Characteristics of condylar joint space, position and morphology in skeletal Class II malocclusion patients with bilateral idiopathic condyle resorption

Characteristics of condylar joint space, position and morphology in skeletal Class II malocclusion patients with bilateral idiopathic condyle resorption | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Characteristics of condylar joint space, position and morphology in skeletal Class II malocclusion patients with bilateral idiopathic condyle resorption Jingyi Liu, Zhengzhan Lv, Yanfei Zhu, Miri Chung, Lingyong Jiang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7570283/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 12 Jan, 2026 Read the published version in BMC Oral Health → Version 1 posted 12 You are reading this latest preprint version Abstract Objective To investigate the condylar joint space, position and morphology in skeletal Class II malocclusion patients with idiopathic condylar resorption (ICR), in order to provide reference for the clinical treatment and efficacy evaluation of ICR. Materials and Methods Skeletal Class II malocclusion patients with ICR and skeletal Class II malocclusion patients with normal temporomandibular joint (TMJ) structure were included in this study. The anterior joint space (AJS), superior joint space (SJS) and posterior joint space (PJS) were measured by computed tomography (CT) and magnetic resonance imaging (MRI). The surface area and volume of condyle were measured through three-dimensional reconstruction using CT scans. Results A total of 55 patients were included in both groups. All ICR patients exhibited bilateral anterior disc displacement without reduction (ADDWOR), with MRI revealing morphological changes in 90.91% of ICR patients. SJS in ICR group significantly decreased by 15.85% on CT and 14.23% on MRI (P<0.05). The typical SJS-PJS difference in healthy TMJs disappeared in ICR patients, and joint space proportions became irregular, indicating condylar instability. Mild resorption was found in 78.18% of ICR patients, mainly affecting the anterior slope and condylar apex, while 21.82% showed more severe resorption. Condylar ratio in ICR patients showed greater variability, reflecting increased instability. Additionally, condylar volume and surface area were significantly reduced by 29.9% and 21.3%, respectively (P<0.05). Conclusion ICR patients exhibit varying degrees of condylar resorption, disrupting the stable joint space proportions. This may be due to morphological changes from condylar resorption, affecting condylar position in the glenoid fossa. Temporomandibular joint Idiopathic condyle resorption Joint space Condyle Class II Craniofacial anomalies Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Temporomandibular joint (TMJ) is the only joint structure in the craniomaxillofacial skeletal system, which is responsible for a series of motor functions involving opening and closing the mouth in daily life, such as chewing and speaking. As an important part of TMJ, the condyle is susceptible to the effects of hormones, mental stress or other unknown systemic factors, resulting in dysfunction and pathologic changes of TMJ. Idiopathic condylar resorption (ICR) is a kind of non-functional reconstruction of temporomandibular joint caused by unknown reasons, characterized by progressive condylar resorption and condylar morphological changes. 1 – 2 ICR was first proposed by Rabey in 1977, describing the condylar resorption as ‘condylolysis’. 3 ICR initiates bone loss and anatomical morphological changes in condyle, accompanied by series of clinical symptoms, including reduced height of the mandibular ascending ramus, mandibular anteroposterior rotation, and anterior open bite, which may result in severe skeletal Class II malocclusion, temporomandibular joint dysfunction and pain, seriously affect the aesthetics and occlusal function of patients. 4 – 5 Due to the presence of the articular disc, there exists a certain physiological gap between the condyle and the glenoid fossa called joint space. 6 Joint space within the normal range is necessary to ensure the functional movement of condyle in the glenoid fossa, such as sliding, rotation and compound movement. 7 Disc displacement or pathological alterations in joint morphology often leads to abnormal joint space, which indicates an improper shift in condylar position. 8 Moreover, abnormal condylar position may also affect the load stress on the disc-condyle complex, which further exacerbates the progression of TMJ disease. 9 Maintaining the normal physiological position of the condyle is crucial for stabilizing the patient's occlusal relationship during the treatment of malocclusion. Therefore, it is of great significance to clarify the changes in joint space during the clinical treatment of TMJ disease and malocclusion. At present, computed tomography (CT) and magnetic resonance imaging (MRI) are widely used to evaluate the bone structure and disc-condyle relationship of TMJ before treatment. Both CT and MRI are ideal techniques for accurate joint space measurement and condylar position assessment, as they have sufficient resolution and can clearly show the boundary of condyle and glenoid fossa. 10 – 12 Current research has found that ICR patients may experience signs and symptoms of temporomandibular joint disorders, as well as reduction of craniofacial bones and masticatory muscles. 13 – 14 However, the changes of condylar position within the glenoid fossa and condylar morphology after resorption have not been clarified yet. In this study, CT and MRI were used to measure the joint space in skeletal Class II malocclusion patients diagnosed with bilateral ICR or healthy TMJ. The purpose of this study was to investigate the characteristics of condylar position and morphology in ICR patients. Materials and Methods Study design This retrospective study was carried out in accordance with ethical principles and approved by the institutional review board of the Ninth People's Hospital, which conformed to the Declaration of Helsinki. (Approval: SH9H-2018-163-T121, Clinical trial number: ChiCTR2100051867, registration date:2021/10/08). Skeletal Class II malocclusion patients with a diagnosis of bilateral ICR who received treatment in the Center of Craniofacial Orthodontics, Department of Oral and Craniomaxillofacial Surgery, Ninth People's Hospital of Shanghai Jiao Tong University School of Medicine from January 2021 to December 2023 were included in this study. To establish a control group, skeletal Class II malocclusion patients with healthy TMJs who sought treatment during the same period were matched one-to-one with the ICR patients based on age and gender, with an age difference of no more than one year. Patients aged between 16 and 30 years were included in this study. This age range was chosen because ICR most commonly occurs in adolescents and young adults, particularly females. This range minimizes the potential interference from condylar growth in younger individuals and degenerative joint changes in older individuals. The inclusion criteria of ICR group were: (1) Age between 16 and 30 years; (2) Chief complaint of mandibular retrusion and diagnosed with skeletal Class II malocclusion (ANB angle > 5°); (3) CT and MRI evidence of destructive changes associated with ICR, including sclerosis, flattening of condylar margins, erosion of the cortical bone and other resorptive features. The control group patients were screened according to the age and gender matching principles mentioned above. The inclusion criteria of control group were: (1) Age between 16 and 30 years; (2) Chief complaint of mandibular retrusion and diagnosed with skeletal Class II malocclusion (ANB angle > 5°), but with no TMJ-related symptoms on clinical examination; (3) CT and MRI showing uniform and continuous cortical bone with normal condylar morphology. (4) MRI demonstrating a normal bilateral disc-condyle relationship. The Exclusion criteria included: (1) history of TMJ-related treatments. (2) history of orthodontic treatment. (3) history of orthognathic surgery. (4) craniofacial trauma, tumor disease and systemic diseases. Finally, a total of 110 patients (55 patients in each group, comprising 4 males and 51 females) were reviewed in this study. Imaging acquisition Whole-head CT scans were acquired using a GE LightSpeed-16 system (GE Healthcare, USA) with the following parameters: 120 kVp, 80 mA, 0.3 mm isotropic voxel size, 1.25 mm slice thickness, and a field of view extending from the cranial vertex to the hyoid bone. During scanning, patients were placed in a supine position with their teeth in centric occlusion, and instructed to avoid swallowing to minimize motion artifacts. MRI scans were acquired using a 1.5T MRI scanner (Signa HDxt, GE Healthcare, USA) with a dedicated 3-inch bilateral surface coil. Oblique sagittal T1-weighted sequences were obtained in the closed-mouth position with the following parameters: TR/TE = 1,800/20 ms, flip angle = 150°, NEX = 2, FOV = 12 cm, slice thickness = 1 mm, and acquisition matrix = 512 × 512. MRI scanning was performed with the patient in the same position and occlusal condition as described above. Joint space measurement The anatomical landmarks and relevant definition during joint space measurement were shown in Table 1 . Table 1 Landmarks and Measurements Used in This Study to Evaluate proportion and changes of joint space Landmarks & Constructed lines & Measurements Definition Condylar landmarks AC Most anterior point of the condyle SC Most superior point of the condyle PC Most posterior point of the condyle SF most superior point of the glenoid fossa Joint space measurements AJS The shortest distances from AC to the glenoid fossa SJS distance between SC and SF PJS The shortest distances from PC to the glenoid fossa Volume and surface area measurement Porion (Po) Uppermost point of external auditory canal Orbitale (Or) Lowest point of orbital margin C Lowest point of sigmoid notch Frankfort horizontal plane (FH plane) Line from Po to Or C-Plane Line passing through point C and parallel to FH plane D-Plane Line passing through point C and perpendicular to FH plane The acquired DICOM file of CT was imported into Dolphin Imaging software (version 11.95; Dolphin Imaging & Management Solutions, USA) for 3D reconstruction. To ensure consistency across patients, head position should