Investigating the intrinsic factors related with anterior disc displacement in temporomandibular disorder: a preliminary MRI study

doi:10.21203/rs.3.rs-5292547/v1

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Investigating the intrinsic factors related with anterior disc displacement in temporomandibular disorder: a preliminary MRI study

https://doi.org/10.21203/rs.3.rs-5292547/v1

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To observe the structure of temporomandibular joint (TMJ) in patients with TMD by magnetic resonance imaging (MRI), and to investigate the related factors of anterior disc displacement in patients with TMD.Which were classified into TMD without displacement group (97 TMJs), anterior displacement (147TMJs, including anterior displacement with reduction 69 TMJs and without reduction 78 TMJs), the observed variables were focused on the bone structures of TMJ ( the depth, the anteroposterior diameter, the index of TMJ fossa, the morphology, location, medial-lateral diameter, anteroposterior diameter and the index of TMJ condyle) and the other structures indexes involved in the temporomandibular movement (mouth opening movement range, soft tissue of bilaminar region, superior band of the bilaminar zone, morphology and signal of the lateral pterygoid muscle(LPM), joint effusion, osteoarthritis). The three groups were subjected to one-way analysis of variance and chi-square test, while binary logistic regression analysis was employed to establish a regression model and construct the receiver operating characteristic curve. The present study demonstrated that various structural and clinical factors, particularly the altered bone structure of the TMJ, hypertrophy of the LPM, and joint effusion, significantly contribute to the ADD in patients with TMDs.

temporomandibular disorders

temporomandibular joint

disc displacement

magnetic resonance imaging

lateral pterygoid muscle

condyle

Temporomandibular disorders (TMDs) are common in young and middle-aged women adults, with a peak incidence of 20–40 years old [1; 2]. Temporomandibular joint (TMJ) disc displacement (anterior displacement more common) is one of the most frequently encountered TMDs[3], which is the primary cause for joint clicking, limited mouth opening or locking. Magnetic resonance imaging (MRI) serves as a common diagnostic modality for TMJ evaluation due to its high soft tissue resolution and multiple planar imaging, which can clearly visualize TMJ structures including the fossa, condyle, articular disc, bilaminar region and lateral pterygoid muscle (LPM) [4–7]. In recent years, the disc displacement had gained significant attention in the field of TMD investigation owing to its potential association with multiple factors such as psychological influences, trauma or occlusal abnormalities[8–10]. However, the precise etiology of the disc displacement remained elusive to date. Therefore, this study aimed to observe the composition and structure of the temporomandibular joint in patients with TMD, aiming to investigate the associated factors contributing to anterior disc displacement in TMD patients by evaluating the structure characteristics of TMJ based on MRI.

This study is a clinical retrospective case-control study, which has been approved by the Medical Ethics Committee of the PLA General Hospital (Approval Number:S2022-03),and all study participants gave informed consent in a written form in accordance with the ethical standards.We confirm that all methods were performed in accordance with the relevant guidelines and regulations.

Subjects

This study retrospectively enrolled 122 patients of 244 joints with TMD who underwent TMJ MRI examinations at First Medical Center and Hainan Hospital of PLA General Hospital from November 2011 to March 2021, 34 patients with no disc displacement on both sides, 59 patients with disc displacement on both sides, and 29 patients with unilateraldisc displacement.

All the subjects were classifed into a normal disc condyle relationship (NDCR) group 97 TMJ joints, anterior disc displacement with reduction(ADDWR) group 69 joints, and anterior disc displacement without reduction (ADDWoR) group 78 joints. The inclusion criteria were listed as follows: (1) Clinical symptoms consistent with TMD diagnosis; (2) Anterior disc displacement can be diagnosed when the angle between the tangent of the posterior margin of the articular disc and a perpendicular line passing through the condyle at 12 o'clock is greater than 10 degrees. The displacement is categorized as reversible or irreversible based on whether the articular disc returns to its normal position in the open position; (3) No prior treatment has been administered before conducting the MRI examination. The Exclusion criteria: (1) TMD symptoms caused by congenital developmental deformities, trauma, or autoimmune diseases affecting the TMJ; (2) Poor MR image quality was not feasible to make the diagnosis of disc displacement.

