The aim was to evaluate the correlation between disc displacements and degenerative bone changes in magnetic resonance images (MRI) of 112 patients of both genders, with signs and symptoms of temporomandibular disorder. For this purpose, a calibrated examiner evaluated 224 MRI by assigning scores for the displacement of the disc and degenerative bone changes. Disc displacement was found in 58.42% of the temporomandibular joints (TMJs) evaluated. Anterior displacement of the disc with reduction was the most common, occurring in 67.18% cases of joints with disc displacement. Degenerative bone changes were observed in 53.94% of the TMJs analysed. There was significant correlation between disc displacement with reduction and condylar flattening, disc displacement without reduction and condylar flattening, disc displacement without reduction, and associated degenerative bone changes (flattening and erosion, flattening, osteophyte and erosion; flattening and osteophytes, erosion and sclerosis, flattening and sclerosis, flattening, osteophytes and sclerosis). The correlation between advanced cases of disc displacement and the occurrence of degenerative bone changes emphasises the importance of MRI for an accurate diagnosis and development of an appropriate treatment plan and in cases in which clinical examination is not sufficient for these purposes.
Articular pathologies frequently affect patients with temporomandibular disorder (TMD) and, in the majority of cases, characterise conditions of mechanical disorders in which an abnormal anatomic relationship may occur between the disc, condyle, and articular eminence. Articular disc displacement is a type of internal derangement that may be present in asymptomatic and symptomatic patients. An alteration in the anatomic position of the disc does not indicate dysfunction of the joint and the need for treatment . Studies have demonstrated an association of disc displacement, with or without reduction, with pain, inability to attain jaw opening (locking), limitation of mouth opening, and osteoarthritis of the temporomandibular joint (TMJ) .
When the articular surfaces are well adapted, the articular disc prevents direct friction between them, regularises the anatomic discrepancy on the bone surfaces, and absorbs loads . It has been reported that changes on the bone articular surfaces, such as osteophytes, erosion, and joint deformities, tend to be associated with advanced cases of articular disc displacement and with pain in the TMJ .
A clinical examination is considered insufficient to determine the condition of a joint, but imaging should only be performed after a thorough physical examination indicates that more information is needed. Diagnostic radiology is part of a larger system the goal of which is to treat patients effectively and efficiently .
Research into the causes and treatment of TMDs must be based on reliable and valid diagnostic criteria. Imaging the TMJ is one step in the diagnostic sequence in addition to clinical findings. The goals of TMJ imaging are to evaluate the integrity of the structures when disorders are suspected, to confirm the extent and stage of the progression of disorders, and to evaluate the effects of treatment. To achieve these goals, the assessment of the TMJ should involve both the hard and the soft tissues .
In some cases, it may be necessary to request images of the joint to evaluate the true position of the disc, because the stage of internal disturbances at the beginning of treatment has a strong correlation with result of treatment . I sberg emphasised that 88% of joints without osteoarthritic alterations may present improvement in symptomatology, while two-thirds of the TMJs with degeneration do not have this prognosis. In this case, the importance of imaging examinations is emphasised, as it is known that these may contribute to an adequate diagnosis and treatment with better prognosis .
Magnetic resonance imaging (MRI) is indicated for the diagnosis and study of articular pathologies that may affect patients with signs and symptoms of TMD, since it allows the simultaneous evaluation of the morphology and position of the articular disc and bone structure of the TMJ, in addition to evaluating the functional relationships between the condyle, articular disc, mandibular fossa, and articular eminence .
The aim of this study was to evaluate, by means of MRI, adults symptomatic for TMD and to evaluate the correlation between articular disc displacement and degenerative bone changes that may affect the TMJ.
Materials and methods
In order to conduct this cross-sectional study, static MRIs of 224 TMJs from the files of the Radiology Course of the School of Dentistry of the UFJF were evaluated. These consisted of images of 91 female and 21 male patients, in the age range 18–70 years, all diagnosed as having signs and symptoms of TMD (arthralgia, joint noises, limitation of mouth opening or inability to attain jaw opening, mandibular locking) and requiring MRI. Sequential sagittal cuts (which included evaluation of the entire latero-medial extension of the TMJ) of the right and left sides were used, both in the closed mouth (maximum intercuspation) and maximum opening positions, the images being acquired in T1. The examinations were conducted in an MRI unit (Signa HDx, General Electric Medical Systems, Milwaukee, USA), 1.5 T, with 3 mm thick planes. All the images were evaluated on the same computer.
Only images shown to be satisfactory for evaluation, with adequate definition and fitting in the TMJ region were included in the sample. MRIs that were shaky due to the patient moving, had inadequate fitting in the TMJ, or were of unsatisfactory quality for visualising the articular components, were excluded from the sample.
