4 TMJ dysfunction and obstructive sleep apnea
The last phase of surgical management consists of maxillomandibular advancement (MMA) by a LeFort I osteotomy and bilateral sagittal split osteotomy of the mandible. The success of this procedure has resulted in its increased use as the primary surgical management of OSA patients.
The prevalence of TMJ and muscle disorder-type pain in a recent survey of over 30 000 Americans was 4.6%.1 Numerous studies have suggested an association of pain with gender, age, socioeconomic factors, or previous dental and orthodontic interventions. Persons with TMJ disorders can suffer from displacement of the articular disc, termed “internal derangement” of the TMJ.2 However similar symptoms of pain and functional limitations of mouth opening may result from myofascial pain syndromes, congenital disorders, inflammatory conditions, and trauma. Medical and occlusal therapies control symptoms for many patients. For those who require surgical intervention, treatment options range from arthroscopy to joint replacement. An understanding of the normal function of the TMJ and the pathophysiology of its degenerative disorders are key to directing treatment.
The first description of TMJ disc repair was in 1887 by Thomas Annandale. He reported the treatment of two patients with clicking jaws by disc repositioning. He wrote that tearing or stretching of the tissues connected to the articular cartilage resulted in its displacement.3 Annandale utilized an incision over the joint. Reports from the early 1900s describe L-shaped incisions located both above and below the zygomatic arch.4,5
The term “snapping jaw” was applied for several decades, with no consensus on its etiology, to painful popping jaws that became stuck in one position. Controversy existed as to whether disc displacement or joint subluxation produced the condition. The direction of disc displacement was also debated. As a result, many procedures were described. Proponents of joint subluxation performed procedures to tighten the joint capsule and limit jaw movement,6,7 while others performed discectomy and repair of ligaments.5,8
In 1936, Costen reported in the Journal of the American Medical Association9 on a series of patients with headache, ear pain, neuralgia, and complaints of abnormal jaw movements. He theorized that pressure exerted through posterior occlusion led to pressure on the TMJ and subsequent destruction and nerve compression. The theory was widely accepted and “snapping jaw” was known for several years as “Costen’s syndrome.” The treatment advocated was dental in nature to open the posterior occlusion. Laskin also shifted the emphasis away from the joint in what he termed myofascial pain syndrome. He associated the masticatory muscle dysfunction with the observed psychological symptoms accompanying the jaw condition.
With the descriptions of TMJ function and pathology offered by Farrar and McCarty2 and Dolwick et al.,11 interest was renewed in joint surgery. Athroscopy of the TMJ had appeared in the Japanese literature in 1975.12 After publication in the English literature in 1986,13 it was readily adopted as a technique in North America. The development of alloplastic joint replacement for TMJ has paralleled that of joint replacement and osseointegrated implants in other fields with the adoption of titanium alloys and computed tomography (CT)-aided fabrication and surgical planning.
The mandibular bone allows for rotational and translational movement through the TMJ. The mandibular condyle articulates with the squamous portion of the temporal bone at the TMJ. The geniohyoid muscles insert on to the genial tubercles and, with the anterior belly of the digastric muscle, depress and retract the mandible. The muscles that elevate or protrude the mandible are the masseter, temporalis, medial, and lateral pterygoid muscles. The inferior portion of the lateral pterygoid muscle inserts on to the neck of the condyle, which helps protrude the mandible when contracting. The superior portion of the lateral pterygoid muscle inserts on the fibrous capsule and meniscus of the TMJ, stabilizing the meniscus during the movement of the mandible. All these muscles are innervated by cranial nerve V. The TMJ articular surfaces are lined with fibrocartilage, an avascular fibrous connective tissue that contains cartilage cells. This differs from other synovial joints that are lined with hyaline cartilage.
The articular disc is a dense fibrous connective tissue structure that separates the joint into two spaces.14 The upper joint space volume of 1 mL extends from the glenoid fossa to the articular eminence. The lower joint space volume of 0.5 mL begins above the insertion of the lateral pterygoid muscle anteriorly and then spreads out over the condyle. The articular disc is an avascular, noninnervated fibrous sheet with some cartilaginous component. The pars gracilis is the thin central zone. The anterior band or pes meniscus is superiorly attached to the articular eminence and superior belly of the lateral pterygoid. Inferiorly, the anterior band attaches to the condyle by a synovial membrane along the attachment of the lateral pterygoid muscle. The posterior band is highly innervated and vascularized tissue, a bilaminar zone or retromeniscal pad. The upper layer of the bilaminar zone attaches to the tympanic plate of the temporal bone, while the lower runs from the posterior meniscus to the neck of the condyle. The disc is not attached to the capsule laterally or medially, but instead bound to the medial and lateral poles of the mandibular condyle.
