15: Disorders of the temporomandibular joint

Disorders of the temporomandibular joint

15.1 Anatomy and examination

Anatomy

The TMJs are the two joints between the mandible and the temporal bones. They are unique in the body in that they contain two joint spaces separated by a fibrocartilage disc (Fig. 15.1).

Components

Examination

Clinical examination

The dental examination should be systematic and include the TMJ and the masticatory muscles.

Radiology

Most clinical problems related to the TMJ are caused by muscular parafunction (e.g. bruxism) or internal disc derangements. Neither is likely to be associated with any relevant bony abnormalities. Consequently, radiography is not normally indicated unless there is any suggestion of bony abnormality, such as might be the case in rheumatoid arthritis or osteoarthrosis. Many panoramic X-ray machines allow specific images of the condyles to be taken without unnecessary radiography of the rest of the jaws. The only radiographic projection to show the whole joint is the transcranial oblique lateral view.

A clinical diagnosis of suspected internal derangement might lead to a requirement for imaging of the disc. This is done by magnetic resonance imaging (MRI) (Fig. 15.3). TMJ arthrography (Fig. 15.4) is mainly of historical interest, but may occasionally be used where patients are unsuitable for MR examination, e.g. because of severe claustrophobia.

15.2 Common disorders of the joint

Disc displacement with reduction

Reduction means that a displaced disc ‘reduces’ into a normal position on opening but reverts to an abnormal position on closing (reciprocal click) (Fig. 15.6A).

Disc displacement without reduction

If there is no reduction, a displaced disc remains in a displaced position regardless of the stage of opening. This interferes with movement and may cause pain (Fig. 15.7A).

Surgical treatment of internal derangement

Surgery is only indicated where non-surgical methods have failed and symptoms are severe. A range of surgical treatments may be used, depending often on the surgeon managing the case. Arthrocentesis involves lavage of the upper joint space, using hydraulic pressure and manipulation to release adhesions. Arthroscopy can be used to release adhesions directly, to perform joint space lavage and to introduce steroids.

‘Open’ surgery may also be used. Meniscoplasty is a procedure to reposition the disc. Access to the joint is gained via a vertical incision in front of the ear (preauricular incision) most commonly, although some favour an incision behind or within the ear. Various techniques have been devised to avoid damage to the facial nerve. The capsule is then opened, the disc visualised, repositioned and sutured in place. Studies suggest various success rates such as 90% of patients show improvement in symptoms, 5% no better and 5% worse. The relative efficacy of arthrocentesis, arthroscopic and open surgery is, however, still not well established.

The disc may be removed (menisectomy) if it cannot be repositioned because of deformity or degeneration. It may have been replaced with an alloplastic material in the past but is more likely to be replaced now with an autogenous tissue such as temporalis muscle or auricular cartilage.

15.3 Other conditions affecting the joint

Osteoarthrosis

Osteoarthrosis is a non-inflammatory disorder of joints in which there is joint deterioration with bony proliferation. The deterioration leads to loss of articular cartilage and bone erosions. The proliferation manifests as new bone formation at the joint periphery and subchondrally. It has an unknown aetiology, but previous trauma, parafunction and internal derangements are all suggested as aetiological factors.

Jan 9, 2015 | Posted by in Oral and Maxillofacial Pathology | Comments Off on 15: Disorders of the temporomandibular joint
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