Classification proposal for fractures of the processus condylaris mandibulae
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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.
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).
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.
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.
KeywordsCondyle of mandible Fracture Classification
For the last decade, the classification/nomenclature of fractures of the mandibular condyle region has been based on the Strasbourg Osteosynthesis Research Group  and Arbeitsgemeinschaft für Osteosynthesefragen (AO) systems . The accurate anatomical description of the classification allows for visualization by most clinicians without the need to memorize numerically ordered types of fractures. Some authors believe that the subjective descriptions of “high” and “low” level fractures in the neck region should be clarified [1, 3]. A new classification system was retrospectively analyzed in a cohort of patients with condylar fractures and found to be simple to use and helpful in the prediction of treatment needs and outcomes .
Unfortunately, as this classification was implemented, it became obvious that nearly all fractures were classified as condylar basal and head fractures. Practitioners had to deliberate to determine whether a third or half of the fracture line was above or below the reference. Ultimately, high-neck fracture disappeared as a classification result. The maintenance and utilization of this fracture classification is important due to the special techniques and fixation materials that are required to treat such high fractures that are still not classified as type C head fractures .
The purpose of this study is to present a modified classification of mandibular condyle fractures.
Material and methods
The first landmark is the line oblique to the sigmoid notch line (known line, designated line A by Loukota), which was selected because the majority of fracture lines are oblique in this region . This line (the proposed line B) runs along the most prominent point of the posterior border of the masseteric tuberosity and the deepest point of the sigmoid notch.
The second landmark is the head anterior border point (Fig. 1), which was selected to establish a recognizable border between the mandibular head and the condylar neck; this border was not clearly established in the old classification system . The point is situated at the top of the angle of the sigmoid notch immediately below the condylar head, as observed from the lateral view. This point marks the anterior boundary of the head and neck in the lateral view of the mandible.
The change in the angle that serves as the basis for coding the condyle fracture was checked in relation to Loukota’s line in a series of 362 computer tomographic (CT) scans (102 cone beam CTs and 260 fan beam CTs). That series contained mandible images from healthy patients of both sexes, whose CTs were retrospectively found in a hospital database. One-way analysis of variance was performed to determine the variability of this angle.
The efficacies of the current and the newly proposed classification systems were retrospectively evaluated based on 95 CT images of mandibular condyle fracture cases that included the following: 60 basal fractures (according to the current classification) vs. 56 (according to the new, modified classification), 9 low-neck fractures (according to the current system) vs. 12 (according to the modified system), 4 high-neck fractures (according to the current system) vs. 7 (according to the modified system), 11 type C head fractures (according to the current system) vs. 9 (according to the modified system), 10 type B head fractures (according to both classifications), and 1 type A head fracture (according to both classifications). The compatibility of the proposed and modified classification systems was examined with a χ2 test of independence. Statistical tests were performed with Statgraphics Centurion XVI, Statpoint Technologies, Inc., The Plains, VA, USA.
The proposed change of an angle upon which the coding of the condyle fracture was based was 52° ± 5° in relation to Loukota’s line (line A). The distribution of the angle’s values was normal. The minimum was 37°, and the observed maximum was 69°. The value was statistically independent of age; the age was 44 ± 18 years (typical for young adults with facial injuries). The value of the angle was also independent of sex (ANOVA p > 0.05) and CT data acquisition method independent (ANOVA p > 0.05).
The head anterior border point is generally highly recognizable (> 97% of cases). Total agreement was noted in the type A and B head fractures in both classifications because the modification did not concern this type of injury. Thus, 11 cases were excluded from later analysis. Notably, only four high-neck fractures were diagnosed among the included cases according to the conventional classification; in contrast, seven high-neck fractures were diagnosed using the proposed modification.
Observed incompatibilities between the classifications of the fracture levels covered by the modification (i.e., type C head fractures and high, low, and basal condylar fractures) were recognized. The classifications shifted upward from basal fractures (according to the current system, i.e., Loukota et al. 2005  and Neff et al. 2014 ) to low-neck fractures in four cases and from low-neck (according to the current system) to high-neck fractures in one case. Downward classification shifts were observed only from type C head fractures (diagnosed according to the current system) to high-neck fractures diagnosed according to the modified system (two cases). No classification changes occurred from basal condylar fractures (according to the current classification) to mandibular ramus fractures, from low-neck to basal fractures, from high-neck to low-neck fractures, or from high-neck (according to the current classification) to type C head fractures. The modified and current classifications fully corresponded only for basal fractures, i.e., all basal fractures according to the modified classification were also basal in the current classification. The same was observed for the type C head fractures. The following incompatibilities were found (Fig. 2): 5% of low-neck fractures (4 cases out of 84) were previously diagnosed as basal fractures using the current classification, and 4% of high-neck fractures (3 cases out of 84) were recategorized, mainly as low-neck fractures, when the proposed classification system was used.
According to the clinical perspective, a condylar process fracture is defined as any fracture that is situated over the foramen mandibulae and runs from within or above the angle of the mandible into the sigmoid notch or the condylar head. Numerous classifications exist [6, 7, 8]; however, this subclassification has always been confused by homonymic classifications that are restricted to the condylar neck region (i.e., the collum mandibulae, according to its anatomical definition) and the use of the homonymic classification terms for completely different fracture levels in papers worldwide. This spectrum of classifications that coexists on an international level makes comparisons between treatment outcomes nearly impossible  and highlights the need for a validated classification system based on reproducible anatomical landmarks.
The assumption of this modification is that the reference lines run obliquely because the fracture lines observed in clinical conditions are also oblique. Because the reference lines are mostly parallel to the fracture lines, the fracture levels will be more accurate in the new classification system, and thus this classification will be more coherent with nature.
The advantages of this classification system are as follows: ease of application (as explained previously), simple criteria for the assignment of a fracture to a defined level (because the reference lines run approximately parallel to the fracture lines that are clinically observed), and diagnoses of high-neck fractures along with low-neck fractures can be established. Moreover, the new classification system makes diagnoses more differential. Practitioners will be able to frankly identify three classes of fractures situated below the mandible head; in contrast, in the current system, only basal condylar fractures and head condyle fractures are observed.
Another disadvantage of the proposed classification is the need for additional anatomical point and topographical lines compared to the previous classification. Moreover, the new classification requires a multicenter systematic evaluation with a large number of cases similar to that which was previously performed  because it is very difficult to perform reliable and useful comparisons between results in meta-analyses .
Generally, the proposed modification influences low- and high-neck fractures, which are underestimated in the currently utilized classification and should be treated surgically with the application of different materials. Slim profile plates or long compression screws  can be effectively applied to high-neck fractures, whereas wider plates should be applied in the treatment of low-neck fractures .
This modification of the classification of mandibular condyle fractures should assist and simplify treatment-related decision making and standardize diagnoses in future work within this field of traumatology.
The author acknowledges Bartosz Bielecki-Kowalski and Agnieszka Kozak-Rusinek for their help with the data collection and Tomasz Wach for help with computer-assisted design.
Source of support is Medical University of Lodz grant no. 1.503/5-061-02/503-51-001.
Compliance with ethical standards
The paper complies with the principles stated in the Declaration of Helsinki “Ethical Principles for Medical Research Involving Human Subjects,” adopted by the 18th World Medical Assembly, Helsinki, Finland, June 1964, and as amended most recently by the 64th World Medical Assembly, Fontaleza, Brazil, October 2013.
Conflict of interest
The author declares that he has no conflict of interest.
This research was approved by Medical University review board no. RNN/125/15/KE.
A formal consent is not required for this type of study.
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