The Comprehensive AOCMF Classification System: Mandible Fractures- Level 2 Tutorial

Temporomandibular joint degenerative changes following mandibular fracture: a computed tomography-based study on the role of condylar involvement

OBJECTIVES

This study assessed the incidence of postfracture radiological temporomandibular joint (TMJ) degeneration in patients with different types of mandibular fractures, focusing on the impact of condylar fractures.

METHODS

This retrospective review included patients diagnosed as having mandibular fractures from 2016 to 2020 who had undergone initial computed tomography (CT) and a follow-up CT scan at least 1-month postfracture. Patient demographics, fracture details, treatment methods, and radiological signs of TMJ degeneration on CT were analyzed to identify risk factors for postfracture TMJ degeneration, with a focus on condylar head fracture and non-head (condylar neck or base) fractures.

RESULTS

The study included 85 patients (mean age: 38.95 ± 17.64 years). The per-patient analysis indicated that the incidence of new radiologic TMJ degeneration on CT was significantly the highest (p < 0.001) in patients with condylar head fractures (90.91%), followed by those with non-head condylar fractures (57.14%), and those without condylar involvement (24.49%). The per-joint analysis indicated nearly inevitable degeneration (93.94%) in 33 TMJs with ipsilateral condylar head fractures. For the remaining 137 TMJs, multivariate logistic regression revealed that other patterns (ipsilateral non-head, contralateral, or both) of condylar fractures (odds ratio (OR) = 3.811, p = 0.007) and the need for open reduction and internal fixation (OR = 5.804, p = 0.005) significantly increased the risk of TMJ degeneration.

CONCLUSIONS

Ipsilateral non-head condylar fractures and contralateral condylar fractures are associated with a high risk of postfracture TMJ degeneration. Indirect trauma plays a vital role in postfracture TMJ degeneration.

Biomechanical analysis and comparison between 'Zeta' miniplate design and conventional miniplate system for fixation of fracture segments in transition zone of parasymphysis body region of mandible - an in vitro study

The parasymphysis area of the mandible is highly dynamic because it is subjected to both occlusal and muscular forces. As a result, the fractures in this transition zone have a special pattern, posing a challenge for surgeons whether to use one miniplate versus two miniplates, as per Champy's recommendations. The commonest complication resulting to treat this area is mental nerve paraesthesia due to the dissection and stretching of the nerve. Hence, an in vitro research study of a newly designed 'Zeta' miniplate is performed, to evaluate the biomechanical behaviour using finite element (FE) analysis and biomechanical analysis along with a comparison study with the conventional miniplate configurations. The results showed that the Zeta miniplate produces the lowest stresses 17.511 MPa and the least total structural deformation of 0.0011 mm after applying the maximum occlusal bite force. On application of torsional load, total structural deformation was 0.0004 mm and von Mises (VM) stress value was 0.24 MPa which was lowest when compared with the two miniplate system. Hence, the newly developed Zeta miniplate is superior in terms of stability. Another benefit of its design is that it helps in preventing mental nerve paraesthesia and tooth root damage while fixing and stabilising the fractured bony segments.

Development and validation of a digital twin of the human lower jaw under impact loading by using non-linear finite element analyses

