Efficacy of PHILOS combined with n-HA/PA66 augmentation for treating three- or four-part proximal humeral fractures in elderly patients

Background Achieving stable fixation in highly unstable proximal humeral fractures (PHFs) remains a significant challenge in orthopedic surgery. Research increasingly highlights the importance of medial calcar support in these complex injuries. This study aimed to compare and analyze the clinical outcomes of two surgical approaches for treating Neer three- and four-part PHF in elderly patients: fixation with the proximal humeral internal locking system (PHILOS) alone, and fixation with PHILOS augmented by a bionic nanohydroxyapatite/polyamide 66 (n-HA/PA66) composite material. Methods From October 2022 to March 2024, a retrospective review identified 62 elderly patients with Neer three- or four-part PHF admitted to our institution. These patients were divided into two groups: the n-HA/PA66 group (n = 27), which was treated with PHILOS plate fixation combined with n-HA/PA66, and the PHILOS group (n = 35), which was treated with PHILOS alone. All patients were followed for 12 months. Functional outcomes were assessed via the Disability of the Arm-Shoulder-Hand (DASH) score, the Constant-Murley score (CMS), the American Shoulder and Elbow Surgeons (ASES) score, and the visual analog scale (VAS) for pain. Radiological outcomes were evaluated by measuring the neck-shaft angle (NSA) and humeral head height (HHH). Postoperative complications were also recorded for each group. Results At baseline, no significant differences in demographic characteristics, injury profiles, fracture classifications, or medical histories were observed between the two groups. The mean operative time in the n-HA/PA66 group (103.5 minutes) was significantly shorter than that in the PHILOS group (128.6 minutes) (P = 0.018). Postoperative follow-up assessments were conducted at 1 day, 1 month, 3 months, 6 months, and 12 months. Both groups demonstrated a reduction in disability over the 12-month follow-up period. At the final follow-up, the n-HA/PA66 group presented a mean DASH score of 25.5 ± 5.1 points, compared with 28.1 ± 4.7 points in the PHILOS group (p = 0.04; 95% CI, -5.1 to 0.1), and a mean ASES score of 78.9 ± 8.9 points, compared with 73.0 ± 10.3 points in the PHILOS group (p = 0.04; 95% CI, -3.9 to 5.7). However, no significant differences were found between the groups at other time points for these measures. Furthermore, there were no statistically significant differences between the two groups in CMS, range-of-motion scores, or VAS pain scores at any of the assessed time points. The mean difference in NSA and HHH was significantly lower in the n-HA/PA66 group than in the PHILOS group (P < 0.001). Regarding complications, 5 patients (18.5%) in the n-HA/PA66 group reported a total of 5 complications, whereas 8 patients (22.9%) in the PHILOS group reported 8 complications over the 12-month period; this between-group difference was not statistically significant (χ² = 0.256, p = 0.92). Conclusion While the PHILOS plate alone demonstrates efficacy in treating PHF, augmenting this fixation with n-HA/PA66 may further mitigate postoperative loss of the neck-shaft angle and humeral head height in elderly patients with three- or four-part fractures. Moreover, this combined approach shows promise in improving specific functional outcomes.