Magnetic resonance imaging

All the MRI examination were performed on a 3.0T MR system: using a conventional 8-channel or 32-channel quadrature head coil. All subjects underwent bilateral axial fat-suppressed T2WI, bilateral oblique sagittal proton density weighted imaging (PDWI), bilateral oblique coronal PDWI, and bilateral oblique sagittal fat-suppressed T2WI with close mouth position and bilateral oblique sagittal and coronal PDWI with open mouth position. The imaging parameters of oblique sagittal PDWI (perpendicular to the long axis of the condyle) and oblique coronal PDWI (parallel to the long axis of the condyle) were as follows: Field of view 18cm×18cm, matrix 332×288, repeat time 1500 ms, echo time 25 ms, slice thickness 2 mm, slice spacing 3 mm, and average times 3. The imaging parameters of transverse axial T2WI were listed as follows: Field of view 24cm×24cm, matrix 320×256, repeat time 2975 ms, echo time 68 ms, slcie thickness 3 mm, slice spacing 3 mm, and average times 2.

MR Image analysis

Evaluation of TMJ bone structure (1) Long diameter (maximal distance from internal side to external side) and short diameter (maximal distance from anterior side to posterior side) measured on the maximum section of the condyle in the axial T2WI in close mouth position. (2) Condyle index = Long diameter×100 / condyle transverse arc length from inside to outside condyle measured on oblique coronal image in close mouth position) (Fig. 1). (3) Condyle morphology: oval, flat and beak types. (4) Condyle position: according to the nearest distance between the anterior and posterior bevel of the condyle and the tangent line of the anterior and posterior bevel of the glenoid fossa in the closed position, the patients were divided into anterior, posterior and neutral positions. (5) Anteroposterior diameter of the glenoid fossa: the distance between the lowest points of the anterior and posterior oblique lateral walls of the glenoid fossa in the oblique sagittal position in the close mouth position; (6) Depth of the glenoid fossa the distance between the vertex of the glenoid fossa and the anteroposterior diameter of the glenoid fossa in the oblique sagittal position in the close mouth position; (7) Glenoid fossa index: depth of glenoid fossa ×100/ anteroposterior diameter of glenoid fossa×0.5.

Assessment of TMJ disc (1) Common disc morphology in both close and open positions including biconvex, thickened posterior band, lengthened, thickened anterior band, folded and quasi-circular types; (2) TMJ disc position, the angle between the tangent line of the posterior edge of the posterior band of the articular disc and the vertical line passing through the 12 o 'clock direction of the condyle can be diagnosed as the anterior displacement of the articular disc when the angle exceeds 10°; (3) Assessment of articular disc signal high signal of TMJ disc on the oblique sagittal PDWI indicates possible degeneration, and then judges whether there is perforation and adhesion in the articular disc on the oblique sagittal fat-suppressed T2WI.

Assessment of TMJ function (1) Evaluation of the bilaminar region: assessing whether the soft tissue of bilaminar region is expanded when the mouth is open, and whether the low signal structure of the line-like of the superior lamina is continuous; (2) TMJ movement state The patients were divided into three groups: limited movement (0 ~ 90°), normal movement (90 ~ 120°), and excessive movement (> 120°) according to the position of the condylar head [the movement angle between the tangent line of the condylar head passing through the intersection point (the intersection of the horizontal line on the top of the glenoid fossa and the vertical line on the top of the articular tuberosity) and the horizontal line on the top of the glenoid fossa]in the open state; (3) Evaluation of LPM morphology, including normal, atrophy, and hypertrophy, as well as edema signals within LPM and muscle gap; (5) Temporomandibular osteoarthritis (TMJOA), include condylar flattening, osteophytes, erosions and sclerosis; (6) Detection for presence or absence of fluid in the joint cavity.

