Comparability and benchmarking of treatment options and potential outcome in terms of quality of life have become a crucial issue within health care systems around the world due to impact on cost effectiveness and financing.
A universally acknowledged concept of agreed rules and definitions to describe fracture patterns within the craniofacial skeleton has become essential to ensure that like is compared with like in a classification scheme on a continuum from less severe to more and most severe.
The objective of the AO CMF classification for midface and orbital fractures is to provide standardized validated recording charts as a basis for diagnosis, treatment decisions, surgical management, and accurate data collection and evaluation.
Since its outset the AO CMF fracture classification project has addressed the need of practitioners for guidelines in the daily care of individual patients as well as for database and evaluation purposes.
Once potential problems and ambiguities which cannot be eliminated by a reconfiguration of the classification concept have been identified, these are outlined and illustrated in an instructional compendium. Instructions should facilitate uniform understanding and common language with the aim of eliminating misinterpretation.
As for any classification, non-essential details were ignored and certain aspects left aside in order to emphasize general rather than individual features of a fracture pattern. This allows assignation of an individual fracture to a limited number of possible classes. This abstraction is in contrast to fracture mapping of minute detail, which would necessitate copying imaging information into the recording forms.
As a long-term perspective the categories and groups within the framework of a fracture classification must correlate to injury severity and the degree of difficulty of treatment.
A prerequisite for quality control and establishing evidence-based treatment modalities is the achievement of adequate consistency, intra- and inter-observer reliability and reproducibility in the initial documentation of trauma cases. A classification proposal requires pragmatic development through an iterative process of pilot and agreement studies under rigorous methodological surveillance and statistical validation.
The current AO CMF fracture classification system has come a long way of trial and errors and is organized in 4 hierarchical levels:
Level 1: Elementary for general trauma assessment
Level 2: Basic for CMF specialty recording
Level 3: Focused modular / subunit CMF specialty recording
Level 4: Research coding
The levels are developed in a stepwise fashion. Level 1 and 2 for the entire craniofacial skeleton are currently sufficiently complete to undergo test runs in multi-center clinical settings.
While Level 1 and 2 refer to the fracture localization, only Level 3 particularly focuses on the fracture morphology (fragmentation, multiplicity of fractures, severity of displacement, etc.) within location-specific modules such as the orbit, the anterior skull base, or cranial vault. Each location-specific module has a similar concept. Level 4 is to be used in the context of future research projects.
The common denominator for the formal Level 1, 2, and 3 fracture classifications is the description of fracture topography and its morphology based on the analysis of diagnostic x-rays, CT, or large volume cone beam imaging. Multi-plane imaging is advantageous and indispensible for the majority of the fracture scenarios.