Effect of motion inputs on the wear prediction of artificial hip joints

Abstract

Hip joint simulators have been largely used to assess the wear performance of joint implants. Due to the complexity of joint movement, the motion mechanism adopted in simulators varies. The motion condition is particularly important for ultra-high molecular weight polyethylene (UHMWPE) since polyethylene wear can be substantially increased by the bearing cross-shear motion. Computational wear modelling has been improved recently for the conventional UHMWPE used in total hip joint replacements. A new polyethylene wear law is an explicit function of the contact area of the bearing and the sliding distance, and the effect of multidirectional motion on wear has been quantified by a factor, cross-shear ratio. In this study, the full simulated walking cycle condition based on a walking measurement and two simplified motions, including the ISO standard motion and a simplified ProSim hip simulator motion, were considered as the inputs for wear modelling based on the improved wear model. Both the full simulation and simplified motions generated the comparable multidirectional motion required to reproduce the physiological wear of the bearing in vivo. The predicted volumetric wear of the ProSim simulator motion and the ISO motion conditions for the walking cycle were 13% and 4% lower, respectively, than that of the measured walking condition. The maximum linear wear depths were almost the same, and the areas of the wear depth distribution were 13% and 7% lower for the ProSim simulator and the ISO condition, respectively, compared with that of the measured walking cycle motion condition.

Comparison of tribological and electrochemical properties of TiN, CrN, TiAlN and a-C:H coatings in simulated body fluid

“…The permissible amount of Cr for human body per day is about 1 mg. In this study, according to the wear rate of CrN coatings (8.81 Â 10 À7 mm 3 /Nm), the release of Cr (7.15 g/cm 3 ) is around 0.01 mg under 2N (79 MPa) and 1000 m. Thus, this amount is affordable for humans because the pressure of a hip joint is much lower, around 1 MPa [27,28]. In addition, Cr is an essential trace element for humans because it helps us to absorb glucose.…”

The Effects of Surface Mechanical Deformation and Bovine Serum Albumin on the Tribological Properties of Polyvinyl Alcohol Hydrogel as an Artificial Cartilage

“…is treatment is a practical treatment for patients with severe joint disease. Unfortunately, the complications of joint replacement are always related to tribological failure [1]. Failures in joint replacement include pain and wear of the joint material including the natural articular cartilage and the arti cial joint material [2][3][4][5].…”

Silicon Nitride Bearings for Total Joint Arthroplasty

“…Furthermore, a number of critical reviews have pointed-out the limitations of the accepted hip simulator testing standards (i.e., ISO 14242-1,3). They currently do not account for common clinically relevant conditions such as microseparation, malpositioning and edge loading, starved lubrication, and stop-motion, rest, and resume-motion sequences [111][112][113]. Each of these conditions has been shown to profoundly affect component wear and longevity.…”

“…Thermally activated dissolution of the bearing surface (or wear debris) and reformation of the tribochemical film ensued which lowered friction, until the bearing once again came to its next stop in the cycle, resulting in a repetition of stick-slip behavior. The collected data from the SWM CoC wear test provide three instructive points: (1) Frictional heating leads to serum degradation and protein precipitation on all bearing couples, which adversely affects observed weight or volumetric changes [62,111,132]. Consequently, hip simulator wear rates need to be tempered with the knowledge that bearing materials of dissimilar thermal conductivities may result in markedly different wear behavior; (2) While the standard Paul cycle is used for test expediency, continuous motion simulation does not adequately represent actual human gait [98,111,113,133].…”

“…The collected data from the SWM CoC wear test provide three instructive points: (1) Frictional heating leads to serum degradation and protein precipitation on all bearing couples, which adversely affects observed weight or volumetric changes [62,111,132]. Consequently, hip simulator wear rates need to be tempered with the knowledge that bearing materials of dissimilar thermal conductivities may result in markedly different wear behavior; (2) While the standard Paul cycle is used for test expediency, continuous motion simulation does not adequately represent actual human gait [98,111,113,133]. Alternatively, a stop-dwell-start protocol is more clinically relevant, and may more effectively discriminate between bearing materials; and, (3) Interruption of the continuous Paul cycle leads to lubrication breakdown for Si3N4 bearings, resulting in increased friction and wear.…”