Minimum 10-Y Follow-Up of Vitamin-E-Diffused Highly Crosslinked Polyethylene Liners in Total Hip Arthroplasty: A Comparative Evaluation From a Prospective, International, Multicenter Cohort Study.

BACKGROUND: Total hip arthroplasty (THA) is a proven and effective treatment for end-stage osteoarthritis. The success of THA is due in part to highly crosslinked polyethylene (XL) implants. In 2007, a new generation of polyethylene liners entered clinical use. The new liners infused polyethylene with vitamin E and became vitamin E infused polyethylene (EP). The EP liner was hypothesized to prevent the loss of mechanical properties caused by oxidation, extending the lifetime of the implant. This international prospective study aimed to quantify the clinical outcomes of a 977 patient cohort receiving EP and XL liners 10 years after surgery. METHODS: The prospective cohort study began in 2007, including eight countries and 17 centers. The final cohort included 977 patients (EP liner: n = 520; XL liner: n = 457). Patients were followed preoperatively, postoperatively, and at 1, 3, 5, 7, and 10 years. Each follow-up visit involved clinical evaluation, radiography, and survey collection. The demographics and revisions were also recorded. Mann-Whitney U tests were used to evaluate statistical differences. RESULTS: At 10 years following surgery, 534 patients were eligible for follow-up. Of those eligible, 352 patients returned for clinical evaluation (65.9% eligible; 36.0% overall). No statistical differences were found (P > 0.05) in the demographics of the followed-up cohort. The linear wear rates were 0.00338 mm/year for EP liners and 0.0236 mm/year for XL liners using individual regression (P < 0.0001). No significant difference was observed in wear rates using cohort regression. Similarly, surveys suggested no significant outcomes between the EP and XL liner cohorts. The overall incidence of revision was 2.3% for EP and 2.0% for XL liners. CONCLUSIONS: The EP liner demonstrated significantly lower wear than its XL counterparts at 10 years after implantation. Results are promising, as vitamin E polyethylene may improve the lifetime performance of THA implants and ensure that arthroplasty innovations reflect the changing patient population.

Minimum 7-Year Follow-Up of Vitamin E-Diffused and Highly Cross-Linked Polyethylene Liners in Total Hip Arthroplasty: Findings From a Prospective, International, Multicenter Study of 977 Patients.

BACKGROUND: Vitamin E-diffused highly cross-linked polyethylene (VEPE) acetabular liners for total hip arthroplasty (THA) have shown favorable results in small cohort studies. However, larger studies are warranted to compare its performance to highly cross-linked polyethylene (XLPE) and demonstrate clinical significance in 10-year arthroplasty outcomes. This study compared acetabular liner wear and patient-reported outcome measures (PROMs) between patients treated with VEPE and XLPE liners in a prospective, international, multicenter study with minimum 7-year follow-up. METHODS: A total of 977 patients (17 centers; 8 countries) were enrolled from 2007 to 2012. The centers were randomly assigned to implants. At 1-year, 3-year, 5-year, and 7-year postoperative visits, radiographs, PROMs, and incidence of revision were collected. Acetabular liner wear was calculated using computer-assisted vector analysis of serial radiographs. General health, disease progression, and treatment satisfaction reported by patients were scored using 5 validated surveys and compared using Mann-Whitney U tests. At 7 years, 75.4% of eligible patients submitted data. RESULTS: The mean acetabular liner wear rate was -0.009 mm/y and 0.024 mm/y for the VEPE and XLPE group, respectively (P = .01). There were no statistically significant differences in PROMs. The overall revision incidence was 1.8% (n = 18). The revision incidence in VEPE and XLPE cohorts were 1.92% (n = 10) versus 1.75% (n = 8), respectively. CONCLUSION: We found that VEPE acetabular liners in total hip arthroplasty led to no significant clinical difference in 7-year outcomes as measured by acetabular liner wear rate, PROMs, and revision rate. While VEPE liners showed less wear, the wear rate for both the VEPE and XLPE liners was below the threshold for osteolysis. Therefore, the difference in liner wear may indicate comparative clinical performance at 7 years, as further indicated by the lack of difference in PROMs and the low revision incidence.

Di-cumyl peroxide cross-linked UHMWPE/vitamin-E blend for total joint arthroplasty implants.

Majority of ultrahigh molecular weight polyethylene (UHMWPE) medical devices used in total joint arthroplasty are cross-linked using gamma radiation to improve wear resistance. Alternative methods of cross-linking are urgently needed to replace gamma radiation due to rapid decline in its supply. Peroxide cross-linking is a candidate method with widespread industrial applications. Oxidative stability and biocompatibility, which are critical requirements for medical device applications, can be achieved using vitamin-E as an additive and by removing peroxide by-products through high-temperature melting, respectively. We investigated compression molded UHMWPE/vitamin-E/di-cumyl peroxide blends followed by high-temperature melting in inert gas as a material candidate for tibial knee inserts. Wear resistance increased and mechanical properties remained largely unchanged. Oxidation induction time was higher than most of the other clinically available formulations. The material passed the local-end point biocompatibility tests per ISO 10993. Compounds found in exhaustive extraction were of no concern with margin-of-safety values well above the accepted level, indicating a desirable toxicological risk profile. Statement of Clinical Significance: Peroxide cross-linked, vitamin-E stabilized, and high-temperature melted UHMWPE has recently been cleared for clinical use in tibial knee inserts. With all the salient characteristics needed in a material that can provide superior long-term performance in total joint patients, peroxide cross-linking can replace the gamma radiation cross-linking of UHMWPE.

Nanoparticle-Based Liquid-Liquid Extraction for the Determination of Metal Ions.

Traditional liquid phase extraction techniques that use optically responsive ligands provide benefits that enable cost-efficient and rapid measurements. However, these approaches have limitations in their excessive use of organic solvents and multistep procedures. Here, we developed a simple, nanoscale extraction approach by replacing the macroscopic organic phase with hydrophobic polymeric nanoparticles that are dispersed in an aqueous feed. The concentration of analytes in polymeric nanoparticle suspensions is governed by similar partition principles to liquid-liquid phase extraction techniques. By encasing optically responsive metal ligands inside polymeric nanoparticles, we introduce a one-step metal quantification assay based on traditional two-phase extraction methodologies. As an initial proof of concept, we encapsulated bathophenanthroline (BP) inside the particles to extract then quantify Fe2+ with colorimetry in a dissolved supplement tablet and creek water. These Fe2+ nanosensors are sensitive and selective and report out with fluorescence by adding a fluorophore (DiO) into the particle core. To show that this new rapid extraction assay is not exclusive to measuring Fe2+, we replaced BP with either 8-hydroxyquinoline or bathocuproine to measure Al3+ or Cu+, respectively, in water samples. Utilizing this nanoscale extraction approach will allow users to rapidly quantify metals of interest without the drawbacks of larger-scale phase extraction approaches while also allowing for the expansion of phase extraction methodologies into areas of biological research.