However, other patients will require diagnostic imaging of the TJS in order to provide information, which is not available from the clinical examination. Indications for TMJ imaging include the following: conservative treatment that has failed or symptoms are worsening, patients with a history of trauma, significant dysfunction, sensory or motor abnormalities, significant changes in occlusion, or if an osseous abnormality or infection is suspected.2 Some practitioners order TMJ imaging if there is a history of TMD and the treatment plan includes extensive reconstructive work or orthodontia, since these types of treatment can significantly alter the occlusion and predispose the patient to a recurrence of their TMD symptoms.
Imaging allows the practitioner to evaluate the integrity and relationships of the TMJ osseous components, confirm the extent or progression of joint disease and evaluate effects of treatment.3 The results of imaging studies must be correlated with the patient history and clinical findings in order to arrive at a diagnosis and plan treatment. Usually the hard tissues are imaged first to evaluate osseous contours, positional relationship of the condole and glenoid fossa, and range of motion.
It gives an overview of the jaws and teeth, allowing evaluation of mandibular symmetry, the maxillary sinuses and the dentition. Mandibular asymmetries may not be clinically apparent and a discrepancy in size of one condole or one side of the mandible may be a contributing factor in the development of TMD.5-7 Maxillary sinus disease or photogenic inflammatory disease, particularly of the posterior maxillary teeth, may refer pain to the TMJ, simulating TMD.
Furthermore, the glenoid fossa does not image clearly and the articulating surfaces of the condoles are distorted due to the angle of the projection so osseous components of the joints cannot be accurately assessed. Cephalometric plain film radiographs are occasionally indicated as an adjunct to the TMJ imaging study, particularly in patients with developmental abnormalities, some neoplasms, fracture of the jaw or condylar necks, or facial asymmetries2 (Figs.
The joints can be imaged in different orientations, achieving the aim of producing views perpendicular to each other. With conventional tomography, several exposures are made with the area of interest moving through the plane of focus.
This produces an undistorted view of joint morphology and allows accurate assessment of condylar position. Normally, several image slices in the sagittal (lateral) and coronal (frontal) plane are made.
Some practitioners also request views with the mandible in the rest or centric relation position, depending on diagnostic needs and treatment goals. Frontal images allow assessment of condylar and glenoid fossa morphology in the medial-lateral orientation and are particularly useful for identifying erosive changes of the articular surfaces.
CT has several advantages over conventional tomography: there is no superimposition of structures outside the area of interest, contrast resolution is improved so that tissues with small differences in density can be distinguished, data from one imaging study can be viewed in various planes and three-dimensional images can be constructed. If the scan includes the rest of the skull, the need for additional cephalometric plain film views may be eliminated.
An exciting advance in CT technology is cone beam computed tomography (CBC), which is particularly suited to imaging hard tissues of the skull and jaws. During the scan, which may take from 17 seconds to over a minute to perform, 360 exposures or projections are made, one for each degree of rotation.
CT's techniques have a distinct advantage over conventional tomography in that large areas can be imaged in one scan and reformatting can be made in multiple planes chosen by the clinician, providing three-dimensional information about the osseous structures. This is particularly valuable for TMJ imaging, since in addition to the TJS, the remainder of the jaws as well as the skull base can be evaluated.
CBC is rapidly growing in popularity and is starting to replace conventional tomography for many dental imaging applications. This technique is useful for visualizing osseous detail of the TJS, including evaluation of osseous ankyloses, neoplasms, hetero topic bone growth and other abnormalities in and around the joints which may not be as well visualized with conventional tomography.2 CBC is not suitable for patients unable to remain motionless for the duration of the scan.
A disadvantage of the technique is volume averaging, which results in artifacts that may simulate erosion son small curved cortical bone surfaces.3 Interpretation of the hard tissue imaging study includes evaluation of condylar and temporal component morphology and integrity of bony articulating surfaces.
The flow of contrast agent as well as disk function on opening and closing is monitored using fluoroscopy. Small perforations of the disk or its attachments can be detected, as both joint spaces fill with contrast agent simultaneously.
Disadvantages of arthrography include post-operative discomfort and inability to detect medial disk displacements. Images can be constructed in either the sagittal or coronal planes and therefore this technique is especially useful for diagnosis of medial disk displacements (Fig.
MRI has the advantage of being non-invasive and enables evaluation of the disk, surrounding muscles, and can image joint effusions.11 Contraindications to MRI include pregnancy, pacemakers, intracranial vascular clips, the presence of metal particles in vital structures, patient claustrophobia, obesity or inability to remain motionless for the examination, which may take several minutes to complete.3 The technique is also relatively expensive and is not readily available in some centers. TMJ imaging is an adjunct to the clinical examination and provides useful information about the joint components.
Consultation with an oral and maxillofacial radiologist is encouraged, particularly if the clinician does not have knowledge and experience in interpreting the imaging study. She maintains an active private practice and consulting service in oral and maxillofacial radiology at CMI Centers in Toronto.
The relationship between frontal facial morphology and causal force in orthodontic patients with temporomandibular disorder. Quarterly publication of the American Association of Dental Maxillofacial Radiographic Technicians.
The bilateral temporomandibular view allows for visualization of the articular tubercle, mandibular condole and fossa and is thus useful to identify structural changes and displaced fractures, as well as assess excursion and joint spaces. Clinical indications include trauma, the presence of joint noises, Erasmus and causal alterations 1.
