E-blended Ultrahigh Molecular Weight Polyethylene Research Articles

Determination of optimal concentration of vitamin E in polyethylene liners for producing minimal biological response to prosthetic wear debris.

The introduction of vitamin E-blended ultra-high molecular weight polyethylene (VE-UHMWPE) for use in prosthetic components of hip implants has resulted in the production of implants that have excellent mechanical properties and substantially less adverse cellular responses. Given the importance of a biological response to wear in the survival of a prosthesis, we generated wear debris from UHMWPE that had been prepared with different concentrations of vitamin E of 0.1, 0.3, 0.5, and 1% and evaluated their biological reaction in vitro and in vivo. All types of VE-UHMWPE debris promoted a significantly lower expression of Tnf-α in murine peritoneal macrophages than that induced by conventional UHMWPE debris. However, levels of Tnf-α were not significantly different among the macrophages that were stimulated with VE-UHMWPE wear at the concentrations tested. The ability of wear debris to induce inflammatory osteolysis was assessed in a mouse calvarial osteolysis model. The expressions of Tnf-α, Il-6, and Rankl in granulomatous tissue formed around the wear debris were significantly reduced in mice that had been implanted with 0.3%VE-UHMWPE debris as compared to the corresponding values for mice that had been implanted with UHMWPE debris. Consistent with this finding, 0.3%VE-UHMWPE debris showed the lowest osteolytic activity, as evidenced by the reduced bone resorption area, the degree of infiltration of inflammatory cells and the TRAP staining area. Our results suggested that a 0.3% vitamin E concentration is the most appropriate concentration for use in prosthetic components with a reduced adverse cellular response for prolonging the life-span of the implant.

Identification of IL-27 as potent regulator of inflammatory osteolysis associated with vitamin E-blended ultra-high molecular weight polyethylene debris of orthopedic implants

Vitamin E-blended ultra-high molecular weight polyethylene (VE-UHMWPE) is a newly introduced material for prosthetic components that has proven a better mechanical performance with lesser adverse cellular responses than conventional polyethylene in experimental animal models. However, the mechanisms by which VE-UHMWPE particles trigger a reduced osteolytic activity are unclear and remain to be investigated. Therefore, the current study aims at exploring a possible anti-osteolytic mechanism associated with VE-UHMWPE particles. Transcriptional profiling and bioinformatic analyses of human macrophages stimulated by VE-UHMWPE particles revealed a distinct transcriptional program from macrophages stimulated with UHMWPE particles. Out of the up-regulated genes, IL-27 was found to be significantly elevated in macrophages cultured with VE-UHMWPE particles as compared to these with UHMWPE particles (p = 0.0084). Furthermore, we studied the potential anti-osteolytic function of IL-27 in osteolysis murine model. Interestingly, administration of recombinant IL-27 onto calvariae significantly alleviated osteolytic lesions triggered by UHMWPE particles (p = 0.0002). Likewise, IL-27 inhibited differentiation of osteoclasts (p = 0.0116) and reduced inflammatory response (p < 0.0001) elicited by conventional UHMWPE particles in vitro. This is the first study demonstrating the involvement of IL-27 in macrophage response to VE-UHMWPE particles and its regulatory role in osteolysis. Our data highlight a novel therapeutic agent for treatment of inflammatory osteolysis induced by polyethylene debris. Statement of SignificanceAseptic loosening due to inflammatory osteolysis remains the major cause of arthroplasty failure and represents a substantial economic burden worldwide. Ideal approach to prevent this failure should be directed to minimize inflammatory response triggered by wear particles at the site of implant. Understanding the mechanism by which VE-UHMWPE particles triggers lesser cellular responses and reduced osteolysis as compared to conventional UHMWPE particles may aid in discovery of regulatory factors. In the current study, we reported that IL-27 is a potent regulator of inflammatory osteolysis involved in the reduced biologic activities and osteolytic potentials associated with VE-UHMWPE particles. Initiating the production IL-27 in vivo after total joint arthroplasties might be a novel strategy to prolong the life-spam of implant.

Wear performance of inverted non-conforming bearings in anatomic total shoulder arthroplasty.

Glenoid component failures still represent the most common complication in total shoulder arthroplasty. These failures depend on several factors, including ultra-high molecular weight polyethylene (UHMWPE) wear. One reason for UHMWPE wear in total shoulder arthroplasty may be the current use of a spherical prosthetic humeral head against a radially mismatched UHMWPE glenoid component, which leads to reduced glenohumeral translations, glenoid edge loading and high translational forces during shoulder motions. The aim of this study was to assess the in vitro wear of an anatomic total shoulder prosthesis with non-spherical non-conforming bearings with inverted conventional materials. The wear of a vitamin E-blended UHMWPE non-spherical humeral head articulating against a non-conforming titanium-niobium nitride (TiNbN)-coated metallic glenoid was tested using a joint simulator. The wear test was performed by applying a constant load of 756 N with angular motions and translations. After 2.5 million cycles, the mean wear rate of the humeral head was 0.28 ± standard deviation (SD) 0.45 mg/million cycles. The low wear rate of the vitamin E UHMWPE humeral head supports the use of non-spherical non-conforming bearings with inverted conventional materials in anatomic total shoulder arthroplasty.

