The outcome of surgical management of proximal humeral fractures using locking plates: comparison between locking plates with different geometry

Background: Locking plate fixation appears to be a standard treatment for proximal humeral fracture. Different locking plate designs might result in different radiographic and functional outcomes. The original version of the Proximal Humeral Internal Locking System (PHILOS; DePuy Synthes, Warsaw, IN, USA) occupied the largest volume of the humeral head by screw distribution, whereas the Zimmer Periarticular Locking Plate (ZPLP) system (Zimmer Biomet, Warsaw, IN, USA) occupied the smallest. Methods: We enrolled 50 patients undergoing ZPLP treatment and 50 undergoing PHILOS treatment. Results: The postoperative amount of impaction was significantly higher using the ZPLP System than using the PHILOS. Subgroup analysis showed that medial calcar support was another critical factor that affected surgical outcomes, especially when using the ZPLP System. Conclusion: The amount of postoperative impaction was significantly higher when the ZPLP was used compared with the PHILOS locking plate. Medial calcar support is another critical factor that affects surgical outcomes. However, no significant differences in functional outcomes (Constant-Murley score) between the ZPLP System and the PHILOS were noted at the 12-month follow-up.