Measurement requirements (1) The measurement software utilized was Medcare AnyPacs software developed by Qingdao Medicom Digital Engineering Co., Ltd.; (2) A blinded approach was employed for the measurements, with one individual responsible for image retrieval and another experienced physician (with 6 years of imaging diagnosis expertise) assigned to perform the measurements. The physician responsible for the measurements remained unaware of the patient's clinical history and diagnosis.

Statistical analysis

SPSS 22.0 software was used for statistical analysis. One-way ANOVA was used to analyze the continuous variables, and the data with normal distribution were expressed as mean ± standard deviation. The chi-square test was used for categorical variables. Binary logistic regression analysis was performed on the significant different variable among three groups (NDCR, ADDWR and ADDWoR) as the dependent variables, and the binary logistic analysis were listed as follows according to the different independent: (1) Logistic regression analysis of bone structure variables: the depth of glenoid fossa, glenoid fossa index, condylar index, condylar short diameter, condylar long diameter, condylar morphology (oval, flat and beak), and condylar position (anterior, neutral and posterior) were used as independent variables for variable selection; (2) Logistic regression analysis of TMJ functional variables: mouth opening movement extent (0–90°, 90–120° and > 120°), bilaminar region (swelling and no swelling), continuity of superior lamina (continuous and discontinuous), LPM morphology (normal, atrophy and hypertrophy), TMJOA (no and yes), and joint cavity effusion(no and yes). Variable selection was performed using the backward method. (3) Logistic regression analysis was performed by integrating all statistically significant variables. The receiver operating characteristic (ROC) curve was drawn and the diagnostic point was determined according to the maximum value of the sum of sensitivity and specificity. A significance level was set of P < 0.05

NDCR (97 joints), ADDWR (69 joints) and ADDWoR (78 joints) presented significant difference for disc morphology in close and open mouth position (P = 0.00) and for disc degeneration in close mouth position (P = 0.00) among three groups. However, there was no significant difference for disc perforation (P = 0.61) and adhesion (P = 0.73) (Table 1).

Table 1

Comparison of the morphology of TMJ discs among normal disk condyle relationship group (97 TMJs), anterior disk displacement with reduction( 69 TMJs )and without reduction (78 TMJs) groups.
group	Mouth closed position(biconvex/thickened posterior band/stretched/thickened anterior band/folded/quasi-circular)	Mouth opening position(biconvex/thickened posterior band/stretched/thickened anterior band/folded/quasi-circular)	Degeneration of articular disc (No/Yes)	Perforation of articular disc (No/Yes)	Adhesion of articular disc (No/Yes)
NDCR	90/7/0/0/0/0	72/23/2/0/0/0	51/46	93/4	90/7
ADDR	12/19/6/2/30/0	12/33/7/2/15/0	14/55	65/4	62/7
ADDWR	1/16/4/0/56/1	1/7/1/0/66/3	15/63	72/6	70/8
P	0.00 ^a	0.00^b	0.00 ^c	0.61^d	0.73 ^e
x²	190.20	213.28	28.63	0.99	0.64
a P _{NDCR VS ADDR} =0.00, P _{NDCR VS ADDWR} =0.00, P _{ADDR VS ADDWR} =0.00
b P _{NDCR VS ADDR} =0.00, P _{NDCR VS ADDWR} =0.00, P _{ADDR VS ADDWR} =0.00
c P _{NDCR VS ADDR} =0.00, P _{NDCR VS ADDWR} =0.00, P _{ADDR VS ADDWR} =0.87
d P _{NDCR VS ADDR} =0.63, P _{NDCR VS ADDWR} =0.32, P _{ADDR VS ADDWR} =0.65
e P _{NDCR VS ADDR} =0.50, P _{NDCR VS ADDWR} =0.48, P _{ADDR VS ADDWR} =0.98

TMJ bone structure parameters present significant difference for fossa depth, fossa index, condylar short and long diameters, condylar index, condylar morphology, condylar position (P = 0.00), and fossa anteroposterior diameter showed no significant difference (P = 0.55) among three groups (Table 2).