Ferreira LA, Grossman E, Jacuzzi E, Paula MVD, Carvalho ACP. Magnetic resonance imaging (MRI) is one of the best diagnostic tools for identification of TMJ pathology, allowing evaluation of TMJ disc position, morphology, mobility, extent of joint degenerative changes, inflammation, and presence of connective tissue/autoimmune diseases.
Importantly it can help in the diagnosis of TMJ pathology in the silent joint where disc displacement and degenerative changes can be present but may not make noise or be particularly uncomfortable or painful but yet result in poor outcomes if only orthographic surgery is performed. Magnetic Resonance Imaging (MRI) is one of the most important diagnostic tools that we have in evaluation and diagnoses of TMJ pathology.
In our study, we evaluated 3 different patient groups that required counter-clockwise rotation and advancement of the maxillomandibular complex. The 3 groups were well-matched relative to the amount of advancement at mention of approximately 13 mm in a counter-clockwise direction.
Group 1 had healthy TMJ joints with the articular discs in position and had just orthographic surgery performed. Group 3, had displaced discs where only orthographic surgery was performed, the average AP relapse was 28% of the amount of advancement or almost 3 mm for every 10 mm of mandibular advancement, indicating post surgical condylar resorption occurring in this group of patients.
The counter-clockwise rotation of the maxilla-mandibular complex is a very stable procedure, if the discs are healthy and/or placed into proper anatomical position. In a previous study, we evaluated 25 patients who had bilateral TMJ displaced articular discs and underwent double jaw maxillomandibular advancement surgery, with an average advancement of 9 mm at point B but the TJS were not addressed, so the articular discs remained anteriorly displaced.
Presurgery, 36% of the patients had pain or discomfort involving the TMJ, head and jaw area. This study also demonstrates the adverse effect of performing orthographic surgery on patients with displaced TMJ articular discs.
The articular disc should sit on top of the condole with the posterior band being about the 12 o’clock position. Upon closing, the condole may slide back off the posterior band of the disc, making a reciprocal click.
This usually occurs only in patients with condylar hyperplasia type 1, where the condole is growing in length at a faster rate than the normal upward migration of the posterior ligament attachment, thus, pulling the disc posterior to the condole. Also, there may be a degenerative process developing in the discs where there is a breakdown of the cartilaginous substance with vascular invasion and degeneration.
Observing information from the MRI will help determine which corrective surgical procedures will provide the best and most predictable outcome. FIGURE 15: The articular disc is anteriorly displaced and significantly deformed, degenerated, and non- reducing rendering it non-salvageable.
FIGURE 16: In this case of condylar hyperplasia Type 1, the condole is growing vertically at an accelerated rate that is faster than the posterior ligament attachment can migrate upward, thus pulling the disc posterior to the condole. Medial and lateral displacements of the disc may create pain and dysfunction, but the joints may be silent since there is no reduction over the posterior band.
This also goes along with posterior displaced discs where the TJS may make no noise, but could contribute to pain and discomfort. Patients who have been in long-term splint therapy with downward and forward posturing of the mandible may create thickening of the bi laminar tissues so that there is a smooth transition onto the disc.
Any Class II mechanics may artificially pull the condole down and forward onto the disc, but this may be an unstable position that the surgeon must be aware of and understand that orthographic surgeries performed with advancement of the mandible, will likely position the condole into a centric relation post surgery and the disc will again be anteriorly displaced. Adolescent internal condylar resorption (AIR) has a relatively classic presentation.
Clinically, the mandible will be noted to slowly Gertrude into a Class II causal and skeletal relationship with a tendency towards anterior open bite. These patients all have high causal plane angle facial morphological profiles.
However, on the MRI, these cases present with a condole that may be slowly becoming smaller in all 3 planes of space. In some cases, there is significant thinning of the cortical bone on top of the condole contributing to the inward collapse of the condylar head in this pathological process.
Our studies demonstrate that AIR is arrested if the articular discs are put back into position on top of the condole and stabilized with the Mites anchor technique. There is some distortion of the MRI imaging because of the metal anchor in the head of the condole but the reduced position of the disc is noted.
After 4 years, the discs may not be salvageable and the indicated treatment may then be custom-fitted total joint prostheses to repair the TJS and advance the mandible. However, importantly, in cases with CH type 2, often the contralateral “normal” joint may be overloaded, developing an anteriorly displaced disc and subsequently arthritic changes which occurs in about 75% of the cases with a unilateral CH type 2.
The indicated treatment includes a low colectomy for removal of the tumor, recon touring of the condylar neck to form a new condole, and repositioning of the articular disc, as long as the disc is salvageable, with a Mites anchor technique, and the recon toured ipsilateral condylar neck will then function as a new condole. FIGURE 19: MRI of right TMJ shows osteochondral with large exophytic growth of the anterior aspect of the condole (CH Type 2Ah).
Reactive arthritis may show a localized area of inflammation with erosion of the condole and/or fossa. FIGURE 20: T2 MRI of right TMJ with reactive arthritis and significant condylar resorption.
The inflammatory process is noted to occupy a significant volume between the fossa and condole. (Figure 21) Relative to the condole, perforations can occur in the middle, medially or laterally.
FIGURE 21: MRI of left condole with perforation of the bi laminar tissue posterior to the anterior disc. FIGURE 22: Coronal view showing a synovial cyst overlying the superior and lateral aspect of the condole.