TMJ Replacement Options

I was recently asked the question: are you getting TMJ Concepts custom made implant or Biomet custom implant? Do you know by any chance what is the difference and which one may be a better one?

This is a question that I've thought a lot about myself, but just sort of trusted my surgeon to recommend what's best. And I still feel that way - whatever he is most comfortable "installing" in my face has got to give the best outcome.  Some might feel differently, but allow me to explain myself.  This is a very uncommon and relatively new surgery. There are fewer surgeons who actually perform the TMJ replacements, so they are on the leading edge of what is being developed and seeing the results of themselves with their patients. However, having a solid Biology background (as in, an undergrad degree), I am keenly interested in the implants that I'm getting and why. 

Without disrespecting anyone who has dealt with this longer than I have, and certainly that's almost anyone who is facing this as a result of a systemic issue rather than a recent trauma (like me), I'm writing this from the perspective that your surgeon has recommended a TJR (total jaw replacement) and a certain type of implant and you're wondering why they might be recommending that type and the history behind it.  In my particular case, I know that this is my only option going forward - foregoing TJR of any type is not an option. I know that there are some folks out there who believe  surgery should be avoided at all costs, and certainly there are cases where this should not be jumped into.  However, I've done enough research and know my own situation well enough to know that this is something that I need and there is no other option.

That being said, here are the options for complete TMJ reconstruction surgery:

1. Autogenous Replacement (rib graft most often)
2. Alloplastic Replacement (manufactured implant)
• TMJ Implant
• TMJ Concepts
• Biomet/Lorenz

Autogenous Replacement is an option where a piece of bone is removed from a donor site on the patient's body (usually the rib, but can be elsewhere) and used to reconstruct the condyle section of the TMJ.  Since it only replaces the "ball" section of the joint (and not the "socket"), it is only a partial reconstruction of the joint.  The main points of this type of reconstruction are:
Pros:

• Cost - since no manufactured parts are required, the cost is lower for this surgery.  However, since there is another surgical site and associated pain, the hospital stay is longer, and the recovery may be longer.  This may offset the cost savings to the patient.
• Growth potential - in children, this is the only option for reconstruction, since they will continue growing and a manufactured implant will not.

Cons:

• Recovery time is long
• Only reconstructs the "ball" and not the "socket" part of the joint
• Often requires re-operation, which may ultimately include a manufactured implant 

In summary, an autogenous replacement is only recommended for the right patient with a well-understood complication. In children, this is the only option available for a reconstruction, as it is the only one that may continue to grow with the child.

Alloplastic Replacement is the replacement of the whole joint (fossa/"socket", condyle/"ball" and ramus - what you think of as the jaw bone) with a manufactured joint.  These implants can be conceptualized as the same as a hip or a knee replacement implant. 

The reasons you might get an alloplastic implant are:

• Ankylosis of the TMJ with severe anatomic abnormalities
• Failure of autogenous grafts
• Failure of Proplast-Teflon or Vitek-Kent or partial joint implants
• Severe inflammatory joint disease resulting in joint mutilation and functional disability

What I didn't know prior to researching this, is that there have been considerable changes in design of these implants, that takes into account both what has been learned in more common hip and knee joint replacements, as well as the specific functional anatomy of the TMJ.  The successes in these new generations of joints are looking promising, despite a lack of long-term use.  As my surgeon put it, - every year there are joints out there that are another year older and still working fine.  Only time will tell.  What seems to be true, however, is that the joints being manufactured today are done so carefully and with the learnings of the Vitek-Kent disaster taken into account.

Some of the benefits of alloplastic joints over autogenous grafting are:

• Immediate jaw function, allowing for physiotherapy to begin on Day 1 of recovery
• No need for a secondary donor site (rib sectioning, etc)
• Custom implant availability

Surgeons seem to see that immediate movement of the joints contributes to a much shorter healing time, and better outcomes. Of course, one of the deciding factors in the relative success of the surgery is dependant on how many prior surgeries a patient has had.  The more surgeries, the lesser the degree of success. 

I hope that this helps to understand the differences between grafting-type TMJ reconstruction and manufactured implants.  In my next post, I will share what I've learned are the subtle differences between TMJ Concepts and Biomet/Lorenz manufactured implants.  

Keep feeding the courage wolf!!