Vitamin E-diffused highly cross-linked UHMWPE particles induce less osteolysis compared to highly cross-linked virgin UHMWPE particles in vivo

Effect of vitamin E-enhanced highly cross-linked polyethylene on wear rate and particle debris in anatomic total shoulder arthroplasty: a biomechanical comparison to ultrahigh-molecular-weight polyethylene

BACKGROUND

Particle-induced osteolysis resulting from polyethylene wear remains a source of implant failure in anatomic total shoulder designs. Modern polyethylene components are irradiated in an oxygen-free environment to induce cross-linking, but reducing the resulting free radicals with melting or heat annealing can compromise the component's mechanical properties. Vitamin E has been introduced as an adjuvant to thermal treatments. Anatomic shoulder arthroplasty models with a ceramic head component have demonstrated that vitamin E-enhanced polyethylene show improved wear compared with highly cross-linked polyethylene (HXLPE). This study aimed to assess the biomechanical wear properties and particle size characteristics of a novel vitamin E-enhanced highly cross-linked polyethylene (VEXPE) glenoid compared to a conventional ultrahigh-molecular-weight polyethylene (UHMWPE) glenoid against a cobalt chromium molybdenum (CoCrMo) head component.

METHODS

Biomechanical wear testing was performed to compare the VEXPE glenoid to UHMWPE glenoid with regard to pristine polyethylene wear and abrasive endurance against a polished CoCrMo alloy humeral head in an anatomic shoulder wear-simulation model. Cumulative mass loss (milligrams) was recorded, and wear rate calculated (milligrams per megacycle [Mc]). Under pristine wear conditions, particle analysis was performed, and functional biologic activity (FBA) was calculated to estimate particle debris osteolytic potential. In addition, 95% confidence intervals for all testing conditions were calculated.

RESULTS

The average pristine wear rate was statistically significantly lower for the VEXPE glenoid compared with the HXLPE glenoid (0.81 ± 0.64 mg/Mc vs. 7.00 ± 0.45 mg/Mc) (P < .05). Under abrasive wear conditions, the VEXPE glenoid had a statistically significant lower average wear rate compared with the UHMWPE glenoid comparator device (18.93 ± 5.80 mg/Mc vs. 40.47 ± 2.63 mg/Mc) (P < .05). The VEXPE glenoid demonstrated a statistically significant improvement in FBA compared with the HXLPE glenoid (0.21 ± 0.21 vs. 1.54 ± 0.49 (P < .05).

CONCLUSIONS

A new anatomic glenoid component with VEXPE demonstrated significantly improved pristine and abrasive wear properties with lower osteolytic particle debris potential compared with a conventional UHMWPE glenoid component. Vitamin E-enhanced polyethylene shows early promise in shoulder arthroplasty components. Long-term clinical and radiographic investigation needs to be performed to verify if these biomechanical wear properties translate to diminished long-term wear, osteolysis, and loosening.

In Vivo Performance of Vitamin E Stabilized Polyethylene Implants for Total Hip Arthroplasty: A Review

BACKGROUND

Vitamin E stabilization was introduced to improve the oxidative stability, wear resistance, and mechanical properties of highly crosslinked polyethylene (HXLPE). In this literature review, we asked: (1) How has vitamin E-stabilized HXLPE (VEPE) performed in vivo for total hip arthroplasty (THA) and how does it compare with conventional ultra-high molecular weight polyethylene (UHMWPE) and HXLPE without vitamin E; and (2) Is there an apparent difference in the clinical performance of VEPE created by blending versus diffusion?

METHODS

We performed a systematic search of the literature according to the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines using PubMed and Embase. Included studies reported the in vivo behavior of VEPE in THA. We reviewed 41 studies.

RESULTS

For all studies that compared polyethylene with and without VE stabilization, outcomes for VEPE were either equivalent or superior to the control group (for HXLPE without VE and conventional UHMWPE controls, respectively). Hip insert wear rates were generally less than 0.1 mm/year and in most cases were less than 0.05 mm/year. No VEPE components were revised for osteolysis or adverse outcomes specific to VE incorporation.

