Nanocrystalline Diamond Coating on a Temporomandibular Joint Resurfacing Device: An Animal Model

The temporomandibular joint is a complex joint with frequent functional demands. It is not uncommon for patients to develop derangements or degenerative changes leading to pain and dysfunction. Several animal models have been used to evaluate form and function in comparison to the human TMJ, and swine TMJs have been shown to more closely resemble human TMJs.¹ The purpose of our study is to evaluate the implantation and long term functional and wear characteristics of a diamond-on-diamond temporomandibular joint resurfacing device using a swine model.

Eight Yucatan (Sinclair) miniature swine were selected to undergo bilateral total temporomandibular joint (TMJ) resurfacing. A nanocrystalline diamond coated prosthesis was placed into seven animals. Plain titanium was used in one animal as a control. All animals were placed in intermaxillary fixation prior to the procedure to maintain occlusion and post operative imaging was utilized to evaluate placement. The animals were monitored clinically for signs of infection at the surgical site as well as for diet tolerance and weight maintenance. Care of the animals and monitoring of the health and behavior of the animals was performed by the veterinarian and surgical team. The animals were sacrificed at one year post implant placement.  Cone beam CT scans were taken of each joint to help study implant positioning and integration. The prosthesis as well as the surrounding soft tissue was harvested and evaluated for wear and surrounding tissue reaction.  Hardware was assessed for degree of osseointegration.

All animals had excellent occlusion after surgery, tolerated their diets well and continued weight gain over the next year. Anterior dislocation was observed in one animal immediately postoperatively but was reduced without further occurrence. Three animals developed unilateral postoperative infections requiring conservative incision and drainage. The control animal developed an infection postoperatively on one side and was found to have loose hardware requiring removal of the device. No animal had evidence of CN VII injury. Cone beam CTs of joints revealed significant heterotopic bone formation in the condylar area in all animals that appeared to laterally displace the condylar portion of the device in some cases.  A loose screw from the fossa component was noted on one animal and another with a loose screw from condylar component was noted.  Despite these issues, the majority of the animals had good retention of the prosthesis and relatively good articulation of the condyle and fossa.  However, the diamond coating of the prosthesis did appear to have significant wear in all cases after one year on analysis.

TMJ replacement materials have required modification over time due to unfavorable outcomes. One alternative to the current implants lies in nanostructured diamond coating of titanium alloy surfaces. The swine as a model of the human TMJ has been supported due to its similar range of motion and its comparable anatomic and articular relationships.² The current goal is focused on development of a device utilizing a more conservative surgical procedure to provide low friction and no wear debris with significantly enhanced articulation.   

 

1. Bermejo, A., O. Gonzalez, and J. M. Gonzalez. The pig as an animal model for experimentation on the temporomandibular articular complex. Oral Surg., Oral Med., Oral Pathol. 75:18–23, 1993.
2. Herring, S. W., J. D. Decker, Z. J. Liu, and T. Ma. Temporomandibular joint in miniature pigs: Anatomy, cell replication, and relation to loading. Anat. Rec. 266:152–166, 2002.