Evolutionary Steps in the Development of a Patient-specific Temporomandibular Joint Prosthesis

Abstract

Study design: Descriptive study (/review containing supporting case studies). Objective: The temporomandibular joint has some distinctive features that were not taken into account during the initial development of temporomandibular joint prostheses, such as laterotrusive movements that are necessary for the proper grinding of food as well as synchronous and congruent movements made in conjunction with the healthy, contralateral joint. The aim of this article is to describe the development of a novel type of TMJ prosthesis that optimizes temporomandibular joint replacement. Methods: The development was initiated by using contemporary technologies like computer-aided design customization, additive manufacturing, and surface treatments. Biocompatibility, proper fixation, and wear resistance, being prerequisites for the longevity of prostheses, were investigated next. Individual variables (condylar path, condylar axis angle, Bennet shift) were introduced as the main basis for physiological movements with the restoration of all functions. Early post-operative results ranging from 1 month to 4.5 years (11 patients, average follow-up period was 23.3 months) were assessed. Results: The experience with 16 individualized total joint replacements in 11 patients is presented. The 1-year and 3-year follow-up results of two-patient detailed studies are discussed, which show evidence of the promising restoration of all mandibular movements, when preoperatively present. Conclusions: By incorporating various innovative and novel features (scaffold for re-attachment of lateral pterygoid, patient-specific functional parametrization, saddle-like design for retention, …) into a novel TMJ prosthesis concept, a major advance in function-reconstructive temporomandibular joint replacement was achieved. Early in vivo results (1 year after surgery) showed promising outcomes, involving both high increases in mandibular movements and decreases in pain scores.