CONCLUSION

Across the literature, we found that VEPE was reported to be clinically effective for THA applications, with much of the research indicating positive clinical outcomes and lower or equivalent wear rates compared to conventional UHMWPE and HXLPE controls without VE. Instances of early component fracture were reported, but have multiple potential causes. There is a gap in the literature for comparison of blended and diffused components, so the in vivo impact of VE incorporation method remains to be seen. Overall, this study provides a comprehensive summary of VEPE clinical performance for THA and may serve as a resource for future investigations.

Wear Analysis of Tibial Inserts Made of Highly Cross-Linked Polyethylene Supplemented with Dodecyl Gallate before and after Accelerated Aging

The wear of the tibial insert is one of the primary factors leading to the failure of total knee arthroplasty. As materials age, their wear performance often degrades. Supplementing highly cross-linked polyethylene (HXLPE) with dodecyl gallate (DG) can improve the oxidation stability of tibial inserts for use in total knee arthroplasty (TKA). This study aimed to evaluate the wear resistance of HXLPE supplemented with DG (HXLPE-DG) tibial inserts before and after accelerated aging. HXLPE-DG tibial inserts were subjected to wear testing of up to 5 million loading cycles according to ISO 14243, and the resulting wear particles were analyzed according to ISO 17853. The wear rate, number, size, and shape of the wear particles were analyzed. The average wear rate of the unaged samples was 4.39 ± 0.75 mg/million cycles and was 3.22 ± 1.49 mg/million cycles for the aged samples. The unaged tibial inserts generated about 2.80 × 107 particles/mL following the wear test, but this was considerably lower for the aged samples at about 1.35 × 107 particles/mL. The average equivalent circle diameter (ECD) of the wear particles from the unaged samples was 0.13 μm (max: 0.80 μm; min: 0.04 μm), and it was 0.14 μm (max: 0.66 μm; min: 0.06 μm) from the aged samples. Moreover, 22.1% of the wear particles from the unaged samples had an aspect ratio (AR) of >4 (slender shape), while this was 15.4% for the aged samples. HXLPE-DG improves the wear performance of the material over time. HXLPE-DG is a novel material that has been demonstrated to have antiaging properties and high wear resistance, making it a promising candidate for use in TKA. Nevertheless, the results are preliminary and will be clarified in further studies.

The Effects of Vitamin E Analogues α-Tocopherol and γ-Tocotrienol on the Human Osteocyte Response to Ultra-High Molecular Weight Polyethylene Wear Particles

Polyethylene (PE) liners are a common bearing surface of orthopaedic prostheses. Wear particles of ultra-high molecular weight PE (UHMWPE) contribute to periprosthetic osteolysis, a major cause of aseptic loosening. Vitamin E is added to some PE liners to prevent oxidative degradation. Osteocytes, an important cell type for controlling both bone mineralisation and bone resorption, have been shown to respond UHMWPE particles by upregulating pro-osteoclastogenic and osteocytic osteolysis. Here, we examined the effects of the vitamin E analogues α-tocopherol and γ-tocotrienol alone or in the context of UHMWPE particles on human osteocyte gene expression and mineralisation behaviour. Human osteoblasts differentiated to an osteocyte-like stage were exposed to UHMWPE wear particles in the presence or absence of either α-Tocopherol or γ-Tocotrienol. Both α-Tocopherol and γ-Tocotrienol induced antioxidant-related gene expression. UHMWPE particles independently upregulated antioxidant gene expression, suggesting an effect of wear particles on oxidative stress. Both vitamin E analogues strongly induced OPG mRNA expression and γ-Tocotrienol also inhibited RANKL mRNA expression, resulting in a significantly reduced RANKL:OPG mRNA ratio (p < 0.01) overall. UHMWPE particles reversed the suppressive effect of α-Tocopherol but not of γ-Tocotrienol on this pro-osteoclastogenic index. UHMWPE particles also upregulated osteocytic-osteolysis related gene expression. Vitamin E analogues alone or in combination with UHMWPE particles also resulted in upregulation of these genes. Consistent with this, both vitamin E analogues promoted calcium release from mineralised cultures of osteocyte-like cells. Our findings suggest that while vitamin E may suppress osteocyte support of osteoclastogenesis in the presence of UHMWPE particles, the antioxidant effect may induce osteocytic osteolysis, which could promote periprosthetic osteolysis. It will be important to conduct further studies of vitamin E to determine the long-term effects of its inclusion in prosthetic materials.

