CRANIOMAXILLOFACIAL TRAUMA Is the Mandible Injury Severity Score a Valid Measure of Mandibular Injury Severity? Rodney N. Nishimoto, DMD, MD,* Thomas B. Dodson, DMD, MPH,y and Melanie S. Lang, DDS, MDz 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. Ó 2018 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 77:1023-1030, 2019 Management of isolated mandibular fractures remains controversial, with highly variable outcome data and complication rates.1-4 Because of the frequency of mandibular fractures, considerable research has been devoted to identifying ideal treatment protocols.2 Although these studies have been useful in improving Received from the Department of Oral and Maxillofacial Surgery, University of Washington School of Dentistry, Seattle, WA. Address correspondence and reprint requests to Dr Lang: Department of Oral and Maxillofacial Surgery, University of Washington *Resident. School of Dentistry, 1959 NE Pacific Street, Health Sciences Center yProfessor and Chairman. B-241, Box 357134, Seattle, WA 98195-7134; e-mail: drmelslang@ zClinical Assistant Professor. gmail.com Conflict of Interest Disclosures: None of the authors have any Received October 9 2018 relevant financial relationship(s) with a commercial interest. Accepted November 30 2018 An abstract for this article was presented at the 2018 Annual Meeting Ó 2018 American Association of Oral and Maxillofacial Surgeons of the American Association of Oral and Maxillofacial Surgeons in Chicago, IL (J Oral Maxillofac Surg 76[suppl]:e10, 2018). 0278-2391/18/31295-3 https://doi.org/10.1016/j.joms.2018.11.027 1023 1024 the efficacy of mandibular fracture treatment, their utility in directing treatment decisions has been limited by the failure to measure and control for fracture severity as a confounding variable.5,6 Oral and maxillofacial surgeons assess the severity of mandibular fractures by assessing anatomic fracture-specific characteristics, such as number of constituent fractures, degree of displacement, presence versus absence of teeth, occlusion, and soft tissue involvement.2,7,8 The degree to which individual surgeons weigh each characteristic in their summary assessment of fracture severity differs and could explain why the management and outcomes of similar fractures can vary.2,8 The Mandible Injury Severity Score (MISS) developed by Shetty et al1 converts numerous disparate anatomic and clinical characteristics of mandibular fractures into a single numeric value. If the MISS is a valid measurement of mandibular injury severity, then it could be used to predict outcomes, allocate resources, and produce a standard measure of fracture severity to compare different treatment alternatives. To date, no external study has validated the MISS in adult patients with isolated mandibular fractures.1,6,9 The purpose of this study was to answer the following clinical question: in patients with isolated mandibular fractures, is the MISS associated with postoperative complications, operative time, and length of hospital stay (LOS)? The authors hypothesized that an increasing MISS is positively correlated with the frequency of postoperative complications, operative time, and LOS. The specific aims of the study were to 1) compute the MISS and 2) measure the association between the MISS and postoperative complications, duration of operation, and LOS. A positive correlation between the MISS and frequency of postoperative complications, duration of operation, and LOS would suggest that the MISS may have validity in quantifying mandibular fracture severity. Materials and Methods STUDY DESIGN AND SAMPLE DESCRIPTION The authors designed and implemented a retrospective cohort study. Because of the retrospective nature of this study, it was granted an exemption in writing by the institutional review board of the University of Washington (Seattle, WA; number 51070). The study sample was derived from the population of patients treated for isolated mandibular fractures at Harborview Medical Center (HMC; Seattle, WA) by the oral and maxillofacial surgery (OMS) service from June 1, 2012 through December 31, 2016. Patients were identified from HMC billing records using the following American Medical Association Current Procedural Terminology classification codes: 21450 VALIDITY OF MANDIBLE INJURY SEVERITY SCORE (closed treatment of mandibular fracture; without manipulation), 21451 (closed treatment of mandibular fracture; with manipulation), 21452 (percutaneous treatment of mandibular fracture; with external fixation), 21453 (closed treatment of mandibular fracture; with interdental fixation), 21454 (closed