Fracture properties of the human mandible

Assessment of the Wisconsin Criteria at a Level I Trauma Center

ABSTRACT

The Wisconsin Criteria was developed for physicians evaluating facial trauma to determine the likelihood of facial fractures. Subsequent studies have not consistently validated these criteria. This study seeks to validate the Wisconsin Criteria and determine its utility in predicting operative facial fractures.Retrospective chart review of the trauma database registry at a Level I Trauma Center was conducted from September 2011 to May 2019. Adult patients who had a complete facial examination by otolaryngology or plastic surgery as well as a head computed tomography scan completed, were included. Fisher exact test was utilized for statistical analysis (P < 0.05) and positive predictive value, and negative predictive value (NPV) were calculated with a 95% confidence interval.After screening, 546 patients met eligibility, 448 had at least 1 finding of the Wisconsin Criteria, and 472 patients had facial fractures. The sensitivity of the Wisconsin Criteria for determining the presence of a facial fracture was 86.23%, the specificity was 44.59%, and the NPV was 33.67% (P < .0001). Malocclusion was the criterion most specific in determining if a facial fracture was present (98.65%), and Glasgow Coma Score < 14 was the least specific (67.57%).The Wisconsin Criteria did aid in the identification of facial fractures in trauma patients with a comparable sensitivity, higher specificity, and much lower NPV than originally described. Further investigation should be done to validate the criteria in other large trauma centers.

Biomechanical evaluation of caudally and buccally screwed customised reconstruction plates for lateral segmental defects of mandible

The aim of this study was to compare locking reconstruction plates with caudobuccally screwed custom mandibular reconstruction plates in bridging lateral mandibular segmental defects. The in vitro study was conducted on 13 polyurethane mandibles. A total of 7 mandibles with lateral segmental defects were bridged with locking reconstruction plates in group I, 6 mandibles with the same standard defect were bridged with caudobuccally screwed customised reconstruction plates in group II. Mean yield displacement, yield load, and displacement at 80 N (Newtons), 100 N, 200 N, 300 N loading were compared among the 2 groups. The mean (SD) displacement for Group I was 11.27 (3.6) mm, Group II was 21.08 (2.5) mm. Group II had significantly greater (p=0.0001) displacement when compared with Group I. The mean (SD) force before failure for Group I was 638.4 N (127.2), Group II was 1398. 3 N (162.7). Group II withstood significantly greater force than Group I (p=0.0001). The study reveals that the caudobuccally screwed custom reconstruction plates can significantly enhance yield load as preserving the preoperative shape of the face and mandible.

Does Fracture Pattern Influence Functional Outcomes in the Management of Bilateral Mandibular Condylar Injuries?

The purpose of this study was to compare the functional outcomes of different types of bilateral mandibular condylar fractures. This was a retrospective study of patients with bilateral mandibular condylar fractures at a level-1 trauma center over a 15-year period. The primary predictor variable was fracture pattern, classified as type I (bilateral condylar), type II (condylar-subcondylar), or type III (bilateral subcondylar). Secondary predictor variables were demographic, injury-related, and treatment factors. Bivariate associations between the predictors and complication rates were computed; a multiple logistic regression model was utilized to adjust for confounders and effect modifiers. Thirty-eight subjects with bilateral condylar injuries met the inclusion criteria. The sample's mean age was 37.6 + 18.2 years, and 16% were female. The most common mechanisms of injury were motor vehicle collisions (53%) and falls (29%). Seventy-four percent had associated noncondylar mandibular fractures, and 32% of cases had concomitant midface fractures. Fifty-three percent of cases were classified as type I, 21% as type II, and 26% as type III. Ten subjects (26%) were managed with open reduction and internal fixation. The average length of follow-up was 4.5 + 6.3 months. After adjusting for confounders and effect modifiers, the type of fracture was a significant predictor of functional complications with type II injuries having the highest likelihood of a poor functional outcome (odds ratio: 7.77, 95% confidence interval: 1.45-41.53, p  = 0.02). Asymmetric bilateral mandibular condylar fractures may be associated with an increased risk of poor functional outcomes.

Comparison of Surgical and Nonsurgical Treatment of Bilateral Condylar Fractures Based on Maximal Mouth Opening

This study presents a comparative analysis of the open surgical and nonsurgical treatment of patients with bilateral condylar fractures. Sixty-seven (67) patients were treated, and the completed data on 55 patients were reviewed to compare both therapeutic modalities, which consisted of nonsurgical and surgical treatment in 37 and 18 patients, respectively. In the nonsurgical group, 23 patients (23/37, 62%) had normal mouth opening. Functional success rate was 79% (15/19) and 44% (8/18) in young adult patients (-29yrs) and older patients (30+yrs), respectively, and there was a significant difference of outcome between the two groups. In nonsurgically treated young patients with disorders, bilateral dislocation and existence of concomitant mandibular fractures were commonly observed. In the open surgical group, seven (7/11, 64%) young adult and three (3/7, 43%) older patients gained normal mouth opening, and no significant difference was observed. Additionally, there was no difference between non-surgical and surgical treatment in any category. Patients undergoing rigid fixation benefited from restoring maximum mouth opening, although there was no significant difference between the rigid and non-rigid fixation groups. Based on these findings, nonrigid fixation should be avoided, and rigid fixation might improve outcome in young adult patients with severe fracture pattern, such as bilateral dislocation and concomitant mandibular fracture.