Vitamin E-enriched polyethylene bearings are not inferior to Arcom bearings in primary total knee arthroplasty at medium-term follow-up

INTRODUCTION

The release of wear particles can be responsible for periprosthetic osteolysis, which can in turn, lead to aseptic loosening. Vitamin E-infused polyethylene (HXLPE Vit-E) has been shown, in vitro, to be more resistant to wear than conventional polyethylene (UHMWPE) by its crosslinking (HXLPE) and its higher resistance to oxidation. After reading a case report of a fracture of a vitamin E-enriched HXLPE bearing, the aim of this retrospective study was to evaluate fracture risk and clinical inferiority or not of vitamin-E HXLPE compared to conventional polyethylene in total knee arthroplasty (TKA).

MATERIALS AND METHODS

Three hundred and forty-nine patients (403 TKAs) were contacted, to find out whether they had undergone revision surgery for any reason after a mean (SD) of 7 (1.5) years. Follow-up control radiographs were analyzed for periprosthetic radiolucent lines (RLL) and loosening. Two different Patient Reported Outcome Measurements Scores (PROMS), KOOS and FJS-12, were utilized to assess the daily functionality and identify potential problems.

RESULTS

No statistically significant difference in revision rate, occurrence of aseptic loosening or RLL nor outcome as measured with PROMS was observed.

CONCLUSIONS

No bearing fractures or clinical inferiority was observed for vitamin E-enriched HXLPE at medium-term follow-up (7 years) compared to conventional Arcom polyethylene.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Antibacterial application of gentamicin-silk protein coating with smart release function on titanium, polyethylene, and Al2O3 materials

Peri-implant infection after hip and knee arthroplasty is a common and serious complication. Titanium (Ti), polyethylene (PE), and Al₂O₃ materials used as joint prosthesis materials have good biocompatibility and mechanical strength but no antibacterial effect. This study aimed to provide a theoretical basis for the design and manufacture of joint prosthesis materials with antibacterial effect. We applied a coating of gentamicin-silk protein (GS-Silk) on the surface of these materials. We characterized the Ti, PE, and Al₂O₃ materials coated with GS-Silk (experimental group) and performed in vivo and in vitro experiments to test antibacterial activity. Scanning electron microscopy confirmed successful GS-Silk coating, and infrared spectroscopy confirmed successful loading of gentamicin onto the three materials. Nanoscratch test proved that the GS-Silk coating is relatively reliable on the surface of these three materials. The antibacterial effect of the coating in vitro and in vivo was verified by performing bacteriostatic ring test in vitro, bacterial adhesion test, and subendothelial implant infection test. We demonstrated that GS-Silk coating can effectively load gentamicin onto Ti, PE, and Al₂O₃ materials and change the gentamicin release rate with a change in the solution pH to achieve intelligent release. The GS-Silk coating is relatively reliable on the surface of these three materials. Ti, PE, and Al₂O₃ materials coated with GS-Silk have good antibacterial ability, both in vivo and in vitro.

Ultra-high molecular weight polyethylene (UHMWPE) for hip and knee arthroplasty: The present and the future

PURPOSE

to review advances and clinical performance of polyethylene in total joint arthroplasty, summing up historical problems and focusing on the latest innovations.

METHODS

search for medical grade Ultra-High-Molecular-Weight-Polyethylene (UHMWPE); Data Sources: PubMed, Scopus, Cochrane Library.

RESULTS

the increasing number of joint arthroplasties and high-activity patients led to progressive developments of bearing surfaces to improve performance and durability. Different strategies such as crosslinking UHMWPE (HXLPE) and the addition of vitamin-E (HXLPE) have been tested to improve wear and oxidation resistance.

CONCLUSION

Recent innovations about UHMWPE showed improvements either for hip and knee, with the potential of long-term survivorship.

Plastics in Total Knee Replacement: Processing to Performance

Polyethylene (PE) is the key component of total knee replacement (TKR). The wear of polyethylene, a common cause of revision surgeries, depends on multiple factors. The mechanical properties, wear characteristics, and oxidative resistance of PE can be manipulated by the techniques of processing, sterilization, and packaging methods. This article describes the making of conventional and cross-linked poly, packaging, sterilization, processing techniques, and a summary of commercially available plastics and their rationale in TKR including the latest advances.