Mandibular fractures are one of the most frequently observed injuries within craniofacial region mostly due to tumor-related problems and traumatic events, often related to non-linear effects like impact loading. Therefore, a validated digital twin of the mandible is required to develop the best possible patient-specific treatment. However, there is a need to obtain a fully compatible numerical model that can reflect the patients' characteristics, be available and accessible quickly, require an acceptable level of modeling efforts and knowledge to provide accurate, robust and fast results at the same time under highly non-linear effects. In this study, a validated simulation methodology is suggested to develop a digital twin of mandible, capable of predicting the non-linear response of the biomechanical system under impact loading, which then can be utilized to design treatment strategies even for multiple fractures of the mandibular system. Using Computed Tomography data containing cranial (skull) images of a patient, a 3-dimensional mandibular model, which consists cortical and cancellous bones, disks and fossa is obtained with high accuracy that is compatible with anatomical boundaries. A Finite Element Model (FEM) of the biomechanical system is then developed for a three-level validation procedure including (A) modal analysis, (B) dynamic loading and (C) impact loading. For the modal analysis stage: Free-free vibration modes and frequencies of the system are validated against cadaver test results. For the dynamic loading stage: Two different regions of the mandible are loaded, and maximum stress levels of the system are validated against finite element analyses (FEA) results, where the first loading condition (i) transfers a 2000 N force acting on the symphysis region and, the second loading condition (ii) transfers a 2000 N force acting on the left body region. In both cases, equivalent muscle forces dependent on time are applied. For the impact loading stage: Thirteen different human mandibular models with various tooth deficiencies are used under the effects of traumatic impact forces that are generated by using an impact hammer with different initial velocities to transfer the impulse and momentum, where contact forces and fracture patterns are validated against cadaver tests. Five different anatomical regions are selected as the impact site. The results of the analyzes (modal, dynamic and impact) performed to validate the digital twin model are compared with the similar FEA and cadaver test results published in the literature and the results are found to be compatible. It has been evaluated that the digital twin model and numerical models are quite realistic and perform well in terms of predicting the biomechanical behavior of the mandible. The three-level validation methodology that is suggested in this research by utilizing non-linear FEA has provided a reliable road map to develop a digital twin of a biomechanical system with enough confidence that it can be utilized for similar structures to offer patient-specific treatments and can help develop custom or tailor-made implants or prosthesis for best compliance with the patient even considering the most catastrophic effects of impact related trauma.

Imaging of Maxillofacial Trauma

Maxillofacial trauma is common. Computed tomography is the primary imaging tool for diagnosis. Study interpretation is aided by understanding regional anatomy and clinically relevant features of each subunit. Common injury patterns and the most important factors related to surgical management are discussed.

Evaluation of Mandibular Fractures in a German Nationwide Trauma Center Between 2015 and 2017

Introduction

This study analyses the treatment of isolated mandibular fractures between 1.1.2015 and 21.31.2017 at Dortmund General Hospital.

Materials and Methods

Patient documentation and radiological images have been assessed, and a descriptive statistical analysis has been performed.

Results

Three hundred and twenty-eight patients were identified with isolated mandibular fractures (259 male, 69 female). The male-to-female ratio is 3.75: 1. A total of 541 fracture sites have been identified (1.65 fractures/patient). Forty of these were observed in the dentoalveolar region (fracture of the alveolar process, dental injuries), and the other 501 injuries were distributed in the remaining parts of the lower jaw.A detailed analysis of the osteosynthesis implants is provided. A total of 20 serious complications were observed (6% in all primary cases, 4.5% without osseointegrated implants).

Discussion

The demographic data and the anatomical distribution of the fracture sites are comparable with international literature. Dentoalveolar injuries mostly occur in younger patients. The complication rate in this study (4.5%) is below the international data; however, we found a considerably higher rate than in the midfacial region (central midface: 0%, lateral midface: 1.43%). Despite this complication rate, the procedure can be considered safe.

Supplementary information

The online version of this article (10.1007/s12663-021-01513-4).

Re-evaluating the need for orthopantomography in the management of mandibular trauma: is computed tomography enough?

BACKGROUND

Mandibular fractures are frequent indications for computed tomography (CT) and orthopantomography (OPG) scans in emergency rooms. Numerous studies found CT to have higher sensitivity and enhanced accuracy compared to OPG in diagnosing mandible fractures. Controversy exists regarding additional need for OPG when evaluating dental trauma. This study investigates whether OPG adds diagnostic value to CT in mandibular trauma and whether additional OPG significantly alters management.

METHODS

A retrospective chart review identified 100 patients ≥ 18 years of age with known mandibular trauma who received CT and OPG in the emergency department between May 2015 and January 2020. All patients demonstrated a fracture in at least one study. CT and OPG studies were anonymized and randomized. A single attending surgeon evaluated mandible fracture and dental trauma characteristics and subsequently compared findings.

RESULTS

One hundred patient CT and OPG scans were reviewed. CT detected mandible fractures in all patients and OPG detected fractures in 93% (p = 0.01). Twenty-eight patients had different findings between scans. CT demonstrated 1 or more additional fracture(s) than OPG in 20 patients and dental trauma not seen on OPG in 4. OPG detected 1 fracture and no dental trauma that was not seen on CT. CT drove treatment-determining differences in 17 cases and OPG in 0 cases.

