Three-Dimensional Measurement and Cluster Analysis for Determining the Size Ranges of Chinese Temporomandibular Joint Replacement Prosthesis

The aim of this study was to investigate the osseous characteristics of Chinese temporomandibular joint (TMJ) and detect the size clusters for total joint prostheses design. Computer tomography (CT) data from 448 Chinese adults (226 male and 222 female, aged from 20 to 83 years, mean age 39.3 years) with 896 normal TMJs were chosen from the Department of Radiology in the Shanghai 9th People's Hospital. Proplan CMF 1.4 software was used to reconstruct the skulls. Three-dimensional (3D) measurements of the TMJ fossa and condyle-ramus units with 13 parameters were performed. Size clusters for prostheses design were determined by hierarchical cluster analyses, nonhierarchical (K-means) cluster analysis, and discriminant analysis. The glenoid fossa was grouped into 3 clusters, and the condyle-ramus units were grouped into 4 clusters. Discriminant analyses were capable of correctly classifying 97.24% of the glenoid fossa and 94.98% of the condyle-ramus units. The means and standard deviations for the parameter values in each cluster were determined. Fossa depth and angles between the condyle and ramus were important parameters for Chinese TMJ prostheses design. 3D measurements and cluster analysis of the osseous morphology of the TMJ provided an anatomical reference and identified the dimensions of the minimum numbers of prosthesis sizes required for Chinese TMJ replacement.