EFFECT OF MODULAR HEAD SEATING ON THE CEMENT-STEM INTERFACE STRENGTH OF FEMORAL PROSTHESES

This study tested the hypothesis that modular head seating in situ red uces the cement-stem interfacial strength. Femoral prostheses were imp lanted in eight pairs of cadaveric femurs; one femur of each pair rece ived a stem for which the modular head was seated by dropping a weight from a given height (treated); the contralateral femur received a non seated stem (control). Transverse sections were cut from four standard ized locations on each implanted femur, and the yield shear stress and ultimate shear stress of the interface were determined from push-out tests. There was no significant difference in cement-stem interfacial strength between seated and nonseated prostheses. These results sugges t that seating modular heads in situ has no deleterious effect on the acute interfacial strength of cemented femoral implants.