Fracture classification and coronal plane position of bolt may affect the prognosis after femoral neck system (FNS) surgery for femoral neck fractures

Purpose This study aims to investigate the risk factors for postoperative complications following Femoral Neck System (FNS) fixation in young patients with femoral neck fractures (FNFs). Methods We retrospective analyzed 133 patients with FNFs who underwent FNS fixation between May 2021 and October 2023. Potential risk factors that may affect the results included age, gender, body mass index (BMI), Pauwels classification, Garden classification, fracture anatomical classification, reduction method, reduction quality, coronal plane position of the FNS bolt. Postoperative complication data, including femoral head necrosis, nonunion, shortening of the femoral neck, fracture displacement, and screw cut-out, were collected. Multivariate logistic regression analysis was used to analyze different influencing factors. Results A total of 133 FNFs patients were divided into a healing group (108 patients) and a failure group (25 patients). 25 patients (18.79%) had postoperative complications, including 8 cases of femoral head necrosis, 3 cases of nonunion, 3 cases of significant shortening of the femoral neck, and 7 cases of fracture displacement, 4 cases of screw cut-out; the remaining patients' fractures all healed. There were no statistical differences between the two groups in age (P = 0.746), gender (P = 0.992), BMI (P = 0.361), Pauwels classification (P = 0.231), fracture anatomical classification (P = 0.459), reduction method (P = 0.383). Garden classification significantly influenced postoperative complications, with the proportion of Garden type IV being significantly higher in the failure group than in the healing group (64% vs. 39.8%, P = 0.01). Multivariate logistic regression analysis showed that coronal position of the FNS bolt and reduction quality were risk factors for postoperative complications. Subgroup analysis using logistic regression showed a positive correlation between coronal plane position of the FNS bolt and reduction quality with the occurrence of postoperative complications, with FNS positioned in the upper 1/3 and negative support being significant risk factors (P < 0.01; P < 0.01). Conclusions FNS is an effective method for treating FNFs in young adults, but there is still a certain risk of failure. The Garden classification is an important evaluation indicator for postoperative complications, with a higher failure rate observed in type IV fractures. Coronal plane position of the FNS bolt and reduction quality are significant risk factors for failure after FNS surgery for FNFs.