2014 jcmtr 01 audige cmf classification introduction

The First AO Classication System for Fracturesof the Craniomaxillofacial Skeleton: Rationale,Methodological Background, DevelopmentalProcess, and ObjectivesLaurent Audig, DVM, PhD1,2 Carl-Peter Cornelius, MD, DDS3 Antonio Di Ieva, MD, PhD4

Joachim Prein, MD, DDS5 CMF Classication Group6

1AO Clinical Investigation and Documentation, AO Foundation,Dbendorf, Switzerland

2Research and Development Department, Schulthess Clinic, Zrich,Switzerland

3Department of Oral and Maxillofacial Surgery, Ludwig MaximiliansUniversitt Mnchen, Germany

4Department of Systematic Anatomy and Department ofNeurosurgery, Medical University of Vienna, Wien, Austria

5Clinic for Oral and Craniomaxillofacial Surgery, University HospitalBasel, Basel, Switzerland

6CMF Classication Group

Craniomaxillofac Trauma Reconstruction 2014;7(Suppl 1):S6S14

Address for correspondence Laurent Audig, DVM, PhD, AOFoundation, AO Clinical Investigation and Documentation,Stettbachstrasse 6, CH-8600 Dbendorf, Switzerland(e-mail: [email protected]).

Keywords

fracture classication system craniomaxillofacial diagnostic process reliability

Abstract Validated trauma classication systems are the sole means to provide the basis forreliable documentation and evaluation of patient care, which will open the gateway toevidence-based procedures and healthcare in the coming years. With the support of AOInvestigation and Documentation, a classication group was established to develop andevaluate a comprehensive classication system for craniomaxillofacial (CMF) fractures.Blueprints for fracture classication in the major constituents of the human skull weredrafted and then evaluated by a multispecialty group of experienced CMF surgeons anda radiologist in a structured process during iterative agreement sessions. At eachsession, surgeons independently classied the radiological imaging of up to 150consecutive cases with CMF fractures. During subsequent review meetings, all discrep-ancies in the classication outcome were critically appraised for clarication andimprovement until consensus was reached. The resulting CMF classication system isstructured in a hierarchical fashion with three levels of increasing complexity. The mostelementary level 1 simply distinguishes four fracture locations within the skull: mandible(code 91), midface (code 92), skull base (code 93), and cranial vault (code 94). Levels 2and 3 focus on further dening the fracture locations and for fracture morphology,achieving an almost individual mapping of the fracture pattern. This introductory articledescribes the rationale for the comprehensive AO CMF classication system, discussesthe methodological framework, and provides insight into the experiences and inter-actions during the evaluation process within the core groups. The details of this systemin terms of anatomy and levels are presented in a series of focused tutorials illustratedwith case examples in this special issue of the Journal.

Copyright 2014 by AO FoundationAOCMFClavadelerstrasse 87270 DavosSwitzerlandTel: +41 44 200 24 20.

DOI http://dx.doi.org/10.1055/s-0034-1389556.ISSN 1943-3875.

IntroductionS6

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Cranial vault, skull base, and face fractures have often beendescribed separately, even though they may be combined.These fractures in the different locations are assigned todifferent specialist competencies, which leads to the needfor several distinct specialists to discuss their views amongeach other, for example, traumatologists, oral and maxillofa-cial surgeons, plastic surgeons, ENTsurgeons, neurosurgeons,ophthalmologists. These professionals have specic expertiseregarding craniomaxillofacial (CMF) injuries, yet these com-petencies can vary across countries and their educationalsystems. The lack of borderlines between the specialties mayalso be due to the lack of clear guidelines or the lack of auniversally validated classication system. Classication sys-tems are important because they offer a structured frame-work to communicate effectively about clinical cases, andsupport the treatment decision process (i.e., conservative vs.surgical management, type of surgical intervention, type ofspecialist required). An integral modular classication systemvalidated by all involved medical disciplines might be anessential cornerstone to improve synergies and mutualacceptance.

In biomedical sciences, classication systems are omni-present. Almost every advent of a new technology or noveldiagnostic/therapeutic regimen is publicized together withthe urge to reconsider former systematization and concep-tions. This is reected in headlines and titles containingvocabulary such as grouping, coding, rating, grading, scaling,scoring, and typifying, which is indicative for a classifyingprocess. A classication scheme is the descriptive informa-tion for an arrangement or division of objects into groupsbased on characteristics which the objects have in common.1

Medical classication is the process of transforming descrip-tions of medical diagnoses and procedures into universalmedical code numbers.2 Known examples of such diagnosesand procedure codes are the WHO Family of InternationalClassications3 including the International Classication ofDiseases, the Medical Dictionary for Regulatory Activities,and the Medical Subject Headings.

