Page 247 - Demo

Development of a patient-specific TMJ prosthesis2459This was done by allowing the replaced side to move synchronously with the other joint during both rotational movements with the other joint and vice versa, as well as during translative movements (e.g., when performing movements of opening and closing, both the healthy and replaced condyle should move without causing interferences in each other’s joint space). In comparison with the Groningen TMJ prosthesis, where a more bulky fossa component with a low rotational point is used, the articular surface of the TMJ is placed more cranial, to allow for a more natural movement.(16) The same study, concerning the Groningen TMJ prosthesis, did indicate that a more accurate planning and prediction was feasible thanks to the patient-specific fit.Furthermore, mastication involves laterotrusion, which is only possible with intact lateral pterygoid muscle function since occasional recruitment of the medial pterygoid muscle and minimal support by the masseter muscle cannot be predicted. Reattachment of the lateral pterygoid muscle is one of the main (innovative) features of the discussed joint.(17) In order to realize this reattachment, a scaffold in the condylar neck area (optionally, with a tunnel for temporary fixation with bioresorbable sutures) was provided, to form a bony union with the enthesis that has been carefully chiseled from the pterygoid fovea prior to condylar resection. (Figs. 1c, f) Therefore, both the condylar axis angle, the Bennett shift and free excursion at the anteromedial joint space should be integrated into the design of the prosthesis.Prosthetic joint design. The occurrence of material wear is unavoidable, due to constant friction during mastication and other jaw movements. Also, to keep the center of rotation as high as possible, so as to mimic the original TMJ position, the HXLPE has a central thickness of only 2 mm. Despite the possible occurrence of a more uneven wear pattern caused by the more natural movements of the TMJ Parametro artificial condyle when compared to regular stock implants, the replacement of the fossa component may be required. This exchange could be facilitated by applying a tongue-andgroove fixation between the HXLPE and titanium parts as to minimize the invasiveness of the revision surgery. However, the use of such a fixation Nikolas de Meurechy NW.indd 245 05-06-2024 10:14