treatment of mandibular fracture; with external fixation), 21461 (open treatment of mandibular fracture; without interdental fixation), 21462 (open treatment of mandibular fracture; with interdental fixation), 21465 (open treatment of mandibular condylar fracture), and 21470 (open treatment of complicated mandibular fracture by multiple surgical approaches, including internal fixation, interdental fixation, and wire if all approaches were intraoral). Patients were excluded from the study if 1) they were younger than 18 years; 2) had a follow-up duration shorter than 4 weeks; 3) had incomplete or unavailable medical records; 4) had pre-existing mandibular pathology; 5) had other maxillofacial fractures; or 6) had a mandibular fracture secondary to gunshot trauma. STUDY VARIABLES The primary predictor variable was the MISS. To calculate the MISS, the authors used the following fracture-specific variables: 1) fracture type (incomplete, simple, comminuted, bone defect); 2) location of fracture (coronoid, symphysis, parasymphysis, alveolar, body, subcondylar, angle, ramus); 3) nature of occlusion (normal, malocclusion, edentulous); 4) extent of damage to the soft tissue envelope (closed, open intraorally, open extraorally, intra- and extraoral, soft tissue defect); 5) presence of infection; 6) extent of interfragmentary displacement (mild [<2 mm], moderate [2 to 4 mm], severe [>4 mm]); and 7) number of fractures. The MISS was computed for each patient using the method described by Shetty et al1 (Fig 1). For patients with multiple fractures, the MISS was calculated for the most severe individual fracture and a value of 4 was added for each additional fracture to compute the summary score.1 Estimates of interfragmentary displacement were obtained from panoramic radiographs or computed tomograms. Fractures without visible step-offs on panoramic imaging were graded to have displacement smaller than 2 mm. Any fracture extending through a tooth-bearing segment was considered open. Fractures extending over 2 contiguous anatomic regions (eg, parasymphysis and body) were assigned a location corresponding to the basal region predominately involved by the fracture.1 The primary outcome variable was postoperative complication (yes or no). Complications included surgical site infection (superficial soft tissue or deep osseous infections associated with mandibular 1025 NISHIMOTO, DODSON, AND LANG FIGURE 1. Mandible Injury Severity Score.1,6 For patients with more than 1 mandibular fracture, the Mandible Injury Severity Score is calculated for the most severe individual fracture and a value of 4 is added for each additional fracture to compute the summary score. Fractures extending over 2 contiguous anatomic regions are assigned a location corresponding to the basal region predominately involved by the fracture. Reprinted with permission from Shetty V, Atchison K, Der-Matirosian C, et al: The Mandible Injury Severity Score: Development and validity. J Oral Maxillofac Surg 65:663, 2007; and Gordon PE, Lawler ME, Kaban LB, Dodson TB: Mandibular fracture severity and patient health status are associated with postoperative inflammatory complications. J Oral Maxillofac Surg 69:2191, 2011. F, forehead; L1, left symphysis; L2, left parasymphysis; L3, left body; L4, left alveolar; L5, left angle; L6, left ramus; L7, left coronoid; L8, left subcondylar; LD, left dentition; LM, left maxilla; LN, left nose; LO, left orbit; LZ, left zygoma; R1, right symphysis; R2, right parasymphysis; R3, right body; R4, right alveolar; R5, right angle; R6, right ramus; R7, right coronoid; R8, right subcondylar; RD, right dentition; RM, right maxilla; RN, right nose; RO, right orbit; RZ, right zygoma. Nishimoto, Dodson, and Lang. Validity of Mandible Injury Severity Score. J Oral Maxillofac Surg 2019. fracture sites, hardware, or surgical incision), wound dehiscence requiring more intervention than local wound care and antibiotics (hardware removal or surgical debridement or incision and drainage), hardware failure (loosening or fracture of plates or screws), malunion or nonunion, osteomyelitis (clinical or radiographic), and malocclusion. Postoperative complications were subcategorized as major or minor. Major complications were those requiring a hospital admission or a second procedure to be carried out under general anesthesia in the operating room. Minor complications were those that could be managed in the clinic on an outpatient basis. Secondary outcome variables were operative time (minutes) and LOS (days). Operative time was computed from anesthesia or nursing records documenting procedural start and