In the making of a classication scheme, a key issue is todetermine the most relevant common characteristics men-tioned above. The extreme heterogeneity of human skeletalfracturesmakes it difcult to identify appropriate parametersand standardization for assigning a clinical series of uniquecases into a xed number of possible classes using a struc-tured mode.

A Multitude of Existing CMF ClassicationSystems

Over more than a century, a multitude of classications werecreated to detail site-specic fracture entities of the cranio-facial skeleton (Table 1). Till date, midface fractures arereferred to worldwide by the name of Le Fort.4 His experi-mental cadaver studies led to an understanding of the hon-eycomb construction of the midfacial skeleton and of themajor lines of weakness. The relation between bony architec-ture and the predictable course of the fractures served todescribe a limited number of well-dened patterns.57 The

simple distinction of three Le Fort type fractures is consideredas a prototype of a classication system for midface fractures.Notably, Buitrago-Tllez et al8 found that only 45% of midfacefractures could be adequately classied according to the LeFort classication in practice. The Le Fort classication hasoften been criticized as obsolete by later authors, since it isconned to the subcranial facial skeleton and does not displaythe full variety of possible fracture types in all details. To hiscredit, Rene Le Fort did not have conventional radiography athis disposal and would not have even dreamed of computedtomography (CT), magnetic resonance imaging, or the use ofoptoelectronic navigational tools in the management of skullfractures.

Rationale for a New Comprehensive CMFClassication

Despite the existence of many classication systems(Table 1), a comprehensive and structured classicationof the whole CMF skeleton that has undergone a structuredvalidation process has not been proposed until now. Aclinically relevant, well-structured, and agreed-upon classi-cation provides a universal language and coding thatfacilitates global communication and collaboration. The con-duction and comparison of clinical studies is not possiblewithout clear descriptors of the trauma patients and theirinjuries. Coding and indexing is a prerequisite to use present-day information and computing media for web-based

Table 1 References of most common fracture classications ofthe craniomaxillofacial skeleton

Location References

Midface Gurin,56 Le Fort,57

Wassmund,57 Donat et al16

Zygoma Zingg et al58

Orbitozygomatic andorbitoethmoid region

Jackson59

Nasoethmoid region Markowitz et al60

Orbit Hammer,61 Carinici,62

Jacquiry et al63

Medial orbital wall Nolasco and Mathog64

Palate Chen et al,65 Park andOck66

Midface in conjunctionwith skull base

Buitrago-Tllez et al,8

Bchli et al,26 Manson et al67

Frontal base Madhusdan et al68

Temporal bone Rafferty et al69

Mandible Spiessl,70 Roth et al,71

Buitrago-Tllez et al,21

Carinci et al72

Condylar process ofthe mandible

Spiessl and Schroll,73

Loukota et al74,75

Panfacial injuries andavulsions

Clark et al76

Craniomaxillofacial Trauma and Reconstruction Vol. 7 Suppl. 1/2014

Introduction to the First Comprehensive AOCMF Classification System Audig et al. S7

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exchange and storage of records on fractures in traumadatabases. A structured classication system enables large-scale documentation (e.g., registries), interinstitutional com-parisons, quality control, and performance evaluation oftreatment modalities,9 and the adoption of benchmarkingmethods to possibly optimize the surgical procedures andeconomic analysis. After all, CMF surgeons could soon berequired by health authorities to document patient care andtreatment performance to justify the increasing costs ofhealthcare.10

In clinical settings, injury classication systems ideallyhelp surgeons in making their decision on the most appro-priate treatment modality; classication categories reectinjury severity and include prognostic factors for clinicallyrelevant patient outcomes.11 A comprehensive CMF fractureclassicationwill provide a sound basis to evaluate treatmentmodalities and outcomes thoroughly and help to integrate theresults into the daily routines of decision making for evi-dence-based CMFmanagement.1215 Based on scientic data,CMF surgeons will be in a stronger position to advise theirpatients on the best course of action to treat their respectiveconditions.

