This study was conducted to investigate the value of magnetic resonance imaging (MRI) in the diagnostic process based on the Research Diagnostic Criteria for Temporomandibular Disorder (RDC/TMD) by evaluating agreement between RDC/TMD and MRI diagnosis of disc displacement (DD) and correlation amongst MRI findings such as DD, joint effusion (JE), degenerative change and superior lateral pterygoid muscle (SLPM) attachment. Randomly selected MRIs of 200 joints from 100 TMD patients differentiated into RDC/TMD group II representing DD by clinical examination were reviewed retrospectively. The results show that Cohen’s kappa value was 0.336 showing overall disagreement between RDC/TMD group II and MRI diagnoses ( P < 0.001). The Cohen’s kappa value for group IIa, DD with reduction (DDWR), was −0.223 ( P < 0.01) showing disagreement, whilst the value was 0.546 for group IIb, DD without reduction (DDWOR) with limited opening, and 0.490 for group IIc, DDWOR without limited opening, showing moderate agreement ( P < 0.001). JE was detected with a higher probability as the state of DD advanced ( P < 0.001) and when degenerative joint changes were present ( P < 0.05). The difference of DD according to SLPM attachment was insignificant. MRI could be used when clinical examination cannot predict the true position of the disc.
Clinical procedures to diagnose temporomandibular disorders (TMD) frequently consist of clinical examination and imaging. The clinical examination assesses the mandibular range of motion and associated pain, joint noises, and muscle and joint tenderness on palpation. Often the findings vary from one assessment to the next in the same individual since the patient’s response to clinical examination may change according to the transient or recurrent nature of TMD and also due to the lack of reproducibility in examination technique.
Efforts to standardise the examination procedure and enhance reliability resulted in the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) by D workin and L eresche . The RDC/TMD consists of guidelines and procedures that help the examiner to gain adequate inter-observer reliability by using diagnostic criteria for investigating muscle origin pain, disc displacement, and arthralgia and degenerative bone change of the temporomandibular joint (TMJ). Imaging examination is not an essential procedure and is necessary only when additional information is needed to underline the results of the clinical examination, to facilitate the clinical diagnosis process, or to take a surgical intervention into consideration in cases that show a refractory nature in spite of sufficient conservative treatment.
The original version of the RDC/TMD indicates that imaging may help to substantiate clinical impressions of bony or soft tissue abnormalities when TMJ arthropathy exists, but by itself lacks the ability to differentiate asymptomatic from symptomatic patients with a high predictive rate .
Some studies report that the RDC/TMD classification of diagnoses based on clinical findings into muscle disorders, disc displacements or arthritis/arthrosis could not consistently be confirmed by findings made through magnetic resonance imaging (MRI) .
MRI defines hard and soft tissue and is usually applied to examine the soft tissue pathology of the TMJ. Studies which compared MRI findings with surgical and autopsy specimens reported an accuracy of about 90–95% for detecting disc position abnormalities when both coronal and sagittal images were evaluated .
Displacement of the articular disc is one of the major findings in TMD patients and is the most common cause of TMJ sounds. Disc displacement with reduction (DDWR) and disc displacement without reduction (DDWOR) are the two most common forms of disc displacement (DD) of the TMJ. A common symptom of DDWR is a reciprocal clicking of the TMJ, whereas DDWOR frequently limits mandibular mobility .
A number of studies were conducted to evaluate the accuracy of clinical diagnosis of TMJ DD but findings are controversial due to the different criteria adopted and the investigation is limited to findings concerning the position of the disc and its reduction on mouth opening.
This study was conducted to investigate the value of MRI in the diagnostic process based on the RDC/TMD by attempting to evaluate the agreement between RDC/TMD and MRI diagnosis of DD. The authors also studied various MRI findings from different RDC/TMD group II patients and analysed their inter-relationship to describe the clinical implication of MRI findings such as DD, joint effusion (JE), degenerative change and lateral pterygoid muscle (LPM) attachment and address their significance in the pathophysiology and diagnosis of TMD patients.
Materials and methods
200 joints of 100 patients that had been differentiated into RDC/TMD group II after clinical examination were randomly selected from patients presenting for TMD treatment from September 2009 to October 2010. A retrospective review of the TMJ MRI taken for the evaluation of TMD was conducted.