Basic movements of the mandible are rotator or hinge movement, which consists of rotation around transverse axis that passes through condyles, and translator or sliding movement, which involves movement of mandible in anteroposterior and/or mediolateral direction. The rotatory movement of the mandible is completed in the inferior joint space (ginglymus), and translation is followed in the superior joint space (arthrodial). During mouth opening, translation moves the condyle and disc forward and downward along the articular eminence. These structures lie anterior to the greatest height of the eminence with maximal mouth opening. Closing returns the jaw to its occlusal position. Protrusion and retrusion of the mandible are mainly accomplished by translatory movements. The lateral ptyerygoids move the condyles and discs forward along the articular eminence, while the elevators and depressors stabilize the position of the jaw relative to the maxilla.
The retromeniscal or retrodiscal pad is believed to be the origin of pain in TMJ dysfunction. If there are abnormal loading forces on the joint surfaces as a result of disc disease, this can lead to TMJ disorders.15 The fibrous joint capsule attaches to the condyle inferiorly and the zygomatic arch superiorly. It is reinforced anteriorly and laterally by the temporomandibular ligament. The auriculotemporal, masseteric, and deep temporal branches of the trigeminal nerve supply innervation to the TMJ.16
The cause of myofascial pain and dysfunction (MPD) is usually related to the masticatory muscles. MPD was first described by Laskin17,18 and is characterized by a limited range of motion, aching pain, and severe tenderness on palpation of the muscles. Certain trigger points within the masticatory muscles refer the pain. The masseter muscle, producing an ache in the jaw, is the most common. Next most common is pain in the temporalis muscle, producing pain in the side of the head. The lateral pterygoid muscle can generate an earache or pain behind the eye. Medial pterygoid involvement causes pain on swallowing or stuffiness in the ear.
The limitation of mandibular movement in MPD usually correlates with the amount of pain. The etiology of MPD can be due to overclosure, occlusal prematurity, bruxism, and severe anxiety. Each of these leads to spasms of the masticatory muscles, focusing pain around the TMJ.
Posterior capsulitis involves the neurovascular bilaminar zone and the posterior capsular ligament. Such inflammation can be due to acute trauma, premature occlusal contact, or infection causing the retrodisc tissues to become edematous. Sprain of the capsular ligaments usually heals in several weeks. Chronic sprain can lead to stretching of the ligaments. Medical occlusal treatment usually addresses these conditions.
Osteoarthritis is a chronic disease that characteristically affects the articular cartilage of synovial joints and is associated with remodeling of the underlying subchondral bone and the development of a secondary synovitis. It is the most common disease affecting the TMJ. It has a gradual onset. Usually, only one side is affected. Radiographically, sclerosis of the subchondral bone, osteophytic lipping, cyst formation, flattening of the condyle, and decreased height of the ramus are observed19 (Fig. 4.1). Chronic anterior disc displacement is associated with posterior–superior condylar resorption, seen as flattening and loss of bone in this area. An open bite deformity and mandibular retrusion may result. Treatment frequently involves drug therapy, occlusal appliance therapy, physical therapy, and, when most severe, surgery.
Rheumatoid arthritis is a chronic inflammatory disease that primarily affects the periarticular structures, such as the synovial membrane, capsule, tendons, and ligaments. More than 50% of rheumatoid arthritis patients have involvement of the TMJ during the course of their disease.20
Progression of the disease includes condylar resorption and fibrous and bony ankylosis. The classic malocclusion is caused by loss of the height of the condyles. Juvenile rheumatoid arthritis affects patients before the age of 16 years. Up to 40% of children with juvenile rheumatoid arthritis have involvement of the TMJ.21 Defective development of the mandible leads to micrognathia. MRI can delineate disc destruction, condylar bone erosion, and cartilaginous thinning. The radiographs of the TMJ include loss of joint space and condylar resorption with anterior subluxation of the condyle.
The treatment goals in rheumatoid arthritis are pain relief, reduction of inflammation, maintenance of function, and prevention of further deformity. This treatment may include drug therapy, occlusal appliance, physical therapy, and dental and surgical procedures of the TMJ and mandible. Most surgery is reserved for correction of joint ankylosis and severe malocclusion.