Expected Attributes of a Valuable CMFClassication

Reecting on a few essential diagnostic and classicationissues allows one to identify the most important attributeswhich are necessary to achieve the objective of theclassication.

As pointed out by Donat et al,16 a classication system formidfacial/craniofacial fractures should be logically struc-tured, systematic, accurate, comprehensive, it should provideinformation regarding the severity of the injury and a guidanceto the therapeutical options.

ComprehensivenessFractures of the human skeleton are particularly varied, thusrendering it a major challenge to identify appropriate param-eters and standardization to assign a clinical series of uniquecases into a xed number of possible classes in a structuredand clinically useful process. While many classication sys-tems have been proposed (Table 1), the link betweenmandible, midfacial, cranial vault, and skull base fracturesis often missing. A comprehensive classication would ad-dress the whole CMF skeleton in a uniform scheme. Inaddition, the classication should be all inclusive, that is,all CMF injuries should be classiable using the proposedsystem as well as mutually exclusive (such that these injuriescannot be classied in more than one classication categoryin the system).

Clinically Relevant Diagnosis and Treatment DecisionInitially, it may seem reasonable to include all conceivablefactors and patient details into the classication. However,this would become unmanageable in routine clinical use.These pertinent factors all contribute to the daily treatmentdecisionsmade by surgeons (Fig. 1). Although, the observed

fracture pattern is only one of these factors, it is still the mostrelevant clinical feature for establishing a diagnosis and thussupporting a treatment decision.

In the development of a classication system, it is thereforeof utmost importance to identify themost relevant items thatwill support the treatment decision.17,18 The resulting cate-gories might be indicative of some specic injury character-istics such as severity, that is, they can reliably distinguishgroups of injuries that differ regarding the complexity of theirtreatment, or the quality of their outcome(s).18 Most impor-tantly, a fracture classication system should be based ontheir essential biological characteristics, that is, fracturetopography and morphology,19 and not explicitly includetreatment-based criteria to ensure universality of the system.

User Friendliness and DiscernibilityA fracture classication system should be simple to use andtherefore limited to a few pertinent parameters. must notallow for complete individualized fracture mapping. Thenecessary process of abstraction in the development of thesystem is always a tradeoff between detailed individualizedinformation and the use of restricted categories associatedwith loss of information.

Reliability/AccuracyIn addition to clinical relevance, a good fracture classicationshould provide a reliable and accurate means of communica-tion. Different observers presented with the same diagnosticimages (e.g., CTscan series)must agree on the classication ofa fracture most of the time (reliability of the diagnosis). Theclassication should also reect the true injury status of thepatient (accuracy of the diagnosis), that is, observers shouldaccurately identify the most clinically relevant fracture pat-terns. If this is not the case, the classication has failed in itsfundamental goala means to communicate informationbased on agreed similarities and differences.

In traumatology, most published reliability studies gener-ally showed poor interobserver reliability of commonly usedclassications.20 In the CMF eld in particular, reliabilitystudies were rarely conducted. Recently, Buitrago-Tellez

Figure 1 Multiple patient and injury factors inuencing treatmentdecision and outcomes. Note: The fracture pattern described bylocation and morphology is only one of the many factors inuencingtreatment decision and outcomes.


Introduction to the First Comprehensive AOCMF Classification System Audig et al.S8

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et al21 reported on one of our initial evaluation sessionsregarding a proposed classication system for mandibularfractures. In orthopedics, it has become a standard that injuryclassication systems be formally validated before theirapproval for clinical and research purposes.20,2224

Fracture Classication versus Injury SeverityScore

The use of an injury severity score implies that themagnitudeof the injuries can be graded on a continuous or ordinal scaleand that this score has some predictive value for treatmentoptions and/or outcome(s). Various attempts were made tobuild up fracture severity scores for the CMF region21,2530

based on several diagnostic parameters. The nal severityscores are calculated by adding points allocated to each ofthese diagnostic parameters and anatomical region found tobe relevant in guiding treatment decisions. The actual pointsystems, however, were elicited by the authors or expertopinion without solid scientic basis, leading to some uncer-tainty pertaining to the validity of the actual numeric nalscore. For instance, Catapano et al31 proposed a new severityscoring of facial fractures which sums a grade of 0 (nofracture) to 3 (bone loss) across 41 anatomical regions.Because all regions received equal weighting, an increasedseverity of some fracture patterns may not be systematicallyassociated with an increased score. Also, the nal score maynot be handled on a continuous scale. The weighting ofdiagnostic categories and regions to generate severity scoresshould have a sound scientic basis, that is, the score calcu-lation algorithm requires clinical data to create prognosticmodels. This process has been applied in the context ofoutcome analysis systems to provide norms for traumacare.3234

