On the Roughness Measurement on Knee Prostheses

Abstract

The majority of total knee replacements currently implanted present an articulation composed of two metal parts, femoral and tibial components, between which there is a polyethylene insert serving as a bearing surface. The finishing surface of the metal components is a very important factor in minimizing the polyethylene wear rate and, later, the gradual production of metal and plastic debris. Considering the role of surface roughness on volumetric wear rates, the purpose of this study is to develop a protocol for the roughness characterization of total knee prosthesis (TKP) metal components, taking into consideration a limited number of points on each surface. Six mobile TKP of different sizes (three size 2 and three size 6) were tested on a knee joint simulator to compare the wear behavior of each group. After 2 million cycles the weight loss by the polyethylene inserts was measured with gravimetric method and the surface roughness of the metallic components was assessed in terms of average surface roughness, Ra, skewness, Rsk, and total roughness, Rt. Roughness measurement involved 29 points on each femoral condyle and 26 points on each metal tibial plate. The data collected has shown an increased roughness upon wear testing for both the investigated TKP sizes. No statistical differences were observed between the two groups for both the parameters Ra, Rsk, and Rt. The surface of all metallic components became more negatively skewed, indicating diminishing peaks. The various parameters were correlated to the volumetric loss using a linear regression analysis.

A Critical Analysis of TKR In Vitro Wear Tests Considering Predicted Knee Joint Loads

“…Before measurements, all components were cleaned with acetone (A.C.E.F., Piacenza, Italy). Ra, Rt, and Rsk were quantified as roughness indicators in agreement with previous studies [6,33]. Ra is the arithmetic average value of the deviations of the roughness profile filtered from the mean line into the sampling length (DIN 4768, ISO 4287), while Rsk is the skewness of the profile and indicates the symmetry of the profile.…”

“…Ideally, the preclinical endurance testing should reproduce on the artificial implants the in vivo conditions of load and motion experimented by the human joint in order to assess the wear of prosthetic components and give information about materials and design optimization for prosthetic implants. The research in this field has been going on for many years [3,4] and is still strongly active in order to further increase the service life of TKRs, as evidenced by the many studies [5,6,7]. At the state of the art, two simulation concepts for the knee joint are available and defined by the International Organization for Standardization (ISO) 14243-1/3 standards: the force control (FC) and the displacement control (DC) [8,9].…”

Tribo-mechanical characterization of reinforced epoxy resin under dry and lubricated contact conditions

“…Fiber Reinforced Polymer (FRP) are widely used in applications with interacting surfaces in relative motion such as seals, gears and dry slide bearing materials1 [1e3], as well as orthopaedic prostheses [4]. In this context, determining the mechanical and tribological behavior of involved components is a key factor.…”

Análisis y modelizado del comportamiento dinámico de articulaciones humanas mediante la caracterización metrológica y tribológica de sus superficies

“…Para evaluar el volumen de desgaste las superficies de las esferas se convirtieron en superficies planas (utilizando el software del equipo óptico), lo que permitió convertir la tapa de la esfera en un cráter de desgaste. Los parámetros de rugosidad elegidos fueron Ra y Rq que describen la morfología de la superficie desgastada [61], [191].…”

“…Actualmente, los implantes quirúrgicos de cadera y de rodilla se someten a degradación después de 10-15 años de uso [55]. A medida que se va prolongando la vida útil de las articulaciones artificiales, los mecanismos de lubricación, de fricción y desgaste en las articulaciones humanas y en implantes protésicos han sido abordados por muchos autores [56]- [61] debido a su importancia en el rendimiento de estos dispositivos. Por lo tanto, el desgaste del polietileno (UHMWPE) ha sido uno de los factores limitantes para el éxito, a largo plazo, de trasplante de rodilla (TKR) [62].…”