The development and mechanical analysis of a synthetic implant for TMJ disc replacement

Abstract

Approximately 12% of the population in the United States suffers from some form of temporomandibular joint (TMJ) pain. For many of these patients, there do not exist permanent solutions to TMJ disorders, as they are ongoing and can last from the point of onset until death. For patients with severe TMJ disorders, the gold standard of care is to undergo total joint replacement of the TMJ. This solution is highly invasive and is a procedure that often is performed due to osteoarthritis (OA) development within the joint. Often, OA originates from sustained damage over time to the TMJ disc, a fibrocartilage tissue that articulates between the mandible and the skull. Moderate to severe cases of TMJ disc degeneration can be treated with grafting materials to replace the disc or to arthroscopic disc repositioning. However, there is a lack of long-term consistency with the outcomes of these solutions. The aim of this work was to develop an artificial TMJ disc replacement for patients with severely damaged TMJ discs. This objective was pursued to preserve the integrity and joint structure of the TMJ to avoid progression towards OA. Therefore, a composite hydrogel was developed and formed around a scaffold to create a synthetic TMJ disc implant. This work was focused around three specific aims to assist with creating a mechanically robust hydrogel implant. The first aim was centered around creating a hydrogel material that could match the mechanical properties of the TMJ disc. An annealed composite hydrogels material was developed and evaluated through mechanical tests. These tests included tensile, compressive, wear, and chemical analyses to better understand the structure and behavior of the material. For the second aim, an implant design and surgical attachment strategy was developed with the aid of veterinary and human orofacial surgeons. A condyle drill guide was developed for assisting the surgeons during the attachment of the implant. The implant was then tested inside of a chewing simulator device to simulate the potential failure modes that could occur in an in vivo animal study. The third and final aim was to evaluate the implant in a pilot animal study. The behavior, weight, and overall health of the animal was monitored throughout the study. Once the animal was sacrificed, the implant and TMJ health were assessed via macroscopic scoring, biomechanics, micro-computed tomography, histology, and histopathology.