Biomechanical and clinical comparison of a novel dual-wing locking plate versus the PHILOS plate for neer three- and four-part proximal humeral fractures: a finite element analysis combined with a retrospective cohort study.

BACKGROUND: Neer three- and four-part proximal humeral fractures treated with conventional PHILOS plating are associated with high complication rates, primarily due to tuberosity re-displacement and calcar screw cut-out. We developed a novel dual-wing locking plate featuring bilateral tuberosity-capturing wing extensions and an omnidirectional ball-head calcar screw. This study compared its biomechanical performance and clinical outcomes with those of the PHILOS plate. METHODS: A three-dimensional finite element model was reconstructed from CT data using Mimics 21.0, Geomagic 2021, and Rhino 7.0, and analyzed in ANSYS 2022R1 under four shoulder abduction angles (0°, 30°, 60°, 90°) with angle-specific physiological rotator cuff loading. Outcome measures included von Mises stress and displacement in the plate and bone, as well as implant stress distribution. Clinically, we reviewed 43 consecutive patients with Neer three- or four-part fractures treated between January 2023 and December 2024: 19 with the dual-wing plate (Group A) and 24 with the PHILOS plate (Group B). Recorded parameters included Visual Analog Scale score, Constant-Murley score shoulder range of motion, fracture union, and complications. RESULTS: Across all abduction angles, peak bone von Mises stress and maximum bone displacement were comparable between constructs (differences <2%). The principal biomechanical difference was stress distribution: the PHILOS plate concentrated peak stress at the proximal calcar screw-plate junction at every angle, whereas the dual-wing plate shifted this concentration to the wing-main plate interface, away from the articular region. Peak plate stress was similar at 0° (42.9 vs. 43.3 MPa) and 30° (59.4 vs. 60.6 MPa), but diverged at 60° (67.2 vs. 82.3 MPa) and 90° (68.4 vs. 108.7 MPa), reflecting progressive wing loading. Clinically, Group A initiated passive pendulum exercises 3.7 days earlier (6.26 ± 0.73 vs. 9.96 ± 1.37 days; p < 0.001), had lower VAS at 1 month (p = 0.005), higher CMS at 1 month (p = 0.003) and 2 months (p < 0.001). No tuberosity nonunion or malunion occurred in Group A versus three cases in Group B. CONCLUSION: The dual-wing plate does not reduce overall bone stress or displacement but fundamentally redirects implant stress concentration from the calcar screw region to the wing-plate interface. This redistribution was associated with earlier passive pendulum exercise initiation and a lower observed rate of tuberosity complications in this small cohort.