Does Excessive Lateralization Influence Tuberosity Healing in Reverse Total Shoulder Arthroplasty for Proximal Humeral Fractures?

Purpose: This study evaluated the influence of stem global lateralization on tuberosity consolidation and functional outcomes in patients undergoing reverse total shoulder arthroplasty (rTSA) for proximal humeral fractures (PHFs). Methods: A retrospective, two-institution study included patients who underwent rTSA for acute PHFs implanted with one of three stems: the Arrow (global lateralization 21.4 mm), the Humelock II (11.2 mm), or the Unique (14.7 mm).Stems were classified as Very Highly Lateralized (VHL; >20 mm, Arrow) or Lateralized (L; 10-15 mm, Unique and Humelock II).Tuberosity consolidation was assessed radiographically at a minimum 12-month follow-up.Functional outcomes included forward flexion, external rotation, VAS pain, and Constant Score.The lateralization shoulder angle (LSA) and distalization shoulder angle (DSA) were measured and compared across groups.Complication and reoperation rates were recorded.Results: A total of 113 patients were included: Arrow (N = 53), Humelock II (N = 40), and Unique (N = 20), comprising 53 in the VHL group and 60 in the L group.The overall consolidation rate was 82.1%.Nonunion rates differed significantly across stems (p = 0.018): 24.5% for the Arrow, 10.0% for the Humelock II, and 0% for the Unique, with a significant dose-response trend between increasing lateralization and increasing nonunion rate (p = 0.022).Patients achieving consolidation demonstrated significantly better forward flexion, external rotation, Constant Score, and VAS pain than those with nonunion (p < 0.05).Even among consolidated patients, the VHL group demonstrated significantly lower forward flexion, higher pain scores, and lower Constant Scores than the L group (p < 0.05).LSA values were similar across all consolidated groups despite a nearly 10 mm difference in global lateralization (p = 0.112).