Residual Byproducts of Peroxide Crosslinked Vitamin E-Blended Ultrahigh Molecular Weight Polyethylene

BackgroundWear resistance of ultrahigh molecular weight polyethylene (UHMWPE) is improved via ionizing radiation crosslinking and subsequent high temperature melting for improved toughness. Our group has previously reported that crosslinking can also be achieved chemically using organic peroxides. However, volatile peroxide byproducts are generated during consolidation. The purpose of this study was to quantify elution of volatile peroxide byproducts from UHMWPE before and after in vivo implantation, and to determine their effects on local tissues. MethodsWe prepared crosslinked UHMWPE samples with 5 times the nominal concentration of peroxide needed for improved wear resistance. Control samples (not crosslinked), crosslinked samples, and crosslinked high temperature melting samples were implanted subcutaneously in New Zealand white rabbits for 28 days. Fourier-transform infrared spectroscopy (FTIR) was used to quantify elution of residual peroxide byproducts, and biocompatibility was determined via histological analysis of periprosthetic tissues. ResultsFourier-transform infrared spectroscopy demonstrated elution of residual peroxide byproducts in vivo. No histological differences were observed between tissues in contact with any of the 3 groups of implants; tissues were characterized by fibrosis and a synovial-like lining for all groups. ConclusionUHMWPE chemically crosslinked with very high concentration of organic peroxide did not show any detrimental changes to surrounding subcutaneous tissues, further demonstrating feasibility of crosslinking UHMWPE with a peroxide, rather than irradiation, for the potential use of the material as a bearing surface for joint arthroplasty.

0930 Vitamin E混合UHMWPEの摩擦特性に及ぼす血清蛋白と荷重の影響(OS20-1:人工関節とバイオエンジニアリング1)

0930 Vitamin E混合UHMWPEの摩擦特性に及ぼす血清蛋白と荷重の影響(OS20-1:人工関節とバイオエンジニアリング1)

Confirmation of Pressure-Induced Leaching of Vitamin E from inside of Ultrahigh Molecular Weight Polyethylene

The possibility of pressure-induced leaching of vitamin E from inside of vitamin E-blended ultrahigh molecular weight polyethylene (UHMWPE) was investigated. UHMWPE specimens were pressed against a base plate, and leached vitamin E was dissolved in ethanol. The quantification of vitamin E in ethanol was carried out by fluorescence spectrophotometry. Vitamin E was confirmed to leach from inside of the vitamin E-blended UHMWPE specimens under compressive load, and the amount of leached vitamin E was positively correlated with the applied load.

Strain-induced crystallization and orientation of vitamin E-blended ultrahigh molecular weight polyethylene

The effects of vitamin E addition on the strain-induced crystallization and molecular chain orientation of ultrahigh molecular weight polyethylene (UHMWPE) were examined in order to clarify the wear mechanism of vitamin E-blended UHMWPE in knee prostheses. The structure changes of vitamin E-blended UHMWPE before and after tensile strain were analyzed by X-ray diffraction, Raman spectroscopy and image correlation method. The vitamin E-blended UHMWPE exhibited lower strain-induced crystallization than virgin UHMWPE but a higher Ic value in Raman spectroscopic analysis. The vitamin E-blended UHMWPE also exhibited a larger percentage of negative areal dilatation under tensile strain. These results suggest that the addition of vitamin E to UHMWPE decreases the strain-induced crystallization and increases the strain-induced orientation of the molecular chains present in the amorphous phase.

The effects of high dose irradiation on the cross-linking of vitamin E-blended ultrahigh molecular weight polyethylene

Vitamin E-stabilized, highly cross-linked ultrahigh molecular weight polyethylene (UHMWPE) is a promising oxidation and wear resistant UHMWPE with improved mechanical strength in comparison with the first generation, irradiated and melted UHMWPE. One approach of incorporating vitamin E in UHMWPE is through blending of vitamin E in UHMWPE powder followed by consolidation and radiation cross-linking. However, radiation cross-linking efficiency of UHMWPE decreases in the presence of vitamin E. Therefore an optimum vitamin E concentration and radiation dose level need to be determined to achieve a cross-link density comparable to 100-kGy irradiated and melted UHMWPE, which has shown excellent wear properties in vivo. We investigated the cross-link density and mechanical properties of vitamin E-blended UHMWPEs as a function of vitamin E concentration in the blend and gamma irradiation doses up to 200 kGy. We found that 0.3 wt% vitamin E-blended UHMWPE could not be cross-linked above a cross-link density achieved at a radiation dose of 65 kGy for virgin UHMWPE and 1.0 wt% vitamin E-blended UHMWPE could not be cross-linked above a cross-link density achieved at a radiation dose of 25 kGy for virgin UHMWPE even when the these UHMWPEs were irradiated to a radiation dose of 200 kGy. In addition, higher plasticity at vitamin E concentrations at and above 0.3 wt% indicated that increased chain scissioning may be prevalent. Since the wear resistance of this irradiated UHMWPE would be expected to be low, vitamin E concentrations equal to or above 0.3 wt% are not recommended for subsequent irradiation to achieve a wear resistant cross-linked UHMWPE. The long-term oxidative stability of irradiated blends with low vitamin E concentrations has yet to be studied to determine an optimum between cross-link density and long-term oxidative stability.