Patient-specific Temporomandibular Joint Endoprosthesis

Description

The temporomandibular joint (TMJ) is the most frequently used joint in the human body; its unique biomechanics allows us to speak and chew. This joint consists of the following two main structures: glenoid fossa and condylar head.
When the temporomandibular joint is damaged as a result of trauma or illness (such as osteoarthrosis, ankylosis, etc.), and usual treatment methods are ineffective or impossible to apply, this joint undergoes replacement surgery – the patient’s TMJ is replaced with an artificial one. This TMJ endoprosthesis is intended to replace a damaged joint, and restore its anatomy and its function. TMJ endoprosthesis may be either standard or patient-specific. In severe cases (for instance, large bone defect / deformity, irregular jaw position, bilateral pathology (both TMJs) or complications of existing implants), the use of a patient-specific TMJ implant is then recommended.
Ortho Baltic manufactures patient-specific TMJ endoprosthesis individually for each patient with regard to the patient’s anatomy, pathology and the surgeon’s specifications for the design and requested set. Patient-specific TMJ implants and patient-specific surgical guides are designed on the patient’s skull-mandible anatomical model that is recreated from CT scan images. If possible, we advise to perform intraoral scan or take dental impressions of patient’s teeth. These highly accurate models are used to design a bite splint (to correctly position the jaws). Therefore, the patient-specific endoprosthesis precisely fits the patient’s anatomy and ensures stable fixation and restoration of anatomical axes. The accuracy (regarding the pre-surgical plan) of resection lines, implant positioning and restoration of occlusion are ensured by using patient-specific surgical guides.

For patient-specific TMJ endoprosthesis components we use the following materials and production technologies:

• patient-specific mandibular (ramus) component is made from medical Grade 5 titanium alloy Ti6Al4V using additive manufacturing technology DMLS (see component 1, imag. 2);
• patient specific fossa component is made from ultra-high molecular weight polyethylene UHMWPE using a 5+1 axis milling technology (see component 2, imag. 2);
• single-use patient-specific surgical guides, patient-specific anatomical and implant models used in presurgical planning as well as for planning and training purposes during surgeries are printed from biocompatible polymer (PA 2200, also known as Nylon-12), using additive manufacturing technology SLS;

The stages of making the TMJ prosthesis: