Page 249 - Demo

Development of a patient-specific TMJ prosthesis2479The size of the anterior extension of the fossa component depends on whether the coronoid process was resected or maintained. With the origin and insertion of the temporalis muscle intact, the anterior shift of the condyle is limited and anterior dislocation of the condyle is not anticipated. The more limited space and less anterior shift are likely to shorten the extension of the condylar path of the fossa component. The reverse situation applies when the coronoid process is resected.If no undercuts are present or when they can be eliminated, a saddle-like design can be used to fit over the resection stump. This physically prevents any potential downward, medial and lateral movements. In doing so, a minimal set of screws are sufficient to counteract upward movements, which by themselves are minimized by the action of the masseter and medial pterygoid muscles.Finally, the design of an improved joint prosthesis should also consider psychosocial functions. Asymmetries in the lower face, which can lead to a compromised self-image, can be addressed by using design software that has mirroring tools (e.g., Geomagic Freeform Plus, 3DSystems, Rock Hill, SC, USA) to achieve correct aesthetic outcomes postoperatively. By correcting side differences in the gonial angle and mandibular border using the mirrored side as a reference and whilst taking into consideration the quantity and quality of overlying soft tissue, the TMJ prosthesis act as a facial contouring implant as well.(Fig. 3) Thus alleviating stigmata of pathological deformations. Patients and MethodologyAfter thoroughly evaluating the proposed implants in sheep experiments,(18,19) eleven patients (2 men, 9 women; mean age at surgery of 49 years, 1 months) received all together 16 customized total TMJ Parametro prostheses. The surgery was performed by one surgeon in the same hospital. Follow-up ranged between 1 month and 4.5 years. Four patients suffered from end-stage degenerative arthrosis/arthritis due to disc pathology. Three had conservatively treated subcondylar fractures with subsequent degenerative joint disease. One patient had osteomyelitis in the ascending ramus after a ballistic trauma. One Nikolas de Meurechy NW.indd 247 05-06-2024 10:14