Idiopathic condylar resorption can also occur in either juvenile or adult individuals. In both forms there is a diminished condylar head. In the juvenile form the exact cause is unknown and is multifactorial but leads to decreased mandibular growth and a class II malocclusion. The adult can follow orthognathic surgery to the mandible or disc displacement. Both types are self-limiting and are treated conservatively until the condition stabilizes. Surgery may then be indicated.22,23
Wilkes established five stages of internal derangement based on clinical and imaging criteria.24 In patients with early stage I derangement, the patient complains of clicking in opening and closing of the jaw (Fig. 4.2). On imaging, the disc is slightly displaced forward on opening, but it is “reduced,” or returns to its normal position, at maximal opening. The oral excursion and lateral movements of the jaw should be within the normal range. The audible clicking sound is produced by reduction of the disc.
Fig. 4.2 Stages in the classic progression of internal derangement of the temporomandibular joint. (A) Internal joint derangement secondary to anterior disc displacement with reduction (intermittent locking may occur). (B) Anterior disc displacement without reduction. (C) Perforation of the bilaminar zone. (D) Osteoarthrosis.
In stage II, the patient begins to complain of intermittent locking. Pain is common at this stage and localized over the TMJ. The disc may appear deformed, but generally still reduces with maximal opening. Osseous contour appears normal. In stage III, the patient has a chronic limitation of opening with frequent locking, headaches, and painful chewing. The mandible deviates to the affected side on opening and with protrusive movements. The internal derangement is anterior disc displacement.
Chronic internal derangement without disc reduction (stage IV) results in injury to the retrodiscal tissue. Pain may diminish because of fibrous changes occurring in the retrodiscal tissue.25 Limited mouth opening is common here as the disc blocks full condylar translation. In stage V, remodeling of the temporal and condylar bone components occurs. This final common pathway of cartilage destruction and bone remodeling is shared with other conditions such as osteoarthritis. Yet there are few long-term longitudinal data to indicate the progression of disc displacement. A reducing disc disorder may be stable for years.26
A patient may describe the pain originating from the TMJ, preauricular area, or surrounding masticatory muscles. Additionally the discomfort may radiate from the ear, teeth, or neck area. Often the onset of pain originating in the morning is due to nocturnal bruxism, grinding of teeth, in which constant pain after jaw function suggests intracapsular joint pathology. Patients with TMJ dysfunction relate a triad of preauricular pain, clicking or grinding noises from the TMJ, and poor mandibular movement. Some patients may describe noises in the joint associated with daily jaw movement. Such clicking may be benign solitary clicks, which occur in 40% of the normal population. When there is anterior subluxation of the disc with jaw opening, condylar contact results in a click. A reciprocal click occurs as the disc subluxes when the condyle repositions into the glenoid fossa. The abnormal joint surfaces lead to a grinding or crepitus from the joint. Closed lock is a sudden irreducible anterior subluxation of the disc, limiting mandibular motion. Other reasons for limited excursion of the jaw may be due to local muscular dysfuction, bony or fibrous ankylosis of the joint, and blocking of the coronoid process by the zygoma.
The examination of the patient with TMJ pain centers on the head, neck, and TMJ. The facial exam includes any soft-tissue aymmetry or skeletal deformities. Examination of the cranial nerves is performed to exclude any central nervous system disorders. The ear canals and tympanic membrane are examined to rule out primary benign or malignant diseases.
Similarly, the oral tissues are evaluated for mucosal lesions, swellings, periodontal disease, alveolar process abnormalities, and evidence of cheek or lip biting. The teeth are examined for caries, mobility of teeth, absent teeth, prosthetics, molar impactions, supraerupted teeth, malocclusion, and displacement of the mandible during contact of the teeth. The incisor relationship is important to delineate overbite, overjet, or open bite, all of which can contribute to the TMJ symptoms. Palpation of the area of the TMJ can detect clicking or crepitus. Joint sounds must be determined as popping, clicking (reciprocal or nonreciprocal), or crepitations.
Palpation of the TMJ can detect swelling, the presence of tenderness, and joint sounds. Auscultation can be more sensitive in determining the type of joint sounds. The masticatory and cervical muscles must also be excluded as areas of tenderness or spasm. The presence or absence of pain, intensity of pain, location of pain, and referred pain must be documented.
The TMJ range of motion should be measured. Any pain or deviation to the left or right on opening is noted. The normal interincisal opening distance is 40–50 mm, and the lateral jaw movement is at least 10 mm on each side of the incisor midline. Any restriction of the interincisal range of motion, lateral restriction, deviation on opening, and development of new anterior open bite can indicate the degree of joint involvement. At this point, diagnostic imaging is required.
