The Impact of Local Physiology on the Corrosion of Orthopedic Alloys

<p><strong>Introduction.</strong> Total knee arthroplasty (TKA) is used in the treatment of end-stage osteoarthritis of the knee. It is one of the most common elective surgeries performed with predictions expecting significant increases in the number of procedures performed over the next decade. However, the patient satisfaction rate after TKA is as low as 80%. Cobalt-chromium-molybdenum (CoCrMo) is regularly used for TKA protheses due to the alloy’s mechanical strength, biocompatibility, and corrosion resistance. The corrosion resistance of this alloy relies on a passive oxide layer. This oxide layer can be impacted by phagocytic cells which can leave pits and craters on implant surfaces in a process termed inflammatory cell-induced corrosion (ICIC). Additionally, the corrosion resistance of implant alloys can be analyzed using electrochemistry. This thesis aims to investigate the effects of local physiology on the corrosion of CoCrMo. The first study in this thesis investigates the relationship between the physical and electrochemical properties of preoperative synovial fluid (SF) and postoperative patient-reported outcomes. The second study investigates the effects of simulated wear particles on ICIC.</p> <p><strong>Methods.</strong> In the first study, SF was collected from 146 patients immediately prior to TKA (IRB approval number: 16-04802-XP and 21-08403-XP). SF volume and pH were recorded. SF was transferred into a three-electrode electrochemical cell with an ASTM F1537 CoCrMo working electrode to perform open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and linear polarization (LP) testing. The approximate instantaneous corrosion rate (1/RP) was obtained from EIS testing. The potentiodynamic curves from LP testing were used to find the corrosion potential (Ecorr) and to determine the existence of a passive region. The Knee injury and Osteoarthritis Outcome Score for Joint Replacement (KOOSJR) was obtained at 3-11 months, 1-3 years, and 3+ years. Patients self-reported knee stiffness, pain, and functionality on a scale from 0 to 100 with 100 being the optimal outcome. Spearman rank correlation tests were done to assess if there was a correlation between KOOSJR scores and volume, pH, OCP, Ecorr, and 1/RP. A Mann-Whitney test was used to determine if there was a difference between the KOOSJR scores of samples with a passive region compared to samples without a passive region. In the second study, a 30-day macrophage-lymphocyte co-culture experiment on ASTM F1537 CoCrMo disks was performed. Simulated CoCrMo wear particles were added to groups in none, low (1:10), medium (1:100), and high (1:500) cell-particle ratios. The activators interferon gamma (IFNγ) and lipopolysaccharide (LPS) were added to select groups. Supernatants were collected on days 10 and 30 to determine tissue necrosis factor alpha (TNFα) and interleukin 6 (IL-6) levels using enzyme-linked immunosorbent assays (ELISA). Cleaned disks were examined for ICIC damage features using scanning electron microscopy (SEM) and the percent weight oxygen on disk surfaces was found using energy dispersion X-ray spectroscopy (EDS). Welch’s one-way ANOVA with Dunnett’s post-hoc tests were used to compare cytokine means between groups. Kruskal-Wallis one-way ANOVA was used to determine if there were differences between the mean percent weight oxygen of groups.</p> <p><strong>Results.</strong> Patients with more synovial fluid had higher long-term KOOSJR scores (1-3 years: r=0.124, p=0.016) (3+ years: r=0.499, p=0.043). Additionally, the KOOSJR scores of patients with at least 2 mL synovial fluid were statistically higher than the scores of patients with less than 2 mL synovial fluid at 1-3 years (p=0.007) and at 3 or more years (p=0.039). No significant correlations were found between KOOSJRs and pH, OCP, Ecorr, and 1/RP. Approximately two-thirds of samples did not have a passive region. Short-term KOOSJRs were significantly higher for samples with passive regions than without passive regions (3-11 months: p=0.047). Damage consistent with previous reports of ICIC was found on most disks. However, there were no significant differences in the mean percent weight oxygen between groups (p=0.772). When compared to groups without particles, day 10 TNFα levels were higher for groups with medium and high particle concentrations, but not for groups with low particle concentrations. TNFα and IL-6 levels were higher in activated groups than non-activated groups for groups with medium and high particle concentrations. Unexpectedly, day 10 IL-6 levels were lower for groups with medium and high particle concentrations than with no particles. However, the activated group with medium particles had higher IL-6 levels than the activated group with no particles on day 30.</p> <p><strong>Conclusion.</strong> The SF study found that CoCrMo appears to exhibit active corrosion behavior in approximately two-thirds of SF samples. Patients whose SF elicited passive corrosion behavior reported better short-term patient satisfaction scores than patients whose SF elicited active corrosion behavior. Additionally, higher SF volumes at time of surgery were associated with higher long-term patient satisfaction scores. Future research will investigate the differences in SF composition which may lead to these differences in corrosion behavior and patient satisfaction. The cell culture study used an in vitro model of ICIC to investigate the effects of simulated wear particles on the cellular response and the extent of ICIC damage. The addition of simulated wear particles showed no difference in the extent of damage to the alloy surfaces. However, there were differences in the cellular response measured by TNFα and IL-6. The 30-day study may have been too short to demonstrate any differences in ICIC damage caused by the addition of simulated wear particles.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Biomedical Engineering

Year dc:date.available

2024

Author dc:creator

• Brown, Madison Nicole

Contributors dc:contributor

• William Mihalko, MD, PhD

• CoCrMo
• Electrochemistry
• Inflammatory Cell-Induced Corrosion
• Patient-Reported Outcomes
• Synovial Fluid
• Total Knee Arthroplasty
• Analytical, Diagnostic and Therapeutic Techniques and Equipment
• Diseases
• Medical Biotechnology
• Medical Physiology
• Medical Sciences
• Medical Specialties
• Medicine and Health Sciences
• Musculoskeletal Diseases
• Orthopedics
• Surgery

Repository record dc:identifier

https://dc.uthsc.edu/dissertations/688

OAI identifier oai:identifier

oai:dc.uthsc.edu:dissertations-1688