Total joint replacement - Alloplastic

The absence of donor site morbidity as well as quicker return to mandibular function are some of the advantages of a total joint prosthesis. A disadvantage is the relatively high cost and potential prosthetic failure.

Total joint prostheses can be either custom made or stock.

Custom made prostheses are fabricated from stereolithographic models made from 3D-CT scans.

When stock prosthesis are used, one should have access to different sizes during the surgery.

Surgical approach is generally from a preauricular incision supplemented by a submandibular/Risdon approach.

For more details on the preauricular approach please click here.

For more details on the submandibular approach, please click here.

The fossa is thoroughly debrided of all soft tissues. The fossa is then reshaped to accommodate the artificial glenoid implant.

The muscle attachments are stripped off the lateral aspect of the ramus to allow for fixation of the condylar prosthesis. Any bony irregularities on the ramus are removed.

The fossa component is inserted and secured to the zygomatic arch with screws.

MMF is applied.

For further information on MMF, please click here.

The condylar component of the prosthesis is placed into the neo-glenoid and the fit to the ramus is verified. If needed, additional osteoplasty is made at this time.

When a satisfactory fit between the ramus and the implant has been achieved, it is secured to the ramus with at least 4-6 bicortical screws.

After completion of the fixation, MMF is removed and the final occlusion is verified.

If MMF screws are used intraoperatively, they are usually removed at the conclusion of surgery. Arch bars may be maintained postoperatively for functional therapy.

Postoperative x-rays are taken within the first days after surgery.

It is imperative that the occlusal relationship and mandibular function be assessed early and on a regular basis. The patient is evaluated at 1 week to verify the occlusion and to assure adequate performance of functional rehabilitation exercises.

If a malocclusion is detected, the surgeon must ascertain its etiology (using the appropriate imaging technique). If the malocclusion is secondary to surgical edema or muscle splinting, training elastics will be beneficial. The lightest elastics possible are used for guidance, because active motion of the mandible is desirable. Patients should be shown how to place and remove the elastics using a hand mirror.

If the malocclusion is secondary to a bony problem due to incorrect bone alignment (mal reduction) or hardware failure or displacement, elastic training will be of no benefit. The patient must return to the operating room for revision surgery. A slight malocclusion can be corrected by orthodontics or dental adjustments with the help of a dentist.

The frequency of follow-up will largely be based on the findings of the 1 week appointment. Typically, if the patient is doing well at 1 week, they will not be seen for 2 more weeks. The necessity and frequency of future appointments will be based upon the findings from this appointment.

Postoperatively, patients will have to follow three basic instructions:

1. Diet:
The patient can consume liquids and semiliquids for the first couple of weeks and then advanced to more solid foods as tolerated and recommended by the surgeon.

2. Oral hygiene
Patients with extraoral approaches are not compromised in their routine oral hygiene measures and should continue with their daily schedule.
Patients with intraoral wounds must be instructed in appropriate oral hygiene procedures. The presence of the arch-bars and any elastics makes this a more difficult procedure than normal. A soft toothbrush (dipping in warm water makes it softer) should be used to clean the surfaces of the teeth and arch-bars. Any elastics are removed for oral hygiene procedures. Chlorhexidine oral rinses should be prescribed and used at least three times each day to help sanitize the mouth. For larger debris, a 1:1 mixture of hydrogen peroxide/chlorhexidine can be used. The bubbling action of the hydrogen peroxide helps remove debris. A Waterpik® or similar device is a very useful tool to help remove debris from the wires. If a Waterpik is used, care should be taken not to direct the jet stream directly over intraoral incisions as this may lead to wound dehiscence. The assistance of a dental hygienist may be helpful.

3. Physiotherapy
Patients are instructed in physical therapy maneuvers to restore mandibular excursions. This includes maximum jaw opening, right and left lateral excursions, and protrusive excursions of the mandible, as well as assistance from a physiotherapist if required. They should perform these exercises several times a day.