Tomography provides sectional images in the sagittal or coronal views, usually taken in the open and closed positions. This modality demonstrates bone pathology and range of condylar motion but provides no information on soft-tissue disease. One study showed that up to 85% with TMJ disease patients had normal tomography.27
The evaluation of the TMJ soft tissue and disc was traditionally with contrast arthrography. Arthrography can be performed either as single-contrast lower compartment2 or as dual-space contrast arthrotomography.28 The information from TMJ arthrography is highly reliable in determining disc disease but has been replaced by the noninvasive modality MRI. It can also give information about the swelling and inflammation in the joint. In sagittal images, the disc is located anteriorly to the condyle in the closed-mouth position (Figs 4.3 and 4.4). Several MRI studies of adults have demonstrated disc displacement in 20–30% of asymptomatic volunteers;29 however the type of disc displacement may be different. Affected patients with disc displacement demonstrated largely complete anterior or complete anterolateral displacement. MRI may also provide insight into the bone marrow abnormalities of the condyle. If the central area of the condyle has a low signal, this may suggest a pathologic condyle consistent with avascular necrosis.
Fig. 4.3 Magnetic resonance imaging of the normal temporomandibular joint (TMJ). Sagittal proton density-weighted image of the TMJ in (A) open-mouth and (B) closed-mouth positions. Articular disc remains over the condylar head as it moves posterior along articular eminence.
Fig. 4.4 Magnetic resonance imaging of anterior disc displacement. Sagittal proton density-weighted image of the temporomandibular joint in (A) open-mouth and (B) closed-mouth positions. Articular disc remains anteriorly displaced.
CT scanning is useful to evaluate bone abnormalities, bony ankylosis, and acute traumatic injuries. Otherwise, CT of the disc is difficult. The advantages of MRI over CT include absence of ionizing radiation, fewer artifacts from dense bone and metal clips, imaging in multiple planes, and good detail of the soft tissues. Cone beam CT (CBCT) is increasingly available and offers lower radiation doses than standard CT. Panoramic and other dental modes of viewing are available with reconstruction software.
The first step in imaging a patient with TMJ pain and dysfunction is a plain film, including panographic film. The next modality should be CBCT of the joint in open and closed positions or an MRI, focusing on the soft tissue and disc.
Following investigation of TMJ pain and dysfunction, patients with pain disorders, sprains, inflammatory disorders, and early stages of internal derangement are started on medical and occlusal management. If a patient fails noninvasive management, or presents at an advanced state of joint degeneration, surgical intervention is indicated. The type of surgical therapy is directed at the underlying cause of joint derangement.
The goal of medical management is to break the cycle of pain and anxiety of myofascial dysfunction. Nonsteroidal anti-inflammatory agents are combined with a soft diet. Muscle relaxants, antidepressants, and local anesthetics for diagnostic blocks are adjunctive measures.30 Recently the use of botulinum toxin in areas of muscle spasm has been reported.31,32 The use of oral corticosteroids is effective for acute pain, but prolonged use will lead to osteoporosis, including of the TMJ. Intra-articular injections of corticosteroids are also effective for acute pain management and diagnosis, but repeated injections risk the destruction of articular cartilage. Physical therapy using modalities of heat, massage, ultrasound, transcutaneous electrical nerve stimulation, and biofeedback may also help in these patients.
Occlusal splints reduce the loading of the joint, muscle hyperactivity, and articular strain due to bruxism. The ease of insertion of the appliance and compliance of the patient affect the success of occlusal therapy. The various types of splints include the muscle relation appliance, anterior bite plate, pivot splint, and the soft appliance. Appliance therapy remains a common treatment of TMJ pain, though a review of studies has shown no definite benefit for its use, or for a specific type of splint.33
Acute dislocations result from the condyle extending anteriorly beyond the articular eminence. If spontaneous reduction does not occur, manual reduction with a muscle relaxant or anesthesia is often needed. The surgeon places downward force along the inferior border of the mandible while moving the jaw posteriorly to slide the condyle into the fossa.
Arthrocentesis and arthroscopy enable the surgeon to perform endoscopic joint examination, biopsy, and lavage. In addition to the arthroscope (1.8–2.6 mm in diameter), a high-intensity light source, video camera, and monitor are required. Measured landmarks for TMJ entry have been reported.34 The point of entry is along a line from the tragus to the lateral canthus of the eye. The site is 10 mm anterior to the tragus and 2 mm inferior to the line. Using these landmarks will help to prevent complications involving the temporal branch of the facial nerve and the auriculotemporal branch of the trigeminal nerve. A needle is inserted at the posterior entry point to insufflate the TMJ with Ringer’s lactate. After the superior compartment of the joint is distended, the arthroscope is gained through the same entry, or the single-portal technique (Fig. 4.5)