Study of The Effect of Model Geometry and Body Mass Index on The Elastohydrodynamic Lubrication Performance of Metal-on-Metal Hip Joints

This study aims to provide benefits on the manufacturing side in considering design parameters for optimization of total hip arthroplasty based on body mass index (BMI) categories. The femoral and cup geometries in Total Hip Arthoplasty (THA) are modeled in a simple ball-on-plane form to analyze the pressure and thickness of the lubricant film in the elastohydrodynamic lubrication of artificial hip joints with vertical loads and parameters based on body mass index using the finite element method. The factor of being overweight is one of the causes of increasing the maximum load during activities. This study applies a maximum load based on BMI which is divided into two categories, namely normal and high BMI to obtain the distribution of contact pressure and fluid pressure on the bearing surfaces that are in contact with each other so that the thickness of the lubricating film formed can be determined. Validation of contact pressure and film thickness was carried out. The femoral head sizes applied were 24mm and 28mm with a radial clearance of 15μm, 30μm and 100μm using CoCrMo metal material. From the simulation the load at high BMI shows an increase by a large enough difference reaching 16.89MPa at contact pressure, 19.88MPa at fluid pressure and 0.004μm at the thickness of the lubricant film compared to normal BMI. This simple modeling provides the benefit of analyzing the effect of body mass index on tribological THA performance and can help reduce the growth rate of THA implantation failure revision surgery.