Ultra-high Molecular Weight Polyethylene Group Research Articles

Multicenter Randomized Clinical Trial of Highly Cross-Linked Polyethylene Versus Conventional Polyethylene in 518 Primary TKAs at 10 Years

Background: Second-generation highly cross-linked polyethylene (HXLPE) has revolutionized total hip arthroplasty. However, the long-term risks and benefits of HXLPE in primary total knee arthroplasty (TKA) remain unknown. This randomized clinical trial evaluated implant survivorship, complications, radiographic results, and clinical outcomes of HXLPE and conventional ultra-high molecular weight polyethylene (UHMWPE) inserts in primary TKAs. Methods: We enrolled 518 patients (518 knees) who underwent primary TKA in 3 centers within 1 tertiary referral network. The mean age was 67 years, the mean body mass index was 32 kg/m2, and 58% of the patients were women. All of the patients underwent primary TKA with a cemented posterior-stabilized tibial insert and patellar resurfacing. Randomization proceeded via stratified dynamic allocation. The patients were blinded to their study group allocation: those in the control group (254 knees) underwent TKA with an UHMWPE insert (N2Vac; Stryker); those in the treatment group (264 knees) received an HXLPE insert (X3; Stryker). Kaplan-Meier survivorship, radiographic results, and clinical outcomes were assessed. This trial was registered with ClinicalTrials.gov. The mean follow-up was 11 years. Results: The 10-year overall survivorship free from any revision and from any reoperation was 96% and 94%, respectively. There were no differences in the risk of revision or reoperation between the groups (p > 0.05). There were a total of 19 revisions. Revision indications included periprosthetic joint infection (14 knees), instability (4 knees), and open reduction and internal fixation (ORIF) for a patellar fracture due to osteolysis around a UHMWPE insert (1 knee). There were no revisions due to polyethylene wear, osteolysis, or fracture of the post in the HXLPE group. The radiographic results and clinical outcomes were otherwise similar. Conclusions: Notably, no wear-related failures were identified in the HXLPE group, but there was 1 case of osteolysis in the UHMWPE group. Level of Evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

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.

PurposeThis 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.MethodsThe 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).ResultsA 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.ConclusionThe 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.

Reduced wear in vitamin E-infused highly cross-linked polyethylene cups: 5-year results of a randomized controlled trial

Background and purpose — Vitamin E-infused polyethylene is a relatively new material in joint arthroplasty; there are no long-term reports, and only few mid-term results. Using radiostereometric analysis (RSA), we primarily determined whether vitamin E-infused highly cross-linked polyethylene (HXLPE/VitE) acetabular cups show less wear than ultra-high molecular weight polyethylene (UHMWPE) acetabular cups at 5 years after total hip arthroplasty (THA). We also assessed whether wear rates correlate with increasing cup inclination angles or cup sizes. Patients and methods — This is a 5-year follow-up of our previously reported randomized controlled trial of 62 patients with 3 years’ follow-up, who received THA with either an HXLPE/VitE or a UHMWPE acetabular cup. At 5 years, 40 patients were analyzed (22 in the HXLPE/VitE and 18 in the UHMWPE group). Results — HXLPE/VitE cups continued to show less cumulative femoral head penetration than UHMWPE cups (HXLPE/VitE: 0.24 mm, UHMWPE: 0.45 mm; p < 0.001). Distribution of wear was also more even with HXLPE/VitE cups than with UHMWPE cups (p = 0.002). Moreover, the difference in PE wear between 1 and 5 years in both groups showed no statistically significant correlation with increasing cup inclination angles or cup sizes. Finally, no osteolysis and implant loosening occurred, and no revision surgeries were required. Interpretation — Wear rates continue to be lower in HXLPE/VitE cups than in UHMWPE cups at 5 years of follow-up without correlation with increasing cup inclination angles or cup sizes. Finally, HXLPE/VitE cups may have the potential to prevent osteolysis and implant loosening.

Long-term performance of oxidized zirconium on conventional and highly cross-linked polyethylene in total hip arthroplasty.