be adjusted before measurement. In the reconstructed frontal view, the horizontal orientation was established by aligning the bilateral infraorbital margins. For each temporomandibular joint, the Frankfort Horizontal (FH) plane was defined individually using the ipsilateral porion (Po) and orbitale (Or) points. The 3D model was rotated until the FH plane was aligned horizontally. This adjustment was performed in a fully 3D environment, where the Po and Or landmarks were clearly visible, in order to ensure accurate orientation. After head orientation, the oblique sagittal plane was determined for each side. This plane was defined as passing perpendicularly through the midpoint of the largest mediolateral diameter of the condyle (Fig. 1 A). The sagittal slice obtained along this plane was used for all subsequent joint space measurements (Fig. 1 B). For MRI images, since head position adjustment is not feasible, the oblique sagittal plane was selected based on the same principle as in CT. This slice was identified by scrolling through axial and coronal planes to localize the condylar center (Fig. 1 D), and the corresponding sagittal section was used for joint space measurements (Fig. 1 E). Although head position could not be fully standardized as in CT, this selection method ensured that measurements were consistently performed on the most representative sagittal section of the condyle. The Kamelchuk method 15 was used for joint space measurement on both CT and MRI (Fig. 1 C, F). Anatomical landmarks were identified using Adobe Photoshop CS5 (Adobe Systems, San Jose, USA), and measurements were performed with MB-Ruler software (Markus Bader, Berlin, Germany). Each joint was measured three times at two-week intervals by the same experienced physician. Pullinger and Hollender’s formula was used to describe the antero-posterior position of condyle within the glenoid fossa 16 : Condylar ratio = (PJS-AJS)/(PJS + AJS)×100. A positive ratio indicates an anterior condylar position, while a negative value indicates a posterior condylar position. Volume and surface area measurement of condyle The acquired DICOM file of CT scanning was imported into Mimics v21.00 (Materialise, Belgium). The threshold range was set to 250-3071HU to obtain the craniomaxillofacial three-dimensional bone structure. 17 First, 3D reconstruction of the CT data was performed (Fig. 2 A), and the mandible was segmented (Fig. 2 B). After establishing the FH plane as described above, the sigmoid notch of the mandible was identified, and its deepest point was marked as point C. A horizontal plane passing through point C and parallel to the FH plane was defined as the C-Plane. A perpendicular plane passing through point C and orthogonal to the C-Plane was defined as the D-Plane. These two orthogonal reference planes were used to segment the condyle from the mandibular ramus (Fig. 2 C), facilitating volumetric and surface area measurements using built-in functions of the software. Statistical analysis Data collection, recording, and analysis were conducted by the same experienced physician. Standardized measurement protocols mentioned above were followed, and data entry was performed blindly. Intra-rater reliability was assessed via the intraclass correlation coefficient (ICC) using a two-way mixed-effects model for absolute agreement ( ICC [3,1] ). Interpretation followed established criteria 18 : 0.90 excellent. ICC values were calculated for all six joint space variables (AJS, SJS, and PJS measured on both CT and MRI), and all exceeded 0.85, indicating good to excellent consistency. SPSS 20.0(IBM Corp., Armonk, NY, USA) was used for statistical analysis. Repeated measures one-way ANOVA was used for within-group comparison of joint space, and independent samples t-test was used for between-group comparison of joint space. All tests were two-tailed, p-value < 0.05 was considered statistically significant. Results Participant demographic characteristics were summarized in Table 2 . A total of 55 patients (4 males and 51 females) were included in each group. The average age was 22.81 ± 2.10 years (range from 19.48 to 28.93 years) in ICR group and 22.75 ± 2.14 years (range from 19.11 to 28.61 years) in control group. Compared to control group (Fig. 3 A), all 55 patients in the ICR group were found to exhibit anterior disc displacement without reduction (ADDWOR) in bilateral TMJ. In MRI, the articular discs of ICR patients were consistently observed to be positioned anterior to the condyle. Additionally, changes in disc morphology were observed, including a shortened anterior-posterior diameter, thickening of the posterior band, and loss of the normal biconvex configuration (Fig. 3 B, n = 50/55). Only a small number of patients showed relatively normal disc morphology despite anterior displacement (Fig. 3 C, n = 5/55). Overall, the joint disc presents a twisted and compressed shape in most patients. Table 2 Participant demographic characteristics ICR group Control group P Patients, n 55 55 Age, years 22.81 ± 2.10 22.75 ± 2.14 0.902 Gender, n (%) > 0.999 Male 4(7.27%) 4(7.27%) Female 51(92.73%) 51(92.73%) Bilateral Disc-Condyle relationship, n < 0.001*** ADDWOR 55 0 Normal 0 55 Joint space measurements obtained from CT and MRI were shown in Table 3 . AJS, SJS and PJS measured by CT in control group were 1.31 ± 0.13 mm, 2.65 ± 0.29 mm and 1.97 ± 0.19 mm, respectively. While in ICR group, AJS, SJS and PJS measured by CT were 1.43 ± 0.61 mm, 2.23 ± 0.81 mm and 2.04 ± 0.72 mm, respectively. Compared to control group, there was no significant difference in AJS and PJS, while SJS of ICR group significantly decreased by 15.85% ( P <0.05). AJS, SJS and PJS measured by MRI were 1.29 ± 0.14 mm, 2.60 ± 0.27 mm and 1.97 ± 0.20 mm in control group, and 1.31 ± 0.49 mm, 2.29 ± 0.83 mm and 2.11 ± 0.90 mm in ICR group, respectively. The statistical analysis of MRI measurements showed that, similar to the joint space measured on CT, there was no significant difference in AJS and PJS, but SJS of ICR group significantly decreased by 14.23% ( P <0.05) compared to control group. Table 3 Inter-group comparison of joint space between control group and ICR group Method Measurement Control group ICR group P CT AJS (mm) 1.31 ± 0.13 1.43 ± 0.61 0.170 SJS (mm) 2.65 ± 0.29 2.23 ± 0.81 < 0.001*** PJS (mm) 1.97 ± 0.17 2.04 ± 0.72 0.488 MRI AJS (mm) 1.29 ± 0.14 1.31 ± 0.49 0.584 SJS (mm) 2.60 ± 0.27 2.29 ± 0.83 0.009** PJS (mm) 1.97 ± 0.20 2.11 ± 0.90 0.242 (* P < 0.05, ** P < 0.01, *** P < 0.001) The between-group comparison among AJS, SJS, and PJS was presented in Table 4 . Statistical analysis revealed significant differences between AJS, PJS, and SJS in the control group (P<0.05). The ratios of AJS, SJS, and PJS were maintained at approximately 1:2:1.5. However, in the ICR group, although there remained a significant difference between AJS and SJS and between AJS and PJS (P<0.05), no statistically significant difference was found between SJS and PJS. The measurements of AJS, SJS, and PJS in the ICR group were more discrete than those in the control group, indicating the instability of condyle position in ICR patients. Table 4 Intra-group comparison of joint space in control group and ICR group Method Group P (AJS vs. SJS) P (AJS vs. PJS) P (SJS vs. PJS) CT Control group < 0.001*** < 0.001*** < 0.001*** ICR group < 0.001*** < 0.001*** 0.275 MRI Control group < 0.001*** < 0.001*** < 0.001*** ICR group < 0.001*** < 0.001*** 0.336 (* P < 0.05, ** P < 0.01, *** P < 0.001) We further summarized the possible changes in condyle morphology as well as joint space in ICR patients and drew corresponding schematic diagrams (Fig. 4 ). Compared to control group (Fig. 4 A), most ICR group patients (Fig. 4 B, n = 43/55, 78.18%) exhibited mild resorption on the anterior slope and top of the condyle, a little ICR patients (Fig. 4 C, n = 9/55, 16.36%) exhibit more severe resorption at the top of the condyle, and very few patients (Fig. 4 D, n = 3/55, 5.46%) have severe condylar resorption that the normal anatomical shape of condyle cannot be distinguished. The condylar ratio of ICR group patients and control group patients was used to describe the antero-posterior position of the condyle in the glenoid fossa (Fig. 5 ). Although there was no statistically significant difference in condylar ratio between the ICR group and the control group, the maximum, minimum, and quartiles of condylar ratio in ICR group patients deviated more from the mean, indicating that the antero-posterior position of the condyle in the glenoid fossa is more unstable in ICR patients. The condylar volume and surface area measurements and statistical analysis are shown in Table 5 . Compared to the control group, the condylar volume in the ICR group decreased by 29.9%, and the condylar surface area decreased by 21.3%. The differences in condyle volume and surface area were statistically significant(P<0.05). Table 5 Surface area and volume of condyle measured by three-dimensional reconstruction of CT Measurement Control group ICR group P Surface area(mm 2 ) 617.04 ± 94.02 485.35 ± 99.61 < 0.001*** Volume(mm 3 ) 1012.64 ± 118.28 709.58 ± 133.74 < 0.001*** (* P < 0.05, ** P < 0.01, *** P < 0.001) Discussion As one of the most complex craniofacial diseases, ICR is considered to occur due to a combination of intrinsic and extrinsic factors. 