Evaluation of the images began after approval of the study was obtained from the Committee on Ethics in Research with Human Beings, of the Federal University of Juiz de Fora, Brazil, under Protocol 323/2009.
The MRIs were evaluated by one examiner with 5 years’ experience in the field of radiology and TMD; the evaluator was trained and calibrated for this procedure. The calibration process of image analysis was performed in two stages. First, a classification study regarding the position of the articular disc and degenerative condylar alterations, so that the authors’ criteria could be used as a diagnostic tool. Second, two evaluations with an interval of 1 month between them, of 20% of the total number of images containing the alterations the study intended to investigate.
To evaluate the reliability and reproducibility of the methods used, the intra-examiner agreement coefficient was defined by means of the Kappa test, with a level of significance of 5%. The evaluator was considered calibrated, when this coefficient was equal to or greater than 0.60 (substantial agreement, according to L andis and K och ).
In the MRI the following aspects were investigated, in sagittal cuts. Classification of the articular disc position in accordance with the criteria presented by A hmad et al. as follows. Normal: in the sagittal plane, relative to the superior aspect of the condyle, in closed mouth position, (maximum intercuspation) posterior band is at 11:30–12:30 position, and the intermediate zone is located between the condyle and the articular eminence. Displacement of the disc: in the sagittal plane, relative to the superior aspect of the condyle, in closed mouth position, the posterior band is located anterior to the 11:30 position, and the intermediate zone of the disc is located anterior to the condyle. Articular disc displacement with reduction (DDR): the displaced disc returns to its normal position of 11:30–12:30 in relation to the condyle during the mouth-opening movement, and the intermediate zone is located between the condyle and the articular eminence. Articular disc displacement without reduction (DDWR): the displaced disc does not reduce to its normal superior position of 11:30–12:30 in relation to the condyle during the mouth opening movement, and the intermediate zone is located anterior to the condylar head. The MRIs in Fig. 1 show the normal position of the TMJ and displacement of the articular disc.
To verify the condylar bone changes, the criteria of A hmad et al. , were followed, which classifies them in the following manner. Without degenerative bone changes: normal relative size of condylar head, and no subcortical sclerosis or articular surface flattening and no deformation due to due to subcortical cyst, surface erosion, osteophytes, or generalized sclerosis. Flattening of the condyle: a loss of the rounded contour of the surface. Osteophyte: marginal hypertrophy with sclerotic borders and exophytic angular formation of osseous tissue arising from the surface. Erosion: loss of continuity of articular cortex. Subcortical sclerosis: any increased thickness of the cortical plate in the load-bearing areas relative to the adjacent nonload-bearing areas. The MRIs in Fig. 2 show degenerative bone changes in the condyle region.
After obtaining the MRI evaluations, the prevalence of the different types of disc displacement and degenerative bone changes were calculated in women and in men, and in both jointly. To correlate disc displacement with the occurrence of degenerative bone changes that affect the TMJ, the χ 2 statistical test was used at a level of significance of 5% ( P < 0.05). Statistical analysis was performed with the program BioEstat ® version 5.0.
MRIs of 224 TMJs were analysed regarding the position of the articular disc and the presence of degenerative bone changes (condyle) in 91 women and 21 men. Tables 1 and 2 show the distribution of the articular disc positions and degenerative bone changes for the TMJs, respectively. The results showed that anterior disc displacement with reduction was the condition most frequently found in men and women ( Table 1 ). Regarding degenerative alterations, condylar flattening and the associated degenerative condylar conditions were the most prevalent in both groups ( Table 2 ).
|Without degenerative bone changes||Flattening||Osteophyte||Erosion||Sclerosis||Others a|
a Association degenerative bone changes: flattening and erosion; flattening, osteophyte and erosion; flattening and osteophyte; erosion and sclerosis; flattening and sclerosis; flattening, osteophyte and sclerosis,
Tables 3–5 show the correlation between the articular disc position and degenerative bone changes for the TMJs. In women, a statistically significant correlation was found between anterior disc displacement without reduction and condylar flattening, and between anterior disc displacement without reduction and the associated degenerative alterations ( Table 3 ). In men, a statistically significant correlation was verified between anterior disc displacement with reduction and condylar flattening, as well as a significant correlation between anterior disc displacement without reduction and the associated degenerative condylar conditions ( Table 4 ). With regard to both groups, the following statistically significant correlations were found: anterior disc displacement with reduction and condylar flattening, and anterior disc displacement without reduction and associated degenerative condylar alterations ( Table 5 ).
|Without degenerative bone changes||Flattening||Osteophyte||Erosion||Sclerosis||Others a|
|DDWR||4.12%||9.34% **||0.54%||–||–||7.96% ***|
a Association degenerative bone changes: flattening and erosion; flattening; osteophyte and erosion; flattening and osteophyte; erosion and sclerosis; flattening and sclerosis; flattening, osteophyte and sclerosis.