CONCLUSIONS

CT appears efficacious in detecting clinically significant mandible fractures and dental trauma with little additional benefit from OPG in emergency settings. Helical CT may be the only imaging necessary in evaluating patients with such trauma.

Detection and classification of mandibular fracture on CT scan using deep convolutional neural network

OBJECTIVES

This study aimed to evaluate the accuracy and reliability of convolutional neural networks (CNNs) for the detection and classification of mandibular fracture on spiral computed tomography (CT).

MATERIALS AND METHODS

Between January 2013 and July 2020, 686 patients with mandibular fractures who underwent CT scan were classified and annotated by three experienced maxillofacial surgeons serving as the ground truth. An algorithm including two convolutional neural networks (U-Net and ResNet) was trained, validated, and tested using 222, 56, and 408 CT scans, respectively. The diagnostic performance of the algorithm was compared with the ground truth and evaluated by DICE, accuracy, sensitivity, specificity, and area under the ROC curve (AUC).

RESULTS

One thousand five hundred six mandibular fractures in nine subregions of 686 patients were diagnosed. The DICE of mandible segmentation using U-Net was 0.943. The accuracies of nine subregions were all above 90%, with a mean AUC of 0.956.

CONCLUSIONS

CNNs showed comparable reliability and accuracy in detecting and classifying mandibular fractures on CT.

CLINICAL RELEVANCE

The algorithm for automatic detection and classification of mandibular fractures will help improve diagnostic efficiency and provide expertise to areas with lower medical levels.

Inferior alveolar nerve dysfunction in mandibular fractures: a prospective cohort study

Objectives

To assess the prevalence and recovery of inferior alveolar nerve dysfunction (IAND) in mandibular fractures.

Materials and Methods

This was a prospective cohort study. Clinical neurosensory testing was done preoperatively and the IAND was categorized as mild, moderate or severe. Postoperatively, neurosensory testing was repeated at 1 day, 1 week, 1 month, 3 months and every 3 months thereafter.

Results

A total of 257 patients with 420 fractures were included in the study with a mean age of 31.7 years. Body fractures (95.9%) had the highest incidence of IAND, followed by the angle fractures (90.1%) and symphysis fractures (27.6%). The condyle and coronoid fractures did not have any IAND and hence were excluded from further study. After eliminating those cases, 232 patients remained in the study with 293 fractures. The overall prevalence of IAND in fractures occurring distal to the mandibular foramen was 56.3%. The changes until 1 week were minimal. From 1 month to 6 months, there was a significant reduction in the severity of IAND. A significant number of cases (60.0%) were lost to follow-up between 6 and 9 months. At 6 months, 23.9% of cases still had some form of IAND and 95.0% of the symphysis, 59.0% of the angle and 34.8% of the body fractures with IAND had become normal.

Conclusion

This study documents the reduction in the degree of severity of IAND in the first six months and provides the basis for future studies with longer periods of follow-up.

Management of Mandible Fracture in 150 Children Across 7 Years in a US Tertiary Care Hospital

Importance

Pediatric mandible fractures are the most common pediatric facial fracture requiring hospitalization, but data are lacking on management methods, outcomes, and complications.

Objective

To analyze management methods, outcomes, and complications of pediatric mandible fractures at an urban academic tertiary care center.

Design, Setting, and Participants

Single-institution cohort study conducted at 2 urban level 1 pediatric trauma centers including all patients aged 0 to 17 years diagnosed with mandible fractures between January 1, 2010, and December 31, 2016. Fractures were treated by multispecialty surgical teams. Data were analyzed between January 1, 2018, and March 1, 2018.

Main Outcomes and Measures

Fracture distributions, mechanisms, treatment methods, complications, and follow-up.

