Computational synovial dynamics of a normal temporomandibular joint during jaw opening.

BACKGROUND/PURPOSE: Synovial fluid in the temporomandibular joint (TMJ) acts as a lubricant and shock absorber, facilitating smooth jaw movements by reducing friction and cushioning the articular cartilage and other tissues in the TMJ. This study investigated the flow pattern of synovial fluid in the articular cavity during jaw opening.

METHODS

The upper TMJ compartment in a healthy individual was studied by computed tomography arthrography, and the intra-articular pressures were measured during jaw opening. The compartment was reconstructed in three dimensions, and finite volume fluid dynamic modeling was used to analyze the pattern of fluid flow and pressure distribution during jaw movements.

RESULTS

In a closed-jaw position, the upper joint compartment assumed a dumbbell shape. During the jaw opening process, the anterior portion of the upper compartment decreased gradually until it disappeared completely when the jaw was opened. As the jaw opened, the posterior space enlarged gradually. During jaw opening, the pressure in the anterior space of the upper compartment was higher than that in the posterior space. The model indicated that synovial fluid circulated anticlockwise, forming local vortices in both anterior and posterior spaces.

CONCLUSION

During jaw opening processes, the three dimensional configuration of a normal upper TMJ compartment changed as the joint disc moved, with the synovial fluid circulating in an anticlockwise direction and local vortices forming.