Whiplash and its effects on the temporo–mandibular joint (TMJ) by Meurig Devonald BDS

Whiplash is the common term for a neck injury which often occurs when riding in a car that is involved in a road accident, particularly a rear-end shunt. Typically, the subject’s head forcibly snaps backward as the body is thrown forward. The head may then snap forward in a recoil motion. This severe backward and forward motion may occur more than once, and damages the neck muscles and especially the soft tissues (muscles and ligaments) supporting the neck, head and jaw.

It is easy to see why this damage happens, when you consider that the head itself weighs up to 15 pounds (the weight of an average bowling ball). When this ‘bowling ball’ snaps backward, it creates 500 to 600lbs of force on the neck. Women are more vulnerable to whiplash injuries than men because their neck muscles are smaller in relation to head weight.

Persistent symptoms of whiplash

Since injuries to soft tissues do not show up on X-rays, it is difficult to immediately see whether or not these symptoms may not be felt until hours or days after the accident. Once symptoms do appear, however, they can be very painful and quite persistent.

Whiplash symptoms include:

• Neck pain, stiffness and decreased range of motion
• Headaches
• Numbness of the head and face
• Blurring of vision and pain behind the eyes
• Problems with balance
• Difficulty swallowing
• Ringing in the ears
• Jaw pain and limited range of motion.

One reason why symptoms may persist is because in many cases of whiplash, the jaw joints and the muscles that support the jaw are damaged as well. The accident may trigger a condition in which these muscles go into spasm and become very painful. Specific clues as to whether this damage occurred include:

• Pain in or around the jaw joints
• Clicking or popping of the jaw joints
• Locking or limited opening the mouth
• Difficulty bringing the teeth together.

Because both patients and healthcare providers often do not suspect that the jaw joints and muscles may have been damaged, this aspect often goes unrecognised. When neither recognised nor treated, it can become the dominant medical problem.

Two recent studies have shown using magnetic resonance imaging (MRI) that between 87 per cent and 94 per cent of people who had suffered a whiplash injury without direct trauma showed damage and dislocation of jaw joint tissue associated with the headaches, spasms and general pain experienced with having their heads whipped backwards and then forwards suddenly.

In 1972, the Preventive Dental Research Group studied 500 people injured in motor vehicle accidents whose cases had been settled, but were still suffering from injuries traced back to the accident itself. This study revealed that the residual symptoms were:

• Headaches
• Hearing Loss
• Neck aches
• Pain in chewing
• Backaches
• Pain in the face and jaws
• Earaches and dizziness
• Ringing in the ear
• Clicking noise when opening and closing the mouth
• Difficulty when swallowing

These are all typical symptoms of a TMJ injury.

A high percentage of these accident victims had had a history of cervical traction that increased the original pain or caused injury where none had occurred before – in the temporo-mandibular joint. (Traction may be helpful in cervical injuries but virtually ensures TMJ pain).

The study concluded that the same uncontrolled whipping of the head that had injured the neck had also forced the jaws out of alignment, causing an injury to the TMJ which was undiagnosed.

Whiplash effects on the jaw joints

In motor vehicle accidents, particularly in rear end collisions, the suddenness 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 excessively open, as the head continues to move backward into hyper-extension. 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 posteriorisation of the mandible.

TMJ disc is normally interposed between the mandibular condyle and the temporal bone. The posterior movement of the mandible displaces the condyle from under the disc resulting in TMJ dysfunction. Disturbance of this disc-bone-condyle function and relationship displaces the condyle even further posteriorly against the sensitive posterior joint tissues, resulting in pain. The anterior displacement of the TMJ disc has been demonstrated to be the primary aetiology of progressive disease, which results in degenerative arthritis known as arthrosis.

When the ligaments holding the disc in place become stretched or torn due to the displacement, this can result in permanent damage. This injury is particularly important because it is well documented that 60 per cent of the people involved in motor accidents do not fully recover. In a whiplash injury, particularly a rear end collision, the whipping of the head backward results in spasm of the anterior cervical musculature.

Spasm of the longus coli muscle results in the loss of the cervical lordotic curve. One of the most common pathological changes in the musculo-skeletal system is the creation of the dysfunctional relationship between the cranium, mandible and cervical vertebrae demonstrated by the loss of the lordotic curve. This loss results in the straightening of the cervical spine which in turn places excessive demands on the sternocleido-mastoid muscle, this then pulls the cranium forward into a pathological head-forward position.

