Surface roughness of retrieved CoCrMo alloy femoral components from PCA artificial total knee joints

Abstract

In this study, we analyzed the surface roughness of retrieved cobalt-chromium-molybdenum (CoCrMo) femoral components of porous coated anatomic (PCA) artificial total knee joints, using a white light interference surface profilometer (WLISP). Thirty-eight PCA retrieved specimens obtained from the Anderson Clinic (Arlington, VA) were used. The artificial knees were originally implanted between 1982-1993, and the specimens were retrieved during revision surgeries between 1988-1996. We examined specimens damaged by three wear modes: femoral component against the ultra high molecular weight polyethylene (UHMWPE) articular surface (mode I), femoral component against the metal tibial tray (because of UHMWPE tibial component wear-through) (mode II), and femoral component against metal-debris-embedded-UHMWPE (with metal debris from the porous coating) (mode III). The mean surface roughness of each femoral component was the average of 80 surface roughness measurements. The in vivo alloy femoral component surfaces were rougher by an order of magnitude over controls, and the alloy surfaces were predominantly worn by the formation of parallel scratches in the direction of articulation. There was no correlation between the surface roughness of the femoral components and patient age, sex, weight, and total time of implantation. Significant surface roughness increases accompanied mode II and mode III wear. Different carbide morphologies were found on different femoral component surfaces, indicating that a variety of sintering processes, with different times and temperatures, may have been applied to the alloy femoral components during manufacture. Metal component roughness may be important to the wear of UHMWPE components and the success of total artificial knee joint.

Wear in total knee arthroplasty—just a question of polyethylene?

“…Due to these aspects the promotion of full fluid film lubrication and therefore a wear reduction should not be expected in PE articulations. Clinically, metallic wear in metal-PE articulations has been attributed to third bodies such as bone cement or bone particles [14]. However, in this simulator study these types of third bodies were not present.…”

“…Total knee arthroplasty implants present large metal surface areas, which could lead to metal ion release due to corrosion processes. Furthermore, explanted femoral components show abrasive wear in the form of scratches on the metallic surfaces [14]. It must therefore be expected that TKA leads to an increasing release of metal wear products.…”

Oxidized Zirconium versus Cobalt-Chromium in TKA: Profilometry of Retrieved Femoral Components

“…Similar studies showed that CoCr retrievals were an order of magnitude rougher than pristine controls [25]. This roughening might explain why UHMWPE inserts paired with CoCr exhibit more surface damage than those paired with OxZr [12] and produce less UHMWPE wear in in vitro studies [4,15,27].…”

“…Sixty measurements (four rows of 15 points, each point covering 600 9 800 lm of the component's bearing surface) were taken per condyle, approximately at the location of contact during 308 of flexion (Fig. 2) as suggested by Que et al [24,25]. One pristine, unimplanted OxZr and one pristine CoCr component were measured to provide an estimate of the initial roughness before implantation.…”

“…In the current study, we limited our selection of retrieved femoral implants to a single design and manufacturer to focus the comparison between implants based primarily on the bearing material: OxZr versus CoCr. We used three-dimensional surface profilometry, a highly accurate technique used in previous studies of CoCr components [19,[23][24][25], to provide objective measurements of the surface roughness of the components.…”