DISCUSSION
The present study investigated the accuracy of clinical findings in
determining the presence or absence of internal derangement of TMJ
according to the set criteria by RDC/TMD and the superior diagnostic
imaging modality like magnetic resonance imaging (MRI).
For this study, 14 patients between 11 to 40 years of age were selected.
The control group of 5 healthy volunteers without any sign & symptoms
of TMD showed a different age distribution; they were between 20 to 30
years.
Out of a total of 14 patients, the study consisted of 9 female & 5 male
patients. The ratio of female to male in this group of patients with
TMDs was 1.8:1. The results of this study show that the prevalence of
TMDs was higher in women than in men. Several related studies have
reported comparable results10,14.
In the present study, the author has investigated the accuracy of five
clinical parameters for determining the presence or absence of anterior
disc displacement. The MRI findings obtained from 28 joints with TMDs
were compared with their initial visits’ clinical findings. The
sensitivity values of the clinical parameters were considerably low, in
contrast with their high specificity. It means that false–negative
diagnoses were made more frequently than false-positive
diagnosis7. It was in accordance with the study
carried out by Yatani et.al15. Thus results obtained
from these studies indicate that it is challenging to predict disc
derangement based on clinical symptoms alone. In other words, not all
joints commonly present characteristic clinical signs and symptoms of
disc derangement2,7,8,16.
The most common clinical sign in this study group was tenderness in the
pre-auricular region (18 out of 28 joints, i.e., 64%), the cause being
unclear. Okeson et al. 10 reported that disc
displacement of TMJ is the crucial cause of facial and TMJ pain. Based
on these observations, pain/tenderness in the preauricular region could
be associated with alteration of retrodiscal tissue17.
A study carried out by Kobs G et al. 9, concluded that
although clicking is a predictor of anterior disc displacement with
reduction, it was not present in his entire study population. In the
present study, joint noise was found in 16 out of 28 joints (57%), thus
indicating that TMJ clicking might occur as a consequence of frictional
incompatibility between the disc and the eminence when the posterior
band of the disc moves anteriorly or posteriorly beyond the apex of the
articular eminence. Other causes may be a deviation in the condylar form
(remodeling), adhesion, or muscular
incordination18-22.
Muscle tenderness and limited mouth opening were found in Thirty-six
percent in the present study. Deflection/deviation was found in 9 joints
out of 28 joints (Thirty-two percent) and was the least among all the
clinical symptoms7.
In anticipation of osseous changes in the long-standing internal
derangement of TMJ and to rule out other TMJ organic pathologies, the
authors could have chosen the various radiographic and imaging
modalities to determine the status of the disc. However, none of the
modalities (conventional radiograph, specialized radiograph, and CT-
axial and coronal view) could substantiate and locate the disc
position23,24,25.
The predictive value of the clinical diagnosis of ADDWR was 0.65 in a
study by Barclay et al. 2. The present study showed a
7 non-symptomatic joint with ADDWR on MRI. 2 joints clinically diagnosed
ADDWR showed anterior disc displacement without reduction with MRI. 1
joint clinically diagnosed as anterior disc displacement without
reduction did reduce on opening. 1 joint clinically diagnosed as
anterior disc displacement without reduction appeared normal on MRI.
Whereas 1 joint clinically diagnosed as anterior disc displacement
without reduction could not be interpreted in MRI, 3 joints clinically
diagnosed as MRI correctly diagnosed ADDWR, and 4 joints clinically
diagnosed as NDD was confirmed by MRI2, 19, 20, 21,
22.
There was a low agreement (33% to 70%) between clinical diagnosis and
MRI diagnosis in symptomatic & asymptomatic joints2,
6, 7-9. The present study showed only 36% (4/11) of the asymptomatic
joints had a normal disc position, detected by MRI. The prevalence of
disc displacement in asymptomatic subjects is between 16% and 33%2.
A previous study has shown that contralateral non-symptomatic joints in
subjects with internal derangement in the other TMJ frequently have disc
displacement10, 14; the present study findings also
correlate with this study (7/11 ADDWR).
In accordance with the available literature, posterior disc displacement
is exceptionally uncommon, and it was not observed in the present
study12. Superior disc position is commonly used to
refer to normal disc positioning in the sagittal oblique closed mouth
view. The method used to judge disc position in this study was the
closed mouth sagittal view assessment of the posterior band’s position
relative to the top of condyle as a superior disc position. It was
considered normal if the posterior band of the disc is at
position17.
In the current study, the medial displacement proportion was more
significant than lateral displacement (4 joints were medial; 2 joints
lateral). These findings are in accordance with the existing
literature18, which suggests that medial displacement
occurs more frequently than lateral displacement and can be attributed
to the force of muscles attached to the disc. It has been speculated
that one reason for medial disc displacement is muscle spasm of the
superior belly of the lateral pterygoid muscle3.
Most clinical studies on anteroposterior arthrography and sagittal &
coronal MRI have shown that the displacement’s medial component is more
frequent than the lateral component. The percentage of medial
displacement was more significant in anterior disc displacement without
reduction, and sideways displacement was also most frequent in anterior
disc displacement without reduction8.
The anterior disc displacement without reduction is the most common
internal displacement depicted among TMJ derangement, but the present
study showed that the NDD was most common in the study population
diagnosed by MRI. (13 NDD; 11ADDWR and 2 anterior disc displacement
without reduction). The limited protrusive movement was the most
accurate clinical sign used for diagnosing anterior disc displacement
without reduction8. However, this study did not
support it as only 1 patient had limited mouth opening out of 2 patients
diagnosed anterior disc displacement without reduction with
MRI18. It could be due to contradicting views in
clinical parameters based on protrusive movements/deflection and no
single specific criteria in diagnosing specific TMJ disc displacement19-25.
The overall diagnostic agreement of 88.25% (15/17) between specific
RDC- diagnosis, and MRI in the current study is in accordance with
various contemporary studies9,13. Several authors have
investigated the reliability of the clinical diagnosis of ID using MRI
as a ’gold standard’. The reported percent agreement ranged from 59% to
90%. A positive RDC examination is predictive for internal derangement
but not reliable with regard to the type of disc displacement. The
clinical examination is of limited value in determining the TMJ disc’s
true position and its functional movement. When accurate information
about the TMJ disc position is clinically essential, MRI should be
performed; the clinical examination alone cannot provide sufficient
information2,7,9,16, 18-20.
The combinations of TMJ radiographs are useful only in long-standing
pathology, leading to visible changes in the osseous structures.
However, these are still relevant in ruling out and eliminating osseous
pathology for a confirmed diagnosis of soft tissue pathology of TMJ.
Based on the results of this study, the main strength is that the
RDC/TMD criteria are not alone sufficient for the diagnosis of the
internal derangement, and perhaps, it should be supported by the MRI to
reach a confirmatory diagnosis so that a comprehensive approach can be
initiated towards the management of the internal derangement of the TMJ
by the clinicians. However, this study’s major drawback was a small
sample size before reaching a definitive conclusion. A further study
examining a group of volunteers with or without a history of TMD and
using the same diagnostic criteria as set by RDC/TMD, MRI with larger
sample size, multi-center trials needs to be conducted.