Does mechanical vibration optimize macro interlock in cemented arthroplasty?

Background Cemented total hip replacement has a high success rate. However, failure is still a problem, and the major reason for failure is aseptic loosening. Current surgical methods to insert prosthetic stems into a cement filled bone cavity are purely manual. Our hypothesis was that the use of vibration can improve the quality of cement interdigitation for implantation of the femoral component in cemented total hip replacement. Methods We investigated the effect that mechanical vibration during insertion has on the area of interlock of the cement with the bone, the depth of cement penetration and the required insertion force. A reusable mold was used to simulate the femoral cavity and enabled quantification of these parameters under vibrated and nonvibrated conditions. Results Our results showed that the area of interlock of cement and mold together was increased by 2.25%, and the force required to insert the stem was decreased by around 30N when the stem was vibrated at a frequency of 36 Hz and an amplitude of 2mm. Conclusion Our results indicated that vibration of the femoral stem has a beneficial effect on the cement-bone interface and that vibrating the prosthesis during insertion into the cement significantly lowers the force needed for insertion.