Identification of Key Candidate Genes Related to Inflammatory Osteolysis Associated with Vitamin E-Blended UHMWPE Debris of Orthopedic Implants by Integrated Bioinformatics Analysis and Experimental Confirmation

PURPOSE

This study aims to identify differentially expressed genes (DEGs) in macrophages exposed to ultra-high-molecular-weight polyethylene (UHMWPE) or vitamin E-blended UHMWPE (VE-UHMWPE) particles, thereby providing potential targets for the treatment of inflammatory osteolysis.

METHODS

The GSE104589 dataset of genome expression in macrophages exposed to UHMWPE and VE-UHMWPE was downloaded from the Gene Expression Omnibus database to identify DEGs. Functional enrichment analysis was performed using DAVID, and the corresponding protein-protein interaction (PPI) network was constructed from the STRING database. Important modules were selected using the molecular complex detection algorithm, and hub genes were identified in cytoHubba. MicroRNAs targeting these DEGs were obtained from the TarBase, miRTarBase, and miRecords databases, while transcription factors (TFs) targeting DEGs were predicted from the ENCODE database. Finally, the top five DEGs were validated by quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

A total of 112 DEGs (44 upregulated and 68 downregulated DEGs) were screened. Immune and inflammatory responses were significantly related in gene ontology analysis, and 18 signaling pathways were enriched according to Kyoto Encyclopedia of Genes and Genomes pathway analysis. The PPI network involving 85 nodes and 266 protein pairs indicated that IL1β, CXCL1, ICAM1, CCL5 and CCL4 showed higher degrees. qRT-PCR analysis of the top five DEGs revealed a decreasing trend in the VE-UHMWPE group compared with the UHMWPE group. Key microRNAs (hsa-miR-144, hsa-miR-21, and hsa-miR-221) and TFs (RELA and NFKB1) were predicted to be correlated with the pathogenesis of inflammatory osteolysis through microRNA-TF regulatory network analysis.

CONCLUSION

The present study helps shed light on the molecular mechanisms underlying the changes in the wear-induced inflammatory process after blending vitamin E with UHMWPE. Hub genes including IL1β, CXCL1, ICAM1, CCL5, and CCL4, key microRNAs (hsa-miR-144, hsa-miR-21, and hsa-miR-221) and TFs (RELA and NFKB1) may serve as prognostic and therapeutic targets of inflammatory osteolysis.

Vitamin E-infused highly cross-linked polyethylene did not reduce the number of in vivo wear particles in total knee arthroplasty

AIMS

Vitamin E-infused highly cross-linked polyethylene (E1) has recently been introduced in total knee arthroplasty (TKA). An in vitro wear simulator study showed that E1 reduced polyethylene wear. However there is no published information regarding in vivo wear. Previous reports suggest that newly introduced materials which reduce in vitro polyethylene wear do not necessarily reduce in vivo polyethylene wear. To assist in the evaluation of the newly introduced material before widespread use, we established an in vivo polyethylene wear particle analysis for TKA. The aim of this study was to compare in vivo polyethylene wear particle generation between E1 and conventional polyethylene (ArCom) in TKA.

METHODS

A total of 34 knees undergoing TKA (17 each with ArCom or E1) were investigated. Except for the polyethylene insert material, the prostheses used for both groups were identical. Synovial fluid was obtained at a mean of 3.4 years (SD 1.3) postoperatively. The in vivo polyethylene wear particles were isolated from the synovial fluid using a previously validated method and examined by scanning electron microscopy.

RESULTS

The total number of polyethylene wear particles obtained from the knees with E1 (mean 6.9, SD 4.0 × 10⁷ counts/knee) was greater than that obtained from those with ArCom (mean 2.2, SD 2.6 × 10⁷ counts/knee) (p = 0.001). The particle size (equivalent circle of diameter) from the knees with E1 was smaller (mean 0.5 μm, SD 0.1) than that of knees with ArCom (mean 1.5, SD 0.3 μm) (p = 0.001). The aspect ratio of particles from the knees with E1 (mean 1.3, SD 0.1) was smaller than that with ArCom (mean 1.4, SD 0.1) (p < 0.001 ).

CONCLUSION

This is the first report of in vivo wear particle analysis of E1. E1 polyethylene did not reduce the number of in vivo polyethylene wear particles compared with ArCom in early clinical stage. Further careful follow-up of newly introduced E1 for TKA should be carried out. Cite this article: Bone Joint J 2020;102-B(11):1527-1534.