The cranium compensates for the forward head position by rotating the head posteriorly and assuming an extended head posture so that normal line of sight is restored. This situation frequently creates and maintains entrapment of the occipital nerves, referring pain to the head and face.

Treatment must be based upon a specific diagnosis for a specific problem, otherwise it will only result in symptomatic relief, which will be temporary in nature.

The goals of treatment are as follows:
1. Reducing the spasm and excessive muscle activity of the masticatory and cervical musculature
2. Reforming a correct lordotic curve
3. Restoration of correct cranial – mandibular – vertebral relationship
4. Recapturing the TMJ disc
5. Relieving pain and restoring proper function.

Treatment

Of the many treatment techniques available, one of the most successful is the repositioning of the mandible utilising an intra-oral mandibular orthopaedic repositioning appliance (splint). The purpose of the appliance is to bring the mandible downwards and forwards.

The effect of this would be as follows:
1. The muscles of mastication are allowed to relax, which relieves the spasms which cause the headaches and facial pain. It is believed that 80 per cent of headaches are muscle spasm related and the major muscles in the head are related to the function of the mandible
2. Forward mandibular repositioning via the hyoid muscles creates anterior forces on the cervical vertebrae and helps in reforming a normal lordotic curve. It also increases the distance between the cervical vertebrae, thus reducing neck pain. Failure to appreciate the significance of this characteristic explains why many chronic neck problems fail to resolve, as the cause of the problem is distant from the point of pain and thus undiagnosed
3. Use of the appliance may also recapture the disc. Restorative procedures may have to be done on the teeth to stabilise the jaw in its new position after treatment is completed.

Mandibular repositioning will decrease the hyper-stimulation of the trigeminal nerve by restoring normal masticatory muscle function and a normal cranial cervical relationship.

TMJ dysfunction will place excessive demands on the musculature producing myofascial pain and dysfunction. Trigger points in the muscles are created as a focus of hyper-irritability giving referred pain to the head and neck.

TMJ dysfunction may be divided into two categories, traumatic and chronic. The aetiologic factors of each category and their subsequent treatments are vastly different and treatment applied to the wrong category can cause incorrectable 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 simply exacerbations of pre-existing conditions. Therefore proper and complete differential diagnosis and the correct treatment planning are essential at this point.

Evaluation of the patient

This should include patient history and presenting symptoms. Objective findings:

Radiology
a. Loss of lordotic curve
b. Cranial extensio;
c. Posture displacement of mandible.

MRI scan
Displacement of the disc?

Medical History
Interdisciplinary evaluation:

• Neurology – negative
• Orthopaedics – negative
• ENT – negative.

Observe for:

• Tenderness to palpation:

– Masticatory musculature
– Cervical musculature
– TMJ joints – pain with or without clicking
– Sub-occipital musculature

• Head forward position
• Range of motion studies.

Interdisciplinary evaluation must be utilised to rule out any organic causes of pain related to other medical specialities. Then a proper referral should be made to a specialist in head, facial and neck pain and TMJ orthopaedics. Other treatments would include: manipulative medicine, physiotherapy, trigger point injection, transcutaneous electrical nerve stimulation (TENS), ultrasound, heat and coolant therapy, spray stretch exercises and biofeedback. Surgery may be required in extreme cases.

Recent studies demonstrating the frequency of occurrence of whiplash injuries with temporomandibular joint dysfunction have led to an increase of interest in new TMJ diagnostic and treatment techniques. The upswing in new patients seeking help for injuries of the head and neck relating to jaw dysfunction has spurred dental surgeons to expand their knowledge by attending a wide variety of courses in the field.

The disagreement between differing camps has been exacerbated by some representatives of the legal and insurance profession who have a financial interest in the outcome of trauma-induced TMJ dysfunction claims. The insurance industry, in particular, bewildered and suspicious because of apparently conflicting opinions of qualified experts, looks upon TMJ-related claims with the same scepticism with which they originally viewed cervical whiplash claims shortly after they were first described by Gay and Abbot in 1953.

Experience in dealing with trauma-induced TMJ patients, where the immediacy of the trauma gives the observer the total picture of the causes and effects of the dysfunction, points to aetiology as the key factor in determining treatment. Interdisciplinary evaluation and treatment is essential and leads to a high success rate in the treatment of this painful condition.

A correct diagnosis will thus establish whether or not there is a direct causal relationship to the accident, which is obviously essential in assessing damages for what in many cases is a permanent injury.

Editor’s note: This article was originally published in Cranio-View, the journal of the BSSCMD, now known as Cranio UK. The author, Meurig Devonald BDS, passed away in 2009.