Development and Validation of a Clinically Applicable Nomogram for Predicting Inferior Alveolar Nerve Injury After Mandibular Cystectomy

Background Mandibular cystectomy carries a considerable risk of inferior alveolar nerve injury (IANI); however, current evidence on modifiable preoperative imaging-based risk predictors remains limited. This knowledge gap underscores the critical need for developing advanced risk stratification models to optimize surgical decision-making. Purpose The purpose of this study was to systematically identify key imaging-derived risk factors for IANI following mandibular cystectomy, quantify their associations, and construct/validate a predictive nomogram for personalized preoperative risk assessment. Study design, setting, sample The authors conducted a retrospective cohort study from 306 patients undergoing mandibular cystectomy from July 2022 to October 2023, at Department of Oral and Maxillofacial Surgery, Stomatology Hospital, Zhejiang University School of Medicine. Exclusion criteria encompassed pre-existing neurological conditions, preoperative sensory deficits, intraoperative nerve transection, and recurrent cysts. Predictor variables The predictor variable was a set of imaging parameters including: cyst volume, mandibular canal (MC) deviation, canal cross-sectional shape, and cyst-canal spatial relationship (including cyst-to-MC contact, relative position, contact distance, destruction distance). Main outcome variable The primary outcome was postoperative neurosensory disturbance within the IAN distribution during hospitalization. Covariates The covariates were demographic factors (age, sex), surgical variables (filling material used in the cyst cavity), and histopathological diagnosis. Analyses Statistical analysis was done with the chi-square test, Fisher's exact test, Mann-Whitney U rank-sum test, poisson regression, generalized estimating equations (GEE) analysis (statistical significance: P < 0.05), as appropriate. A nomogram was constructed using R software, with validation by ROC, calibration curves, Hosmer-Lemeshowχ2 test, and decision curve analysis. Results The study sample consisted of 306 patients with an average age of 36.77 ± 15.07 years, and a sex distribution of 58.8% (180) male and 41.2% (126) female, totally 315 cysts. IANI occurred in 20.95% (66) cases. Independent risk factors including MC deviation (OR = 2.99; 95% CI=1.04-8.60; P=0.042), cyst-to-MC contact (OR = 11.57; 95% CI=1.15-116.70; P=0.038), and destruction distance (OR = 1.23; 95% CI=1.13-1.33; P < 0.001), along with contact distance (OR = 0.93; 95% CI=0.86-1.00; P=0.051), were incorporated into construction of nomogram model. The model achieved an AUC of 0.898 (95% CI=0.856–0.939). The calibration curve and Hosmer-Lemeshowχ2 test showed good calibration performance. Decision curve analysis demonstrated high net benefit. Conclusions and Relevance MC deviation, cyst-to-MC contact, and specific distance measurements independently predict IANI following cystectomy. Our validated nomogram demonstrated superior discriminatory ability for quantifying IANI risk, enabling precision surgical planning through preoperative simulation of critical anatomical interactions. Collectively, these findings advocate for the integration of imaging-based predictors into clinical guidelines for mandibular cyst management.