Results

Of 150 patients with 310 total mandible fractures, the mean (SD) age was 12.8 (4.6) years; 108 (72.0%) were male; 107 (71.3%) were white; and 109 (72.7%) had 2 or more mandible fractures. There were 78 condylar or subcondylar fractures (60 patients), 75 ramus or angle fractures (69 patients), 69 body fractures (62 patients), 78 symphyseal or parasymphyseal fractures (76 patients), and 10 coronoid fractures (10 patients). The most common mechanisms of injury were assault and battery, motor vehicle collisions, falls or play, and sports-related mechanisms. Thirty-eight (25%) patients were treated with observation and a soft diet. Children 12 years and older were more likely to receive open reduction internal fixation (ORIF) (P = .02). Of 112 patients treated with surgery, 63 (56.2%) were treated with maxillomandibular fixation (MMF), 24 (21.4%) received ORIF, and 20 (17.9%) received both MMF and ORIF. Nonabsorbable plating was used in all but 1 of the ORIF procedures. Five of 44 (11.4%) patients receiving ORIF or ORIF and MMF had follow-up beyond 6 months, and 8 of the 44 (18.2%) had documented plating hardware removal; hardware was in place for a mean (SD) 180 (167) days. Sixty of the 150 patients (40.0%) had some form of follow-up, a mean (SD) 90 (113) days total after initial presentation. Thirteen patients experienced complications, for a total complication rate of 8.7%.

Conclusions and Relevance

Conservative management, using MMF and a soft diet, was favored for most operative pediatric mandible fractures. Open reduction internal fixation with titanium plating was less commonly used. Outcomes were favorable despite a lack of consistent follow-up.

Level of Evidence

4.

Pediatric Midface Fractures: Outcomes and Complications of 218 Patients

Objective

To analyze management, outcomes, and complications of pediatric midface fractures.

Methods

Retrospective cohort study at an urban, single‐institution, multispecialty surgical teams, at two level 1 pediatric trauma centers. Query included subjects aged 0–17 diagnosed with midface fractures between 2012 and 2016.

Results

A total of 218 pediatric patients presented with 410 total midface fractures. The most common etiologies included motor vehicle collisions (MVC) (n = 56, 25.7%), sport‐related (n = 35, 16.1%), and assault/battery (n = 32, 14.7%). Fracture site distribution included: 125 maxillary (34 with exclusively the nasal/frontal process), 109 nasal, 47 ethmoid, 40 sphenoid, 33 zygoma, 29 frontal sinus, 21 lacrimal, and 6 palatal. Among these, there were 105 orbital, 17 naso‐orbito‐ethmoid, and 12 Le Fort fractures. One‐quarter of patients received at least one midface‐related operation during the initial encounter. Operative intervention rates for specific midface fracture subsites were not significantly different (X² = 6.827, P = .234). One hundred thirty‐five patients (63.4%) attended follow‐up, thus known complication rate was 14.6% (n = 31). Complication rates between midface fracture subsites were not significantly different (X² = 5.629, P = .229). Complications included facial deformity (n = 18), nasal airway obstruction (n = 8), diplopia (n = 4), hardware‐related pain (n = 3), and paresthesias (n = 3).

Conclusions

The most common sites of pediatric midface fractures involved the maxilla, and nasal bones. Three quarters of pediatric midface fractures were treated conservatively, with low rates of complications. Facial deformity was the most common complication; as such, proper management and follow‐up are important to ensure normal growth and development of the pediatric facial skeleton.

Level of Evidence

4

The Comprehensive AO CMF Classification System for Mandibular Fractures: A Multicenter Validation Study

The AO CMF has recently launched the first comprehensive classification system for craniomaxillofacial (CMF) fractures. The AO CMF classification system uses a hierarchical framework with three levels of growing complexity (levels 1, 2, and 3). Level 1 of the system identifies the presence of fractures in four anatomic areas (mandible, midface, skull base, and cranial vault). Level 2 variables describe the location of the fractures within those defined areas. Level 3 variables describe details of fracture morphology such as fragmentation, displacement, and dislocation. This multiplanar radiographic image-based AO CMF trauma classification system is constantly evolving and beginning to enter worldwide application. A validation of the system is mandatory prior to a reliable communication and data processing in clinical and research environments. This interobserver reliability and accuracy study is aiming to validate the three current modules of the AO CMF classification system for mandible trauma in adults. To assess the performance of the system at the different precision levels, it focuses on the fracture location within the mandibular regions and condylar process subregions as core components giving only secondary attention to morphologic variables. A total of 15 subjects individually assigned the location and features of mandibular fractures in 200 CT scans using the AO CMF classification system. The results of these ratings were then statistically evaluated for interobserver reliability by Fleiss' kappa and accuracy by percentage agreement with an experienced reference assessor. The scores were used to determine if the variables of levels 2 and 3 were appropriate tools for valid classification. Interobserver reliability and accuracy were compared by hierarchy of variables (level 2 vs. level 3), by anatomical region and subregion, and by assessor experience level using Kruskal-Wallis and Wilcoxon's rank-sum tests. The AO CMF classification system was determined to be reliable and accurate for classifying mandibular fractures for most levels 2 and 3 variables. Level 2 variables had significantly higher interobserver reliability than level 3 variables (median kappa: 0.69 vs. 0.59, p  < 0.001) as well as higher accuracy (median agreement: 94 vs. 91%, p  < 0.001). Accuracy was adequate for most variables, but lower reliability was observed for condylar head fractures, fragmentation of condylar neck fractures, displacement types and direction of the condylar process overall, as well as the condylar neck and base fractures. Assessors with more clinical experience demonstrated higher reliability (median kappa high experience 0.66 vs. medium 0.59 vs. low 0.48, p  < 0.001). Assessors with experience using the classification software also had higher reliability than their less experienced counterparts (median kappa: 0.76 vs. 0.57, p  < 0.001). At present, the AO CMF classification system for mandibular fractures is suited for both clinical and research settings for level 2 variables. Accuracy and reliability decrease for level 3 variables specifically concerning fractures and displacement of condylar process fractures. This will require further investigation into why these fractures were characterized unreliably, which would guide modifications of the system and future instructions for its usage.

