TMJ Surgeon.com Surgery and Alloplast Materials, Part II. Joint Replacement Surgery
Total Joint Replacement System of the TM Joint
This prosthesis, manufactured by Biomet, Inc. is one of two prosthetic systems which borrows from bio-mechanical principles and lessons learned from the experiences of Charnley’s hip orthopedic prosthetic development. A second system is produced by TMJ Concepts, Inc. of Ventura, California . Both systems employ an onlayed prosthetic condyle to the mandible to replace a severely diseased or destroyed condyle. It articulates with a high density polyethelene fossa component and both are fixated to their respective sites as shown. The difference between the two systems is that the TMJ Concepts product (see TMJconcepts.com) is a custom made prosthesis, constructed from a CT scan of the patient to precisely fit the nuances of variable anatomies. Both systems have followed FDA developmental protocols and are now marketed world wide for specific indications. Both systems have been developed by surgical pioneers who faced their own particular and private “Charnley learning curves” as discussed in the previous blog on alloplasts.
A difficult history
Modern Maxillofacial surgery and surgeries developed to correct significant facial disfigurement benefited from both from the understanding gained from facial injuries sustained during wartime (Vietnam) and the fact that animal studies, particularly those studies which researched blood supply and proposed surgeries on humans, could indeed be performed with confidence. Until the decade of the 60s, maxillofacial surgeries performed to correct unfortunate victims of accidents and other forms of injury, birth defects and other causes of distorted facial skeletal development were risky and fraught with complications. Certain world centers could achieve acceptable results, but by in large these were not frequently performed surgeries.
In the heroic attempts to save life and improve quality of life, surgeons in wartime often are forced to adapt basic techniques or attempt new ones, particularly in reconstructive surgical efforts. During the Vietnam conflict, US military surgeons made tremendous strides in refining techniques such as bone grafting and other reconstructive facial surgical techniques. When the war ended, many returned to academic careers to perfect the full spectrum of the science that allowed this specialty to explode upon the health care scene, and provide a new era of services. The decades of the 70s and 80s saw remarkable advancements. It included the use of animal studies to test the feasibility of developing jaw and facial surgery technique improvements.
Unfortunately, the decade of the 80s saw the attempted development of an artificial cartilage or “disc” material to replace diseased TMJ cartilage. There were two main problems with its development and use. One was ignoring history (which seems to be a world wide epidemic phenomenon in many aspects of life these days) and the other was lack of ability to employ animal studies (primates) to test whether such products were suitable prior to use in humans. This material was a sheet like material with teflon on one side and another material made of a material designed of poly carbon and other hydrocarbon materials designed to allow scar tissue to surround it and stabilize it. Politically to this day, animal rights activists create the difficulty to study new surgical techniques and materials in animals. This fact circumvents a huge necessity in surgical sciences…..and that is to observe the response of such efforts to improve human life, in an animal first. Though I do not wish to debate with animal rights activists, their efforts are responsible for significant problems and the reality that there were many things developed in the 80s and 90s without the ability to test in animals first. The artificial TMJ disc development was such a disaster. Developers ignored Charnley’s experience in the hip. He had significant failure with the attempted use of teflon lining the artificial cup of the hip socket. The “theory” of its use in the first place was to somehow reduce friction during rotation function in the hip. In the jaw, it was to reduce friction during the sliding or gliding function and prevent scar tissue from preventing this gliding function. Lack of animal studies led to use of a product without knowlege of how the second component of the replacement would react in the unique environment of a synovial joint system ( a critical immunology field not to be taken for granted).
In this light, the product (used over a period of 3-5 years ) created its own aggravation of the arthritic process and was rightfully recalled by the FDA and its use prohibited. Development of the total joint replacement to manage severe problems was put on the fast track by surgeons and a surgical field that needed a total replacement system. This history parallels Sir John Charnley’s in the hip. The end of the story is the development of prosthetics based on good surgical science from other fields, employment of bio-mechanical and biomedical engineers who did the appropriate R&D and the use of materials well tolerated by the body’s immune system. They serve a unique purpose in the surgical armamentarium in the attempt to make impaired and disabled humans better.
A total replacement should be placed by an experienced surgeon. There are basic indications:
1. Gross arthritic, injury, or pathologic destruction of the human jaw joint which has created a lower jaw deformity, asymmetry, etc and has created a severe malocclusion .
2. Ankylosis or fusion of the jaw joint from a severe arthritic process.
Maxillofacial surgeons have historically debated the use of prosthetic joints for TMJ replacement versus other reconstructive attempts using one’s own tissues, mainly rib grafting to substitute for diseased or destroyed TMJ condyles in an attempt to reconstruct an arthritic joint. Rib grafting definitely has it place in the growing patient.
Rib grafting has its advantages and disadvantages. The use of one’s own natural tissues appeal to many patients and surgeons. However, taking a rib(s) is not always a benign procedure either, particularly with chronic pain issues from the surgery site and risks of chest complications. Also, in cases of systemic arthritis (rheumatoid, psoriatic, juevenile osteo and rheumatoid arthritis conditions), the risk of using a rib is that the systemic arthritic disease process can lead to long term complication with or frustrating destruction/ankylosis (fusion of joint) of the rib graft. In this light, alloplastic TMJ surgery has its rightful place of consideration, particularly if associated with significant jaw deformity, an agressive arthritic joint, tumors, trauma reconstruction and all associated with malocclusion.