Pontomedullary lacerations and concomitant head and neck injuries: their underlying mechanism. A prospective autopsy study

It is a well-documented fact that pontomedullary lacerations (PML) occur as a result of severe craniocervical injury, but their underlying mechanism has yet to be fully clarified. The aim of this prospective study has been to give greater insight into the underlying mechanism of PML through determining the site of blunt head-impact, as well as the presence of concomitant head and neck injuries in cases of brainstem PML. A total of 56 cases with partial PML have been analysed for this study. The case group was composed of 40 men and 16 women, averaging in age 44.2 ± 19.2 years and consisting of 7 motorcyclists, 4 bicyclists, 18 car occupants, 16 pedestrians, and 10 victims of falls from a height, as well as 1 victim of a fall from standing height. The presented study has shown that there are several possible mechanisms of PML. Impact to the chin, with or without a skull base fracture, most often leads to this fatal injury, due to the impact force transmission either through the jawbone or vertebral column; most likely in combination with a fronto-posterior hyperextension of the head. Additionally, lateral head-impacts with subsequent hinge fractures and PML may also be a possible mechanism. The jawbone and other facial bones are able to act as shock absorbers, and their fracture may diminish the energy transfer towards the skull and protect the brain and brainstem from injury. The upper cervical spine can act as damper and energy absorber as well, and may prevent any occurrence of fracture to the base of the skull.

The significance of pontomedullar laceration in car occupants following frontal collisions: A retrospective autopsy study

The aim of this study was to determine the frequency of brainstem pontomedullar lacerations among fatally injured car occupants in head-on collisions, as well as the concomitant cranial injuries, and to establish a possible underlying mechanism for brainstem laceration. Brainstem pontomedullar lacerations (PML) are often associated with fractures of the skull base (hinge, ring or pyramidal fractures) or with cervical spine fractures. Out of 705 cases of deceased car occupants involved in head-on car collisions, some form of head injury was present in 447 cases (63.4%). These cases included 353 men and 94 women with an average age of 38.2±15.8 years (range 16-89 years). The collected cases included 229 drivers, 164 front-seat and 54 rear-seat passengers. PML were present in 67 of these cases (15%), 50 men and 17 women with an average age of 42.9±15.6 years (range 15-77 years), including 32 drivers, 26 front-seat and 9 rear-seat passengers. In all of these cases the brainstem laceration was partial and the depth varied approximately from 4mm to 8mm. To understand the mechanisms by which PML occurs, we classified the head impact areas into frontal, lateral, posterior and chin area, depending on the injuries to the soft tissue of the head and scalp, as well as facial and cranial fractures. Injury impact area of the head was a good predictor of PML occurrence (χ(2)=131.112, df=3, p=0.000). Chin impact was most often associated with PML-38 cases (Wald. coeff.=5.805, df=1, p=0.016). Presence or absence of mandibular fracture was significant for PML occurrence (χ(2)=11.413, df=1, p=0.001): persons without mandibular fracture have 2.3 times greater risk for PML than those with fracture (odd ratio=7.196). Among the observed skull base fractures, the best predictor of PML was ring fracture (Wald. coeff.=30.729, df=2, p=0.000). Our study showed that PML was present in a significant number of car occupants sustaining head injuries in head-on collisions (15%). Impact to the chin with or without a ring fracture to the skull base most often led to this fatal injury, probably after collision with the dashboard.

Biomechanics of mandibular reconstruction: a review

Knowledge of the biomechanics of the mandible allows the surgeon to understand the forces acting on the mandible during function and the resulting deformation that can occur. This allows the appropriate selection and placement of osteosynthesis plates to neutralize these forces. Many methods have been proposed for mandibular reconstruction, each of which has strengths and weaknesses. Most papers evaluating these techniques have focused on survival rates and the quality of the grafted bones, and there have been few studies of the biomechanics (stress distribution and strength) of the various types of reconstructed mandibles. This paper reviews the biomechanics of the mandible and the various methods of reconstruction reported in past studies.

Feet rolled over by cars: radiological and histological considerations from experiments

This study investigates the question of whether bone structures are injured when a vehicle rolls over a foot. A total of 15 detached feet from deceased persons who had donated their bodies to research were rolled over using a VW Passat station wagon. The feet were enclosed in various types of shoes. The front left tire of the vehicle, inflated to 1.8 bar and driven at walking speed, ran over the feet at a right angle to the long axis. The feet were dissected, and histological and radiological examinations were carried out. The only macroscopically well-defined abrasions of the epidermis were on the back of the foot in the area of contact with the tire and only where the foot had not been covered by a shoe. These abrasions were also well presented histologically. No injuries to the bone structures of the feet, in the form of incomplete fractures, corticalis interruptions or spongiosa compressions were ascertained, either radiologically or microradiologically.

Finite element modelling of human head injuries caused by a fall

Finite element models (FEMs) can be used as prediction tools for human head injuries caused by falls. The purpose of this paper is to demonstrate the relevance of using human head FEM to assess the possible mechanism for the origin of head injuries. The FEM of the human head used in this study was developed in the late 1990s at the University Louis Pasteur of Strasbourg (ULP) and has been validated for human head impacts for simulating human head injuries caused by car accidents. Its use in legal medicine appears to be very useful for comparing different injury mechanisms. We present the simulation obtained for two witnessed falls of the same individual, and compare our results to tolerance limits of the main human head injuries. We show that this tool can be used to discuss the possible mechanism of injury encountered for the observed lesions in a forensic case. It can also help to distinguish between possible and impossible human head injury mechanisms.