The Gazette 1993

GAZETTE

of the impact snapping the head backward, happens so quickly that the anterior neck muscles do not have a chance to relax. As a result they act as an anchor on the mandible holding it still and forcing the mouth open excessively, as the head continues to move backwards. This action, the whipping excessively open of the mouth and its subsequent closure into normal position, results in a self-reducing dislocation of the TMJ. The masticatory and cervical musculature, ligaments and the synovial tissues of the temporo- mandibular joint are simultaneously injured. A frequent result of this type of injury is the anterior displacement of the TMJ disc and posteriorization of the mandible as seen in figure 2.

The cranium compensates for the forward head position by rotating the head posteriorly and assuming an extended head posture so that normal line sight is restored. This situation frequently creates and maintains entrapment of the occipital nerves referring pain to the head and face. TMJ dysfunction will place excessive demands on the musculature producing myofascial pain and dysfunction. Trigger points in the muscles are creat- ed as a focus of hyper-irritability giving referred pain to the head and neck. TMJ dysfunction may be divided into two categories: trauma and chronic. The causative factors of each category and their subsequent treatments are vastly different and treatment applied to the wrong category can cause incorrect- able harm to those who come for treatment. Insurance companies are besieged with claims for injuries which appear to be trauma induced when, in fact, they are pre-existing conditions that are non-accident related or exacer- bations of pre-existing conditions. Therefore, proper and complete differential diagnosis and the correct treatment planning is essential at this point.

Figure 3. The clicking sound that occurs during the opening movement of the mandible, is actually the repositioning of the mandibular condyle under the TMJ disc and the restoration of the normal functional relationship. In a whiplash injury, particularly a rear end collision, the whipping of the head backward results in spasm of the anterior cervical musculature. One of the most common pathological changes in the musculoskeletal system is the creation of the dysfunctional relationship between the cranium, mandible and cervical vertebrae demonstrated by the loss of the neck's lordotic curve. This loss results in the straightening of the cervical vertebrae which pulls the cranium forward into the pathological head forward position.

Normal Disc Relationship

Anterior Disc Displacement Posteriorization of Mandible

Longus r^ Colli \ \

SCM

SCM

Figure 2

FORWARD HEAD POSITION

STRAIGHTENING OF CERVICAL VERTEBRAE

Figure 4 The forward position does not allow for normal vision because the cranium is directing the eyes toward the ground.

The anterior displacement of the TMJ disc has been demonstrated to be the primary aetiology of progressive disease which results in degenerative arthritis. When the ligaments holding the disc in place become stretched or torn due to the displacement, this can result in permanent damage.

— Occipital Nerves

This injury is particularly important because it is well documented that 60%

of the people involved in motor accidents do not fully recover.

Figure 5

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