Of greatest concern to any patient is the expected lifespan of the prosthesis. The present prototypes of total TMJ replacement, (using Charnley protocols of dissimilar articulating materials of the condyle and fossa) have been in use for over 15 years. For both systems, long term failure rates are currently reported less than 3%. The greatest risk of these devices is infection, and an infection is most likely to occur within the first 2-3 months of placement. Such issues are similar to placement of knees and hips.( Less than 1- 1.6%) (1) (2). Westermark has reported on the Biomet prosthesis with 8 year follow up. There is no untoward reaction of tissues seen microscopically suggesting any unfavorable reaction . (4,5). Mercuri has reported similar acceptance of body tissues and the TMJ Concepts with a 12 year follow up. (6) The Biomet prosthesis was developed at the University of Pennsylvania. Of greater than 650 that were placed at that institution and tracked by Biomet, there have been only 9 requiring removal due to issues such as infection or some mechanical failure. (8)
Failures due to wear and tear is much less of a risk in the TMJ with the prostheses discussed here, than a knee or hip, mainly due to the realities that compressive loads are not in play relatively as much as those in knees or hips. Charnley’s and later orthopedic failure experience included the use of cements for fixation which created their own immunologic reaction problems. The total TMJ replacement systems do not use a fixating cement. Rather, elements such as titanium which is “bone friendly” and bone fuses to it for stability, eliminating the need for use of cements. The total TMJ replacement prosthesis however does not have the potential degree of translation or “gliding” that a natural joint has. By necessity, a total TMJ replacement must be a much simpler biomechanical design than the most complex joint of the human body….paradoxically to increase lifespan and wear and tear of the prosthesis. Its main benefit is to restore most joint function but with a more simple hinge or rotation function….and to correct facial asymmetry and disfigurement due to arthritic destruction of a jont(s). A total TMJ replacement results in less mouth opening potential than normal ranges of motion. But the improvements from the pre-operative state can be remarkable particularly in cases of joint fusion or ankylosis. Post operative jaw mobility can improve significantly from less than a centimeter of mouth opening (barely large enough to fit a spoon, fork, or brush one’s teeth) to 3.5 cm or a range of mouth opening large enough to place 3 fingers between the front teeth. (4,5,7)
Early technical failures in the hip led to a better understanding and advancement in “biophysics”. The same advancements and knowledge data base are now being accumulated in this field.
As an alternative to alloplasts, Biomechanical engineers and other bioscientists are researching developmental growth of biologic joint replacement transplantable “parts” using stem cell research from umbilical cord stem cells. This is remarkable work and may present as an alternative in the future . This work is being conducted by some of the finest bioengineers in the world at Rice University, The University of Kansas, Columbia University, and U. of California. (3)
Presently, in the United States , companies and surgeons which use these alloplastic joint replacements are under company and FDA reporting criteria relative to use and failure (as is the case will all orthopedic prosthetics) and this is not going to change in the foreseeable future. Other countries of the world are employing what are called patient registry systems….where tremendous data is being generated for long term follow-up. Such a system is likely to come to the United States eventually. Nevertheless and currently, there are numerous steps along the way to assess these developments and uses. In my view, low risks of infection will continue to be the problematic issue with these devices (as in any prosthetic joint system)….and that current risk with these total TMJ replacement systems is low based on published data.
Refer to ASTMJS.org to find US and international surgeons who will perform these cases in selected circumstances. Readers can also google British Asssociation of Temporomandibular Joint Surgeons, European Society of Temporomandibular Joint Surgeons for qualified surgeons.
1. Wolford, LM, Rodrigues, DB and McPhillips,A: Management of the Infected Temporomandibular Joint Total Joint Prosthesis. Journal Oral/Maxilofac. Surg. 68:2810-2823, 2010.
2. In current Publication:
Mercuri,LG and Psutka, D: Perioperative, Postoperative, and Prophylactic Use of Antibiotics in Alloplastic Total Temporomandibular Joint Replacement Surgery: A Survey and Preliminary Guidelines. Jnl of Oral and Maxillofacial Surgery, 2011.
3. 2nd TMJ Bioengineering Conference. U. of Kansas. Dr. Michael Detamore, PhD. Chair. Broomfield, Colorado. October 17,18 2009.
4. Westermark,A: Total reconstruction of the temporomandibular joint. Up to 8 years follow-up of patients treate with Biomet total joint prosthesis”, International Journal of Oral and Maxillofacial Surgery, 2010,39:951-955.
5. Westermark, A. , Leiggener, Aagaard, and Lindskog: “Histological findings in soft tissues around temporomandibular joint prostheses after up to eight years of function” International Journal of Oral and Maxillofacial Surgery, 2011, article in press.
6. Mercuri LG, Edibam NR, Giobbe-Hurder: 14 year follow-up of a patient fitted total temporomandibular joint reconstruction system. J Oral Maxillofac Surg 2007: 65: 1140-1148.
7. Wolford, et al: “TMJ Concepts/Techmedica custom-made TMJ total joint prosthesis: 5 year follow-up study. Int J Oral Maxillofac Surg 2003: 32: 268-274.
8. Biomet Corporation, Personal Communication.