Customization Is Crucial to Expert Jaw Joint Replacement

When we hear about someone undergoing joint replacement, most of us imagine hip or knee surgery - the most commonly performed total joint replacement procedures. But for some people, injury, illness or even genetics can lead to chronic facial pain or dysfunction that can only be relieved by replacing the temporomandibular joint.

Total joint replacement surgery can be among the most successful surgical procedures, promising patients better function and less pain than before. But until the past few years, success was mixed when it came to total replacement of the jaw joint - technically the temporomandibular joint, or TMJ.

Because of the many differences in the structure and shape of the human skull, it's difficult to replace a jaw joint successfully with anything other than a highly customized prosthesis (artificial joint), says Steven R. Sewall, DDS, chief of the Division of Oral and Maxillofacial Surgery (OMFS), part of the Medical College of Wisconsin Department of Surgery. By contrast, prostheses for knees and hips are fairly similar and vary little, except for the size of the patient.

Using custom-designed, specially fabricated total joint prostheses made from a model of the patient's own anatomy, Sewall and colleagues have successfully replaced 52 damaged TM joints since 1999. Froedtert & Medical College is so far the only site in the state to offer the procedure, although Dr. Sewall recently trained a specialist from Green Bay.

Not for 'TMJ Syndrome' Patients
Dr. Sewall emphasizes that the procedure is not appropriate for every patient who's told he or she has "TMJ syndrome," which typically refers to popping, clicking or pain in the jaw joint, located near the ear, and pain in the surrounding muscles that control opening and closing the mouth, chewing, swallowing and speaking. Often these problems can resolve over time or can be treated non-surgically.

"This procedure is for patients with severe restrictions of the joint - bone fused to bone from advanced degenerative arthritis, for example, or from trauma, infection, malignant or benign tumor and, rarely, congenitally fused joints. These patients can't open their mouths, can't chew and have chronic pain, including headaches and earaches. Because of these restrictions, they can be limited to liquid nutrition or soft foods. What they do consume is usually too high in carbohydrates, and they aren't getting appropriate nutrition."

It's severe cases like those that are referred to the OMFS from dentists and other specialists. Frequently they see patients who have had previous surgeries on their jaws, including removal of the joint disk and replacement with a synthetic material, or with muscle, fat or other tissue from their own bodies. These procedures often produce less than desirable results, often because of failure of the replacement material.

Approved by FDA
Since 1999, when the newer custom-designed TMJ prostheses won approval from the Food and Drug Administration, "we have had no failure due to the material," Dr. Sewall says, adding that a 10-year-study reaffirms the procedure's efficacy. "So, yes, the surgery is successful."

He cautions, however, that although patients do recover some function, not all find pain relief. "That's because many of the patients we see have had one, two or even three previous surgeries using other methods. If they've had one or two previous surgeries - or none at all - they should gain adequate pain control. If they've had three or more previous procedures, they're likely suffering from chronic pain due to permanent injury to the tissue, and that pain may never go away."

Creating an accurate model of each patient's jaw takes several steps, Dr. Sewall says.

1. The patient undergoes a CT scan of the area of the jaw to be reconstructed.
2. A stereolithographic model is fabricated from the CT scan. According to ProtoMED, a Colorado company that makes the models, stereolithography creates precise models using lasers and epoxy resin.
3. The model is returned to the Division of OMFS and the surgeon performs the necessary surgery on the model.
4. The area of the jaw to be reconstructed is digitized and computerized by a California company called TMJ Concepts in preparation for making the prosthesis.
5. The surgeon and an engineer review the design and make any necessary changes.
6. The prosthesis is fabricated and milled, then sterilized and sent back to Froedtert & Medical College for the scheduled surgery date.

"Once the prosthesis is ready, the actual surgery takes from three to 12 hours, depending on the severity of the problem," Dr. Sewall says. "The patient is hospitalized for one to three days, and rehabilitation takes another three to six weeks."

Insurance Coverage
With all the custom work this procedure requires, as well as the surgery, recovery and rehabilitation, such facial reconstruction is expensive, costing between $50,000 and $75,000. But for patients suffering from pain and debilitation caused by severe TMJ-related problems, the benefits and success rate offset the financial considerations. Insurance usually covers the procedure because the cause and severity of the patients' conditions make it a medical necessity.

Dr. Sewall and colleagues perform similar reconstruction procedures using the custom-designed and fabricated models to repair other defects of the skull and the orbit (the bony structure surrounding the eye opening of the skull), and the mandible (lower jaw) resulting from traumas like car accidents and gunshot wounds. They also use the procedure in patients with benign and malignant tumors.

In addition, the Medical College OMFS Clinic provides specialty services for patients including office anesthesia, removal of impacted teeth, dental implants, surgical correction of dentofacial and cleft palate deformities that cause malocclusion and dysfunction, primary management and secondary reconstruction of hard and soft tissue tumors, arthroscopic and reconstructive surgery of the TM joint, surgical management of obstructive sleep apnea, and microscopic surgery to repair nerve injuries.

Barbara Abel
HealthLink Contributing Writer

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.