New Jaw Joints
The panoramic film above shows the results of a surgery that replaced both of the temperomandibular joints. The prosthetic joints consist of a vertical component including a ball which rotates in a horizontal component, a prosthetic socket. The vertical component replaces a part of the lower jaw called the condyle, and the horizontal component is called the fossa. The fossa is a somewhat complex structure since the condyle does not merely rotate within the socket. It must also slide forward (translate) onto the condylar eminence which is located in front of the socket itself. Below is a diagram of a dried skull with the parts of a natural joint drawn and labeled, for comparison. If you look carefully, you can see that both condyles were removed in their entirety, and the portion of the skull containing the natural fossa was modified to receive the titanium fossa implant. For more on the mechanics of the joint, including an explanation of the rotational and translational components of jaw opening, see my pages on occlusion.
Above is the same panorex, but without the labels to show an unobstructed view of the x-ray. In addition to the TM Joint surgery, the patient also underwent surgery to correct other skeletal deformities. The entire maxilla (the bone that holds the upper teeth and the palate) was moved forward and secured with titanium alloy screws and brackets. The chin was also resected to correct severe underdevelopment. The metal used in all prosthetic parts, including the screws, is a titanium alloy. Click here to read the history of osseous implants to see how it was discovered that titanium would integrate with bone.