Date of Award
Master of Science (MS)
Biomaterials and Regenerative Technology
William M. Mihalko, PhD
Erno I. Lindner, DSc.; Richard A. Smith, PhD
Cellular Corrosion, CoCrMo, TiAlV, TKA, TKA Alloys, TKA Pain
Introduction. Total knee arthroplasty (TKA) is a common surgical procedure used to treat end-stage osteoarthritis. The implants used in TKA typically consist of a Cobalt Chromium Molybdenum (CoCrMo) femoral component and a Titanium Aluminum Vanadium (TiAlV) alloy baseplate. These metal alloys are chosen for their mechanical properties, corrosion resistance, high affinity for bone, and biocompatibility. However, they can be susceptible to mechanical and electrochemical wear, leading to the release of metal ions. Osteoarthritis and inflammation can alter the composition of Synovial Fluid (SF), potentially causing implant corrosion and the release of metal ions into the surrounding tissue. These metal ions can trigger innate and adaptive responses, further enhancing implant corrosion. As the number of primary TKA (PTKA) procedures increases, the incidence of revision surgeries due to implant failure is also expected to rise. Approximately 20% of TKA recipients report dissatisfaction after surgery. To reduce this number, it is crucial to investigate the modes of failure in TKA and their correlation with patient quality of life.
Methodology.The study employed a methodology to examine the effects of SF on orthopedic implant alloys. SF samples were collected from patients before their TKA surgery (IRB approval number: 16-04802-XP and 21-08403-XP) and transferred to an electrochemical cell (Bioanalytical Systems, Inc.), in which the metal alloy electrodes served as working electrodes. To obtain the corrosion rates of TiAlV and CoCrMo alloys in each patient SF, passivated rods of ASTM F1537 CoCrMo and ASTM F136 TiAlV alloys were used. The volumes and pH of the collected SF samples were recorded with the electrochemical potential of the metal alloy electrodes in the SF samples against an Ag|AgCl|3M NaCl reference electrode. Patients were contacted 3 months post-op to answer the KOOSJR (Knee injury and Osteoarthritis Outcome Score, Joint Replacement) survey to assess their knee pain, stiffness, and function. After electrochemical testing, samples were stored at -80 °C until the metal ion content in the individual SF samples was determined. To determine the effects of the innate and adaptive responses in vitro on orthopaedic implant metal, IC-21 murine macrophages and D10.G4.1 murine lymphocytes were cultured. Select groups of macrophages were activated using Interferon Gamma (IFNγ) and Lipopolysaccharide (LPS). CoCrMo and TiAlV alloy disks were cut, polished, passivated, and placed into 24 well plates. After seeding the cells, the culture medium was replaced every 24 hours, and the supernatant fluid was collected every day starting on the second day of the experiment. After 30 days, cells were removed from the surface of the alloy specimens, counted, tested for viability, and digested. The metal concentrations found in the supernatant and digested cell mixture were assessed using inductively coupled plasma spectrometry (ICP-MS), conducted at Brooks Applied Labs (Bothwell, WA). The oxygen (oxide) levels on the metal alloy specimen surfaces were determined as percent weight using Scanning Electron Microscopy and Energy Dispersion X-ray Spectroscopy (SEM-EDS). Statistical analysis was conducted using Microsoft Excel (Microsoft, Redmond, WA) and IBM SPSS (Armonk, NY).
Results. The open circuit potential (OCP) values ranged from -0.274 to 0.123 V and -0.322 to 0.027 V for CoCrMo and TiAlV respectively. However, no significant association was found between the electrochemical parameters and the KOOSJR scores, indicating no direct correlation between corrosion rates and patient-reported outcomes. The SF volume was found to be a significant factor, with patients having greater SF volumes exhibiting higher KOOSJR scores. Patients with greater than 2 mL SF volumes had significantly higher KOOSJR scores than those who had less than 2 mL SF (p = 0.004). All patients with higher SF pH values (pH values ranged from 7.09 to 8.5) had smaller SF volumes (p < 0.05). Patients with CoCrMo implants and higher pH values had lower OCP (p = 0.002), Rp (p = 0.013), and Ecorr (p = 0.012) values but higher corrosion rates (p = 0.03). No similar relationships were found for patients' SFs with TiAlV alloy implants. No differences in cell counts were found. The macrophages and supernatant were sent for ICPMS (Inductively Coupled Plasma Spectrometry) testing to determine their metal ion concentration. Activated MO + Disks in both alloy groups had elevated metal content compared to non-activated MO + Disk groups. The Activated MO + lymphocytes + Disks had lower metal ion levels compared to Nonactivated MO + lymphocytes + Disks groups for CoCrMo groups and TiAlV groups. Ti, Al, Cr, and Mo metal concentration in the supernatants of the compared groups were the same but Co metal ion levels were significantly higher in Activated + MO + TiAlV disks (p = 0.004) and Nonactivated + MO + TiAlV disks (p = 0.007) groups compared to their control groups (Activated + MO + no disks and Nonactivated + MO + no disks respectively). V metal ion levels were significantly higher in Activated + MO + TiAlV disks (p = 0.007) and Nonactivated + MO + TiAlV disks (p = 0.026) groups compared to their control groups (Activated + MO + no disks and Nonactivated + MO + no disks respectively). SEM (Scanning Electron Microscopy) imaging was used to analyze the surface of the CoCrMo and TiAlV disks. Features with the size of inflammatory cells were identified as valleys. The possibility that these features were the result of the sanding process could be excluded, as the “streaks” crossed in a different direction. Oxide levels were analyzed to detect corrosion for CoCrMo and TiAlV groups with EDS (Energy Dispersive X-ray Spectrometry) SE (Secondary Electron). The Disks + Non-Activated Medium groups for both CoCrMo and TiAlV had significantly higher oxide levels compared to all other groups (p< 0.001). The Activated MO + Lymphocytes + CoCrMo disks group had significantly higher oxide levels than the Nonactivated MO + CoCrMo disks and Activated MO + CoCrMo groups.
Conclusions. In conclusion, this study aimed to investigate the electrochemical properties of SF in relation to CoCrMo and TiAlV orthopedic alloy implants and their impact on patient-reported outcomes. The findings contribute to understanding the processes that lead to patient pain and TKA failure. Further research is ongoing to enroll more patients and assess their outcomes up to a year after surgery, aiming to identify protocols that can improve patient satisfaction. The study also explored the effects of macrophages and lymphocytes on the corrosion mechanisms of the implant surfaces, which is essential for reducing the burden on patients and preventing complications such as ALVAL.
Phan, Lisa (https://orcid.org/0000-0002-8070-298X), "The Effects of Synovial Fluid and Inflammatory Cells on Orthopaedic Implant Alloys" (2023). Theses and Dissertations (ETD). Paper 645. http://dx.doi.org/10.21007/etd.cghs.2023.0632.