Patient specific facial implants
"Patient-matched implants were one of the first great applications of 3D printing in surgery"
Temporomandibular joint implant
The temporomandibular joint forms the connection between the temporal bone and the lower jaw. The lower jaw is the only bone piece in the human body with a joint on both sides. The jaw joint consists of an upper and a lower compartment, separated by a connective tissue / cartilaginous discus.
During chewing, speaking and breathing through the mouth, the joint opens and closes like a hinge and the jaw head also moves forward, backward and sideways. Movement on one side is automatically accompanied by movement on the other side, therefore not an identical one. Disorders of the jaw joint give problems in the joint itself, with the masticatory muscles or with both.
Sometimes psychological factors play a role. Clinically the most frequent are pain complaints and mouth opening limitations caused by muscle spasms (usually by nightly grinding teeth), discus movement forward, arthritis, osteoarthritis or bony deformity.
A temporomandibular joint can be deformed from birth, then usually found as a symptom within a hemifacial microsomal syndrome. Usually it is arthritis that gives rise to a condition in the end stage. Arthritis in a temporomandibular joint may result from rheumatoid arthritis (in 17%), infectious arthritis and trauma, especially if it is associated with bleeding in the joint (eg in children who have suffered a blow to the side of the chin).
Osteoarthritis may resemble arthritis but is more common in the elderly. The cartilage in the temporomandibular joint is not as robust as in other joints. Osteoarthritis occurs mainly as a result of discus pathology, and the latter often occurs.
Indications for tissue replacement in a condition in the end stage
A jaw joint whose disc is damaged is the cause of an altered load on chewing, of pain in the contralateral joint and of a diminishing chewing function.
Recovery by means of an artificial jaw joint normalizes the load. The clinic confirms that minimal damage to one joint can indeed cause pain on both sides. There is a ladder of conservative measures (pharmacological pain relief, dietary measures, heat therapy, physiotherapy, bite-plate therapy) and minimally invasive interventions (steroid injections, joint flushing) to climb, before surgery can be thought of.
The "American Academy of Oral and Maxillofacial Surgery" (AAOMS) remains vague about the indications for a jaw joint: only with gout, degenerative osteoarthritis, hypo- and hypercondylia, as the last measure. The American Food and Drug Administration (FDA) mentions the following indications for implantation of a custom-made artifact joint: inflammatory arthritis that does not respond to other forms of therapy, recurrent fibrous or bony deformity that does not correspond to other forms of therapy, failed tissue graft, failed artifact joint implantation, loss of jaw height which is the cause of an altered load on chewing, of pain in the contralateral joint and of a diminishing chewing function.
Idle et al. Presented the 1994-2012 "baseline data" of their prospective 577 alloplastic register FGMs (402 patients). This is probably the largest multicenter database that provides the best descriptive statistics. The indications listed in the largest multicenter database are degenerative arthrosis (48%), failed prior surgery (including rib graft - 22%), bony or fibrosis (16%), seronegative arthritis (12%), revision of a cervical joint (10%), rheumatoid arthritis (7%). Posttraumatic bone loss, oncological resective defects and congenital abnormalities are minor indications. In the aforementioned indications, pain and functional decline must still be considerable after conservative treatment, so that an artificial jaw joint could be thought of.
° Short-term edema and medium-term temporary reduced facial mimics are commonly observed
° The physiotherapy protocol has to be respected carefully
° The operated side of the face will appear bigger around the jaw corner
° Diet score <5/10 (liquid 0, normal diet 10)
° Mouth opening less than 35 mm
° Occlusion disorder due to bone resorption in the jaw (open bite, lowered mandible)
° Pronounced jaw-head resorption and loss of height of the ascending branch of the lower jaw
° Pain score> 5 out of 10 (no pain 0, insufferable pain 10), combined with other criteria
° Other aspects of reduced quality of life