title: Calcium phosphate cement augmentation of cancellous bone screws can compensate for the absence of cortical fixation.
abstract: An obvious means to improve the fixation of a cancellous bone screw is to augment the surrounding bone with cement. Previous studies have shown that bone augmentation with Calcium Phosphate (CaP) cement significantly improves screw fixation. Nevertheless, quantitative data about the optimal distribution of CaP cement is not available. The present study aims to show the effect of cement distribution on the screw fixation strength for various cortical thicknesses and to determine the conditions at which cement augmentation can compensate for the absence of cortical fixation in osteoporotic bone. In this study, artificial bone materials were used to mimic osteoporotic cancellous bone and cortical bone of varying thickness. These bone constructs were used to test the fixation strength of cancellous bone screws in different cortical thicknesses and different cement augmentation depths. The cement distribution was measured with microCT. The maximum pullout force was measured experimentally. The microCT analysis revealed a pseudo-conic shape distribution of the cement around the screws. While the maximum pullout strength of the screws in the artificial bone only was 30±7N, it could increase up to approximately 1000N under optimal conditions. Cement augmentation significantly increased pullout force in all cases. The effect of cortical thickness on pullout force was reduced with increased cement augmentation depth. Indeed, cement augmentation without cortical fixation increased pullout forces over that of screws without cement augmentation but with cortical fixation. Since cement augmentation significantly increased pullout force in all cases, we conclude that the loss of cortical fixation can be compensated by cement augmentation.
authors: Laboratory of Biomechanical Orthopedics, Institute of Bioengineering, EPFL, EPFL/STI/IBI/LBO, Station 15, 1015 Lausanne, Switzerland.
authors: Vincent A
authors: VA
authors: Stadelmann
authors: Elise
authors: E
authors: Bretton
authors: Alexandre
authors: A
authors: Terrier
authors: Philip
authors: P
authors: Procter
authors: Dominique P
authors: DP
authors: Pioletti
mesh_terms: D001696:Biomechanical Phenomena; D001843:Bone Cements; D001863:Bone Screws; D018786:Bone Substitutes; D002130:Calcium Phosphates; D019544:Equipment Failure Analysis; D005593:Fracture Fixation, Internal / Q000379:methods*; D006801:Humans; D066298:In Vitro Techniques; D016268:Internal Fixators; D008422:Materials Testing; D010024:Osteoporosis / Q000503:physiopathology / Q000601:surgery; D011475:Prosthesis Failure; D055114:X-Ray Microtomography
chemical_list: D001843:Bone Cements; D018786:Bone Substitutes; D002130:Calcium Phosphates; C020243:calcium phosphate