end times. LOS was computed from hospital admission and discharge records; patients discharged on the same day of surgery were assigned a LOS of 0 days. Other study variables were grouped into the following categories: demographic (age, gender), risk factor (American Society of Anesthesiologists classification I to V, presence of immune-related disease [diabetes, human immunodeficiency virus, cancer, transplantation], presence of substance abuse [alcohol, tobacco, illicit drugs], fracture etiology [assault, other]), and perioperative (time from injury to repair [days], incision type [none, intraoral, extraoral, intra- and extraoral], fixation type [closed treatment with intermaxillary fixation {IMF}, open treatment with open reduction and internal fixation with or without postoperative IMF], intraoperative antibiotics [administered #1 hour before surgical incision], and perioperative antibiotics [>24 hours preoperatively and >24 hours postoperatively if administered]). DATA COLLECTION, MANAGEMENT, AND ANALYSES The authors used a custom data-collection form in the University of Washington–sponsored Research Electronic Data Capture (REDCap) database.10 Data were collected and the MISS was computed by a single investigator (R.N.N.) using operative, inpatient, and clinic notes and panoramic and computed tomographic imaging from each patient’s electronic health record. Descriptive statistics were computed for each study variable. Bivariate and multiple logistic regression statistics were computed to measure the association between study variables and postoperative complications using SPSS Statistics 23.0 (IBM Corp, 1026 VALIDITY OF MANDIBLE INJURY SEVERITY SCORE Table 1. SUMMARY OF STUDY VARIABLES Table 2. SUMMARY OF STUDY VARIABLES VERSUS MISS Study Variables Study Variables Demographic variables Total sample size Age (yr) Men Risk factor variables ASA class I II III Immune-related disease (yes) Substance abuse (yes) Fracture variables Etiology Assault Other (MVC, fall, sports, work) Number of fractures MISS Perioperative variables Time to treatment (days) Operative time (minutes) Length of stay (days) Incision type None Intraoral Extraoral Intra- and extraoral Treatment Closed (IMF) Open (ORIF or ORIF + IMF) Intraoperative antibiotics Perioperative antibiotics None Pre- postoperative Postoperative complication Yes 415 32.7 14.3 335 (81) 185 (45) 198 (48) 32 (8) 21 (5) 285 (69) 271 (65) 144 (35) 1.8 0.6 13.4 3.5 10.9 11.1 136.8 65.2 0.4 2.1 92 (22) 299 (72) 14 (3) 12 (3) 92 (22) 323 (78) 415 (100) 184 (44) 231 (56) 88 (21) Note: Data are presented as mean standard deviation or number (percentage). Abbreviations: ASA, American Society of Anesthesiologists physical status classification; IMF, intermaxillary fixation; MVC, motor vehicle crash; MISS, Mandible Injury Severity Score; ORIF, open reduction and internal fixation. Nishimoto, Dodson, and Lang. Validity of Mandible Injury Severity Score. J Oral Maxillofac Surg 2019. Armonk, NY). The level of statistical significance for all analyses was set at a P value less than or equal to .05. To measure intra-examiner variability in MISS scoring, 25 patients were randomly selected and rescored. The intraclass correlation coefficient (ICC) was computed to assess intra-examiner reliability (2-way mixed-effects model, single measures, absolute agreement, ICC [3,1]). Intra-examiner agreement for Demographic variables Sample size Age Men Women Risk factor variables ASA class I II-IV Immune-related disease (yes) Substance abuse (yes) Fracture variables Etiology Assault Other (MVC, fall, sports, work) Number of fractures Perioperative variables Time to treatment (days) Operative time (minutes) Length of stay (days) Incision type None Intraoral Extraoral Intra- and extraoral Treatment Closed (IMF) Open (ORIF or ORIF + IMF) Perioperative antibiotics None Pre- postoperative MISS P Value 415 not applicable 0.017* .730 13.6 3.4 12.6 3.5 .026y 13.2 3.6 13.6 3.3 15.1 3.7 .240 .026y 13.7 3.5 .015y 13.8 3.3 12.7 3.6 .003y 0.681* <.001y 0.122* 0.529* 0.114* .013y <.001y .020y 10.5 3.2 14.1 2.9 15.1 4.1 17.6 3.9 <.001y 10.5 3.1 14.3 3.1 <.001y 12.5 3.6 14.1 3.1 <.001y Note: Data are presented as mean standard deviation. Abbreviations: ASA, American Society of Anesthesiologists physical status classification; IMF, intermaxillary fixation; MVC, motor vehicle crash; MISS, Mandible Injury Severity Score; ORIF, open reduction and internal fixation. * By Pearson correlation. y Statistically significant. Nishimoto, Dodson, and Lang. Validity of Mandible Injury Severity Score. J Oral Maxillofac Surg 2019. MISS scoring was excellent (ICC = 0.93: 