Locking plate fixation for proximal humerus fractures: are four proximal screws adequate? A clinical and radiological analysis of 105 consecutive cases

Abstract

Proximal humerus fractures are common injuries, and achieving stable fixation is essential to prevent complications such as varus collapse and screw perforation. While optimal screw positioning has been emphasized biomechanically, clinical evidence regarding the required number of screws in the humeral head, particularly when minimally invasive aiming devices limit placement to four screws, remains limited. This study evaluated whether fixation with four cranial screws provides adequate clinical and radiological stability. A retrospective cohort study was conducted including 105 patients with displaced proximal humerus fractures treated with plate osteosynthesis. Patients were grouped according to the number of proximal screws used: four screws ( n = 58) or more than four screws ( n = 47). The primary outcome was the Constant–Murley Score. Secondary outcomes included secondary screw perforation, head–shaft angle maintenance, restoration of medial cortical support, and avascular necrosis. Mean follow-up was 18 ± 6 months. Functional outcomes were comparable between groups, with Constant–Murley Scores of 78 ± 7 in the four-screw group and 73 ± 13 in the multi-screw group ( p = 0.23). Rates of screw perforation (8.6% vs. 10.6%; p = 0.72) and postoperative head–shaft angles were likewise similar, and no significant alignment change occurred during follow-up. Medial cortical support was restored more frequently in the multi-screw group (82% vs. 63%; p = 0.001), but this did not translate into superior clinical or radiographic outcomes. Avascular necrosis occurred in 3 and 13% of patients, respectively. When fracture reduction/alignment is adequately restored, the use of four cranial screws appears sufficient to maintain alignment and prevent mechanical complications in minimally invasive plate osteosynthesis of proximal humerus fractures. Further prospective studies with longer follow-up are required to validate these findings.