The MRI of patients with major deformities, TMJ fractures or systemic diseases known to affect the TMJ, such as rheumatoid arthritis, were excluded from the study. Clinical records including clinical signs and symptoms, such as, pain and comfortable or maximum mouth opening range measured between upper and lower incisors were reviewed to confirm the initial diagnosis given according to the RDC/TMD. The subjects consist of 32 males and 68 females, and their mean age was 25.3 ± 13.12 years and 31.9 ± 12.3 years, respectively. The research protocol was approved by the Institutional Review Board of the University Hospital (#CR110036).
Clinical assessment was conducted using a standardised clinical protocol including evaluation of patient history, palpation of TMJs, auscultation of joint noises and measurement of mandibular range of motion. According to the RDC/TMD guidelines , the patients were differentiated into three distinct groups. Disc position was categorised as: DDWR; DDWOR with limited mouth opening; DDWOR without limited mouth opening.
Criteria for inclusion of joints in the different categories were as follows. More detailed clinical diagnostic criteria of all 3 RDC/TMD axis I groups are described in Table 1 .
|RDC/TMD group||Diagnosis||Definition||Diagnostic criteria|
|Group I||Ia||Myofascial pain||Pain of muscle origin including a complaint of pain as well as pain associated with localised areas of tenderness to palpation in muscle.||1. Report of pain or ache in the jaw, temples, face, preauricular area, or inside the ear at rest or during function; plus
2. Pain reported by the subject in response to palpation of three or more of the following 20 muscle sites (right side and left side count as separate sites for each muscle): posterior temporalis, middle temporalis, anterior temporalis, origin of masseter, body of masseter, insertion of masseter, posterior mandibular region, submandibular region, lateral pterygoid area, and tendon of the temporalis. At least one of the sites must be on the same side as the complaint of pain.
|Ib||Myofascial pain with limited opening||Limited movement and stiffness of the muscle during stretching in the presence of myofascial pain.||1. Myofascial pain as defined in Ia; plus
2. Pain-free unassisted mandibular opening of less than 40 mm; plus
3. Maximum assisted opening (passive stretch) of 5 mm or more greater than pain-free unassisted opening.
|Group II||IIa||Disc displacement with reduction||The disc is displaced from its position between the condyle and the eminence to an anterior and medial or lateral position, but reduces on full opening, usually resulting in a noise. Note that when this diagnosis is accompanied by pain in the joint, a diagnosis of arthralgia (IIIa) or osteoarthritis (IIIb) must also be assigned.||1. Either: (a) reciprocal clicking in TMJ (click on both vertical opening and closing that occurs at a point at least 5 mm greater interincisal distance on opening than on closing and is eliminated on protrusive opening, reproducible on two of three consecutive trials; or (b) click in TMJ on both vertical range of motion (either opening or closing), reproducible on two of three consecutive trials, and click during lateral excursion or protrusion, reproducible on two of tree consecutive trials.|
|IIb||Disc displacement without reduction, with limited opening||A condition in which the disc is displaced from normal position between the condyle and the fossa to an anterior and medial or lateral position, associated with limited mandibular opening.||1. History of significant limitation in opening; plus
2. Maximum unassisted opening ≤ 35 mm; plus
3. Passive stretch increases opening by 4 mm or less over maximum unassisted opening; plus
4. Contralateral excursion < 7 mm and/or uncorrected deviation to the ipsilateral side on opening; plus
5. Either: (a) absence of joint sounds, or (b) presence of joint sounds not meeting criteria for disc displacement with reduction.
|IIc||Disc displacement without reduction, without limited opening||A condition in which the disc is displaced from its position between the condyle and the eminence to an anterior and medial or lateral position, not associated with limited opening.||1. History of significant limitation of mandibular opening; plus
2. Maximum unassisted opening > 35 mm; plus
3. Passive stretch increases opening by 5 mm or more over maximum unassisted opening; plus
4. Contralateral excursion ≥ 7 mm; plus
5. Presence of joint sounds not meeting criteria for disc displacement with reduction.
|Group III||IIIa||Arthralgia||Pain and tenderness in the joint capsule and/or the synovial lining of the TMJ.||1. Pain in one or both joint sites (lateral pole and/or posterior attachment) during palpation; plus
2. One or more of the following self-reports of pain: pain in the region of the joint, pain in the joint during maximum unassisted opening, pain in the joint during assisted opening, pain in the joint during lateral excursion.