Do Polyethylene Supra-Macroparticles Lead to Pseudotumor Formation in Metal-on-Polyethylene Total Hip Arthroplasty?

We describe 2 cases of pseudotumors induced by an unusual size of polyethylene wear particle after metal-on-polyethylene total hip arthroplasty (MoP THA). The supra-macroparticles of size >100 μm originated from a polyethylene liner with relatively small cup anteversion, potentially leading to excessive loading and increased wear of the anterior edge of the polyethylene liner. Histopathology showed a foreign-body reaction to the polyethylene particles without an adverse reaction to metal debris and with no severe signs of corrosion at the head-neck junction, which have been noted in past reports of pseudotumors in MoP THA. It has been suggested that the large polyethylene wear particles might be the cause of pseudotumor formation in MoP THA.

The effect of vitamin E-enhanced cross-linked polyethylene on wear in shoulder arthroplasty-a wear simulator study

BACKGROUND

Wear of the polyethylene glenoid component and subsequent particle-induced osteolysis remains one of the most important modes of failure of total shoulder arthroplasty. Vitamin E is added to polyethylene to act as an antioxidant to stabilize free radicals that exist as a byproduct of irradiation used to induce cross-linking. This study was performed to assess the in vitro performance of vitamin E-enhanced polyethylene compared with conventional polyethylene in a shoulder simulator model.

METHODS

Vitamin E-enhanced, highly cross-linked glenoid components were compared with conventional ultrahigh-molecular-weight polyethylene glenoids, both articulating with a ceramic humeral head component using a shoulder joint simulator over 500,000 cycles. Unaged and artificially aged comparisons were performed. Volumetric wear was assessed by gravimetric measurement, and wear particle analysis was also subsequently performed.

RESULTS

Vitamin E-enhanced polyethylene glenoid components were found to have significantly reduced wear rates compared with conventional polyethylene in both unaged (36% reduction) and artificially aged (49% reduction) comparisons. There were no differences detected in wear particle analysis between the 2 groups.

CONCLUSION

Vitamin E-enhanced polyethylene demonstrates improved wear compared with conventional polyethylene in both unaged and artificially aged comparisons and may have clinically relevant benefits.

Comparison of a vitamin E-infused highly crosslinked polyethylene insert and a conventional polyethylene insert for primary total knee arthroplasty at two years postoperatively

AIMS

The use of vitamin E-infused highly crosslinked polyethylene (HXLPE) in total knee prostheses is controversial. In this paper we have compared the clinical and radiological results between conventional polyethylene and vitamin E-infused HXLPE inserts in total knee arthroplasty (TKA).

PATIENTS AND METHODS

The study included 200 knees (175 patients) that underwent TKA using the same total knee prostheses. In all, 100 knees (77 patients) had a vitamin E-infused HXLPE insert (study group) and 100 knees (98 patients) had a conventional polyethylene insert (control group). There were no significant differences in age, sex, diagnosis, preoperative knee range of movement (ROM), and preoperative Knee Society Score (KSS) between the two groups. Clinical and radiological results were evaluated at two years postoperatively.

RESULTS

Differences in postoperative ROM and KSS were not statistically significant between the study and control groups. No knee exhibited osteolysis, aseptic loosening, or polyethylene failure. Additionally, there was no significant difference in the incidence of a radiolucent line between the two groups. One patient from the study group required irrigation and debridement, due to deep infection, at six months postoperatively.

CONCLUSION

Clinical results were comparable between vitamin E-infused HXLPE inserts and conventional polyethylene inserts at two years after TKA, without any significant clinical failure. Cite this article: Bone Joint J 2019;101-B:559-564.

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 SIGNIFICANCE: Aseptic 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.