19 – 21 In this study, we quantitatively evaluated the joint space and condylar morphology in patients with ICR through CT and MRI. The key findings include a significant reduction in the SJS, a disruption of the AJS: SJS: PJS ratio, and decreased condylar volume and surface area in ICR patients. These results suggest notable morphological and positional instability of the condyle in the glenoid fossa in the context of ICR. In our institution, CT and MRI examinations are performed for all patients undergoing orthognathic-orthodontic treatment planning, as part of a comprehensive assessment of craniofacial and temporomandibular joint structures. This protocol allows clinicians to detect any potential joint abnormalities, even in asymptomatic patients, and provides a complete imaging dataset for retrospective analysis. During patient enrollment, we restricted the age range to 16–30 years. Although previous studies have reported that ICR may occur in a broader age range, typically between 10 and 40 years 22 , 23 , this range was chosen to enhance the consistency of the study population. Younger patients under 16 years of age may still be undergoing active condylar growth, which could introduce variability in joint morphology and space measurements. On the other hand, individuals over 30 years are more likely to present with degenerative changes that may not be related to ICR. Therefore, limiting the age range helped to minimize the potential influence of age-related factors and allowed for a more accurate evaluation of ICR. Additionally, we found that while most ICR patients exhibited clear TMJ symptoms, such as popping, cracking sounds, pain in the TMJ area, and intermittent closed lock, a small subset lacked prominent symptoms. Consequently, we did not use TMJ symptoms from clinical examination as the primary inclusion criterion. Instead, CT and MRI findings were employed as the gold standard for diagnosing ICR and determining eligibility, to minimize potential selection bias. The role of TMJ symptoms in ICR remains controversial. Kasper et al. reported that while most ICR patients displayed TMD symptoms, 12% had no clinical signs or symptoms of TMD. 1 This underscores that TMJ symptoms do not always correlate with the extent of condylar resorption, suggesting the need for more objective diagnostic methods, such as imaging, in ICR diagnosis. In this study, we focused on assessing the condylar morphology and joint space, key indicators in evaluating ICR severity and progression. These morphological changes may have significant implications for the progression and management of ICR. Previous studies have shown that under normal physiological conditions, the proportion of joint space in healthy TMJ is relatively fixed. Hansson et al. 24 measured the thickness of articular disc and found that the posterior zone was the thickest and the middle zone was the thinnest, which suggested that the AJS was the narrowest and the SJS was the widest. Ikeda et al. 25 measured the joint space of 22 adults with no abnormal mandibular function, articular disc displacement or articular effusion through CBCT. The results showed that the average width of the AJS, SJS and PJS were 1.3 ± 0.2 mm, 2.5 ± 0.5 mm and 2.1 ± 0.3 mm, relatively. Yang et al 26 measured the joint space of patients with skeletal Class II malocclusion using CBCT, and similar results were obtained. In the control group, the joint space measured by both methods was consistent, with the proportion of SJS > PJS > AJS, approximately 1:2:1.5, similar to 1:1.9:1.6 in previous study. 25 In contrast, the joint space proportions in ICR patients were inconsistent, indicating instability of the condyle within the glenoid fossa. This may explain the frequent occurrence of double occlusion in ICR patients. 27 Nogami et al. 28 suggested that condylar resorption in ICR patients begins from the anterior slope and leads to a series of TMJ dysfunction thereafter. Upon further examination of condylar changes, we observed mild resorption of the anterior slope and apex of the condyle was observed in most ICR patients, and SJS significantly decreased. This indicates that condylar resorption may lead to compensatory upward displacement of condyle within the glenoid fossa, restoring AJS to normal levels and leading to narrowing of SJS. However, as ICR continuously progresses, the resorption of the condyle becomes increasingly severe. In few patients, the apical, anterior and posterior slopes of the condyle were absorbed more severely, resulting in a decrease in the height of the ramus. The condyle is unable to obtain sufficient compensatory displacement in the glenoid fossa to maintain itself as stable as possible. As a result, the patient cannot obtain stable occlusion. Moreover, the mandible of ICR patients tends to rotate in a clockwise direction due to the decrease in vertical height, resulting in anterior open bite and early contact of the posterior teeth. This study has some limitations. First, only two variables, sex and age, were one-to-one corresponding between control patients and ICR patients. More variable controls can be considered for a more comprehensive classification of patients. Second, although joint space measurements were performed in all ICR patients who met the inclusion criteria within three years, the sample size of male ICR patients included in this study was still too small to summarize the differences between male and female patients. Last but not least, the patients included in this study were all Asian. Since there are slight differences in craniomaxillofacial skeleton among people from different regions, whether the conclusions drawn in this study are applicable to other ethnic groups needs to be further verified. In conclusion, our study suggested that skeletal Class II malocclusion patients with healthy TMJ have relatively consistent joint space width, while skeletal Class II malocclusion patients with bilateral ICR have significant reduction in SJS. The condyle of ICR patients is in a relatively unstable state within the glenoid fossa, and most patients with relatively mild resorption show compensatory upward condylar displacement. Stabilizing the condyle in the normal physiological position is important for the treatment of ICR and malocclusion. This study provides a comprehensive analysis of joint space, condylar position, and morphology in ICR patients, emphasizing the importance of stabilizing the condyle in its normal physiological position for effective treatment. Conclusion SJS significantly reduced in ICR group. AJS, SJS, and PJS maintained a ratio close to 1:2:1.5 in healthy TMJ, but the proportion of joint space in bilateral ICR patients is not fixed as the condyle has varying degrees of resorption. The condyle of bilateral ICR patients is in an unstable state within the glenoid fossa. The surface area and volume of the condyle in ICR patients significantly reduced. Abbreviations ICR: Idiopathic condylar resorption TMJ: Temporomandibular joint CT: Computed tomography MRI: Magnetic resonance imaging AJS: Anterior joint space SJS: Superior joint space PJS: Posterior joint space ADDWOR: Anterior disc displacement without reduction FH: Frankfort Horizontal Po: Porion Or: Orbitale ICC: Intraclass correlation coefficient Declarations Human Ethics and Consent to Participate declarations This retrospective study was carried out in accordance with ethical principles and approved by the institutional review board of the Ninth People's Hospital, which conformed to the Declaration of Helsinki (ethics approval number: SH9H-2024-T151-1). Clinical trial number: ChiCTR2100051867, registration date:2021/10/08. All participants provided written informed consent, which guaranteed their confidentiality, voluntary involvement, and right to withdraw from the study without penalty at any time. For any participants under the age of 16, informed consent to participate was obtained from their parents or legal guardians. Consent for publication Not applicable. Data availability The data underlying this study are available from the corresponding author upon reasonable request. Conflicts of interest The authors declare that there is no conflict of interest. Funding This work was supported by the Fundamental Research Funds for the Central Universities (Grant no. YG2023ZD14); “Two-hundred Talents” Program of Shanghai Jiao Tong University School of Medicine (Grant no. 20221809); Shanghai Shenkang Hospital Development Center Clinical Three Year Action Plan (Grant no. SHDC2020CR4084); Project of Biobank of Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine (Grant no. YBKB202216); Shanghai Science and Technology Innovation Action Plan-International Science and Technology Cooperation Program (Grant no. 23410713600). Author contributions Jingyi Liu : Methodology, Data curation, Formal analysis, Investigation, Visualization, Writing–original draft. Zhengzhan Lv : Methodology, Formal analysis, Supervision, Writing–original draft. Yanfei Zhu : Funding acquisition, Validation, Writing–review & editing. Miri Chung : Supervision, Writing–review & editing. Lingyong Jiang : Conceptualization, Funding acquisition, Project administration. References Kristensen KD, Schmidt B, Stoustrup P, Pedersen TK. Idiopathic condylar resorptions: 3-dimensional condylar bony deformation, signs and symptoms. Am J Orthod Dentofacial Orthop. 2017 Aug;152(2):214-223. Tanimoto K, Awada T, Onishi A, Kubo N, Asakawa Y, Kunimatsu R, Hirose N. Characteristics of the Maxillofacial Morphology in Patients with Idiopathic Mandibular Condylar Resorption. J Clin Med. 2022 Feb 11;11(4):952. Rabey GP. Bilateral mandibular condylysisa morphanalytic diagnosis. Br J Oral Surg. 1977 Nov;15(2):121-34. 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Assessment of optimal condylar position with limited cone-beam computed tomography. Am J Orthod Dentofacial Orthop. 2009 Apr;135(4):495-501. Yang W, Chen Y, Li J, Jiang N. Assessment of condylar positional changes in severe skeletal class II malocclusion after surgical-orthodontic treatment. Clin Oral Investig. 2023 Apr 5. Mercuri LG, Handelman CS. Idiopathic Condylar Resorption: What Should We Do? Oral Maxillofac Surg Clin North Am. 2020 Feb;32(1):105-116. Nogami S, Yamauchi K, Odashima K, Ito K, Iikubo M, Kumasaka A, Martinez-de la Cruz G, Gaggl A, Kumamoto H, Takahashi T. Influence of oestrogen deficiency and excessive mechanical stress on condylar head of mandible. Oral Dis. 2020 Nov;26(8):1718-1726. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 12 Jan, 2026 Read the published version in BMC Oral Health → Version 1 posted Editorial decision: Revision requested 18 Nov, 2025 Reviews received at journal 09 Nov, 2025 Reviewers agreed at journal 27 Oct, 2025 Reviews received at journal 21 Oct, 2025 Reviews received at journal 15 Oct, 2025 Reviewers agreed at journal 13 Oct, 2025 Reviewers agreed at journal 13 Oct, 2025 Reviewers invited by journal 08 Oct, 2025 Editor assigned by journal 07 Oct, 2025 Editor invited by journal 03 Oct, 2025 Submission checks completed at journal 01 Oct, 2025 First submitted to journal 01 Oct, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7570283","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":530348935,"identity":"ee91b22c-f735-432e-8349-b9aac9789422","order_by":0,"name":"Jingyi Liu","email":"","orcid":"","institution":"Shanghai Jiao Tong University School of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Jingyi","middleName":"","lastName":"Liu","suffix":""},{"id":530348936,"identity":"8a8a7479-f977-4244-92ad-2ae5a0a0e2f0","order_by":1,"name":"Zhengzhan Lv","email":"","orcid":"","institution":"Shanghai Jiao Tong University School of 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1","display":"","copyAsset":false,"role":"figure","size":9606205,"visible":true,"origin":"","legend":"\u003cp\u003eMeasurement of joint space on CT and MRI.