Hip Instability Leading to Metallosis, Polyethylene Wear, and Failure of an Oxinium Femoral Head: A Case Report and Review of Literature

Oxinium is a zirconium metal alloy with an oxidized (ceramicized) surface that aims to mimic the superior wear properties of a ceramic femoral head while maintaining the high strength of metal-bearing surfaces. There are several reports that illustrate the wear and/or failure of Oxinium femoral heads following abnormal head contact with metal cup, with only a few studies reporting on the occurrence of metallosis. We present a case of metallosis and failure of Oxinium femoral head following two incidents of hip instability and one closed reduction. Successful revision was performed with cemented cup and metal femoral head, with 68 months of follow-up. We aimed to highlight the importance of achieving stable and well-oriented hip components when using Oxinium-bearing surfaces and to present a short literature review regarding the wear of oxidized zirconium-bearing surfaces in hip arthroplasty.

The Influence of Oxide Color on the Surface Characteristics of Zirconium Alloy ZrNb7 (wt%) After Different Heat Treatments

Oxidized zirconium alloys can appear as black, white and all gray shades depending on the heat treatment process. The black color results from a high amount of oxygen vacancies in non-stoichiometric zirconia (ZrO2−x) that effectively reduces the band gap of the material. In this work we compare the surface properties of black and white zirconia on ZrNb7 substrate. An oxidation in air at 600 °C for 1 h results in a dark-gray oxide with only a few micro cracks. Oxidation at low oxygen partial pressure at 600 °C for 8 h (pO2 = 10–19 Pa) generates a dense, totally black oxide scale. A three step heat treatment process, that was introduced for better coating adhesion, results in a white oxide layer with many micro cracks parallel to the surface. From the results of various microscopy and spectroscopy techniques, we derive a model of the layer formation of zirconia on ZrNb7 and give reason why black zirconia, and therefore the oxidation at low oxygen partial pressure, is favorable for tribological applications (e.g., artificial joint replacements).

Allergic Dermatitis Following Bilateral Oxidized Zirconium Total Knee Replacements

Introduction: Total knee replacement (TKR) utilization is expected to increase by 673% in 2030, with patients between the ages of 45 to and 64 years representing the fastest-growingfastest growing age group requiring joint replacement. This group not only demands a higher- performinghigher performing, durable prosthesis but are is also the most likely to be dissatisfied if their expectations are not met. Hypo-allergenic implants have been developed by some implant manufacturers to fill this need, so the occurrence of allergic skin reactions after surgery is unanticipated and can have unwanted consequences if not recognized and managed appropriately. Case Report: We present the case of a 55-year-old woman who underwent bilateral staged TKR using oxidized zirconium implants and subsequently developed eczematous skin reactions. In both instances, she presented with a peri-incisional erythematous blistering skin reaction that was successfully treated with topical corticosteroids. Investigations revealed no evidence of infection or allergic-typeallergic type reactions to the metals contained in the knee replacements. Conclusion: Allergic skin reactions following TKR are very rare, and are not necessarily due to a metal hypersensitivity. Infection must be excluded in all cases and a trial of topical corticosteroids is useful before prior to more aggressive treatment, with the removal of the implant reserved as a last resort. To the best of our knowledge, this is the first case in the literature that reports the occurrence of allergic skin reactions following oxidized zirconium TKRs, and highlights the fact that allergic skin reactions can occur when using hypo-allergenic implants. Surgeons should be aware of this possibility and counsel their patients appropriately during the informed consent process. Keywords: Metal allergy, hypo-allergenic implants, oxidized zirconium, hypersensitivity.

Can the Choice of Cementless Implants and Bearings during Total Hip Arthroplasty Have an Impact on the Overall Costs within a Bundled Payment Model?

The comprehensive care for joint replacement model from the Center for Medicare and Medicaid Services and similar programs from other payers make hospitals and health care systems more responsible for better clinical and economic outcomes of total hip arthroplasty (THA) patients. The objective of the study was to evaluate hospital-related clinical and economic outcomes of using the cementless R3 cup and Polarstem with an oxidized zirconium bearing compared with other cementless hip systems using a ceramic bearing in THA patients. We retrospectively reviewed primary THA patients from the premier perspective database between 2014 and 2018Q3. Patients with R3 cup and Polarstem with an oxidized zirconium bearing were identified using appropriate keywords from billing records and compared against cementless and ceramic-on-polyethylene (CoP) THA patients who did not meet the keywords' criteria. Patients were excluded if they were < 21 years of age; outpatient hospital discharges; evidence of revision THA; bilateral THA in same discharge or different discharges. 1:3 propensity score matching was used to control patients' demographic, clinical, and hospital characteristics. Generalized estimating equation model with appropriate distribution and link function was used to estimate hospital-related cost while logistic regression models were used to estimate discharged status, transfusion, and 30-days readmission. The study matched 818 R3/Polarstem with oxidized zirconium bearing patients with 2,454 CoP cementless THA patients. Length of stay for the R3/Polarstem patients (mean = 1.61 days; confidence interval [CI] = 1.41–1.80) was significantly lower (p-value ≤ 0.0001) than CoP THA patients (mean = 2.06 days; CI = 1.95–2.17). R3/Polarstem hip patients were 36% (odds ratio [OR] = 1.36; CI = 1.07–1.72; p-value = 0.0112) more likely to be discharged to home/home health care, 18% (OR = 0.82; CI = 0.63–1.06; p-value = 0.1235) less likely to be discharged to a skilled nursing facility (SNF), 84% less likely to have transfusion (OR = 0.16; CI = 0.09–0.29; p-value ≤ 0.0001), and 44% (OR = 0.56; CI = 0.32–0.98; p-value = 0.0412) less likely to readmitted within 30 days than CoP THA patients. Mean total hospital costs was marginally higher for R3/Polarstem patients (mean = $15,611; vs. $15,002; p-value = 0.0041) than CoP THA patients. While the total hospital costs for the R3/Polarstem was higher than CoP, the reduced length of stay, reduced discharge to SNF, and lower readmission rates can help to save money in the bundled payment and make the use of certain cementless hip systems a potential cost saving solution.