95% confidence interval [CI], 0.78-0.97; P < .001).11 Results During the study interval from June 1, 2012 through December 31, 2016, 415 patients met the inclusion criteria. Table 1 presents the descriptive statistics. The sample’s mean age was 32.7 14.3 years 1027 NISHIMOTO, DODSON, AND LANG Table 3. BIVARIATE ANALYSES OF ALL STUDY VARIABLES VERSUS POSTOPERATIVE COMPLICATION (YES OR NO) Study Variables Demographic variables Sample size Age (yr) Men Risk factor variables ASA class I II-IV Immune-related disease (yes) Substance abuse (yes) Fracture variables Etiology Assault Other (MVC, fall, sports, work) Number of fractures Perioperative variables Time to treatment (days) Operative time (minutes) Length of stay (days) Incision type None Intraoral Extraoral Intra- and extraoral Treatment Closed (IMF only) Open (ORIF or ORIF + IMF) Perioperative antibiotics None Pre- postoperative Complication—Yes Complication—No P Value 88 (21) 32.7 13.3 76 (86) 327 (79) 32.7 14.6 259 (79) not applicable .998 .131 36 (41) 52 (59) 4 (5) 70 (85) 149 (46) 178 (54) 17 (5) 215 (66) .472 .804 .014* 66 (75) 22 (25) 205 (63) 122 (37) .031* 2.0 .6 1.8 .6 .027* 9.8 8.4 175.9 63.0 0.5 1.0 11.2 11.8 126.3 61.8 0.4 2.3 .307 <.001* .713 2 (2) 76 (86) 5 (6) 5 (6) 89 (27) 222 (68) 9 (3) 7 (2) <.001* 2 (2) 86 (98) 90 (28) 237 (72) <.001* 26 (30) 62 (71) 158 (48) 169 (52) .002* Note: Data are presented as mean standard deviation or number (percentage). Abbreviations: ASA, American Society of Anesthesiologists physical status classification; IMF, intermaxillary fixation; MVC, motor vehicle crash; MISS, Mandible Injury Severity Score; ORIF, open reduction and internal fixation. * Statistically significant. Nishimoto, Dodson, and Lang. Validity of Mandible Injury Severity Score. J Oral Maxillofac Surg 2019. (mean standard deviation) and 80% of patients were men. Assault accounted for 65% of fractures and substance abuse was present in 69% of patients. The average number of fractures per patient was 1.8 0.6. The average MISS was 13.4 3.5 (range, 6 to 25). The average time to treatment was 10.9 11.1 days and average LOS was 0.4 2.1 days. Open treatment was performed in 78% of patients. All patients received intraoperative antibiotics in accord with hospital policy. Perioperative antibiotics were given to 56% of patients. Postoperative complications occurred in 21% of patients, of which 57% were major (hospital admission or second procedure to be carried out under general anesthesia in the operating room) and 43% were minor (managed in the clinic on an outpatient basis). Table 2 presents bivariate associations between the study variables and the MISS. Gender, immune-related disease, substance abuse, fracture etiology, number of fractures, time to treatment, operative time, LOS, incision type, fixation type, and perioperative antibiotics were statistically associated with the MISS. Table 3 presents a summary of bivariate associations between the study variables and postoperative complications (yes or no). Substance abuse, number of fractures, operative time, incision type, fixation type, and perioperative antibiotics were statistically associated with postoperative complications. Open treatment was significantly associated with an increased risk for postoperative complications compared with closed treatment (27 vs 2%; P < .001). 1028 VALIDITY OF MANDIBLE INJURY SEVERITY SCORE Table 4. MISS VERSUS POSTOPERATIVE COMPLICATION (YES OR NO) Table 5. SUMMARY OF MULTIPLE LOGISTIC REGRESSION ANALYSIS Postoperative Complication MISS Yes No P Value 16.3 3.3 12.6 3.1 <.001* Note: Data are presented as mean standard deviation. Abbreviation: MISS, Mandible Injury Severity Score. * Statistically significant. Nishimoto, Dodson, and Lang. Validity of Mandible Injury Severity Score. J Oral Maxillofac Surg 2019. Table 4 presents the association between postoperative complications (yes or no) and the MISS. 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). Table 5 presents the multiple logistic regression analysis. Multivariate analysis included the following variables (reference group within parentheses): MISS (increasing), age, gender (men), substance abuse (yes), fracture etiology (assault), fixation type (open), and perioperative antibiotics (yes). The MISS (odds ratio [OR] = 1.4; 95% CI, 1.3-1.6; P < .001) and open treatment (OR = 7.6; 95% CI, 1.6-35.6; P = .01) were significantly associated with increased risk for postoperative complications. Table 6 presents the association between the secondary outcome variables (operative time and LOS) and the MISS. Operative time (r = 0.529; P < .001) and LOS (r = 0.114; P = .02) were significantly associated with an increasing MISS. Discussion The purpose of this study was to assess the validity of the MISS by measuring the association between the MISS and fracture management outcomes (ie, postoperative complications, operative time, and LOS) of operative treatment of isolated mandibular fractures. If the MISS were a valid measurement of fracture severity, the authors hypothesized that the MISS would be positively correlated with complications, operative time, and LOS. The specific aims of the study were to 1) compute the MISS and 2) measure the association between the MISS and postoperative complications, duration of operation, and LOS. The study results confirmed the hypothesis that an increasing MISS is meaningfully associated with an increased risk for postoperative complications. After adjusting for age, gender, substance abuse, etiology, treatment, and perioperative antibiotics, the MISS was statistically significantly associated with postoper- Study Variables (Reference) OR (95% CI) P Value MISS Age Gender (men) Substance abuse (yes) Etiology (assault) Treatment (open) Pre- postoperative antibiotics (yes) 1.4 (1.3-1.6) 1.0 (1.0-1.0) 0.9 (0.4-2.1) 0.7 (0.4-1.4) 0.8 (0.4-1.6) 7.6 (1.6-35.6) 0.6 (0.3-1.1) <.001* .890 .893 .359 .520 .010* .077 Abbreviations: CI, confidence interval; MISS, Mandible Injury Severity Score; OR, odds ratio. * Statistically significant. Nishimoto, Dodson, and Lang. Validity of Mandible Injury Severity Score. J Oral Maxillofac Surg 2019. ative complications (OR = 1.4; 95% CI, 1.3-1.6; P < .001) and open treatment (OR = 7.6; 95% CI, 1.635.6; P = .01). The MISS also was significantly associated with increased operative time (r = 0.529; P < .001) and LOS (r = 0.114; P = .02). 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. The MISS was developed by Shetty et al1 as a system for converting multiple anatomic and clinical characteristics of isolated mandibular fractures that contribute to their severity into a single numeric score. Individual components of the MISS are summarized by the acronym FLOSID (fracture type [F], location of fracture [L], nature of occlusion [O], extent of damage to the soft tissue envelope [S], presence of infection [I], and extent of interfragmentary displacement [D]), with the elements of each component assigned a numeric weight depending on their perceived contribution to fracture severity.1 In the original study, the MISS was found to have a statistical association with surrogate markers of injury severity, Table 6. OPERATIVE TIME AND LENGTH OF STAY VERSUS MISS Study Variables Operative time (minutes) Length of stay (days) MISS P Value 0.529* 0.114* <.001y .02y Abbreviation: MISS, Mandible Injury Severity Score. * By Pearson correlation. y Statistically significant. Nishimoto, Dodson, and Lang. Validity of Mandible Injury Severity Score. J Oral Maxillofac Surg 2019. 1029 NISHIMOTO, DODSON, AND LANG such as sensory nerve deficit, need for hospitalization after surgery, and pain at 1-month follow-up; however, the study did not show a meaningful association between the MISS and clinical indicators of postoperative wound healing complications (infection, nonunion, malunion, malocclusion).1 Gordon et al6 conducted a case-and-control study in adults ($18 yr old) with isolated mandibular fractures and found that an increasing MISS and pre-existing medical problems were associated with an increased risk for postoperative inflammatory complications (recurrent swelling, fever, increased pain, or trismus; wound dehiscence with purulent drainage; exposed or infected hardware; abscess formation; radiographic evidence of osteomyelitis; and presence of a fistula) after operative treatment. Christensen et al12 conducted a retrospective study to identify risk factors for major complications (hospital readmission; return to the operating room for a second procedure; or prolonged, unexpected postoperative stay >24 hours) developing after the operative treatment of isolated mandibular fractures in adult patients and did not find a relevant association between the MISS and major postoperative complications. The study did not include complications treated in the outpatient setting and excluded fractures managed by closed treatment with IMF, making the study’s association between the MISS and complications difficult to interpret.12 Swanson et al9 studied the application of the MISS in a cohort of pediatric (<18 yr old) patients treated for mandibular fractures and found that complications (unerupted teeth, facial asymmetry, hyperplasia, restricted movement, malocclusion, temporomandibular