Objective: Horizontal condylar angle (HCA) of the temporomandibular joints is the cephalometric angle between the condylar latero-medial axis and a horizontal reference line on an axial plane. This angle has thought to affect the prevalence and severity of TMJ-related clinical symptoms but contradictory findings were reported in previous studies. Hence, the present study was undertaken. Prior inconclusive outcomes were believed to be the result of the lack of reliability in the methods used. The choice of anatomical landmarks may have resulted in incorrect HCA measurements. Reference lines may also be varied due to the erroneous positioning of the patient while obtaining SMV radiographs. Therefore, in this study, we developed a new method to calibrate HCA with SMV radiographs using more reliable landmarks.
Methods: SMV radiographs of the patients who underwent TMJ tomography at our facility between 1999-2001 were used. The center of the left and right condyles were identified and used to construct an inter-condylar horizontal reference plane by joining the two centers. The HCAs were measured with respect to the new reference plane. 104 TMJs with and without symptoms were evaluated and their HCAs were measured using the new method.
Results: A total of 28 asymptomatic joints were evaluated and their HCAs ranged from 18° to 61°, with an average angle of 38°. Conversely, HCA in 76 symptomatic joints ranged from -18° to 75°, with an average angle of 35°. Student t-test was employed and the difference between HCA of asymptomatic and symptomatic joints was statistically insignificant (p = 0.4458).
Conclusion: The role of HCA in the predisposition of TMJ pathology is still debatable. Further studies utilizing the above protocol are needed to confirm its validity and reliability in the future.