Table 2

Comparison of bone structure of TMJ among normal disk condyle relationship group, anterior disk displacement with reduction and without reduction groups.
group	Depth of articular fossa (mm)	Anterior and posterior diameter of articular fossa (mm)	Index of articular fossa	Anterior and posterior diameter of condyle (mm)	Internal and external diameters of condyle (mm)	Index of condyle	Morphology of condyle (oval/flat/beak)	Position of condyle (anterior/neutral/posterior)
NDCR	6.37 ± 1.24	14.67 ± 2.27	86.50 ± 13.71	8.06 ± 1.41	21.45 ± 3.05	72.94 ± 6.93	74/15/8	12/73/12
ADDR	5.58 ± 1.01	15.00 ± 2.14	74.73 ± 10.66	6.41 ± 1.20	18.35 ± 2.75	75.81 ± 7.44	40/12/17	1/40/28
ADDWR	5.06 ± 1.12	14.98 ± 2.12	68.07 ± 13.66	6.37 ± 1.56	18.29 ± 2.92	77.19 ± 7.98	35/16/27	0/43/35
P	0.00 ^a	0.55 ^b	0.00 ^c	0.00^d	0.00^e	0.00 ^f	0.00 ^g	0.00 ^h
F/x²	25.49	0.61	43.60	39.21	31.88	7.24	22.37	36.30
a P _{NDCR VS ADDR} =0.00, P _{NDCR VS ADDWR} =0.00, P _{ADDR VS ADDWR} =0.01
b P _{NDCR VS ADDR} =0.36, P _{NDCR VS ADDWR} =0.36, P _{ADDR VS ADDWR} =0.97
c P _{NDCR VS ADDR} =0.00, P _{NDCR VS ADDWR} =0.00, P _{ADDR VS ADDWR} =0.00
d P _{NDCR VS ADDR} =0.00, P _{NDCR VS ADDWR} =0.00, P _{ADDR VS ADDWR} =0.87
e P _{NDCR VS ADDR} =0.00, P _{NDCR VS ADDWR} =0.00, P _{ADDR VS ADDWR} =0.91
f P _{NDCR VS ADDR} =0.02, P _{NDCR VS ADDWR} =0.00, P _{ADDR VS ADDWR} =0.29
g P _{NDCR VS ADDR} =0.01, P _{NDCR VS ADDWR} =0.00, P _{ADDR VS ADDWR} =0.27
h P _{NDCR VS ADDR} =0.00, P _{NDCR VS ADDWR} =0.00, P _{ADDR VS ADDWR} =0.51

The other variables related with TMD presented significant difference for TMJOA, LPM morphology, opening mouth extent, superior lamina continuity and joint cavirty effusion (P = 0.00), and LPM edema, LPM space edema and bilaminar expension showed no significant difference (P value was 0.23, 0.24 and 0.16, respectively) among three groups. (Table 3).

Table 3

Comparison of the characteristics of TMJ movement among normal disk condyle relationship group, anterior disk displacement with reduction and without reduction groups.
Group	Expansion of bilaminar region (Yes/No)	Continuous superior band of the bilaminar (continuous/discontinuous)	Morphology of lateral pterygoid muscle (normal/atrophy/hypertrophy)	Edema of lateral pterygoid muscle (No/Yes)	Edema of intermuscular space of lateral pterygoid muscle (No/Yes)	Open mouth movement (limited movement/normal/excessive movement)	Osteoarthritis (No/Yes)	Joint cavity effusion (No/Yes))
NDCR	87/10	88/9	87/8/2	71/26	24/73	8/49/40	86/11	60/37
(ADDR	66/13	62/7	54/8/7	43/26	10/59	11/42/16	38/31	30/39
ADDWR	75/3	57/21	57/6/17	49/29	14/64	25/47/6	29/49	22/56
P	0.16^a	0.00^b	0.00^c	0.23^d	0.24^e	0.00^f	0.00^g	0.00^h
x²	3.71	12.35	15.26	2.97	2.90	34.19	51.39	19.94
a P _{NDCR VS ADDR} =0.16, P _{NDCR VS ADDWR} =0.11, P _{ADDR VS ADDWR} =0.88
b P _{NDCR VS ADDR} =0.85, P _{NDCR VS ADDWR} =0.00, P _{ADDR VS ADDWR} =0.01
c P _{NDCR VS ADDR} =0.05, P _{NDCR VS ADDWR} =0.00, P _{ADDR VS ADDWR} =0.26
d P _{NDCR VS ADDR} =0.14, P _{NDCR VS ADDWR} =0.14, P _{ADDR VS ADDWR} =0.95
e P _{NDCR VS ADDR} =0.11, P _{NDCR VS ADDWR} =0.28, P _{ADDR VS ADDWR} =0.57
f P _{NDCR VS ADDR} =0.03, P _{NDCR VS ADDWR} =0.00, P _{ADDR VS ADDWR} =0.01
g P _{NDCR VS ADDR} =0.00, P _{NDCR VS ADDWR} =0.00, P _{ADDR VS ADDWR} =0.03
h P _{NDCR VS ADDR} =0.02, P _{NDCR VS ADDWR} =0.00, P _{ADDR VS ADDWR} =0.05