\u003c/p\u003e\n\u003cp\u003e(A) Horizontal cross-section of head on CT; (B) Oblique sagittal section of condyle on CT; (C) Joint space measurement on CT; (D) Horizontal cross-section of head on MRI; (E) Oblique sagittal section of condyle on MRI; (F) Joint space measurement on MRI.\u003c/p\u003e","description":"","filename":"FIG1.png","url":"https://assets-eu.researchsquare.com/files/rs-7570283/v1/c1eaf1c71bcb84f65e18fa18.png"},{"id":94050020,"identity":"33cf07d7-7334-4865-a449-ce72c84d15cf","added_by":"auto","created_at":"2025-10-21 23:43:52","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":2236778,"visible":true,"origin":"","legend":"\u003cp\u003e3D reconstruction and Segmentation of mandible and condyle on CT.\u003c/p\u003e\n\u003cp\u003e(A) Craniofacial 3D Reconstruction; (B) Segmentation of mandible; (C) Segmentation of condyle through C-Plane and D-Plane.\u003c/p\u003e","description":"","filename":"FIG2.png","url":"https://assets-eu.researchsquare.com/files/rs-7570283/v1/2f71c2cbc1b7899d3053b1a2.png"},{"id":94049988,"identity":"783c2f08-77d3-4a7b-a469-762699210857","added_by":"auto","created_at":"2025-10-21 23:43:50","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":3128396,"visible":true,"origin":"","legend":"\u003cp\u003eMRI observation of articular disc changes in ICR patients.\u003c/p\u003e\n\u003cp\u003e(A) Normal position and morphology of the joint disc in control group patients; (B) Anterior disc displacement with twisting and compression observed in the majority of ICR patients (n=50/55); (C) Anterior disc displacement with preserved morphology seen in a minority of ICR patients (n=5/55).\u003c/p\u003e","description":"","filename":"FIG3.png","url":"https://assets-eu.researchsquare.com/files/rs-7570283/v1/2b677b39f30246958d93d654.png"},{"id":94049974,"identity":"d702e5ef-a2f5-4dea-8024-a84c12f83ccc","added_by":"auto","created_at":"2025-10-21 23:43:50","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":3879345,"visible":true,"origin":"","legend":"\u003cp\u003eDiagrams of condyle-fossa relationship.\u003c/p\u003e\n\u003cp\u003e(A) The proportion of joint space in the control group was close to 1:2:1.5. (B-D) The proportion of joint space in the ICR group varies depending on the severity.\u003c/p\u003e","description":"","filename":"FIG4.png","url":"https://assets-eu.researchsquare.com/files/rs-7570283/v1/7382f40b2231154a5d2e7726.png"},{"id":94049976,"identity":"9c77b42e-4584-49f4-9077-4a03cdeeb4a6","added_by":"auto","created_at":"2025-10-21 23:43:50","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":462706,"visible":true,"origin":"","legend":"\u003cp\u003eCondylar ratio of ICR group patients and control group patients.\u003c/p\u003e\n\u003cp\u003e(A) Condylar ratio based on CT. (B) Condylar ratio based on MRI.\u003c/p\u003e","description":"","filename":"FIG5.png","url":"https://assets-eu.researchsquare.com/files/rs-7570283/v1/8f3e8b8a6f232391c52d26d0.png"},{"id":100614786,"identity":"3cd5a091-47b2-467b-a5a0-07a07e6e1e9c","added_by":"auto","created_at":"2026-01-19 17:25:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":18112685,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7570283/v1/14ac8070-5d1f-47ee-80bc-3d38fc446080.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Characteristics of condylar joint space, position and morphology in skeletal Class II malocclusion patients with bilateral idiopathic condyle resorption","fulltext":[{"header":"Introduction","content":"\u003cp\u003eTemporomandibular joint (TMJ) is the only joint structure in the craniomaxillofacial skeletal system, which is responsible for a series of motor functions involving opening and closing the mouth in daily life, such as chewing and speaking. As an important part of TMJ, the condyle is susceptible to the effects of hormones, mental stress or other unknown systemic factors, resulting in dysfunction and pathologic changes of TMJ. Idiopathic condylar resorption (ICR) is a kind of non-functional reconstruction of temporomandibular joint caused by unknown reasons, characterized by progressive condylar resorption and condylar morphological changes.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e ICR was first proposed by Rabey in 1977, describing the condylar resorption as \u0026lsquo;condylolysis\u0026rsquo;.\u003csup\u003e3\u003c/sup\u003e ICR initiates bone loss and anatomical morphological changes in condyle, accompanied by series of clinical symptoms, including reduced height of the mandibular ascending ramus, mandibular anteroposterior rotation, and anterior open bite, which may result in severe skeletal Class II malocclusion, temporomandibular joint dysfunction and pain, seriously affect the aesthetics and occlusal function of patients.\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eDue to the presence of the articular disc, there exists a certain physiological gap between the condyle and the glenoid fossa called joint space.\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e Joint space within the normal range is necessary to ensure the functional movement of condyle in the glenoid fossa, such as sliding, rotation and compound movement.\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e Disc displacement or pathological alterations in joint morphology often leads to abnormal joint space, which indicates an improper shift in condylar position.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e Moreover, abnormal condylar position may also affect the load stress on the disc-condyle complex, which further exacerbates the progression of TMJ disease.\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e Maintaining the normal physiological position of the condyle is crucial for stabilizing the patient's occlusal relationship during the treatment of malocclusion. Therefore, it is of great significance to clarify the changes in joint space during the clinical treatment of TMJ disease and malocclusion.\u003c/p\u003e\u003cp\u003eAt present, computed tomography (CT) and magnetic resonance imaging (MRI) are widely used to evaluate the bone structure and disc-condyle relationship of TMJ before treatment. Both CT and MRI are ideal techniques for accurate joint space measurement and condylar position assessment, as they have sufficient resolution and can clearly show the boundary of condyle and glenoid fossa.\u003csup\u003e\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eCurrent research has found that ICR patients may experience signs and symptoms of temporomandibular joint disorders, as well as reduction of craniofacial bones and masticatory muscles.\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e However, the changes of condylar position within the glenoid fossa and condylar morphology after resorption have not been clarified yet.\u003c/p\u003e\u003cp\u003eIn this study, CT and MRI were used to measure the joint space in skeletal Class II malocclusion patients diagnosed with bilateral ICR or healthy TMJ. The purpose of this study was to investigate the characteristics of condylar position and morphology in ICR patients.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStudy design\u003c/h2\u003e\u003cp\u003e This retrospective study was carried out in accordance with ethical principles and approved by the institutional review board of the Ninth People's Hospital, which conformed to the Declaration of Helsinki. (Approval: SH9H-2018-163-T121, Clinical trial number: ChiCTR2100051867, registration date:2021/10/08).\u003c/p\u003e\u003cp\u003e Skeletal Class II malocclusion patients with a diagnosis of bilateral ICR who received treatment in the Center of Craniofacial Orthodontics, Department of Oral and Craniomaxillofacial Surgery, Ninth People's Hospital of Shanghai Jiao Tong University School of Medicine from January 2021 to December 2023 were included in this study. To establish a control group, skeletal Class II malocclusion patients with healthy TMJs who sought treatment during the same period were matched one-to-one with the ICR patients based on age and gender, with an age difference of no more than one year. Patients aged between 16 and 30 years were included in this study. This age range was chosen because ICR most commonly occurs in adolescents and young adults, particularly females. This range minimizes the potential interference from condylar growth in younger individuals and degenerative joint changes in older individuals.\u003c/p\u003e\u003cp\u003eThe inclusion criteria of ICR group were: (1) Age between 16 and 30 years; (2) Chief complaint of mandibular retrusion and diagnosed with skeletal Class II malocclusion (ANB angle\u0026thinsp;\u0026gt;\u0026thinsp;5\u0026deg;); (3) CT and MRI evidence of destructive changes associated with ICR, including sclerosis, flattening of condylar margins, erosion of the cortical bone and other resorptive features. The control group patients were screened according to the age and gender matching principles mentioned above. The inclusion criteria of control group were: (1) Age between 16 and 30 years; (2) Chief complaint of mandibular retrusion and diagnosed with skeletal Class II malocclusion (ANB angle\u0026thinsp;\u0026gt;\u0026thinsp;5\u0026deg;), but with no TMJ-related symptoms on clinical examination; (3) CT and MRI showing uniform and continuous cortical bone with normal condylar morphology. (4) MRI demonstrating a normal bilateral disc-condyle relationship.\u003c/p\u003e\u003cp\u003eThe Exclusion criteria included: (1) history of TMJ-related treatments. (2) history of orthodontic treatment. (3) history of orthognathic surgery. (4) craniofacial trauma, tumor disease and systemic diseases.\u003c/p\u003e\u003cp\u003eFinally, a total of 110 patients (55 patients in each group, comprising 4 males and 51 females) were reviewed in this study.