An antioxidant stabilized, chemically cross-linked UHMWPE with superior toughness

Chemical cross-linking of ultrahigh molecular weight polyethylene (UHMWPE) using an organic peroxide followed by high temperature melting results in a large increase in toughness accompanied by a decrease in cross-link density, which, surprisingly does not compromise the wear resistance. We compared the mechanical properties and wear behavior of a vitamin E blended, chemically cross-linked and high temperature melted UHMWPE produced by ram extrusion (PRX HTM) to those measured with the clinically available 100-kGy irradiated and melted UHMWPE (CISM 100). We also assessed the local biocompatibility of PRX-HTM in rabbit subcutaneous pouch and osteochondral defect models. The ultimate tensile strength and pin-on-disc wear rate were similar to CISM 100; whereas the elongation-at-break and impact toughness were much higher with PRX-HTM. The stress intensity factor range at crack inception was also higher with PRX-HTM. Accelerated aging did not result in any measurable oxidation or changes in mechanical properties. Hip simulator wear rate of acetabular liners made with PRX-HTM was 0.3 ± 0.4 mg/million-cycle, similar to that reported for CISM 100 liners. The wear particles were largely spherical with a number-averaged particle size of 0.95 μm with ~75% of particles below 1 μm. The subcutaneous and osteochondral rabbit implantations showed no histological differences between PRX-HTM and the control CISM 100. Pre-clinical wear, mechanical, and biocompatibility testing of PRX HTM showed feasibility for the use of this material as a total joint arthroplasty implant bearing surface. This process has the potential of eliminating the additional step of radiation cross-linking by combining consolidation and cross-linking while improving toughness. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1945-1952, 2019.

Effects of vitamin E incorporation in polyethylene on oxidative degradation, wear rates, immune response, and infections in total joint arthroplasty: a review of the current literature

Highly cross-linked ultrahigh molecular weight polyethylene (UHMWPE) was introduced to decrease wear debris and osteolysis. During cross-linking, free radicals are formed, making highly cross-linked polyethylene vulnerable to oxidative degradation. In order to reduce this process, anti-oxidant vitamin E can be incorporated in polyethylene. This review provides an overview of the effects of vitamin E incorporation on major complications in total joint arthroplasty: material failure due to oxidative degradation, wear debris and subsequent periprosthetic osteolysis, and prosthetic joint infections. Secondly, this review summarizes the first clinical results of total hip and knee arthroplasties with vitamin E incorporated highly cross-linked polyethylene. Based on in vitro studies, incorporation of vitamin E in polyethylene provides good oxidative protection and preserves low wear rates. Incorporation of vitamin E may have the beneficial effect of reduced inflammatory response to its wear particles. Some microorganisms showed reduced adherence to vitamin E-incorporated UHMWPE; however, clinical relevance is doubtful. Short-term clinical studies of total hip and knee arthroplasties with vitamin E-incorporated highly cross-linked UHMWPE reported good clinical results and wear rates similar to highly cross-linked UHMWPE without vitamin E.

Osteolysis Complicating Total Knee Arthroplasty

Osteolysis is a process mounted by the host immune system that relies on several variables, including patient-related factors, type of insert material, modes of wear, and implant design. Imaging techniques such as radiography, computed tomography (CT) scans, magnetic resonance imaging (MRI), and tomosynthesis aid in diagnosing osteolysis. Surgical options for the treatment of osteolysis include the insertion of bone grafts, bone cement, and prosthetic augmentation. Although no approved pharmacological therapies for the specific treatment of osteolysis exist, the use of bisphosphonates and statins decreases the risk of osteolysis.

Vitamin E Phosphate Coating Stimulates Bone Deposition in Implant-related Infections in a Rat Model

BACKGROUND

Implant-related infections are associated with impaired bone healing and osseointegration. In vitro antiadhesive and antibacterial properties and in vivo antiinflammatory effects protecting against bone loss of various formulations of vitamin E have been demonstrated in animal models. However, to the best of our knowledge, no in vivo studies have demonstrated the synergistic activity of vitamin E in preventing bacterial adhesion to orthopaedic implants, thus supporting the bone-implant integration.

QUESTIONS/PURPOSES

The purpose of this study was to test whether a vitamin E phosphate coating on titanium implants may be able to reduce (1) the bacterial colonization of prosthetic implants and (2) bone resorption and osteomyelitis in a rat model of Staphylococcus aureus-induced implant-related infection.

METHODS

Twelve rats were bilaterally injected in the femurs with S aureus UAMS-1-Xen40 and implanted with uncoated or vitamin E phosphate-coated titanium Kirschner wires without local or systemic antibiotic prophylaxis. Eight rats represented the uninfected control group. A few hours after surgery, two control and three infected animals died as a result of unexpected complications. With the remaining rats, we assessed the presence of bacterial contamination with qualitative bioluminescence imaging and Gram-positive staining and with quantitative bacterial count. Bone changes in terms of resorption and osteomyelitis were quantitatively analyzed through micro-CT (bone mineral density) and semiquantitatively through histologic scoring systems.