The binary logistic regression analysis of TMJ bone structure variables generated a regression model, P_{(NDCR VS ADDR+ADDWR) =1/1+e−}^{(18.01 −0.10 joint fossa index −0.47 condylar long diameter −0.77 condylar short diameter +1.86 condylar position)}. The area under the ROC curve (AUC) was 0.94 (Fig. 2). The diagnostic point was determined to be 0.69 according to the maximum sum of sensitivity and specificity. If P > 0.69, the probability of anterior disc displacement in TMD patients increased. The sensitivity and specificity of the diagnostic point was 0.83 and 0.93, respectively. The prediction accuracy of the prediction model in this group of data was 83.2%.

The binary logistic regression analysis of the other variable related with TMD generated a regression model, P_{(NDCR VS ADDR+ADDWR)=1/1+e}^{−(−0.08–0.87open mouth extent+2.37TMJOA+0.83LPM morphology+1.16articular cavity effusion)}. The AUC was 0.84 (Fig. 2). The diagnostic point was 0.59 according to the maximum sum of sensitivity and specificity. If P > 0.59, the probability of anterior disc displacement in TMD patients increased, and the sensitivity and specificity of the diagnostic point was 0.73 and 0.84 respectively.

The binary logistic regression analysis of all the variable related with TMD generated a regression model. P_{(NDCR VS ADDWR+ADDWoR)=1/1+e}^{−(16.43−0.11 joint fossa index−0.52 condylar long diameter−0.88 condylar short diameter+2.67 condylar position+1.18 LPM morphology+2.63 joint cavity effusion)}, the AUC was 0.97 (Fig. 2). The diagnostic point was 0.41 according to the maximum sum of sensitivity and specificity. If P > 0.41, the probability of anterior disc displacement in TMD patients increased, and the sensitivity and specificity of the diagnostic point was 0.94 and 0.86, respectively. The prediction accuracy of the prediction model in this set of data was 89.8%.

TMJ disc is fibrocartilage with certain hardness and toughness, which locates between the joint fossa and condyle and exhibits a double concave bending shape to relieve intraarticular pressure. TMJ disc displacement is a common type of TMD. MRI can clearly show the corresponding changes of TMJ fossa, condyle, articular disc, bilaminar region and LPM when TMD occurs. In this study, the observation of articular disc morphology suggested that the double concave type was the majority in the non-displacement group, and the proportion of other morphologies increased significantly when the joint disc displaced forward, among which the folded type increased significantly in the forward displacement group. A previous study have pointed out that the morphology of the articular disc is closely related with the pressure it bears[11]. Therefore, it could be speculated that when the joint disc displaced forward, the pressure on each band of the articular disc would change due to abnormal traction of the LPM and other masticatory muscles, and then damage the superior lamina, generate abnormal condylar movement, and change TMJ bone structure. The above abnormal structural changes showed statistical differences in the current study. Also the displaced disc cannot be recycled into the joint fossa - condylar space, and induce an increased probability of other morphologies of the articular disc.

