Controversy has surrounded all aspects of fractures of the condylar process. There have been several proposed classification methods of these types of fractures.
Following, the AO classification is presented along with a simplified version. The AO classification allows for better communication between radiologists and surgeons. On the other hand, the simplified version better reflects the clinical treatment implications.
The condylar process and head is a subunit of the mandible and is defined by an oblique line running backward from the sigmoid notch to the upper masseteric tuberosity. The condylar process is differed into three subregions:
- Subcondylar (caudal) area
Three lines are used to define these subregions:
- The first line parallels the posterior border of the mandible
- The sigmoid notch line runs perpendicular to the first line at the deepest portion of the sigmoid notch
- A line below the lateral pole of the condylar head that is also perpendicular to the first line.
Clinical pearl: the neck region can be divided into high and low halves by equally dividing the distance between the sigmoid notch line and the lateral pole line.
Treatment implications – simplified classification
In contrast to the descriptive, previously defined anatomical classification, a more simplified one is outlined and used in the Surgery Reference.
The surgeon decides to treat condylar process fractures in an open or closed method. To perform an open reduction and internal fixation, there must be room in the superior fragment for at least two screws fixing the same plate.
Clinically, this equates to open treatment of condylar neck fractures or subcondylar (caudal) fractures (A). The surgeon may elect to place one or two plates depending on the location and configuration of the fracture.
Fractures at a level where there is inadequate space for two holes to be drilled for the plate (B) require special techniques of osteosynthesis. For that reason, among others, most surgeons choose closed treatment for these joint fractures.
Fractures of the condylar process (unilateral or bilateral) can occur in isolation. They are more often combined with other mandibular fractures.
Routine diagnosis of this type of fracture should include radiographs taken
in two planes at 90° to each other; the minimum requirement is a PA view and a
CT or digital volume tomography (DVT) imaging may be used as an alternative.
Panoramic view showing left condylar process fracture in association with an anterior body fracture.
Towne’s (oblique PA) view of the above patient. X-ray taken at 90° to show displacement of left condylar process fracture. Vertical shortening of the left mandible is noted along with the right anterior body fracture.
CT scans give the surgeon the best information with regard to fracture location, morphology, fragmentation, and associated injuries.
CT scan 3-D reconstruction illustrates right condylar process fracture.
Coronal view of the above patient shows angulation and luxation of the condylar process fracture.
The dental occlusion can give orientation about the fracture location. With a unilateral condylar process fracture and subsequent reduction of height in the ramus region, the clinician will see an ipsilateral premature occlusion and contralateral open bite. The dental midline will shift toward the side of fracture.
The occlusion shows premature contact on the right with the deviation of the jaw to the affected side that is commonly seen with a right mandibular condyle fracture.
Bilateral fractures with shortening and dislocation result in anterior open bite with minimal deviation of the midline.
Pitfall: widening of the lower face
Bilateral condyle fractures associated with fractures of the symphysis and body region often produce a widening of the mandible and subsequent malocclusion. These fractures are very difficult to treat. Great care must be taken when performing the open reduction and internal fixation of the body fractures to assure the mandible is narrowed to its pre-injury status. Failure to recognize and/or correct the widening of the body fractures will prevent anatomic reduction of the condylar fractures and subsequent occlusal and functional complications.
Bilateral condylar process fracture
CT and/or digital volume tomography (DVT) is extremely useful especially in cases of high and/or intracapsular fractures of the condyle.
This coronal view demonstrates bilateral condylar process fracture with displacement. On the patient’s right side there is a condylar neck fracture with angulation and on the left side there is sagittal condylar head fracture medial to the lateral pole. On the right side, the height of the mandible is not reduced.
The increased width of the mandible in ramus/condyle region may indicate that there is an associated fracture in the anterior mandibular arch.
Detail of a panoramic x-ray showing a subcondylar fracture.
Example of (low) neck fracture
Plain x-ray taken at 90° to demonstrate displacement of condylar process fracture.
… and panoramic views of a (low) neck fracture.
Example of a (high) neck fracture
3-D reconstructions are useful in identifying fracture height, direction and severity of displacement.
This 3-D reconstruction illustrates a (high) neck fracture with displacement. Note the associated anterior body fracture of the contralateral side.
Nondisplaced, nondislocated fracture
Nondisplaced, nondislocated fractures suggest the presence of periosteal support for stability and may not require open treatment.
X-ray in the PA plane shows no vertical shortening.
X-ray shows that no displacement occurred.
Hunting bow concept
The mandible is similar to a hunting bow in shape, strongest in the midline (symphysis) and weakest at both ends (condyles). The most common area of fracture in the mandible is therefore the condylar region.
A blow to the anterior mandibular body is the most common reason for condylar fracture. The force is transmitted from the body of the mandible to the condyle. The condyle is trapped in the glenoid fossa. Commonly, a blow to the ipsilateral mandible causes a contralateral fracture in the condylar region. If the impact is in the midline of the mandible, fractures of the bilateral condylar region are very common.
Direct trauma to the TMJ area is unusual but may be associated with fractures of the zygomatic complex.
With a condylar fracture, there is very often shortening of the ramus on the affected side. This will result in an ipsilateral premature contact of the teeth. In case of bilateral fractures, the patient may present an anterior open bite. The condylar fragment may be displaced (most often laterally) based on the angulation of the fracture and predominant muscle pull.