Micromotions in the primary fixation of cementless femoral stem prostheses.

Thirty cementless femoral stems of six different types of hip endoprostheses were implanted in femurs taken at autopsy and underwent static loading and afterwards dynamic loading of 50,000 cycles to simulate walking during the early months after implantation. After that, the static load tests were performed again. During both static load series a certain amount of micromotion between stem and implantation bed occurred in the frontal and sagittal planes and also during rotation. The six prostheses exhibited clearly differing results. The influence of dynamic load on the extent of micromotion was small.