title: An experimental study to investigate biomechanical aspects of the initial stability of press-fit implants.
abstract: Initial fixation of press-fit implants depends on interference fit, surface morphology, and bone material properties. To understand the biomechanical effect of each factor and their interactions, the pull-out strength of seven types of CoCrMo tapered implants, with four different interference fits, three different surface morphologies (low, medium and high roughness), and at two time points (0 and 30 min) were tested in trabecular bone with varying density. The effect of interference fit on pull-out strength depended on the surface morphology and time. In contrast with our expectations, samples with a higher roughness had a lower pull-out strength. We found a similar magnitude of bone damage for the different surface morphologies, but the type of damage was different, with bone compaction versus bone abrasion for low and high frictional surfaces, respectively. This explains a reduced sensitivity of fixation strength to bone mineral density in the latter group. In addition, a reduction in fixation strength after a waiting period only occurred for the low frictional specimens. Our study demonstrates that it is essential to evaluate the interplay between different factors and emphasizes the importance of testing in natural bone in order to optimize the initial stability of press-fit implants.
authors.affiliation: Radboud university medical center, Radboud Institute for Health Sciences, Orthopaedic Research Lab, PO Box 9101, 6500 HB Nijmegen, The Netherlands. Electronic address: sanaz.berahmani@radboudumc.nl.
authors.forename: Sanaz
authors.initials: S
authors.lastname: Berahmani
authors.affiliation: Radboud university medical center, Radboud Institute for Health Sciences, Orthopaedic Research Lab, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Dennis
authors.initials: D
authors.lastname: Janssen
authors.affiliation: Radboud university medical center, Radboud Institute for Health Sciences, Orthopaedic Research Lab, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Sal
authors.initials: S
authors.lastname: van Kessel
authors.affiliation: DePuy Synthes Joint Reconstruction, LS11 0BG Leeds, UK.
authors.forename: David
authors.initials: D
authors.lastname: Wolfson
authors.affiliation: Radboud university medical center, Radboud Institute for Health Sciences, Department of Orthopaedics, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Maarten
authors.initials: M
authors.lastname: de Waal Malefijt
authors.affiliation: Radboud university medical center, Radboud Institute for Health Sciences, Orthopaedic Research Lab, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Pieter
authors.initials: P
authors.lastname: Buma
authors.affiliation: Radboud university medical center, Radboud Institute for Health Sciences, Orthopaedic Research Lab, PO Box 9101, 6500 HB Nijmegen, The Netherlands; Laboratory of Biomechanical Engineering, University of Twente, Enschede, The Netherlands.
authors.forename: Nico
authors.initials: N
authors.lastname: Verdonschot
mesh_terms: D001696:Biomechanical Phenomena; D015519:Bone Density; D005269:Femur / Q000502:physiology; D017276:Friction; D006801:Humans; D055595:Mechanical Phenomena; D019736:Prostheses and Implants