A typical limitation of severity scores is that the score itselfcannot be reversed into the fracture pattern and, stand-alone,only provides prognostic information. For that reason, afterhaving considered the potential value of a CMF injury severityscore at the initial development stages,21 the objective of thisproject was strictly focused on the development of a clinicallymeaningful classication system allowing intelligible pictur-ing of the fracture patterns. This systemmay be subsequentlytranslated into a severity score following appropriate clinicaldocumentation.

AOCMF Classication GroupA Brief History

An international Craniomaxillofacial Classication Group(CMCG) including an extended company of multispecialtysurgeons experienced in the management of CMF fractureswas established in 2004 with the task of developing aclinically relevant and valid CMF comprehensive fractureclassication system. Scientic coordination and organiza-tional support to the group were provided by AO ClinicalInvestigation and Documentation. The list of participatingsurgeons involved in the initial classication activities ispresented in the Acknowledgment section. This group ini-tially followed on the craniofacial fracture work of Buitrago-

Tellez et al,8 and adapted the same approach to the mandi-ble.21 However, after several evaluation sessions, consensuscould not be achieved among evaluating surgeons. An alter-native classication concept was required. As a consequence,a critical step toward the development of the present systemwas done. The CMCG was reorganized in 2007 with asmaller core membership of ve experienced CMF surgeons(J.P., CP.C., C.K., J.F., R.R.), one radiologist (C.B.), and a scienticcoordinator (L.A.). In addition, two specically focused Classi-cation Groups (CGs) were established to develop part of thesystem addressing skull base fractures (C.M., A.D., K.S., B.K.)and condylar process fractures (M.R., A.N., CP.C).

Broad international acknowledgment and changeover asstandard application of the comprehensive CMF system inclinical institutions worldwide was a key objective of thisproject. The involvement of experienced surgeons from vari-ous geographical and clinical backgrounds (e.g., CMF sur-geons, ENT surgeons, plastic surgeons, neurosurgeons) inclassication groups facilitates identication of cross-culturaldifferences in training and understanding of basic clinicalconcepts and denitions.

Classication Development and ValidationPathway

According to the AOCMF and its CMF classication groups, alist of expected properties for the classication system wasdrawn up (Table 2).

Table 2 Targeted properties of the CMF classication system

1 Address only traumatic CMF fractures

2 Be comprehensive, including the whole CMF skeleton

3 Be applicable to the mature skeletona

4 Consider a hierarchical system from very simple for allsurgeons to more detailed and focused for speciclocations and specialist surgeons

5 Describe fracture location and morphology basedessentially on CT scans (or for mandibular fractures,Panorex and/or conventional radiographs in twoplanes)

6 Be consistent with well-accepted systems such asthe Le Fort classication in the midfacial skeleton57

7 Be perceived by CMF surgeons as simple, practical,and clinically meaningful

8 Demonstrate a reasonable level of reliability andaccuracy for most common fractures

9 Provide a rational basis for prospective (functionaland patient reported) treatment outcome studies,from which algorithms for clinical decision makingcan be derived

10 Reach international acceptance

11 Be incorporated into an electronic database, such asa specialized software solution to facilitate teaching,classication, and documentation of CMF cases

Abbreviation: CMF, craniomaxillofacial.aMaxillofacial trauma in pediatric patients requires different consider-ations from those of adults, with different therapeutic approaches.77



