Effect of lateralization and distalization on tuberosity healing and functional outcomes after reverse total shoulder arthroplasty with the Univers Revers Total Shoulder System for proximal humerus fractures: a randomized controlled trial comparing 135° and 155° uncemented stems.

BACKGROUND: Controversy remains regarding whether humeral neck shaft angle influences tuberosity healing in reverse total shoulder arthroplasty for proximal humerus fracture (PHF). This study aimed to compare the tuberosity healing rates between reverse total shoulder arthroplasty using a lateralized and a distalized configuration of the Univers Revers Total Shoulder System for PHFs. The secondary objective was to evaluate functional outcomes based on stem inclination and tuberosity healing status.

METHODS: This randomized controlled trial enrolled patients ≥65 years with a Neer 3- or 4-part PHF or a displaced Neer 2-part PHF with osteoporosis and/or a rotator cuff tear. Patients were randomized into 2 groups: 135° stem with 4 mm of lateralization or 155° stem with 2.5 mm of distalization. An a priori power analysis determined a sample size of 78 patients to detect a 15% difference in tuberosity healing between groups with statistical significance. Healing of the tuberosities was assessed by 2 independent shoulder surgeons on radiographs at 6, 12, and 24 months postoperatively. Range of motion (ROM) and patient-reported outcomes (PROs) were compared. PROs included the visual analog scale for pain, Constant-Murley score, and Quick-Disabilities of the Arm, Shoulder and Hand. Post hoc analyses compared outcomes by greater tuberosity healing and implant configuration.

RESULTS: A total of 79 patients were enrolled, and 38 in each group completed at least a 2-year follow-up. Nonhealing of the greater tuberosity occurred in 3 patients in the 155°-distalized group and 12 in the 135°-lateralized group (P = .009). The relative risk of greater tuberosity nonhealing in the 135°-lateralized group compared to the 155°-distalized group was 4.0 (95% CI: 1.23-13.05, P = .022) at 24 months. ROM and PROs were similar between groups (P > .050). In nonhealed greater tuberosity cases, the 155°-distalized configuration showed significantly lower external rotation than the 135°-lateralized configuration (-17° ± 6 vs. 15° ± 19, P = .006). No significant differences in ROM and PROs were found between implant types in healed cases (P > .050). Within the 155°-distalized group, nonhealed greater tuberosity was linked to reduced external rotation compared to healed greater tuberosity (-17° ± 6 vs. 20° ± 18, P = .006), while ROM and PROs were comparable in the 135° group regardless of healing status (P > .050).

CONCLUSION: Tuberosity healing with the Univers Revers Total Shoulder System was more frequent with the 155°-distalized configuration, although functional outcomes were comparable to those achieved with the 135°-lateralized design. While successful tuberosity healing was critical to optimize shoulder rotation in the 155°-distalized group, healing had minimal influence on functional outcomes in the 135°-lateralized group.