Micromotion affected by taper and neck design

Fretting corrosion has emerged as one important reason for failure of modular hip prostheses during the last decade. This increase might be associated with the reduction of the taper diameter to improve the range of motion of the hip joint, which occurred about 20 years ago. The magnitude of the micromotion at the taper junction is an important factor for the risk of fretting, which is speculated to occur with thinner tapers due to larger differences of the bending stiffness between the prosthesis head and stem. This study investigates how micromotion is affected by taper diameters and neck geometries. Less rigid tapers are shown to lead to increased micromotion between the head and stem, enlarging the risk for fretting corrosion. The influence of the neck design on micromotion appears to be small.