The linear intra-articular motions of the temporomandibular joint in individuals with severe forward head posture: A cross-sectional study.

Background: The cervical vertebrae and the temporomandibular joint (TMJ) may be linked through their common muscles.

Objectives: The aim of the present study was to compare the linear intra-articular motions of the TMJ between individuals with the normal craniocervical posture (CCP) and severe forward head posture (FHP).

Design: Cross-sectional study.

Methods: Volunteers (N = 38) were equally assigned to either the severe FHP group or the normal CCP group according to their craniovertebral angle (CVA). The CVA angles greater than 49° were considered as the normal CCP while angles between 44 and 40° were regarded as the severe FHP. The TMJ was imaged at the closed, median, and maximum open positions of the mouth using an ultrasound machine with a 7.5 MHz linear transducer in the sitting position. The best-fitting curve in the contour registration method was employed to measure displacement of the mandibular condyle on the transverse and vertical axes.

Results: The forward displacement of the mandibular condyle in the severe FHP group was significantly (p-value = 0.037) reduced compared to the normal CCP group at maximum open position of the mouth, while no significant difference was revealed at closed (p-value = 0.937) or median open (p-value = 0.699) positions. The perpendicular displacement of the mandibular condyle exhibited no significant (p-value>0.107) difference between groups at any mouth position.

Discussion: The current study demonstrated, for the first time, that severe FHP may impact the intra-articular motion of the TMJ. This study presumed that individuals with severe FHP may encounter a force imbalance in the anterior-posterior direction.