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In the development and validation of classication sys-tems, Audig et al35 suggested implementing a methodologi-cal pathway with three successive research phases (Fig. 2).The rst phase involves clinical experts developing a blue-print for the classication system, as well as dening theassessment technique (e.g., clinical information, image mo-dalities, measurement aids). Precise denitions and instruc-tions need to be worked out to dene a common language bywhich surgeons should be able to understand, identify, anddescribe injuries in a uniformway. Successive pilot agreementstudies are conducted to evaluate the reproducibility of theclassication performed by clinical experts. The natural ten-dency of all CGs was to initiate the development by proposinga very detailed system to address all injury patterns. Partic-ipants realized after a few evaluation sessions that simpli-cation is only warranted, along with the clarication ofdenitions for terms that are commonly used (e.g., fragmen-tation or comminution). This process is not easy andinvolves translating clinical experience (pattern recognition)into a set of standardized denitions. At this stage, thepredictive clinical value of any proposed system is evaluatedby expert opinion (concept of face validity, that is, theclassication should look good on clinical ground). Thesecond phase involves a multicenter agreement study toensure that future users with less clinical experience canunderstand and agree on the classication system. Thiscreates the basis for a classication tool to be used fordocumentation and evaluation of treatment options. Onlyafter these rst two phases have been completed can a thirdphase involving prospective clinical documentation be im-plemented to support future recommendations for patientcare based on the classication.

This methodological pathway has been adopted and im-plemented successfully within all classication projects sup-ported by the AO Foundation and its specialties, in particularfor the development of the established AO pediatric long-bone fracture classication system,36,37 and the developmentof a comprehensive AO-Spine injury classication.38

The currently proposed CMF fracture classication is theproduct after completion of phase 1. More specically, itinvolved for each CG a series of face-to-face meetings togradually build up the classication system itself as well asthe prerequisites (e.g., imaging type and quality) under whichit can be reliably used. In the period between the meetings,

surgeons evaluated the proposed or revised system by con-ducting classication sessions using imaging series (conven-tional radiographs and CT scans) of up to 150 consecutivecases. Overall, the image documentation of 494 consecutiveCMF fracture cases collected from 6 European centers wasanonymized and centralized at AOCID for use in successiveevaluation sessions. Cases were sent to surgeons on digitalvideo disks together with a DICOM viewer. They classied thecases independently each time according to themost updatedversion. Classication data were collected either on paperforms or electronically using MS Excel (Microsoft Corpora-tion, Redmont, WA) or specically designed AOCOIAC soft-ware (AO Comprehensive Injury Automatic Classier, AOFoundation, Dbendorf, Switzerland; www.aofoundation.org/aocoiac). The datasets were analyzed for classicationreliability and accuracy as well as for identication of casesshowing most coding discrepancies between surgeons. Theselatter cases were discussed during the subsequent face-to-face meetings to identify the probable reasons for the inter-observer disparities in order for adjustments and claricationof the actual version. Group members also had to agree thatthe proposed system would meet initial expectations(Table 2); further evaluation is to come and should involveawider circle of CMF surgeons (phase 2 validation process) tosupport the current consensus, and allow nal adaptations ofthe system.

Consensus, Challenges, Strength, andLimitations

The development of this comprehensive CMF fracture classi-cation used a strong consensus process among experiencedsurgeons aimed at measuring and resolving disagreement(consensus development). There are many traditional meth-ods used to reach group consensus.3943 In the medical eld,the application of group consensus has mainly been used inthe development of standards and guidelines for diagnosisand treatment,44,45 and has provided relatively consistentand reliable results.4648 Our consensus approach towardclassication development incorporated an immediate prac-tical application through classication evaluation sessions.These sessions allowed surgeons to gain experience using theproposed system, and after considering the classicationdiscrepancies, review meetings could be focused on theessential issues to improve the system.

Experienced surgeons are busy professionals and therepetition of classication sessions on a series of 50 to 150cases required a high level of dedication and investingpersonal time from the participants. It was a great challengeto maintain the CGs motivation and commitment throughoutthe consensus process. A phase 1 development project oftenrequires 3 to 4 years to reach a solid and scienticallysupported consensus.36,49

Some limitations should be mentioned. Initially, surgeonsclassied cases during meetings; however, the process waschanged to reserve meetings for case discussion based oncoding disagreements. Classication sessions were then con-ducted at home. There was always a tradeoff between

Figure 2 Methodological pathway for the development and validation ofinjury classication systems. Reprintedwith permission fromAudig et al.35



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methodological concerns and practical issues. The number ofconsecutive cases that can be classied in any session islimited by the surgeons time and thus only themost frequentfracture patterns were examined. To address rare fractures,subsequent follow-up evaluation projects should beimplemented.

