP approach, only postoperatively ( P = .042), but there were no significant differences in either preoperative angles ( P = .580) or net change thereof ( P = .528). Conclusion Beta-s was slightly but significantly greater for shoulders operated by DP approach, while beta-h and sigma depended primarily on preoperative scapular inclination and glenoid tilt, rather than on surgical approach. At a minimum of 2 years following RSA, neither constant scores nor net improvements thereof were significantly associated with any of the angles. Level of evidence IV, case series