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eImaging acquisition\u003c/h3\u003e\n\u003cp\u003eWhole-head CT scans were acquired using a GE LightSpeed-16 system (GE Healthcare, USA) with the following parameters: 120 kVp, 80 mA, 0.3 mm isotropic voxel size, 1.25 mm slice thickness, and a field of view extending from the cranial vertex to the hyoid bone. During scanning, patients were placed in a supine position with their teeth in centric occlusion, and instructed to avoid swallowing to minimize motion artifacts.\u003c/p\u003e\u003cp\u003eMRI scans were acquired using a 1.5T MRI scanner (Signa HDxt, GE Healthcare, USA) with a dedicated 3-inch bilateral surface coil. Oblique sagittal T1-weighted sequences were obtained in the closed-mouth position with the following parameters: TR/TE\u0026thinsp;=\u0026thinsp;1,800/20 ms, flip angle\u0026thinsp;=\u0026thinsp;150\u0026deg;, NEX\u0026thinsp;=\u0026thinsp;2, FOV\u0026thinsp;=\u0026thinsp;12 cm, slice thickness\u0026thinsp;=\u0026thinsp;1 mm, and acquisition matrix\u0026thinsp;=\u0026thinsp;512 \u0026times; 512. MRI scanning was performed with the patient in the same position and occlusal condition as described above.\u003c/p\u003e\n\u003ch3\u003eJoint space measurement\u003c/h3\u003e\n\u003cp\u003eThe anatomical landmarks and relevant definition during joint space measurement were shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eLandmarks and Measurements Used in This Study to Evaluate proportion and changes of joint space\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLandmarks \u0026amp; Constructed lines \u0026amp; Measurements\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDefinition\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCondylar landmarks\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMost anterior point of the condyle\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMost superior point of the condyle\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMost posterior point of the condyle\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSF\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emost superior point of the glenoid fossa\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eJoint space measurements\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAJS\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eThe shortest distances from AC to the glenoid fossa\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSJS\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003edistance between SC and SF\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePJS\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eThe shortest distances from PC to the glenoid fossa\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVolume and surface area measurement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePorion (Po)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eUppermost point of external auditory canal\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOrbitale (Or)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLowest point of orbital margin\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLowest point of sigmoid notch\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFrankfort horizontal plane (FH plane)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLine from Po to Or\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC-Plane\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLine passing through point C and parallel to FH plane\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eD-Plane\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLine passing through point C and perpendicular to FH plane\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe acquired DICOM file of CT was imported into Dolphin Imaging software (version 11.95; Dolphin Imaging \u0026amp; Management Solutions, USA) for 3D reconstruction. To ensure consistency across patients, head position should be adjusted before measurement. In the reconstructed frontal view, the horizontal orientation was established by aligning the bilateral infraorbital margins. For each temporomandibular joint, the Frankfort Horizontal (FH) plane was defined individually using the ipsilateral porion (Po) and orbitale (Or) points. The 3D model was rotated until the FH plane was aligned horizontally. This adjustment was performed in a fully 3D environment, where the Po and Or landmarks were clearly visible, in order to ensure accurate orientation. After head orientation, the oblique sagittal plane was determined for each side. This plane was defined as passing perpendicularly through the midpoint of the largest mediolateral diameter of the condyle (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA). The sagittal slice obtained along this plane was used for all subsequent joint space measurements (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFor MRI images, since head position adjustment is not feasible, the oblique sagittal plane was selected based on the same principle as in CT. This slice was identified by scrolling through axial and coronal planes to localize the condylar center (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eD), and the corresponding sagittal section was used for joint space measurements (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eE). Although head position could not be fully standardized as in CT, this selection method ensured that measurements were consistently performed on the most representative sagittal section of the condyle.\u003c/p\u003e\u003cp\u003eThe Kamelchuk method\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e was used for joint space measurement on both CT and MRI (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC, F). Anatomical landmarks were identified using Adobe Photoshop CS5 (Adobe Systems, San Jose, USA), and measurements were performed with MB-Ruler software (Markus Bader, Berlin, Germany). Each joint was measured three times at two-week intervals by the same experienced physician.\u003c/p\u003e\u003cp\u003ePullinger and Hollender\u0026rsquo;s formula was used to describe the antero-posterior position of condyle within the glenoid fossa \u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e: Condylar ratio = (PJS-AJS)/(PJS\u0026thinsp;+\u0026thinsp;AJS)\u0026times;100. A positive ratio indicates an anterior condylar position, while a negative value indicates a posterior condylar position.\u003c/p\u003e\n\u003ch3\u003eVolume and surface area measurement of condyle\u003c/h3\u003e\n\u003cp\u003eThe acquired DICOM file of CT scanning was imported into Mimics v21.00 (Materialise, Belgium). The threshold range was set to 250-3071HU to obtain the craniomaxillofacial three-dimensional bone structure.\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e First, 3D reconstruction of the CT data was performed (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA), and the mandible was segmented (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). After establishing the FH plane as described above, the sigmoid notch of the mandible was identified, and its deepest point was marked as point C. A horizontal plane passing through point C and parallel to the FH plane was defined as the C-Plane. A perpendicular plane passing through point C and orthogonal to the C-Plane was defined as the D-Plane. These two orthogonal reference planes were used to segment the condyle from the mandibular ramus (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC), facilitating volumetric and surface area measurements using built-in functions of the software.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eData collection, recording, and analysis were conducted by the same experienced physician. Standardized measurement protocols mentioned above were followed, and data entry was performed blindly. Intra-rater reliability was assessed via the intraclass correlation coefficient (ICC) using a two-way mixed-effects model for absolute agreement (\u003cem\u003eICC [3,1]\u003c/em\u003e). Interpretation followed established criteria \u003csup\u003e18\u003c/sup\u003e: \u0026lt;0.50 poor, 0.50\u0026ndash;0.75 moderate, 0.75\u0026ndash;0.90 good, \u0026gt;\u0026thinsp;0.90 excellent. ICC values were calculated for all six joint space variables (AJS, SJS, and PJS measured on both CT and MRI), and all exceeded 0.85, indicating good to excellent consistency.\u003c/p\u003e\u003cp\u003eSPSS 20.0(IBM Corp., Armonk, NY, USA) was used for statistical analysis. Repeated measures one-way ANOVA was used for within-group comparison of joint space, and independent samples t-test was used for between-group comparison of joint space. All tests were two-tailed, p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eParticipant demographic characteristics were summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. A total of 55 patients (4 males and 51 females) were included in each group. The average age was 22.81\u0026thinsp;\u0026plusmn;\u0026thinsp;2.10 years (range from 19.48 to 28.93 years) in ICR group and 22.75\u0026thinsp;\u0026plusmn;\u0026thinsp;2.14 years (range from 19.11 to 28.61 years) in control group. Compared to control group (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA), all 55 patients in the ICR group were found to exhibit anterior disc displacement without reduction (ADDWOR) in bilateral TMJ. In MRI, the articular discs of ICR patients were consistently observed to be positioned anterior to the condyle. Additionally, changes in disc morphology were observed, including a shortened anterior-posterior diameter, thickening of the posterior band, and loss of the normal biconvex configuration (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB, n\u0026thinsp;=\u0026thinsp;50/55). Only a small number of patients showed relatively normal disc morphology despite anterior displacement (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC, n\u0026thinsp;=\u0026thinsp;5/55). Overall, the joint disc presents a twisted and compressed shape in most patients.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eParticipant demographic characteristics\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eICR group\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eControl group\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePatients, n\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge, years\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e22.81\u0026thinsp;\u0026plusmn;\u0026thinsp;2.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22.75\u0026thinsp;\u0026plusmn;\u0026thinsp;2.