RESULTS

Six weeks after implantation, we found only a mild decrease in bacterial count in coated versus uncoated implants (Ti versus controls: mean difference [MD], -3.705; 95% confidence interval [CI], -4.416 to -2.994; p < 0.001; TiVE versus controls: MD, -3.063; 95% CI, -3.672 to -2.454; p < 0.001), whereas micro-CT analysis showed a higher bone mineral density at the knee and femoral metaphysis in the vitamin E-treated group compared with uncoated implants (knee joint: MD, -11.88; 95% CI, -16.100 to -7.664; p < 0.001 and femoral metaphysis: MD, -19.87; 95% CI, -28.82 to -10.93; p < 0.001). We found decreased osteonecrosis (difference between medians, 1.5; 95% CI, 1-2; p < 0.002) in the infected group receiving the vitamin E-coated nails compared with the uncoated nails.

CONCLUSIONS

These preliminary findings indicate that vitamin E phosphate implant coatings can exert a protective effect on bone deposition in a highly contaminated animal model of implant-related infection.

CLINICAL RELEVANCE

The use of vitamin E coatings may open new perspectives for developing coatings that can limit septic loosening of infected implants with bacterial contamination. However, a deeper insight into the mechanism of action and the local release of vitamin E as a coating for orthopaedic implants is required to be used in clinics in the near future. Although this study cannot support the antimicrobial properties of vitamin E, promising results were obtained for bone-implant osseointegration. These preliminary results will require further in vivo investigations to optimize the host response in the presence of antibiotic prophylaxis.

Ultra-High Molecular Weight Polyethylene: Influence of the Chemical, Physical and Mechanical Properties on the Wear Behavior. A Review

Ultra-high molecular weight polyethylene (UHMWPE) is the most common bearing material in total joint arthroplasty due to its unique combination of superior mechanical properties and wear resistance over other polymers. A great deal of research in recent decades has focused on further improving its performances, in order to provide durable implants in young and active patients. From "historical", gamma-air sterilized polyethylenes, to the so-called first and second generation of highly crosslinked materials, a variety of different formulations have progressively appeared in the market. This paper reviews the structure-properties relationship of these materials, with a particular emphasis on the in vitro and in vivo wear performances, through an analysis of the existing literature.

Influence of analyzed lubricant volumes on the amount and characteristics of generated wear particles from three different types of polyethylene liner materials

The articulating components of artificial joints consist mainly of metals, ceramics, or polymers. Resulting abrasive wear particles can promote osteolysis and aseptic loosening of the endo-prosthetic implants. Ultra-high-molecular-weight-polyethylene is the material used most for bearing couples in total hip replacement. In the present study, three types of polyethylene (PE) liners varying in material composition, i.e., (1) conventional PE (C-PE), (2) sequentially cross-linked PE (SX-PE), (3) cross-linked PE blended with vitamin E (EX-PE) articulating with two types of femoral heads were used. After ultrasound treatment of each simulator lubricant, different concentrations (0.1/0.25/0.5/1.0 mL) were taken and dissolved in hydrochloric acid (37%) in a similar manner. The aim was to analyze the characteristics of wear particles generated in a hip simulator, with respect to different volumes of the lubricant. Within the scope of particle analysis, distinct alterations for particle characteristics were determined in the lubricant volumes and types of PE material used. A significant decrease in particle number for SX-PE liners, compared to the C-PE inserts and even more for EX-PE inserts, was detected at each lubricant volume. Particle morphologies varied depending on PE material. Alterations in particle size and other morphologic parameters between the four tested volumes, could be proven for each PE type. In general, particle sizes and parameters (e.g., length and width) increased with increasing serum volumes. In conclusion, the chosen volume of the simulator lubricant used for particle analysis has a crucial influence on detected particle number, size distribution, and morphologic parameters. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1299-1306, 2018.

