TMJ CUSTOM TOTAL JOINT REPLACEMENT

 

INDICATIONS

The essential functions for life of mastication, speech, swallowing and deglutination rely on proper functioning of the temporomandibular joint. These functions put the TMJ under more cyclic loading than any other joint in the body. End stage temporomandibular joint disease that leads to architectural destruction and physiologic dysfunction dictates the need for total joint replacement.

BACKGROUND

Although often viewed as a new technology, custom TMJ TJR is not. It has been successfully used in degenerative TMJ disease for over two decades. Success rates are higher than 90% which is documented in current literature.

TMJ Concepts (Ventura, Ca, USA) manufactures a patient-fitted prosthesis for the reconstruction of the temporomandibular joint. Each prosthesis is individually fabricated for the unique anatomy of the patient. This is based on CT imaging and utilizes computer aided design and manufacturing. Precise implant components allow excellent adaptation, fixation and optimum function. All materials utilized for manufacturing (titanium, cobalt-chromium-molybdenum, and ultra-high-molecular-weight polyethylene) have several decades of successful clinical use in reconstruction of hip and knee prosthesis.

PROSTHESIS FABRICATION

Once decided a total joint replacement is for you, a high definition CT scan will be taken to produce a three-dimension model of your jaws. A design process is started and a custom fitted joint with two components resembling a ball and socket will be fabricated. The first component will be the fossa(socket) component attached to the skull. The condylar(ball) component will rest against this. It will be designed to maintain or restore a stable bite enabling you to function well.

 Figure: Design of a TMJ Concepts Prosthesis for Replacement Therapy

Figure: The fabricated prosthesis ready for insertion. 

HOW IS THE SURGERY PERFORMED?

Total joint replacement requires a completely sterile environment. The operating theatre will facilitate this by enforcing a specialised protocol to minimise the risk of infection before, during and after the procedure. Issues will be discussed at your consultation appointment and beyond such as hair washing and antibiotic protocols.

Two incisions will be made on the face and will be as camouflaged and minimal as possible. A small incision will me made just in front of the ear and another just behind the jaw line. This allows access to the jaw from above and below for placement of the artificial joint.

Once wiring of the upper and lower jaw into the correct anatomical position takes place, the components are screwed into the bone with custom screws at specific lengths to avoid damage to the underlying structures. 
The operation sites are closed with sterile stiches and the jaw wiring is released.

Figure: Two lines indicating the incision locations normally within crease lines.

After several months, these heal well and minimally visible.

HOW WELL DOES THIS WORK?

The aim of joint replacement is to restore form and function. As you will be receiving an artificial component that mimics the natural tissues of the body, you will not gain 100% of normal function but with good case selection, should significantly improve your current jaw function. 

Success rates are in the vicinity of 95% and most recent studies are currently demonstrating survival rates for up to and over 20 years.

WHAT ARE THE MAIN RISKS?

Facial Nerve Injury

Due to the anatomy of the facial nerve, there is a risk that this will be injured during the procedure. The outcomes of this are a “drooping face” and the inability to raise your eyebrows. In most cases, this is only temporary and you will regain the function with time. The rates of permanent nerve injury range between 1 to 5%.

Freys Syndrome

Unwanted sweating around the incision lines can occur due to "haywired" nerve healing after the operation. The nerves that supply the salivary glands can reattach to the sweat glands in the skin. 

Altered Occlusion/Bite

Although TMJ Ttotal placement is a precision procedure, a potential complication is inaccurate fabrication and surgery. This is uncommon and could mean a secondary corrective procedure if it occurs. 

Neuropathic/Chronic Pain

The primary aim of TMJ TJR is to regain function. Any pain relief is a secondary benefit. Often patients with chronic pain for many years will develop an element of "centralised pain" within the nervous system which is difficult to completely resolve even after total joint replacement. This residual pain becomes "managed". 

Infection

A small percentage of total joint replacements become chronically infected. This can be a devasting event event which usually means further revision surgery with removal and replacement of the prosthesis.