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.902\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGender, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;0.999\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4(7.27%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4(7.27%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFemale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e51(92.73%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e51(92.73%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBilateral\u0026nbsp;Disc-Condyle relationship, n\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cem\u003e\u0026lt;\u003c/em\u003e\u0026thinsp;0.001***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eADDWOR\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNormal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eJoint space measurements obtained from CT and MRI were shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. AJS, SJS and PJS measured by CT in control group were 1.31\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13 mm, 2.65\u0026thinsp;\u0026plusmn;\u0026thinsp;0.29 mm and 1.97\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19 mm, respectively. While in ICR group, AJS, SJS and PJS measured by CT were 1.43\u0026thinsp;\u0026plusmn;\u0026thinsp;0.61 mm, 2.23\u0026thinsp;\u0026plusmn;\u0026thinsp;0.81 mm and 2.04\u0026thinsp;\u0026plusmn;\u0026thinsp;0.72 mm, respectively. Compared to control group, there was no significant difference in AJS and PJS, while SJS of ICR group significantly decreased by 15.85% (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05). AJS, SJS and PJS measured by MRI were 1.29\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14 mm, 2.60\u0026thinsp;\u0026plusmn;\u0026thinsp;0.27 mm and 1.97\u0026thinsp;\u0026plusmn;\u0026thinsp;0.20 mm in control group, and 1.31\u0026thinsp;\u0026plusmn;\u0026thinsp;0.49 mm, 2.29\u0026thinsp;\u0026plusmn;\u0026thinsp;0.83 mm and 2.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.90 mm in ICR group, respectively. The statistical analysis of MRI measurements showed that, similar to the joint space measured on CT, there was no significant difference in AJS and PJS, but SJS of ICR group significantly decreased by 14.23% (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05) compared to control group.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eInter-group comparison of joint space between control group and ICR group\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMethod\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMeasurement\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eControl group\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eICR group\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eCT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAJS (mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e1.31\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e1.43\u0026thinsp;\u0026plusmn;\u0026thinsp;0.61\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.170\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSJS (mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e2.65\u0026thinsp;\u0026plusmn;\u0026thinsp;0.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e2.23\u0026thinsp;\u0026plusmn;\u0026thinsp;0.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePJS (mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e1.97\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e2.04\u0026thinsp;\u0026plusmn;\u0026thinsp;0.72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.488\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eMRI\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAJS (mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e1.29\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e1.31\u0026thinsp;\u0026plusmn;\u0026thinsp;0.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.584\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSJS (mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e2.60\u0026thinsp;\u0026plusmn;\u0026thinsp;0.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e2.29\u0026thinsp;\u0026plusmn;\u0026thinsp;0.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.009**\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePJS (mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e1.97\u0026thinsp;\u0026plusmn;\u0026thinsp;0.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e2.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.90\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.242\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003e(*\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05, **\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01, ***\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001)\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe between-group comparison among AJS, SJS, and PJS was presented in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. Statistical analysis revealed significant differences between AJS, PJS, and SJS in the control group (P\u0026lt;0.05). The ratios of AJS, SJS, and PJS were maintained at approximately 1:2:1.5. However, in the ICR group, although there remained a significant difference between AJS and SJS and between AJS and PJS (P\u0026lt;0.05), no statistically significant difference was found between SJS and PJS. The measurements of AJS, SJS, and PJS in the ICR group were more discrete than those in the control group, indicating the instability of condyle position in ICR patients.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eIntra-group comparison of joint space in control group and ICR group\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMethod\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eGroup\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e (AJS vs. SJS)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e (AJS vs. PJS)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e (SJS vs. PJS)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eCT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eControl group\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eICR group\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.275\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eMRI\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eControl group\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eICR group\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.336\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003e(*\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05, **\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01, ***\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001)\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eWe further summarized the possible changes in condyle morphology as well as joint space in ICR patients and drew corresponding schematic diagrams (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Compared to control group (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA), most ICR group patients (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB, n\u0026thinsp;=\u0026thinsp;43/55, 78.18%) exhibited mild resorption on the anterior slope and top of the condyle, a little ICR patients (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eC, n\u0026thinsp;=\u0026thinsp;9/55, 16.36%) exhibit more severe resorption at the top of the condyle, and very few patients (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eD, n\u0026thinsp;=\u0026thinsp;3/55, 5.46%) have severe condylar resorption that the normal anatomical shape of condyle cannot be distinguished.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe condylar ratio of ICR group patients and control group patients was used to describe the antero-posterior position of the condyle in the glenoid fossa (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Although there was no statistically significant difference in condylar ratio between the ICR group and the control group, the maximum, minimum, and quartiles of condylar ratio in ICR group patients deviated more from the mean, indicating that the antero-posterior position of the condyle in the glenoid fossa is more unstable in ICR patients.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe condylar volume and surface area measurements and statistical analysis are shown in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. Compared to the control group, the condylar volume in the ICR group decreased by 29.9%, and the condylar surface area decreased by 21.3%. The differences in condyle volume and surface area were statistically significant(P\u0026lt;0.05).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSurface area and volume of condyle measured by three-dimensional reconstruction of CT\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMeasurement\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eControl group\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eICR group\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSurface area(mm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e617.04\u0026thinsp;\u0026plusmn;\u0026thinsp;94.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e485.35\u0026thinsp;\u0026plusmn;\u0026thinsp;99.61\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVolume(mm\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e1012.64\u0026thinsp;\u0026plusmn;\u0026thinsp;118.28\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e709.58\u0026thinsp;\u0026plusmn;\u0026thinsp;133.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003e(*\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05, ** \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01, *** \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001)\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eAs one of the most complex craniofacial diseases, ICR is considered to occur due to a combination of intrinsic and extrinsic factors.\u003csup\u003e\u003cspan additionalcitationids=\"CR20\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e In this study, we quantitatively evaluated the joint space and condylar morphology in patients with ICR through CT and MRI. The key findings include a significant reduction in the SJS, a disruption of the AJS: SJS: PJS ratio, and decreased condylar volume and surface area in ICR patients. These results suggest notable morphological and positional instability of the condyle in the glenoid fossa in the context of ICR.