Vitamin E-stabilized highly crosslinked polyethylenes: The role and effectiveness in total hip arthroplasty

Morphology and design of ultra-high molecular weight polyethylene (UHMWPE or simply PE) acetabular components used in total hip arthroplasty (THA) have been evolving for more than half a century. Since the late-1990s, there were two major technological innovations in PE emerged from necessity to overcome the wear-induced periprosthetic osteolysis, i.e., the development of highly crosslinked PEs (HXLPEs). There are many literature reporting that radiation crosslinked and remelted/annealed (first-generation) HXLPEs markedly reduced the incidence of osteolysis and aseptic loosening. Regardless of such clinical success in the first-generation technologies, there were some recent shifts in Japan toward the use of new second-generation HXLPEs subjected to sequential irradiation/annealing or antioxidant vitamin E (α-tocopherol) incorporation. Although the selection rate of first-generation liners still account for more than half of all the PE THAs (∼58% in 2015), the use of vitamin E-stabilized liners has been steadily growing each year since their clinical introduction in 2010. In these contexts, it is of great importance to evaluate and understand the real clinical benefits of using the new second-generation liners as compared to the first generation. This article first summarizes structural evolution and characteristic features of first-generation HXLPEs, and then provides a detailed description of second-generation antioxidant HXLPEs in regard to the role of vitamin E incorporation on their chemical and mechanical performances in THA.

Impact of vitamin E-blended UHMWPE wear particles on the osseous microenvironment in polyethylene particle-induced osteolysis

Aseptic loosening mediated by wear particle-induced osteolysis (PIO) remains the major cause of implant loosening in endoprosthetic surgery. The development of new vitamin E (α-tocopherol)-blended ultra-high molecular weight polyethylene (VE-UHMWPE) with increased oxidation resistance and improved mechanical properties has raised hopes. Furthermore, regenerative approaches may be opened, as vitamin E supplementation has shown neuroprotective characteristics mediated via calcitonin gene-related peptide (CGRP), which is known to affect bone remodeling in PIO. Therefore, the present study aimed to further clarify the impact of VE-UHMWPE wear particles on the osseous microenvironment and to identify the potential modulatory pathways involved. Using an established murine calvaria model, mice were subjected to sham operation (SHAM group), or treated with UHMWPE or VE-UHMWPE particles for different experimental durations (7, 14 and 28 days; n=6/group). Morphometric analysis by micro-computed tomography detected significant (p<0.01) and comparable signs of PIO in all particle-treated groups, whereas markers of inflammation [tumor necrosis factor (TNF)-α/tartrate resistant acid phosphatase (TRAP) staining] and bone remodeling [Dickkopf-related protein 1 (DKK-1)/osteoprotegerin (OPG)] were most affected in the early stages following surgery. Taking the present data into account, VE-UHMWPE appears to have a promising biocompatibility and increased ageing resistance. According to the α-CGRP serum levels and immunohistochemistry, the impact of vitamin E on neuropeptidergic signaling and its chance for regenerative approaches requires further investigation.

Effectiveness of Vitamin-E-Doped Polyethylene in Joint Replacement: A Literature Review

Since polyethylene is one of the most frequently used biomaterials, such as in bearing components in joint arthroplasty, strong efforts have been made to improve the design and material properties over the last decades. Antioxidants, such as vitamin-E, seem to be a promising alternative to further increase durability and reduce polyethylene wear and degradation in the long-term. Nevertheless, even if several promising in vitro results are available, there is yet no clinical evidence that vitamin-E polyethylenes show these advantages in vivo. The aim of this paper was to provide a comprehensive overview on the current knowledge regarding the biological and mechanical proprieties of this biomaterial, underlying the in vitro and in vivo evidence for effectiveness of vitamin-E-doped polyethylene in joint arthroplasty.

An uncemented iso-elastic monoblock acetabular component: preliminary results

Little is known about the clinical application of highly cross-linked polyethylene (HXLPE) blended with vitamin E. This study evaluates an uncemented iso-elastic monoblock cup with vitamin E blended HXLPE. 112 patients were followed up for 2years. 95.5% completed the follow-up. The mean VAS score for patient satisfaction was 8.8 and the mean Harris Hip Score was 94.2. In 7 cases initial gaps behind the cup were observed, which disappeared completely during follow-up in 6 cases. The mean femoral head penetration rate was 0.055mm/year. No adverse reactions or abnormal mechanical behavior was observed with the short term use of vitamin E blended HXLPE. This study shows the promising performance of this cup and confirms the potential of vitamin E blended HXLPE.