Does Surgical Technique Influence Radial and Axillary Nerve Injury After Long PHILOS Plate Fixation in Proximally Extending Humeral Shaft Fractures?

Abstract Background: Proximally extending humeral shaft fractures (PEHSFs) pose significant surgical challenges due to the complex fracture anatomy and proximity to the axillary and radial nerves. While long proximal humeral internal locking system (PHILOS) plates are commonly used, the impact of surgical technique and implant length on neurological safety remains unclear. This study aimed to evaluate the relationship between surgical technique (Open Reduction–Internal Fixation [ORIF] versus Minimally Invasive Plate Osteosynthesis [MIPO]) and the occurrence of iatrogenic nerve palsy in patients with PEHSFs. Methods: A retrospective study was conducted on 18 patients treated with long PHILOS plates for PEHSFs between January 2022 and January 2025. Patients were stratified into ORIF (n=10) and MIPO (n=8) groups. Axillary and radial nerve functions were assessed preoperatively, immediately postoperatively, and at the final follow-up. The impact of surgical approach, intraoperative nerve exploration, and plate length (9-, 11-, and 12-hole) on neurological outcomes were analyzed. Results: The overall rate of immediate postoperative nerve palsy was 16.7% for the axillary nerve and 22.2% for the radial nerve. After a median follow-up of 8 months, persistent nerve palsy was observed in 3 patients (16.7%). Although the difference did not reach statistical significance (p=0.147), all permanent nerve injuries occurred in the ORIF group (30%), whereas no long-term deficits were observed in the MIPO group (0%). A statistically significant association was identified between plate length and persistent nerve palsy (p=0.002); all cases of permanent nerve palsy were associated with the use of 12-hole plates. Conclusion: While MIPO demonstrated a favorable safety profile with no permanent nerve injuries, the use of 12-hole long locking plates emerged as a significant independent risk factor for persistent neurological deficit in PEHSFs. These findings suggest that adopting soft-tissue-sparing techniques and selecting the shortest implant capable of providing adequate stability may reduce the risk of iatrogenic nerve injury.