The present classication system and evaluation sessionswere limited by the type and quality of the images madeavailable. Cases with images considered insufcient for clas-sication purposes were excluded from the series. It shouldbe noted that some part of the CMF classication system willrequire more advanced imaging for a thorough evaluationprocess, such as craniomidfacial fractures documented bymultidetector CT.50Wemust also accept that imperfections inthe systemwill be detected by further technological advancesresulting in improved (computer-assisted) diagnosis pro-cesses and classication, by means of new algorithms andimaging sequences such as those using high-resolutionmulti-planar reformations.51

The Present AOCMF Fracture ClassicationSystemHistory Outline and Structure

From Maurice Mller to International CollaborationIn 1986, the AO Foundation ofcially adopted The Compre-hensive Classication of Fractures of the Long Bones devel-oped by Maurice Mller and his group as a groundwork forits activities in documentation. This system introduced astandardized alphanumeric code to indicate the affectedbone and fracture morphology within the specic bonelocation, according to three types (A, B, and C), three groupswithin each type (A1, A2, and A3), and three subgroupswithineach group (A1.1, A1.2, and A1.3) ranging from low (A1.1) tohigh (C3.3) severity. The latter relates to the complexities ofthe fractures, the assumed difculties inherent in theirtreatment, and their perceived prognosis.52 This classicationconcept became a standardworldwide for long bone fracturesand was later adopted for fractures of the pelvis/acetabu-lum,53 the hand54 as well as spine injuries.55

On the same path, the AO Foundation has made persistentefforts to create a classication of craniofacial injuries. Theproject was launched by the work of Buitrago-Tllez et al,8

who initially designed a CT-based diagnostic algorithm forcraniomidfacial fractures to establish a hierarchical classi-cation of increasing severity. The elementary concept was tosplit craniofacial fracture patterns analogous to the AO triadsystem. The craniofacial region was divided into three units:the lower midface (I), the upper midface (II), and the cranio-basal-facial unit (III). Lateral and central fractures were alsodistinguished. This allowed a standardization of themidfacialand craniofacial fractures in a special way described withregard to their severity. With the subsequent establishmentof a rst CMF classication expert panel, a classicationsystem for the mandible differentiating vertical mandibularcompartments and a horizontal subdivision of the body andparasymphyseal region was proposed on the same princi-ples.21 At the same time, the AO Classication Advisory groupand the OTA Classication Committee agreed on a uniform

numerical coding of the bones and anatomical regions of thehuman skeleton, with fractures of the CMF skeleton beingcoded with the number 9 (Fig. 3).18 The presented AO CMFclassication system is anchored within a global and uniformsystem to support surgeons documenting their fracturessimilarly.

New Hierarchical Classication SystemThe rst classication evaluation sessions and review meet-ings led to the realization that the initial system was notintuitive enough to achieve consensus among surgeons in-volved in the evaluation process. An agreement concerningthe denitions using the AO triad system8,21 could not beachieved in the evaluation meetings to continue the imple-mentation of this system. One of the reasons may be hypo-thetically due to the adoption of the AO-Mller triad scheme,well accepted for long bones,17 but not very familiar amongCMF specialties.

So the triad system was not considered mandatory for theCMF skeleton anymore. A paradigm shift was required towardthe development of a streamlined classication system con-sidered as practical, clinically meaningful, and still scienti-cally sound. Despite the present system being built on allprevious endeavors and published classication work(Table 1), it had to be accepted a priori that the systemwas not meant to map each and every conceivable combina-

Figure 3 Unied classication system for fractures of the humanskeleton. Adapted from Marsh et al.18



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tion of every single fracture line in a CMF injury, and restric-tion to the most relevant diagnostic items for clinical practicewas essential.

The present AOCMF fracture classication system is basedon a hierarchical structure of three levels from very simple tomore focused and complex:

Level 1: elementary system for gross fracture location:mandible (code 91), midface (code 92), skull base (code93), cranial vault (code 94)

Level 2: basic system for rened fracture location in theCMF skeleton (outlining the topographic boundaries of theanatomical regions within the fundamental units of theCMF skeleton as a basis for a more precise localization)

Level 3: focused modular system assessing fracture mor-phology (i.e., fracture lines, level of fragmentation, anddisplacement)

While levels 1 and 2 serve as approved anatomicallocalizers, level 3 describes the fracture morphology in anarray of modules representing anatomical regions andsubregions.

