Is the Mandible Injury Severity Score a Valid Measure of Mandibular Injury Severity?

Purpose: Developing a valid method for assessing mandibular injury severity could permit standardized comparisons of treatment-specific outcomes between and among various mandibular fracture studies. The study purpose was to assess the validity of the Mandible Injury Severity Score (MISS) developed by Shetty et al (J Oral Maxillofac Surg 65:663, 2007) by measuring the association between the MISS and postoperative complications, operative time, and length of hospital stay (LOS) after operative treatment of isolated mandibular fractures.

Materials and methods: The authors designed and implemented a retrospective cohort study and enrolled a sample derived from patients treated for isolated mandibular fractures at Harborview Medical Center (Seattle, WA) by the oral and maxillofacial surgery service from June 2012 through December 2016. The primary predictor variable was the MISS. The primary outcome variable was postoperative complication (yes or no). Secondary outcome variables were operative time and LOS. Descriptive, bivariate, and multiple logistic regression statistics were computed to measure the association between the MISS and postoperative complications. The level of statistical significance was set at a P value less than or equal to .05.

Results: The study sample was composed of 415 patients with a mean age of 32.7 ± 14.3 years and 80% were men. The average MISS was 13.4 ± 3.5 (range, 6 to 25). The postoperative complication rate was 21%. The average MISS was significantly higher in patients with postoperative complications than in patients without complications (16.3 ± 3.3 vs 12.6 ± 3.1; P < .001). In the adjusted model, postoperative complications were significantly associated with an increasing MISS (odds ratio [OR] = 1.4; 95% confidence interval [CI], 1.3-1.6; P < .001) and open treatment (OR = 7.6; 95% CI, 1.6-35.6; P = .01). The MISS was positively correlated with operative time (r = 0.529; P < .001) and LOS (r = 0.114; P = .02).

Conclusion: The results of this study suggest that the MISS may be a valid measurement of mandibular injury severity as evidenced by the positive correlation between the MISS and postoperative complications, duration of operation, and LOS.