Patterns of maxillofacial fractures in Hofuf, Saudi Arabia: A 10-year retrospective case series

Objectives

This retrospective study was performed to analyze the incidence, etiology, and types of maxillofacial fractures in a major city in Eastern Province, Saudi Arabia.

Materials and methods

The medical records of all patients treated in the operating rooms for maxillofacial fractures by the Oral and Maxillofacial Surgery Department at King Fahad Hospital, Hofuf, Al-Ahsa, Saudi Arabia, between January 1, 2007, and December 31, 2016, were reviewed. A total of 270 patients with complete records were included. The data extracted included the age, gender, nationality, causes of injury, and patterns of maxillofacial fractures involved.

Results

Among the 270 patients, 241 (89.3%) were males, and 29 (10.7%) were females. The young adult (19-44 years) age group was the most affected (65.6%). Road traffic accidents (63.3%) were found to be the most frequent causes of maxillofacial fractures; falls were the second most common (15.9%). The rate of mandibular (54.6%) fractures was higher than that of mid-facial (45.4%) fractures. Among the mandibular fractures, the most common type was the parasymphyseal fracture (24.6%). Zygomatic fractures were the most common (48.6%) of midface fractures.

Conclusions

Similar to reports of other studies in different regions of Saudi Arabia, Al-Ahsa showed that road traffic accidents were the most predominant etiology of maxillofacial fractures affecting most frequently males of young adult age group. These findings emphasize the need for better education of road safety and enforcement of traffic laws, especially for the most affected age group.

Classification proposal for fractures of the processus condylaris mandibulae

OBJECTIVE

The current classification of mandibular condyle fractures as basal, low neck, and high neck as reported by Loukota et al. (Br J Oral Maxillofac Surg 43:72-73, 2005) and Neff et al. (Craniomaxillofac Trauma Reconstr 7:S44-S58, 2014) has a weakness. Nearly no high-neck fractures are reported (they are typically classified as type C head fractures) contrary to basal condylar fractures, which are overestimated (nearly all low-neck fractures are classified as basal). The aim of this study is to present a modified AO/SORG classification of mandibular condyle fractures.

MATERIAL AND METHODS

A new arrangement of the reference lines is proposed because the fracture lines are mainly oblique in this region. The proposed classification was validated using a series of 84 cases that were treated surgically.

RESULTS

The diagnoses using the proposed new classification system significantly differed from those based on the old system (p < 0.005). All basal fractures in the new classification system were also classified as basal in the old system. The same was true for type C head fractures. The differences were found for low-neck fractures (4 of 84 diagnoses differed between the old and new classifications, i.e., they were previously classified as basal fractures) and high-neck fractures (3 of 84 fractures were diagnosed as low-neck fractures or type C head fractures using the old classification).

CONCLUSION

The epidemiology of the condyle injury should be based on a classification, which reveals types of fractures which are represented by factually and frequently observed cases. That is why a relatively common AO/SORG classification can be modified for the benefit of assessing incidences of high-neck and low-neck fractures.

