The effects of a total TMJ endoprosthesis on the contralateral condyle.

OBJECTIVE

To correlate the magnitude of the amount of translation of prosthesis and the native joint, and the postoperative change in the volume of the contralateral condylar process after unilateral total joint replacement.

MATERIAL AND METHODS

The study examined 16 patients with post-traumatic jaw deformation treated with unilateral TMJ replacement using total endoprosthesis. The mandible kinematics was recorded using the Cadiax Diagnostic system and correlated with the remodeling of the native joint.

RESULT

On average, the group showed an 8.5% decrease in the volume of the native condylar process. In 13 patients, the amplitude of the native joint movement in the mouth opening and the mandible pro- and laterotrusion markedly deviated quantitatively that combined with the translational movement of the TMJ endoprosthesis in all types of mandibular abduction in all the patients. Correlation analysis showed a moderate negative relationship (= -0.43) in opening the mouth between the amplitude of movement of the native joint and of the endoprosthesis, as well as a noticeable negative strength of relationship. Also, the correlation analysis showed a moderate positive relationship between the change in the native condylar process volume and movement amplitude when opening the mouth, and an inverse correlation of the high strength of relationship between the change in the native condylar process volume and movement amplitude of the TMJ endoprosthesis.

CONCLUSION

Electronic axiography found that patients in the postoperative period could restore some of the translational movements even with the attachment of the lateral pterygoid muscle cut off. The main factor influencing the magnitude of the endoprosthesis translational movement is the design of the fossa component: the ratio of the circumferential surface of the fossa to the diameter of the head of the endoprosthesis, as well as the presence of lateral stoppers. The study showed that unilateral TMJ reconstruction provides changes in the volume of the native joint directly related to the amplitude of the movement of the joint itself and inversely correlated with the amplitude of the movement of the endoprosthesis.