A detailed presentation of each classication level andmodule is presented in the following series of tutorial papersin this special issue of the Journal along with typical anddifcult case examples according to specic anatomicallocations:

Level 2 craniomidface Level 2 mandible Level 3 mandible (excluding the condylar process) Level 3 condylar process Level 3 midface (excluding the orbit) Level 3 orbit Levels 2 and 3 skull base and cranial vault

In addition, practical applications of the present systemare considered with specic regard to radiological and diag-nostic issues as well as electronic documentation using asoftware solution. A large case collection is made availableelectronically on the AOCMF website (www.aocmf.org/clas-sication). Each presented case include selected diagnosisimages, a description of identied fractures, as well as thefracture coding using the AOCOIAC (AO Comprehensive InjuryAutomatic Classier) software solution.

TerminologyRoutinely used clinical terms sometimes lack denitionand are used in a more ambiguous way in contrast tointernational anatomical designations which are wellillustrated in atlases and clearly referenced in an ofcialnomenclature (FCAT, Federative Committee of AnatomicalTerminology). The clinical terms often relate to importantlandmarks or substructures that bear no formal anatomicalnameplates.

Both anatomical nomenclature and clinical terminologyare used to identify the skeletal components. To precludeerrors and misunderstanding in context with the level 2CMF Classication, some ambiguous clinical expressions arepresented in an appendix glossary.

Concluding Notes

Our consensus approach allowed bringing together the per-spectives from different CMF specialties toward a commongoal of having a comprehensive classication system.

As expected and accepted, this system is simplistic andimperfect. Some CMF surgeons will possibly reject it as beingnot detailed enough for their purpose, or not providing themthe immediate clinical application they look for. Yet, the onlyway to make it a valuable tool for documenting CMF cases ata chosen level of details is to install it as a standard and aimfor continuous improvement. This will promote more validclinical research. With the use of rened diagnostic imagingtechniques, the classication systemwill evolve and incorpo-rate additional well-thought and validated diagnostic fea-tures we are not even dreaming of at present just as Le Fort athis time.

Presently, the authors encourage the whole community ofsurgeons involved in the management of CMF trauma toembark on the use of the proposed system, apply it in dailypractice and research, and to push help its limit eventually tothe benet of their patients.

AcknowledgmentsThis CMF classication project was funded by the AOFoundation and its AOCMF Specialty. Buitrago-Tellez C,Institute of Radiology, Zongen Hospital, Switzerland,initiated this development with support from an AOResearch Grant and developed in cooperation with SauterD and Marschelke H, Ingenieurbro Marschelke, Reich-enau, Germany the rst software version for semiauto-matic classication of craniomaxillofacial fractures(Buitrago CAFFACCrAniomaxillo-Facial-Fracture-Auto-matic-Classier). Illustrations were prepared by AO Edu-cation (publishing) by Jecca Reichmuth and her colleagues.

The authors are grateful to all surgeons (as listed belowin alphabetical order) who participated in the successiveclassication sessions and provided their fruitful supportin the development and validation of this craniomaxillo-facial fracture classication system:

Alpert B, Louisville, KY; Brad S, Sacramento, CA; Bui-trago-Tellez C, Zongen, Switzerland; Cornelius CP, Mu-nich, Germany; Dala Torre D, Innsbruck, Austria; Di Ieva A,Vienna, Austria; Ehrenfeld M, Munich, Germany; Figari M,Buenos Aires, Argentina; Frodel J, Danville, PA; Hirsch J,Uppsala, Sweden; Kellman B, Syracuse NY; Kunz C, Basel,Switzerland; Kushner G, Louisville, KY; Lindqvist C, Hel-sinki, Finland; Manley G, San Francisco, CA; Matula C,Vienna, Austria; Neff A, Marburg, Germany; Patrick L,Birmingham, AL; Prein J, Basel, Switzerland; Rasse M,Innsbruck, Austria; Rudderman R, Alpharetta, GA; Shum-rick K, Cincinnati, OH; Sugar A, Wales, United Kingdom.

NotesLaurent Audig, DVM, PhD and Carl-Peter Cornelius, MD,DDS, have contributed equally to this article and share lead



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authorship. Members of the CMF Classication Groupwere: Core: Prein J. (Chair), Cornelius P., Buitrago-TellezC. (radiologist), Kunz C., Frodel J., Rudderman R.; CondylarProcess: Rasse M. (Chair), Neff A., Cornelius CP.; Skull Base:Matula C. (Chair), Di Ieva A., Shumrick K., Kellman B.;Scientic coordinator: Audig L.

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2014 jcmtr 01 audige cmf classification introduction

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