CLINICAL RELEVANCE

Considering that the treatment of the high-neck fractures is much technically complicated than the low-neck ones, this will have an influence on the management of trauma to the area.

The Comprehensive AOCMF Classification System: Mandible Fractures-Level 3 Tutorial

This tutorial outlines the details of the AOCMF image-based classification system for fractures of the mandibular arch (i.e. the non-condylar mandible) at the precision level 3. It is the logical expansion of the fracture allocation to topographic mandibular sites outlined in level 2, and is based on three-dimensional (3D) imaging techniques/computed tomography (CT)/cone beam CT). Level 3 allows an anatomical description of the individual conditions of the mandibular arch such as the preinjury dental state and the degree of alveolar atrophy. Trauma sequelae are then addressed: (1) tooth injuries and periodontal trauma, (2) fracture involvement of the alveolar process, (3) the degree of fracture fragmentation in three categories (none, minor, and major), and (4) the presence of bone loss. The grading of fragmentation needs a 3D evaluation of the fracture area, allowing visualization of the outer and inner mandibular cortices. To document these fracture features beyond topography the alphanumeric codes are supplied with distinctive appendices. This level 3 tutorial is accompanied by a brief survey of the peculiarities of the edentulous atrophic mandible. Illustrations and a few case examples serve as instruction and reference to improve the understanding and application of the presented features.

The Comprehensive AOCMF Classification System: Midface Fractures - Level 2 Tutorial

The AOCMF Classification Group developed a hierarchical three-level craniomaxillofacial classification system with increasing level of complexity and details. The highest level 1 system distinguish four major anatomical units including the mandible (code 91), midface (code 92), skull base (code 93), and cranial vault (code 94). This tutorial presents the level 2 system for the midface unit that concentrates on the location of the fractures within defined regions in the central (upper, intermediate, and lower) and lateral (zygoma, pterygoid) midface, as well as the internal orbit and palate. The level 2 midface fracture location outlines the topographic boundaries of the anatomical regions. The common nasoorbitoethmoidal and zygoma en bloc fracture patterns, as well as the time-honored Le Fort classification are taken into account. This tutorial is organized in a sequence of sections dealing with the description of the classification system with illustrations of the topographical cranial midface regions along with rules for fracture location and coding, a series of case examples with clinical imaging and a general discussion on the design of this classification. Individual fracture mapping in these regions regarding severity, fragmentation, displacement of the fragment or bone defect is addressed in a more detailed level 3 system in the subsequent articles.

The Comprehensive AOCMF Classification System: Condylar Process Fractures - Level 3 Tutorial

This tutorial outlines the detailed system for fractures of the condylar process at the precision level 3 and is organized in a sequence of sections dealing with the description of the classification system within topographical subdivisions along with rules for fracture coding and a series of case examples with clinical imaging. Basically, the condylar process comprises three fracture levels and is subdivided into the head region, the condylar neck, and the condylar base. Fractures of the condylar head show typical fracture lines either within the lateral pole zone, which may lead to loss of vertical height, or medially to the pole zone, with the latter ones usually not compromising the vertical condyle to fossa relation. In condylar head fractures, the morphology is further described by the presence of minor or major fragmentation, the vertical apposition of fragments at the plane of the head fracture, the displacement of the condylar head with regard to the fossa including a potential distortion of the condylar head congruency resulting in dystopic condyle to fossa relations and the presence or absence of a loss of vertical ramus height. A specific vertical fracture pattern extending from the head to the neck or base subregion is considered. Fractures of the condylar neck and base can be differentiated according to a newly introduced one-third to two-thirds rule with regard to the proportion of the fracture line above and below the level of the sigmoid notch, which is presented in the classification article, and are basically subdivided according to the presence or absence of displacement or dislocation. In both condylar neck and base fractures, the classification is again based on the above mentioned parameters such as fragmentation, displacement of the condylar head with regard to the fossa, including dystopic condyle to fossa relations and loss of vertical ramus height, that is, according to the measurement of the condylar process. In addition, the classification assesses a sideward displacement including the respective displacement sector at the neck or base fracture site as well as the angulation of the superior main fragment and also considers a potential displacement of the caudal fragment with regard to the fossa, which may occur in fractures affecting additional fracture locations in the mandible. The design of this classification is discussed along with a review of existing classification systems. The condylar process for fracture location was defined according to the level 2 system presented in a previous tutorial in this special issue.