The current results revealed that the articular disc with the anterior displacement was prone to have high signals on PDWI, indicating the possibility of degeneration in the articular disc [12],which pathologically presented cracks, fibrillation, hyperplasia and hyalinization in the displaced articular disc. These articular disc injuries would increase the risk of articular disc perforation, and there were a few cases with disc perforation in the current study. Joint disc adhesion also occurred in a few cases in the three groups of data. When the articular disc adhered to the articular tubercle and articular capsule, the activity of the articular disc was limited. The anteriorly displaced disc had little or no activity. Because the condyle moves forward when the mouth is open, the posterior band of the articular disc and the condyle returned relatively normal position by less than 10 degrees in the direction of 12 o'clock of the condyle. Therefore, a few patients with joint disc adhesion occurred in the anterior displacement with reduction group.

The TMJ bone structure indexes, including the depth of TMJ fossa, fossa index, short diameter of the condyle, long diameter of the condyle, condylar morphology, condylar index, and condylar position presented statistically significant differences among the three groups. The condylar long and short diameters were identified to be smaller in the ADDWR and ADDWoR groups compared with NDCR group. These parameters measured on the largest cross-section of the condyle reflected the size of the condylar articular surface to a certain extent. Simultaneously, the analysis of condylar morphology revealed a significantly higher proportion of beak-shaped condyles in the ADDWoR group (27 joints, 34.6%) compared with the NDCR group (8 joints, 8.2%). Furthermore, the articular surface size of beak-shaped condyles was found to be smaller than that of the other two types. These findings suggested a potential association between variations in condylar bone measurements and the presence of beak-shaped condyles, which has been previously reported by some researchers as being linked to anterior disc displacement[12].The posterior position of the condyle increased in ADDWR and ADDWoR groups compared with NDCR group (12/97, 42.9%). Following anterior disc displacement, there was an increase in the joint space between the anterior slope of the condyle and the anterior slope of the articular fossa. Previous studies have indicated that posterior positioning of the condyle is predominantly observed in patients with anterior disc displacement[13–15]. The joint fossa index reflects the relationship between the depth of the joint fossa and the anteroposterior diameter and lateral wall slope of the joint fossa. The larger the index, the deeper the joint fossa and the greater the slope of the lateral wall. The condylar index can effectively quantify the convexity of the condyle, with an increasing index indicating a transition from a rounded convex shape to a flatter one. In this study, our results revealed that both the joint fossa index and depth were significantly smaller in ADDWR and ADDWoR groups compared with NDCR group. Conversely, the condylar index was found to be larger in patients with disc displacement, suggesting a shift towards shallower depths and decreased lateral wall slope and a transformation from round convexity to flatness in TMD patients. Besides these, it was demonstrated that the morphological changes of the bony structure of ADDWoR group were more obvious than those of ADDWR group.

The current study also revealed that mouth opening extent, the superior lamina of the bilaminar zone, LPM morphology, TMJOA, and joint cavity effusion were significantly related with TMJ disc anterior displacement. The proportion of opening mouth restriction increased in the ADD group. During the TMJ MRI scan with opening mouth position, a mouth opener was used by the patient and the degree of opening was primarily based on their comfort level. Anterior disc displacement led to an increase in TMJ dysfunction and pain during mouth opening, which would result in a higher proportion of condylar activity restriction. In this study, the incidence of 21 joints (27.0%) with discontinuous superior lamina in the ADD group was significantly higher than that in the NDCR group (9 joints). In the open position, the articular disc slides forward with the condyle, the elastic fibers in the bilaminar zone are tightened, and the discontinuous signal of the superior lamina indicates the existence of tears [16], which suggests that the probability of tears increases with the anterior disc displacement. The LPM participates in the movement of the TMJ, and its upper belley is attached to the articular disc. Some studies[17] have demonstrated that the volume change of the LPM is related with the anterior disc displacement. The volume of the LPM increases in patients with ADDWR, and decreases in patients with ADDWoR. In this study, the proportion of hypertrophic morphology of the LPM increased in the ADDWoR group, and there was no statistically significant difference in the edema of LPM and LPM gap. The incidence of TMJOA was significantly increased in the ADD group. Previous studies had confirmed that TMJOA was associated with disc displacement, abnormal habits, and joint functional overload[10; 18]. The articular disc plays a buffering role in condylar-fossa joint movement. When the disc is anteriorly displaced, impact erosion directly occurs in the bone structure of the TMJ, and then a series of changes in articular cartilage degeneration, destruction, and subchondral bone occur. The prevalence of joint cavity effusion increased in the ADD group. The articular disc anatomically separates the metatarsal bone and condyle into two distinct compartments, characterized by a larger and laxer upper compartment and a smaller and tighter lower compartment. A minimal amount of synovial fluid is present within the joint cavity to facilitate smooth articulation. A previous studies[19]have demonstrated an association between disc displacement and a certain degree of joint effusion. However, the precise underlying mechanism remains unclear. Joint effusion is linked to elevated levels of proteins and pro-inflammatory cytokines in the joint tissue. Therefore, it is reasonable to assume that the anterior disc displacement would lead to TMJ dysfunction, osteoarthritis, synovitis, and other conditions, which would trigger synovial secretion within the joint cavity. The increased effusion could impede the sliding movement of both the disc and condyle, which present a relationship between interactions and corresponding effects between cavity effusion and condylar movement.

