Original Research
Initial Stability of Press-Fit Acetabular Components: An In Vitro Biomechanical Study
Am J Orthop. 2008 October;37(10):519-522
Author and Disclosure Information
Khaled J. Saleh, MD, MSc, FRCSC, Brian Bear, MD, Mathias Bostrom, MD, Timothy Wright, PhD, and Thomas P. Sculco, MD
Dr. Saleh is Professor, Departments of Orthopaedic Surgery & Public Health Sciences, and Division Head and Fellowship Director, Adult Reconstruction, University of Virginia Health System, Charlottesville, Virginia.
Dr. Bear is Clinical Assistant Professor, University of Illinois College of Medicine, Rockford, Illinois, and is with Rockford Orthopedic Associates, Rockford, Illinois.
Dr. Bostrom is Attending Orthopaedic Surgeon, Hospital for Special Surgery, New York, New York, and Professor of Orthopaedic Surgery, Weill Medical College of Cornell University, New York, New York.
Dr. Wright is Senior Scientist, Hospital for Special Surgery, New York, New York, and Professor of Applied Biomechanics, Department of Orthopaedics, Weill Medical College of Cornell University, New York, New York.
Dr. Sculco is Surgeon-in-Chief, Hospital for Special Surgery, New York, New York, and Professor of Orthopaedic Surgery, Weill Medical College of Cornell University, New York, New York.
Component shape, surface finish, and presence of holes for adjuvant screw fixation should all affect initial stability and hence long-term fixation of total hip acetabular components. We conducted a study to determine stability against edge loading and torsion in commercial implants that differed in these design variables. Components were seated into synthetic cancellous bone blocks, and loads and insertion energies necessary to seat the components were measured. Components were then edge-loaded or twisted to failure. Compared with several hemispherical components, an elliptical component without holes and sintered beads had significantly more stability under both loading conditions. The presence of more holes in hemispherical components significantly improved stability in edge loading but not in torsion. Finally, plasma-spray and small-bead coatings showed improved stability compared with fiber-mesh and large-bead coatings.