Title	Temporomandibular Joints with Larger-Than-Average Horizontal Condylar Angles May Be Indicative of Internal Derangement and Degenerative Joint Disease
Clinical Question	Are temporomandibular joints with a greater-than-average horizontal condylar angle, as measured by cone-beam computed tomography, at greater risk for joint disease in the long term?
Clinical Bottom Line	A greater-than-average horizontal condylar angle (HCA) is associated with degenerative joint changes. This is supported by a retrospective study of patients with unilateral osteoarthritic joint changes. Two small studies show that a 3D reconstructed model based on CBCT is a more accurate method of measuring the HCA than 2D CBCT images.
Best Evidence
PubMed ID Author / Year Patient Group Study type (level of evidence) 29065621 Zhang/2017 10 patients with asymptomatic temporomandibular joints Cross-sectional study Key results In these asymptomatic subjects, there was a significant difference in the HCA as measured in 2D CBCT images vs. 3D reconstructed models. The HCAs were significantly smaller (p<0.05) when measured on 2D CBCT images compared to the 3D reconstruction model measuring method. Furthermore, there was a significant difference (p<0.05) between right and left sides when measuring on 2D CBCT images, but no significant difference between sides when measuring 3D reconstructed images. 28189528 Lee/2017 60 patients with unilateral osteoarthritic joint changes; 43 control patients Retrospective cohort study Key results Condylar angles in the joints of control patients and the unaffected joints in OA patients were not significantly different. The mean HCA in the unilaterally OA-affected joints was larger than in the contralateral unaffected joints (p<0.001). In the OA-affected joints, flattening and erosion of the articular eminence was associated with a greater condylar angle (p< 0.05). 27043669 Zhang/2016 5 patients with facial asymmetry; 5 asymptomatic patients Cross-sectional study Key results For the asymptomatic patients, there was no significant difference between right and left side HCA when measured from 3D models based on CBCT, while there was a significant difference when measured from 2D CBCT images. This suggests that that the HCA as measured in the 3D model may be closer to the real value. With the 3D measuring method, the HCA of subjects with facial asymmetry was significantly larger than the HCA of asymptomatic subjects (P = 0.000 for both deviation and non-deviation sides).
Evidence Search	(horizontal condylar angle[MeSH Terms]) AND (Temporomandibular joint[MeSH Terms]) AND(Cone-beam computed tomography[MeSH Terms])
Comments on The Evidence	Validity: In Lee /2017, two senior radiologists (with 15 and >30 years of experience) were blinded to the treatment groups of the joints they were measuring. The condylar angle for all joints was measured three times at least 1 week apart by one radiologist; each series of measurements was independent and previous measurements could not be seen. A second radiologist measured 20 randomly selected images by the same method to calculate inter-observer reliability. There was no significant difference between measurement by the same observer or between different observers; the intra-observer correlation coefficient was 0.979 for the three separate measurements. The inter-observer correlation coefficient was 0.930. In Zhang/2016 it is unclear if the three PhD/medical radiologists performing the measurements were blinded to whether they were measuring asymmetric or control joints. Correlation coefficients for the result in each measurement were >0.95 for both Zhang papers; the repeatability of the measurements was acceptable. All methods of measurement, comparison and selection in these studies are reproducible and accepted as standard methods of measuring TMJ angles. This adds validity to all three studies. It would be beneficial if the two Zhang studies had a larger patient population (as the Lee study did). Perspective: It is beneficial to have three similar studies with two different perspectives for comparison. We have retrospective and cross-sectional studies within the same time frame that have similar patient populations.
Applicability	These studies show promise in the area of TMJ comparison and diagnosis for the application of HCA in the diagnosis of degenerative joint disease (DJD); additional longitudinal studies of healthy joints with greater-than-average HCA are necessary to verify the role of HCA in the early diagnosis of DJD and/or its ability to predict future disease. HCA measurement has the potential to aid in early intervention and prevention - limiting morbidity, costly surgery and palliative treatment. Limitations of measuring HCA on CBCT of healthy TMJs are that CBCTs are not used for screening, and thus TMJs could only be assessed as an additional service when CBCTs are acquired for another reason; this adjunctive service of assessing the HCA of TMJs could aid in the early diagnosis and interventional treatment of DJD.
Specialty	(Oral Medicine/Pathology/Radiology) (Orthodontics) (Prosthodontics)
Keywords	temporomandibular joint, horizontal condylar angle, cone-beam computed tomography
ID#	3418
Date of submission	12/05/2019
E-mail	hoikka@UTHSCSA.edu
Author	Angela Marie Hoikka
Co-author(s)	Nayla Baaaklini
Co-author(s) e-mail	baaklini@uthscsa.edu
Faculty mentor	Hassem Geha
Faculty mentor e-mail	Geha@uthscsa.edu
Basic Science Rationale (Mechanisms that may account for and/or explain the clinical question, i.e. is the answer to the clinical question consistent with basic biological, physical and/or behavioral science principles, laws and research?) None available
Comments and Evidence-Based Updates on the CAT (FOR PRACTICING DENTISTS', FACULTY, RESIDENTS and/or STUDENTS COMMENTS ON PUBLISHED CATs) None available