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

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