\u003c/p\u003e\u003cp\u003eIn our institution, CT and MRI examinations are performed for all patients undergoing orthognathic-orthodontic treatment planning, as part of a comprehensive assessment of craniofacial and temporomandibular joint structures. This protocol allows clinicians to detect any potential joint abnormalities, even in asymptomatic patients, and provides a complete imaging dataset for retrospective analysis.\u003c/p\u003e\u003cp\u003eDuring patient enrollment, we restricted the age range to 16\u0026ndash;30 years. Although previous studies have reported that ICR may occur in a broader age range, typically between 10 and 40 years \u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e, this range was chosen to enhance the consistency of the study population. Younger patients under 16 years of age may still be undergoing active condylar growth, which could introduce variability in joint morphology and space measurements. On the other hand, individuals over 30 years are more likely to present with degenerative changes that may not be related to ICR. Therefore, limiting the age range helped to minimize the potential influence of age-related factors and allowed for a more accurate evaluation of ICR. Additionally, we found that while most ICR patients exhibited clear TMJ symptoms, such as popping, cracking sounds, pain in the TMJ area, and intermittent closed lock, a small subset lacked prominent symptoms. Consequently, we did not use TMJ symptoms from clinical examination as the primary inclusion criterion. Instead, CT and MRI findings were employed as the gold standard for diagnosing ICR and determining eligibility, to minimize potential selection bias. The role of TMJ symptoms in ICR remains controversial. Kasper et al. reported that while most ICR patients displayed TMD symptoms, 12% had no clinical signs or symptoms of TMD.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e This underscores that TMJ symptoms do not always correlate with the extent of condylar resorption, suggesting the need for more objective diagnostic methods, such as imaging, in ICR diagnosis.\u003c/p\u003e\u003cp\u003eIn this study, we focused on assessing the condylar morphology and joint space, key indicators in evaluating ICR severity and progression. These morphological changes may have significant implications for the progression and management of ICR. Previous studies have shown that under normal physiological conditions, the proportion of joint space in healthy TMJ is relatively fixed. Hansson et al.\u003csup\u003e24\u003c/sup\u003e measured the thickness of articular disc and found that the posterior zone was the thickest and the middle zone was the thinnest, which suggested that the AJS was the narrowest and the SJS was the widest. Ikeda et al.\u003csup\u003e25\u003c/sup\u003e measured the joint space of 22 adults with no abnormal mandibular function, articular disc displacement or articular effusion through CBCT. The results showed that the average width of the AJS, SJS and PJS were 1.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2 mm, 2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5 mm and 2.1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3 mm, relatively. Yang et al\u003csup\u003e26\u003c/sup\u003e measured the joint space of patients with skeletal Class II malocclusion using CBCT, and similar results were obtained. In the control group, the joint space measured by both methods was consistent, with the proportion of SJS\u0026thinsp;\u0026gt;\u0026thinsp;PJS\u0026thinsp;\u0026gt;\u0026thinsp;AJS, approximately 1:2:1.5, similar to 1:1.9:1.6 in previous study.\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e In contrast, the joint space proportions in ICR patients were inconsistent, indicating instability of the condyle within the glenoid fossa. This may explain the frequent occurrence of double occlusion in ICR patients.\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e Nogami et al.\u003csup\u003e28\u003c/sup\u003e suggested that condylar resorption in ICR patients begins from the anterior slope and leads to a series of TMJ dysfunction thereafter. Upon further examination of condylar changes, we observed mild resorption of the anterior slope and apex of the condyle was observed in most ICR patients, and SJS significantly decreased. This indicates that condylar resorption may lead to compensatory upward displacement of condyle within the glenoid fossa, restoring AJS to normal levels and leading to narrowing of SJS. However, as ICR continuously progresses, the resorption of the condyle becomes increasingly severe. In few patients, the apical, anterior and posterior slopes of the condyle were absorbed more severely, resulting in a decrease in the height of the ramus. The condyle is unable to obtain sufficient compensatory displacement in the glenoid fossa to maintain itself as stable as possible. As a result, the patient cannot obtain stable occlusion. Moreover, the mandible of ICR patients tends to rotate in a clockwise direction due to the decrease in vertical height, resulting in anterior open bite and early contact of the posterior teeth.\u003c/p\u003e\u003cp\u003eThis study has some limitations. First, only two variables, sex and age, were one-to-one corresponding between control patients and ICR patients. More variable controls can be considered for a more comprehensive classification of patients. Second, although joint space measurements were performed in all ICR patients who met the inclusion criteria within three years, the sample size of male ICR patients included in this study was still too small to summarize the differences between male and female patients. Last but not least, the patients included in this study were all Asian. Since there are slight differences in craniomaxillofacial skeleton among people from different regions, whether the conclusions drawn in this study are applicable to other ethnic groups needs to be further verified.\u003c/p\u003e\u003cp\u003eIn conclusion, our study suggested that skeletal Class II malocclusion patients with healthy TMJ have relatively consistent joint space width, while skeletal Class II malocclusion patients with bilateral ICR have significant reduction in SJS. The condyle of ICR patients is in a relatively unstable state within the glenoid fossa, and most patients with relatively mild resorption show compensatory upward condylar displacement. Stabilizing the condyle in the normal physiological position is important for the treatment of ICR and malocclusion. This study provides a comprehensive analysis of joint space, condylar position, and morphology in ICR patients, emphasizing the importance of stabilizing the condyle in its normal physiological position for effective treatment.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eSJS significantly reduced in ICR group.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eAJS, SJS, and PJS maintained a ratio close to 1:2:1.5 in healthy TMJ, but the proportion of joint space in bilateral ICR patients is not fixed as the condyle has varying degrees of resorption.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eThe condyle of bilateral ICR patients is in an unstable state within the glenoid fossa.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eThe surface area and volume of the condyle in ICR patients significantly reduced.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eICR: Idiopathic condylar resorption\u003c/p\u003e\n\u003cp\u003eTMJ: Temporomandibular joint\u003c/p\u003e\n\u003cp\u003eCT: Computed tomography\u003c/p\u003e\n\u003cp\u003eMRI: Magnetic resonance imaging\u003c/p\u003e\n\u003cp\u003eAJS: Anterior joint space\u003c/p\u003e\n\u003cp\u003eSJS: Superior joint space\u003c/p\u003e\n\u003cp\u003ePJS: Posterior joint space\u003c/p\u003e\n\u003cp\u003eADDWOR: Anterior disc displacement without reduction\u003c/p\u003e\n\u003cp\u003eFH: Frankfort Horizontal\u003c/p\u003e\n\u003cp\u003ePo: Porion\u003c/p\u003e\n\u003cp\u003eOr: Orbitale\u003c/p\u003e\n\u003cp\u003eICC: Intraclass correlation coefficient\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eHuman Ethics and Consent to Participate declarations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis retrospective study was carried out in accordance with ethical principles and approved by the institutional review board of the Ninth People's Hospital, which conformed to the Declaration of Helsinki (ethics approval number: SH9H-2024-T151-1). Clinical trial number: ChiCTR2100051867, registration date:2021/10/08.\u003c/p\u003e\n\u003cp\u003eAll participants provided written informed consent, which guaranteed their confidentiality, voluntary involvement, and right to withdraw from the study without penalty at any time.\u0026nbsp;For any participants under the age of 16, informed consent to participate was obtained from their parents or legal guardians.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data underlying this study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that there is no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Fundamental Research Funds for the Central Universities (Grant no. YG2023ZD14); “Two-hundred Talents” Program of Shanghai Jiao Tong University School of Medicine (Grant no. 20221809); Shanghai Shenkang Hospital Development Center Clinical Three Year Action Plan (Grant no. SHDC2020CR4084); Project of Biobank of Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine (Grant no. YBKB202216); Shanghai Science and Technology Innovation Action Plan-International Science and Technology Cooperation Program (Grant no. 23410713600).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eJingyi Liu\u003c/strong\u003e: Methodology, Data curation, Formal analysis, Investigation, Visualization, Writing–original draft.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eZhengzhan Lv\u003c/strong\u003e: Methodology, Formal analysis, Supervision, Writing–original draft.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eYanfei Zhu\u003c/strong\u003e: Funding acquisition, Validation, Writing–review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMiri Chung\u003c/strong\u003e: Supervision, Writing–review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLingyong Jiang\u003c/strong\u003e: Conceptualization, Funding acquisition, Project administration.