Date of Award
Master of Science (MS)
William M. Mihalko, MD, PhD
Denis J. DiAngelo, PhD; Richard A. Smith, PhD
Introduction. Total joint arthroplasty is considered one of the most beneficial aspects of modern orthopedic surgery. Due to the increase in population, obesity rates, and medical advances, total joint replacements have become more commonplace in the United States. Recently, a unique type of damage has been investigated in cobalt-chrome (CoCr) implants that remains poorly understood and highly controversial. Originally, it was believed that this damage type was caused by inflammatory cells directly attacking the metal surface, leading to damage of the oxide layer. However, damage caused by electrocautery tools has shown identical characteristics, leading some to believe this is the true cause. This study aims to distinguish between these two damage mechanisms and investigate the biological response of inflammatory cells to common orthopaedic metal alloys.Methods. Following institution review board approval, 41 Cobalt-Chromium-Molybdenum (CoCrMo) cadaveric primary total knee arthroplasty specimens were collected. After removal and cleaning, light microscopy was utilized to identify areas of ICIC-like damage scares. CoCrMo, zirconium nitride (ZrN)coated, and Oxinium knee implants were intentionally damaged by electrocautery from both Bovie and Aquamantys sources by a three second hover method. Bovie electrocautery damage was done at 30W, 45W, and 60W. Aquamantys electrocautery damage was done at 140W, 180W, and 220W. Using a scanning electron microscope 20 kV backscatter detection (BSD), and energy dispersive X-ray spectrometry (EDS) (Oxford, High Wycombe, UK) corroded regions were analyzed for both groups and the elemental compositions were reported. White light interferometry was utilized to examine the surface topography of the implants. Average roughness (Ra), max peak-to-valley height (Rmax,), kurtosis (Rk), and skewness (Rsk) measurements were collected to represent the topography on the damaged areas for the CoCr and Zirconium Nitride coated implants. After failing normality testing, Mann Whitney Rank Sum tests were utilized to determine any significant differences.In a separate experiment, IC-21 ATCC peritoneal macrophages were cultured with growth medium of RPMI 1640 with 10% fetal bovine serum (FBS), L-glutamine, and gentamicin. Interferon Gamma (IFNγ) and Lipopolysaccharide (LPS) were used to induce activation of macrophages. Stainless Steel, CoCr, and Titanium (Ti) discs were cut, polished, and placed into a 96 well plate. Stainless steel testing included 6 groups: standard medium, 20,000 cells, 40,000 cells, 20,000 activated cells, 40,000 activated cells. CoCr and Ti testing included the following: medium, 40,000 cells, 20,000 activated cells, cells, no disc + 20,000 cells, no disc + 40,000 cells. After cells were attached to the surface, culture medium was replaced and collected every 24 hours for stainless steel and every 12 hours for Ti and CoCr. Cell viability and number were measured with CellTiter 96® Aqueous One Solution Assay (Promega). The Griess Reagent Assay (ThermoFisher) was used to indirectly measure nitric oxide (NO) production from supernatant. Inductively coupled plasma mass spectrometry (ICP-MS), conducted at Brooks Applied Labs (Bothell, WA), was utilized to determine metal concentrations found in the supernatant. All statistical analysis was conducted using SigmaPlot (Systat Software, Chicago, IL)Results. Necropsy implants showed signs of ICIC in 7 out of 41 implants (17 %) examined. Iron (Fe), Nickel (N), Carbon (C), and Oxygen (O) content were taken from the data collected to serve as surrogate markers of corrosion. Fe/C ratios of the Bovie electrocautery damaged knee implant were shown to be statistically higher than that of necropsy retrieved implants. Median Ra measurements were shown to be statistically less (p=0.008) for Bovie damaged areas compared to ICIC damaged areas on CoCr. Median Rmax and Ra measurements were shown to be statistically less (p= 0.012, p< 0.001 respectively) for Aquamantys damaged areas compared to ICIC damaged areas on CoCr. Median Rmax, Ra, and Rk, measurements were shown to be statistically higher for Bovie damaged areas compared to non-damaged areas on ZrN coated implants. Rsk measurements were shown to be statistically lower for both Bovie and Aquamantys damaged areas compared to non-damaged areas on ZrN coated implants.Activated IC-21 cells on stainless steel discs produced significantly more NO compared to their control counterparts after 8-10 days and remained elevated for the duration of the experiment. Cell viability and cell coun
Heise, Griffin (https://orcid.org/0000-0002-3767-0468), "Cellular Corrosion of CoCrMo Total Knee Implants: Understanding Underlying Mechanisms Through Retrieval Analysis and Simulated Inflammatory Conditions" (2019). Theses and Dissertations (ETD). Paper 502. http://dx.doi.org/10.21007/etd.cghs.2019.0487.
Available for download on Monday, October 26, 2020