The Comprehensive AOCMF Classification System: Classification and Documentation within AOCOIAC Software

The AOCMF Classification Group developed a hierarchical three-level craniomaxillofacial (CMF) fracture classification system. The fundamental level 1 distinguishes four major anatomical units including the mandible (code 91), midface (code 92), skull base (code 93) and cranial vault (code 94); level 2 relates to the location of the fractures within defined topographical regions within each units; level 3 relates to fracture morphology in these regions regarding fragmentation, displacement, and bone defects, as well as the involvement of specific anatomical structures. The resulting CMF classification system has been implemented into AO comprehensive injury automatic classifier (AOCOIAC) software allowing for fracture classification as well as clinical documentation of individual cases including a selected sample of diagnostic images. This tutorial highlights the main features of the software. In addition, a series of illustrative case examples is made available electronically for viewing and editing.

The Comprehensive AOCMF Classification System: Radiological Issues and Systematic Approach

The AOCMF Classification Group developed a hierarchical three-level craniomaxillofacial (CMF) classification system with increasing level of complexity and details. The basic level 1 system differentiates fracture location in the mandible (code 91), midface (code 92), skull base (code 93), and cranial vault (code 94); the levels 2 and 3 focus on defining fracture location and morphology within more detailed regions and subregions. Correct imaging acquisition, systematic analysis, and interpretation according to the anatomic and surgical relevant structures in the CMF regions are essential for an accurate, reproducible, and comprehensive diagnosis of CMF fractures using that system. Basic principles for radiographic diagnosis are based on conventional plain films, multidetector computed tomography, and magnetic resonance imaging. In this tutorial, the radiological issues according to each level of the classification are described.

The Comprehensive AOCMF Classification: Skull Base and Cranial Vault Fractures - Level 2 and 3 Tutorial

The AOCMF Classification Group developed a hierarchical three-level craniomaxillofacial classification system with increasing level of complexity and details. The highest level 1 system distinguish four major anatomical units, including the mandible (code 91), midface (code 92), skull base (code 93), and cranial vault (code 94). This tutorial presents the level 2 and more detailed level 3 systems for the skull base and cranial vault units. The level 2 system describes fracture location outlining the topographic boundaries of the anatomic regions, considering in particular the endocranial and exocranial skull base surfaces. The endocranial skull base is divided into nine regions; a central skull base adjoining a left and right side are divided into the anterior, middle, and posterior skull base. The exocranial skull base surface and cranial vault are divided in regions defined by the names of the bones involved: frontal, parietal, temporal, sphenoid, and occipital bones. The level 3 system allows assessing fracture morphology described by the presence of fracture fragmentation, displacement, and bone loss. A documentation of associated intracranial diagnostic features is proposed. This tutorial is organized in a sequence of sections dealing with the description of the classification system with illustrations of the topographical skull base and cranial vault regions along with rules for fracture location and coding, a series of case examples with clinical imaging and a general discussion on the design of this classification.

The Comprehensive AOCMF Classification System: Fracture Case Collection, Diagnostic Imaging Work Up, AOCOIAC Iconography and Coding

The AO classification system for fractures in the adult craniomaxillofacial (CMF) skeleton is organized in anatomic modules in a 3 precision-level hierarchy with account for an increasing complexity and details. Level-1 is most elementary and identifies no more than the presence of fractures in 4 separate anatomical units: the mandible (code 91), midface (92), skull base (93) and cranial vault (94). Level-2 relates the detailed topographic location of the fractures within defined regions of the mandible, central and lateral midface, internal orbit, endo- and exocranial skull base, and the cranial vault. Level-3 is based on an even more refined topographic assessment and focuses on the morphology - fragmentation, displacement, and bone defects - within specified subregions. An electronic fracture case collection complements the preceding tutorial papers, which explain the features and options of the AOCMF classification system in this issue of the Journal. The electronic case collection demonstrates a range of representative osseous CMF injuries on the basis of diagnostic images, narrative descriptions of the fracture diagnosis and their classification using the icons for illustration and coding of a dedicated software AOCOIAC (AO Comprehensive Injury Automatic Classifier). Ninety four case examples are listed in two tables for a fast overview of the electronic content. Each case can serve as a guide to getting started with the new AOCMF classification system using AOCOIAC software and to employ it in the own clinical practice.