The binary logistic regression analysis of the bone structure indexes of the TMJ identified four significant variables such as the joint fossa index, condylar position, condylar long and short diameters,and these variables in the model effectively reflected the anatomical characteristics of the TMJ bone structure, which indicated that their substantial influence on anterior disc displacement. Moreover, the prediction model exhibits a remarkable AUC 0.94.The closer the area under the curve approaches 1, the higher the accuracy of the detection method becomes. For the logistic regression analysis of the other variable related with TMD, the AUC is measured to be 0.84. As is known that the AUC value reflects the diagnostic efficacy of the variable, therefore, the bone structural model had a relatively higher diagnostic value for ADD, and it also suggested that TMJ bone parameters played a important role in the ADD in TMD patients. In the comprehensive model, apart from four variables including the joint fossa index, condylar position, condylar long and short diameter, two additional variables LPM and joint cavity effusion also stayed in the model. These findings suggested that the hard and soft tissue parameters of TMJ participated the ADD, which would provide a new evidence and clue for the TMD therapy.

There are some limitations in this study: (1)This study was a cross-sectional observation, and the further confirmation is required to investigate whether these bone structure changes contribute to the development of anterior disc displacement. In future studies, follow-up data from the same group of TMD patients can be included to conduct a comparative analysis of bone structure data before and after the occurrence of ADD. (2) The occurrence of observational signs such as disc perforation and adhesion were relatively infrequent in both the NDCR group and ADD group, which limited the statistical analysis. Further investigation is required to identify the impact on anterior disc displacement of the disc. In future studies, expanding the sample size would facilitate comprehensive data analysis.

In summary, multiple parameters including TMJ fossa depth, fossa index, condylar long and short diameter, condylar morphology, condylar index, condylar position and opening mouth extent, the superior lamina of the bilaminar, articular cavity effusion, osteoarthritis, and LPM morphology presented significant correlations with anterior disc displacement in patients with TMD. ADDWoR exerted a more profound impact on the morphological characteristics and motor function of the TMJ compared with ADDWR.

Data availability

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Acknowledgments

This study is a clinical retrospective case-control study, which has been approved by the Medical Ethics Committee of the PLA General Hospital (Approval Number:S2022-03).The scientific guarantor of this publication is Zhiye Chen. The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.

Author contributions

B.W.,M.W.and Z.C.wrote the main manuscript text. B.W. and M.W. prepared the tables and the figures. All authors reviewed the manuscript.

Competing interests

The authors declare no competing interests

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No competing interests reported.

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Investigating the intrinsic factors related with anterior disc displacement in temporomandibular disorder: a preliminary MRI study

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Abstract

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INTRODUCTION

MATERIALS AND METHODS

Subjects

Magnetic resonance imaging

MR Image analysis

Statistical analysis

RESULTS

DISCUSSION

CONCLUSION

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References

Additional Declarations

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