Finite Element Analysis of Contact Stress Distribution on Insert Conformity Design of Total Knee Arthroplasty

The tibial insert conformity is one of the essential parameters concerned with the contact stress distribution of biomechanics characteristics in total knee arthroplasty (TKA). This study aimed to evaluate the effect of tibial insert conformity design on contact stress distribution using Finite Element (FE) analysis. The three-dimensional (3D) FE model of the posterior stabilized type of TKA was analyzed according to the standard knee implant loading. The 3k factorial experimental design was performed for the response surface of different insert curvatures consisting of the curve, partial flat, and flat insert conformity in sagittal and coronal planes. According to the result, the coronal and sagittal plane conformity displayed the effect of the change on the contact stress, including the contact area for the flexion angle of the knee joint. The maximum contact stress increased while the contact area value decreased during the flexion angle of the knee joints raised. The changing insert conformity value in the sagittal plane displayed higher sensitivity to contact stress than the changing conformity in the coronal plane. The relationship between the contact stress and tibial insert conformity under knee flexion angle indicates highly regression suitable for the prediction. In addition, the FE simulation result was then verified by compared to mechanical testing using the Fujifilm technique. The result of FE analysis exhibited similar to that of the mechanical test. The study indicated that the different geometric designs of the insert conformity played a crucial role that influenced and relationship to the contact stress of TK

Morphometric Analysis and Three-Dimensional Computed Tomography Reconstruction of Thai Distal Femur

This study evaluates the distal femur morphology of the Thai population using a three-dimensional (3D) measurement method, measuring the distance between the triangular point of the femoral 3D model. The 3D model of 360 Thai femoral obtained from 180 volunteers (90 males, 90 females; range 20–50 years, average 32.8 years) was created using reverse engineering techniques from computed tomography imaging data. Using the 3D identified landmark method, the morphometric parameters evaluated included transepicondylar axis length (TEA), mediolateral length (ML), anteroposterior width (AP), medial anteroposterior width (MAP), lateral anteroposterior width (LAP), medial condyle width (MCW), lateral condyle width (LCW), intercondylar notch width (WIN), intercondylar notch depth (DIN), medial posterior condyle height (MPC), lateral posterior condyle height (LPC), femoral aspect ratio (ML/AP), lateral femoral aspect ratio (ML/LAP), and medial femoral aspect ratio (ML/MAP). The measured data were summarized for the analysis of an average value and standard deviation. Statistical analysis was performed using the independent samples t-test, unequal variances t-test, and linear regression. A p-value less than 0.05 (<0.05) was regarded as statistically significant and indicates strong evidence of the hypothesis. Additionally, the K-means clustering analysis of Thai distal femoral to the optimum size of the prosthesis with the correlation between ML length and AP width was performed. The results found that the morphometric parameters of the Thai male distal femur were significantly different and higher than those of Thai females, except for the ratio of ML/AP and ML/MAP. Comparatively, there was a significant difference between the specific size of Thai distal femur and that of the Korean population, which was also smaller than that for Caucasians. In addition, there was a mismatch between the distal femoral component sizing of knee prosthesis and what is available and commonly used in Thailand. At least six sizes of ML and/or AP should be recommended for the reasonable design of distal femoral prosthesis for covering the anatomy of Thais. These data are useful for predicting the morphometric parameters in forensic anthropology and provide basic data for the design of knee prostheses suitable for the Thai population