| Popis: |
In TMJ patients, with severe pain and TMJ destruction causing a strong limitation of function, a small group remains therapy resistant. For these patients, after failure of open joint surgery, a total joint prosthesis may be indicated to treat these mutilated TMJs. One of the challenges in replacing the TMJ is the imitation of the complex movements of the natural TMJ, including both a rotational and translational component. A small number of TMJ prostheses have been realised, which were reported to have limitations with regards to the translational component of the joint movement. The major causes of the small numbers are the complex shape and wide range of movements of the natural TMJ and the small market, in combination with high financial risks in the case of failing devices. The Groningen TMJ Research Group, aiming at the realisation of a Groningen TMJ prosthesis (G-TMJ prosthesis) that meets all necessary requirements, was faced with three major challenges. The first problem was to imitate the large translatory movements of a healthy TMJ. Second, the considerable variation in size and shape of the cranial part of degenerated TMJs complicates the fitting of the prosthesis to the skull. Third, the long remaining lifetime of TMJ patients makes it essential that a TMJ prosthesis has a similar long lifetime. Prior to the first clinical application, the design was evaluated and tested and finally animal tests were performed with the complete TMJ prosthesis. From the in vitro and the in vivo tests, it was concluded that the TMJ prosthesis met the needed requirements, regarding reactions to wear particles, biocompatible materials and simple and reliable implantation methods. The presented G-TMJ prosthesis design is a mixture of well-known and accepted techniques, and new inventions. Among the well-known techniques are screw fixation and the use of proven biocompatible materials. The main new developments are a double articulation with a strongly reduced articulation stress, including an inferiorly located centre of rotation and a rigid screw-prosthesis connection. The G-TMJ prosthesis successfully made the difficult step from prototype to patient application. From the first studies on the G-TMJ prosthesis by the Groningen TMJ Research Group, it was found that the natural sliding movement of the condyle can be imitated with a fixed, ‘inferiorly located’ centre of rotation. |