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eKristensen KD, Schmidt B, Stoustrup P, Pedersen TK. Idiopathic condylar resorptions: 3-dimensional condylar bony deformation, signs and symptoms. Am J Orthod Dentofacial Orthop. 2017 Aug;152(2):214-223.\u003c/li\u003e\n\u003cli\u003eTanimoto K, Awada T, Onishi A, Kubo N, Asakawa Y, Kunimatsu R, Hirose N. Characteristics of the Maxillofacial Morphology in Patients with Idiopathic Mandibular Condylar Resorption. J Clin Med. 2022 Feb 11;11(4):952. \u003c/li\u003e\n\u003cli\u003eRabey GP. Bilateral mandibular condylysisa morphanalytic diagnosis. Br J Oral Surg. 1977 Nov;15(2):121-34. \u003c/li\u003e\n\u003cli\u003eShen P, Zhang D, Luo Y, Abdelrehem A, Yang C. Characteristics of patients with temporomandibular joint idiopathic condylar resorption. Cranio. 2022 Jul 26:1-7. \u003c/li\u003e\n\u003cli\u003eChamberland S. Progressive idiopathic condylar resorption: Three case reports. Am J Orthod Dentofacial Orthop. 2019 Oct;156(4):531-544. \u003c/li\u003e\n\u003cli\u003eCederberg RA. Temporomandibular joint space analysis. Cranio. 1994 Jul;12(3):172; discussion 177-8. \u003c/li\u003e\n\u003cli\u003eG\u0026ouml;r\u0026uuml;rg\u0026ouml;z C, İ\u0026ccedil;en M, Kurt MH, Aksoy S, Bakırarar B, Rozylo-Kalinowska I, Orhan K. Degenerative changes of the mandibular condyle in relation to the temporomandibular joint space, gender and age: A multicenter CBCT study. Dent Med Probl. 2023 Jan-Mar;60(1):127-135.\u003c/li\u003e\n\u003cli\u003eTăut M, Buduru SD, Tălmăceanu D, Ban A, Roman R, Leucuța D, Barbur I, Ilea A. Occlusal Splint Therapy Combined with Cranio-Temporomandibular Kinesiotherapy in Patients with Temporomandibular Disorders-A CBCT Study. Life (Basel). 2022 Dec 19;12(12):2143. \u003c/li\u003e\n\u003cli\u003eNakao Y, Konno-Nagasaka M, Toriya N, Arakawa T, Kashio H, Takuma T, Mizoguchi I. Proteoglycan expression is influenced by mechanical load in TMJ discs. J Dent Res. 2015 Jan;94(1):93-100.\u003c/li\u003e\n\u003cli\u003eLee YH, Hong IK, An JS. Anterior joint space narrowing in patients with temporomandibular disorder. J Orofac Orthop. 2019 May;80(3):116-127. \u003c/li\u003e\n\u003cli\u003eMa Z, Xie Q, Yang C, Zhang S, Shen Y, Cai X. Changes in the temporomandibular joint space after functional treatment of disk displacement with reduction. J Craniofac Surg. 2015 Mar;26(2):e78-81.\u003c/li\u003e\n\u003cli\u003eYu W, Jeon HH, Kim S, Dayo A, Mupparapu M, Boucher NS. Correlation between TMJ Space Alteration and Disc Displacement: A Retrospective CBCT and MRI Study. Diagnostics (Basel). 2023 Dec 25;14(1):44. \u003c/li\u003e\n\u003cli\u003eYu Y, Wang S, Wu M, Chen X, He F. Signs and Symptoms of Temporomandibular Dysfunction and Radiographic Condylar Morphology in Patients with Idiopathic Condylar Resorption. J Clin Med. 2022 Jul 23;11(15):4289. \u003c/li\u003e\n\u003cli\u003eGe J, Bo L, Zhang D, Wei X, Li J, Zhao J, Yue S, Xie Q, Shen P, Ma Z, Fang B, Yang C. Association between bilateral condylar resorption and reduced volumes of the craniofacial skeleton and masticatory muscles in adult patients: A retrospective study. Heliyon. 2024 Jan 23;10(3):e25037. \u003c/li\u003e\n\u003cli\u003eKamelchuk LS, Grace MG, Major PW. Post-imaging temporomandibular joint space analysis. Cranio. 1996 Jan;14(1):23-9. \u003c/li\u003e\n\u003cli\u003ePullinger AG, Hollender L, Solberg WK, Petersson A. A tomographic study of mandibular condyle position in an asymptomatic population. J Prosthet Dent. 1985 May;53(5):706-13. \u003c/li\u003e\n\u003cli\u003eBrunetto DP, Velasco L, Koerich L, Ara\u0026uacute;jo MT. Prediction of 3-dimensional pharyngeal airway changes after orthognathic surgery: a preliminary study. Am J Orthod Dentofacial Orthop. 2014 Sep;146(3):299-309. \u003c/li\u003e\n\u003cli\u003eKoo TK, Li MY. A Guideline of Selecting and Reporting Intraclass Correlation Coefficients for Reliability Research. J Chiropr Med. 2016 Jun;15(2):155-63. \u003c/li\u003e\n\u003cli\u003eJi YD, Resnick CM, Peacock ZS. Idiopathic condylar resorption: A systematic review of etiology and management. Oral Surg Oral Med Oral Pathol Oral Radiol. 2020 Dec;130(6):632-639. \u003c/li\u003e\n\u003cli\u003eYuan M, Xie Q, Shen P, Yang C. Do sex hormone imbalances contribute to idiopathic condylar resorption? Int J Oral Maxillofac Surg. 2021 Sep;50(9):1244-1248.\u003c/li\u003e\n\u003cli\u003eYuan M, Xie Q, Shen P, Yang C. Low skeletal bone mineral density as a potential aetiological factor towards idiopathic condylar resorption. Int J Oral Maxillofac Surg. 2021 May;50(5):665-669. \u003c/li\u003e\n\u003cli\u003eWolford LM, Cardenas L. Idiopathic condylar resorption: diagnosis, treatment protocol, and outcomes. Am J Orthod Dentofacial Orthop. 1999 Dec;116(6):667-77.\u003c/li\u003e\n\u003cli\u003eAlali YS, Al Habeeb KM, Al Malhook KA, Alshehri S. Diagnosis and management of idiopathic condylar Resorption: A review of literature. Saudi Dent J. 2024 Nov;36(11):1397-1405.\u003c/li\u003e\n\u003cli\u003eHansson T, Oberg T, Carlsson GE, Kopp S. Thickness of the soft tissue layers and the articular disk in the temporomandibular joint. Acta Odontol Scand. 1977 May;35(2):77-83. \u003c/li\u003e\n\u003cli\u003eIkeda K, Kawamura A. Assessment of optimal condylar position with limited cone-beam computed tomography. Am J Orthod Dentofacial Orthop. 2009 Apr;135(4):495-501. \u003c/li\u003e\n\u003cli\u003eYang W, Chen Y, Li J, Jiang N. Assessment of condylar positional changes in severe skeletal class II malocclusion after surgical-orthodontic treatment. Clin Oral Investig. 2023 Apr 5.\u003c/li\u003e\n\u003cli\u003eMercuri LG, Handelman CS. Idiopathic Condylar Resorption: What Should We Do? Oral Maxillofac Surg Clin North Am. 2020 Feb;32(1):105-116.\u003c/li\u003e\n\u003cli\u003eNogami S, Yamauchi K, Odashima K, Ito K, Iikubo M, Kumasaka A, Martinez-de la Cruz G, Gaggl A, Kumamoto H, Takahashi T. Influence of oestrogen deficiency and excessive mechanical stress on condylar head of mandible. Oral Dis. 2020 Nov;26(8):1718-1726. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Temporomandibular joint, Idiopathic condyle resorption, Joint space, Condyle, Class II, Craniofacial anomalies","lastPublishedDoi":"10.21203/rs.3.rs-7570283/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7570283/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjective\u003c/h2\u003e\u003cp\u003eTo investigate the condylar joint space, position and morphology in skeletal Class II malocclusion patients with idiopathic condylar resorption (ICR), in order to provide reference for the clinical treatment and efficacy evaluation of ICR.\u003c/p\u003e\u003ch2\u003eMaterials and Methods\u003c/h2\u003e\u003cp\u003eSkeletal Class II malocclusion patients with ICR and skeletal Class II malocclusion patients with normal temporomandibular joint (TMJ) structure were included in this study. The anterior joint space (AJS), superior joint space (SJS) and posterior joint space (PJS) were measured by computed tomography (CT) and magnetic resonance imaging (MRI). The surface area and volume of condyle were measured through three-dimensional reconstruction using CT scans.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eA total of 55 patients were included in both groups. All ICR patients exhibited bilateral anterior disc displacement without reduction (ADDWOR), with MRI revealing morphological changes in 90.91% of ICR patients. SJS in ICR group significantly decreased by 15.85% on CT and 14.23% on MRI (P\u0026lt;0.05). The typical SJS-PJS difference in healthy TMJs disappeared in ICR patients, and joint space proportions became irregular, indicating condylar instability. Mild resorption was found in 78.18% of ICR patients, mainly affecting the anterior slope and condylar apex, while 21.82% showed more severe resorption. Condylar ratio in ICR patients showed greater variability, reflecting increased instability. Additionally, condylar volume and surface area were significantly reduced by 29.9% and 21.3%, respectively (P\u0026lt;0.05).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003eICR patients exhibit varying degrees of condylar resorption, disrupting the stable joint space proportions. This may be due to morphological changes from condylar resorption, affecting condylar position in the glenoid fossa.\u003c/p\u003e","manuscriptTitle":"Characteristics of condylar joint space, position and morphology in skeletal Class II malocclusion patients with bilateral idiopathic condyle resorption","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-21 23:43:34","doi":"10.21203/rs.3.rs-7570283/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-11-18T08:54:07+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-09T21:08:39+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"252052187009213015785333642147075820031","date":"2025-10-27T06:11:48+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-22T03:21:14+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-16T02:41:21+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"330129234788514032020107059327779692807","date":"2025-10-13T21:36:18+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"248300635087538041031597128288545285340","date":"2025-10-13T14:36:27+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-10-09T00:19:31+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-10-07T10:45:42+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-10-03T09:05:12+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-10-01T17:13:07+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Oral Health","date":"2025-10-01T14:32:00+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"80e0995b-f0c1-4672-b15b-735cbb250fb2","owner":[],"postedDate":"October 21st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-01-19T16:50:31+00:00","versionOfRecord":{"articleIdentity":"rs-7570283","link":"https://doi.org/10.1186/s12903-026-07681-4","journal":{"identity":"bmc-oral-health","isVorOnly":false,"title":"BMC Oral Health"},"publishedOn":"2026-01-12 16:31:01","publishedOnDateReadable":"January 12th, 2026"},"versionCreatedAt":"2025-10-21 23:43:34","video":"","vorDoi":"10.1186/s12903-026-07681-4","vorDoiUrl":"https://doi.org/10.1186/s12903-026-07681-4","workflowStages":[]},"version":"v1","identity":"rs-7570283","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7570283","identity":"rs-7570283","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}