joint dysfunction, exposure of hardware, dystonia, gingival recession, and periodontal bone loss) were meaningfully associated with an increasing MISS. To date, the MISS has been used in several studies to control for fracture severity in treatment-specific outcomes research, develop a model for identifying patients suitable for outpatient management of mandibular fractures, and correlate fracture severity with alcohol use and interpersonal violence.13-16 Currently, most studies attempt to classify fracture severity by using multiple variables (eg, open or closed, tooth in the line of fracture, number of fractures, displacement). As such, one routinely needs several variables to describe fracture severity. The power of a study is based on the sample size, the size of the difference between groups, and the number of variables in the statistical model. More variables mean less power for a given sample size. The major advantage of using a single variable (MISS) to score mandibular fracture severity is that it improves the efficiency of a study. In other words, one could detect a smaller difference between treatment groups for a given sample or one could enroll a smaller sample for a given prespeci- fied difference between study groups. Alternatively, one could categorize the fracture severity score (eg, simple, intermediate, or complex). However, definitions of these 3 severity categories can vary among studies. In addition, categorical variables, when compared with a continuous variable (MISS), are less efficient (eg, more patients are needed to detect relevant differences when using a categorical variable compared with a continuous variable). In addition, if one collects the outcome as a continuous variable, then it can be converted to a categorical variable. A categorical variable cannot be converted to a continuous variable. In essence, severity scoring systems aim to convert multivariate data into a single meaningful index of severity that can increase statistical power in data analyses.17 The strengths of this study include a large generalizable sample with demographics and complication rate comparable to previous studies, inclusion of all fracture types (condylar and non-condylar fractures), and treatments (open and closed), and multivariate statistical analysis and calculation of the ICC.6,12,18,19 Weaknesses of the study include the retrospective design, limitation of the study sample to patients treated by the OMS service at HMC, and treatment performed by multiple OMS attending and resident surgeons with different levels of experience from 2012 to 2016. Incorporation of a validated severity scoring system into the management and study of isolated mandibular fractures is long overdue. The ability to objectively quantify the nature and extent of injury into a single score will allow surgeons to communicate the complexity of injury, predict outcomes, guide treatments, and stratify patients in clinical research.1 The results of this study suggest that the MISS is a valid measurement of mandibular fracture severity that is positively correlated with increased risk for postoperative complications and can be used in evidence-based decision making and patient-oriented clinical research. References 1. Shetty V, Atchison K, Der-Matirosian C, et al: The Mandible Injury Severity Score: Development and validity. J Oral Maxillofac Surg 65:663, 2007 2. Ellis E: An algorithm for the treatment of noncondylar mandibular fractures. J Oral Maxillofac Surg 72:939, 2014 3. Nasser M, Pandis M, Fleming PS, et al: Interventions for the management of mandibular fractures. Cochrane Database Syst Rev 7: CD006087, 2013 4. Joos U, Meyer U, Tkotz T, et al: Use of a mandibular fracture score to predict the development of complications. J Oral Maxillofac Surg 57:2, 1999 5. Dodson TB: Discussion: Complication rates associated with different treatments of mandibular fractures. J Oral Maxillofac Surg 58:280, 2000 6. Gordon PE, Lawler ME, Kaban LB, Dodson TB: Mandibular fracture severity and patient health status are associated with 1030 7. 8. 9. 10. 11. 12. postoperative inflammatory complications. J Oral Maxillofac Surg 69:2191, 2011 Shetty V, Atchison K, Der-Martirosian C, et al: Determinants of surgical decisions about mandible fractures. J Oral Maxillofac Surg 61:808, 2003 Shetty V, Atchison K, Belin TR, et al: Clinician variability in characterizing mandible fractures. J Oral Maxillofac Surg 59:254, 2001 Swanson EW, Susarla SM, Ghasemzadeh A, et al: Application of the Mandible Injury Severity Score to pediatric mandibular fractures. 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