3. For a diagnosis of simple arthralgia, coarse crepitus must be absent.
|IIIb||Osteoarthritis of the TMJ||Inflammatory condition within the joint that results from a degenerative condition of the joint structures.||1. Arthralgia; plus
2. Coarse crepitus in the joint.
|IIIc||Osteoarthrosis of the TMJ||Degenerative disorder of the joint in which joint form and structure are abnormal.||1. Absence of all signs of arthralgia, i.e., absence of pain in the region of the joint, and absence of pain in the joint on palpation, during maximum unassisted opening, during maximum assisted opening, and on lateral excursions; plus
2. Coarse crepitus in the joint.
RDC/TMD axis I group IIa, diagnosis of DDWR: either reciprocal clicking in TMJ (click on both vertical opening and closing that occurs at a point at least 5 mm greater interincisal distance on opening than on closing and is eliminated on protrusive opening), reproducible on two of three consecutive trials; or clicking in TMJ on both vertical range of motion (either opening or closing), reproducible on two of three consecutive trials, and click during lateral excursion or protrusion, reproducible on two of three consecutive trials.
RDC/TMD axis I group IIb, diagnosis of DDWOR, with limited opening: history of significant limitation in opening; maximum unassisted opening ≤35 mm; passive stretch increases opening by 4 mm or less over maximum unassisted opening; contralateral excursion <7 mm and/or uncorrected deviation to the ipsilateral side on opening; absence of joint sounds, or presence of joint sounds not meeting criteria for DDWR.
RDC/TMD axis I group IIc, diagnosis of DDWOR, without limited opening: history of significant limitation of mandibular opening; maximum unassisted opening >35 mm; passive stretch increases opening by 5 mm or more over maximum unassisted opening; contralateral excursion >7 mm; presence of joint sounds not meeting criteria for DDWOR.
MRI of the TMJ
MRI of the TMJ was taken with GE Signa Exite HD 1.5T. Images were digitally reconstructed and read by two examiners on a computer. To evaluate the inter- and intra-examiner reliability, images of 30 randomly selected patients were read twice at a 2-week interval by two examiners after mutual calibration.
The degree of JE in the superior compartment on MRI was divided into 2 grades: absent, no area of high signal intensity; present, presence of any of the following: lining or spot of high intensity along the articular surface, band of high intensity, and collection with pooling in the compartment .
The disc position of the TMJ was also determined with MRI. Normal position, when a disc in the superior position in the closed mouth position maintained a position interposed between the condyle and the articular eminence in the open mouth position. DDWR, when a displaced disc in the closed mouth position assumed a position interposed between the condyle and the articular eminence in the open mouth position. DDWOR, when a displaced disc in the closed mouth position did not achieve a position between the condyle and the articular eminence in the open mouth position .
LPM attachments were categorised into two different types: type 1, where fibres of the superior head of the lateral pterygoid muscle (SLPM) were attached to the disc only; and type 2, where fibres of the SLPM were attached to both the disc and condyle .
MRI diagnosis of degenerative change of the TMJ was defined by the presence or absence of the following changes: erosion, defined as an interruption or absence of the cortical lining; sclerosis, a condition in which bone density is significantly increased; flattening, defined as a loss of the round contour; osteophyte, defined as marginal hypertrophic bone formation . When more than one type of degenerative change was observed, the joint was determined to have degenerative change.
Cohen’s kappa value was used to analyse the RDC/TMD diagnosis and MRI diagnosis reliability. The associations amongst DD, JE, degenerative change, and attachment of SLPM were analysed using the χ 2 -test. All statistical analyses were performed with the PASW 18.0 program.
Cohen’s kappa value was 0.336 ( P < 0.001) showing disagreement between RDC/TMD and MRI diagnoses. The Cohen’s kappa value for the RDC/TMD IIa group that showed DDWR on MRI was −0.223 ( P < 0.01) showing disagreement. The Cohen’s kappa value for the RDC/TMD IIb group that showed DDWOR on MRI and maximum mouth opening ≤35 was 0.546 ( P < 0.001) showing moderate agreement. The Cohen’s kappa value for the RDC/TMD IIc group that showed DDWOR on MRI and maximum mouth opening > 35 was 0.490 ( P < 0.001) showing moderate agreement.
JE was detected with a higher probability as the state of DD advanced ( P < 0.001). 21% of those with a normal disc position and 24% of those with DDWR showed JE on MRI whilst 59% of those with DDWOR showed joint effusion on MRI.
There was no significant difference in DD according to the attachment of SLPM. The SLPM appeared to be more commonly attached to both the disc and condyle in both DDWR and DDWOR.
Although mouth opening limitation was most common with DDWOR, there was no significant difference in the presence of mouth opening limitation according to DD ( Table 2 ).