Groningen temporomandibular joint prosthesis. Development and first clinical application.

Patients with a severely degenerated temporomandibular joint (TMJ) may benefit from an alloplastic TMJ replacement. The aim of the study was to develop a safe and properly functioning TMJ prosthesis. The design was based on imitation of anterior condylar translation by an inferiorly located centre of rotation, unrestricted mandibular movements by a double articulation, correct fit to the skull by a self-adjusting skull part consisting of two connected parts, and stable fixation by bone screws that are rigidly connected to the prosthesis parts. The prosthesis consists of a titanium skull part with ceramic inlay, a titanium mandibular part with a ceramic spherical head, and an intervening polyethylene disc. Titanium-alloy bone screws are used for fixation. All parts are available in a number of different shapes. In vitro laboratory and in vivo animal tests showed a low wear rate, the possibility of a close fit to the skull, a stable fixation, sufficient mechanical strength, appropriate choice of materials and proper functioning. Thereafter the step to first patient application was made. First patient application was carried out without adverse events. In conclusion, the presented TMJ prosthesis passed the pre-clinical tests and has progressed to clinical application. The fit to the skull, the expected lifetime of the device and the reliability of the implantation procedure require further evaluation in well-designed clinical trials.