The impact of fracture fragment displacement on sensory function recovery of the inferior alveolar nerve in mandibular angle fractures.

OBJECTIVE

To investigate the correlation between the initial, three-dimensionally quantified displacement of mandibular angle fractures and the prognosis of inferior alveolar nerve (IAN) sensory function recovery following open reduction and internal fixation (ORIF).

METHODS

This retrospective cohort study included patients with unilateral mandibular angle fractures treated with ORIF between March 2022 and August 2025. Preoperative cone-beam computed tomography (CBCT) was used to measure the maximum 3-dimensional (3D) displacement of the fracture fragments. Patients were stratified into three groups based on displacement: mild (<2 mm), moderate (2-5 mm), and severe (>5 mm). IAN sensory function was systematically evaluated through objective tests (light touch, two-point discrimination, and pinprick) and subjective tests (Visual Analog Scale) at preoperative, 1 week, 1 month, 3 months, 6 months, and 12 months follow-ups. Multivariate logistic regression was used to identify independent predictors for complete sensory recovery.

RESULTS

A total of 128 patients were included: 45 in the mild, 52 in the moderate, and 31 in the severe displacement groups. The incidence of preoperative IAN sensory deficit was significantly higher in the severe group (67.7%) compared to the moderate (34.6%) and mild (11.1%) groups (p < 0.001). At the 12-month follow-up, the complete recovery rates were 91.1%, 63.5%, and 22.6% for the mild, moderate, and severe groups, respectively (P < 0.001). Multivariable logistic regression identified severe displacement (OR = 0.09, 95% CI: 0.03-0.29), moderate displacement (OR = 0.28, 95% CI: 0.11-0.71), and age>40 years (OR = 0.41, 95% CI: 0.18-0.93) as independent negative predictors for complete sensory recovery.

CONCLUSION

The initial 3D displacement of mandibular angle fractures is a significant predictor of IAN injury severity and postoperative sensory recovery. Preoperative quantitative assessment using CBCT may aid in personalized prognosis, patient counseling, and surgical planning.