Hard-on-hard lubrication in the artificial hip under dynamic loading conditions

• Published in: PloS one 2013-08, Vol.8 (8), p.e71622-e71622
• Main Authors: Sonntag, Robert, Reinders, Jörn, Rieger, Johannes S, Heitzmann, Daniel W W, Kretzer, J Philippe
• Format: Article
• Language: English
• Subjects: Analysis; Bearings; Biomechanical Phenomena; Biomechanics; Biomedical materials; Ceramics - chemistry; Debris; Elastohydrodynamic lubrication; Engineering; Equipment Failure Analysis; Experimental data; Female; Fluid; Fluids; Friction; Gait; Hip; Hip joint; Hip Prosthesis; Hip replacement arthroplasty; Humans; Joint surgery; Kinematics; Laboratories; Load; Loosening; Lubrication; Male; Materials Science; Materials Testing; Mathematical models; Mechanical loading; Medicine; Metals; Metals - chemistry; Models, Biological; Numerical models; Orthopedics; Particulate matter; Physiology; Pressure distribution; Prostheses and implants; Prosthesis Design; Steady state models; Studies; Surface Properties; Surgery; Surgical implants; Tribology; Walking; Wear particles
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0071622

The tribological performance of an artificial hip joint has a particularly strong influence on its success. The principle causes for failure are adverse short- and long-term reactions to wear debris and high frictional torque in the case of poor lubrication that may cause loosening of the implant. Therefore, using experimental and theoretical approaches models have been developed to evaluate lubrication under standardized conditions. A steady-state numerical model has been extended with dynamic experimental data for hard-on-hard bearings used in total hip replacements to verify the tribological relevance of the ISO 14242-1 gait cycle in comparison to experimental data from the Orthoload database and instrumented gait analysis for three additional loading conditions: normal walking, climbing stairs and descending stairs. Ceramic-on-ceramic bearing partners show superior lubrication potential compared to hard-on-hard bearings that work with at least one articulating metal component. Lubrication regimes during the investigated activities are shown to strongly depend on the kinematics and loading conditions. The outcome from the ISO gait is not fully confirmed by the normal walking data and more challenging conditions show evidence of inferior lubrication. These findings may help to explain the differences between the in vitro predictions using the ISO gait cycle and the clinical outcome of some hard-on-hard bearings, e.g., using metal-on-metal.