Introduction: Polyethylene wear and subsequent osteolysis remain obstacles to the long-term survivorship of total hip arthroplasty (THA). Highly cross-linked polyethylene (XLPE) with radical quenching represents a massive leap forward with dramatically improved wear rates compared to ultra-high molecular weight polyethylene (UHMWPE). In this study we evaluate the wear of UHMWPE and XLPE coupled with oxidized zirconium (OxZr) femoral heads. Methods: A longitudinal, retrospective analysis was performed identifying consecutive patients who received a 28-mm OxZr-on-polyethylene primary THA from 2003 to 2004 by a single, high-volume arthroplasty surgeon. Patients were divided into two groups: those that received (1) UHMWPE liner and (2) a highly XLPE liner. Patients were included if clinical follow-up was complete to 2014 or later. Radiographic analysis was performed by two blinded observers. Measures included cup position, annual linear wear rate, and presence of osteolysis. Pairwise comparisons, correlations, and inter-rater reliability were calculated. Results: Eighty patients were in the UHMWPE group with an average follow-up of 10 ± 1.23 years and 88 patients in the XLPE group with an average of 10 ± 1.03-year follow-up. Average age (68) was similar between groups (p = 0.288). Observer reliability was excellent for cup abduction (ICC = 0.940), anteversion (ICC = 0.942), and detection of osteolysis (ICC = 0.811). Annual linear wear rates were significantly higher (p = 1 × 10−19) with UHMWPE (0.21 ± 0.12 mm/year) compared to XLPE (0.05 ± 0.03 mm/year). Linear wear rate was significantly correlated to decreasing acetabular abduction (p = 0.035). Osteolysis was noted only in the UHMWPE group, with 17 patients (21.2%) exhibiting acetabular osteolysis and 37 (46.3%) patients exhibiting femoral osteolysis. Conclusions: OxZr coupled with XLPE showed minimal wear and no osteolysis at 10-year follow up. The yearly linear penetration rate is similar to that seen in other studies of XLPE THA. A careful longitudinal follow-up will be required to determine if advanced bearings such as OxZr or ceramic can show improved performance in the second decade of implantation.

Wear Rates of XLPE Nearly 50% Lower Than Previously Thought After Adjusting for Initial Creep: An RCT Comparing 4 Bearing Combinations.

Background:The ideal bearing combination for total hip arthroplasty (THA) remains debatable. Highly cross-linked polyethylene (XLPE) is widely used, but long-term wear rates are not fully known, nor is how much the initial “creep,” if any, affects overall wear. Additionally, the use of oxidized zirconium (OxZir) is purported to lower polyethylene wear rates, but this has not been proven. We present the 10-year data of a cohort of patients who underwent THA. Patients were prospectively randomized to 1 of 4 bearing combinations: a conventional ultra-high molecular weight polyethylene (UHMWPE) or XLPE acetabular liner coupled with either a cobalt-chromium (CoCr) or OxZir femoral head. The aims of the study were to (1) assess the extent to which creep affected overall wear rates and (2) assess wear rates between OxZir and CoCr with polyethylene.Methods:A total of 92 hips (92 patients) between the ages of 22 and 65 years (mean, 52.2 ± 9.3 years) were randomized to 4 groups. At 10 years, 70 (76%) of the hips were available for analysis; patients who had undergone revision, had died, or were lost to follow-up were excluded from final analysis. Radiographic analysis was performed using a validated digital assessment program to determine linear, volumetric, and directional wear of the polyethylene for all 4 bearing couples. Radiographic assessments were performed immediately postoperatively, at 6 and 12 weeks, and then annually for a minimum of 10 years.Results:XLPE had significantly lower wear rates than UHMWPE. Once creep was eliminated, annual and overall wear rates were nearly 50% lower than have been previously reported. This was proportionally more important in the XLPE group than in the UHMWPE group. There was a nonsignificant trend toward a lower wear rate with OxZir heads.Conclusions:Creep plays a notably more important role than first thought. Once creep was eliminated, the overall wear rate was even lower than previously assumed. This has important implications for the overall survivorship of hip arthroplasty implants.Level of Evidence:Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Carbon-fibre-reinforced PEEK: An alternative material for flexion bushings of rotating hinged knee joints?

BackgroundFor prosthetic knee joints of the hinged type, typically polyethylene (PE) flexion bushings are used between axis and femoral component to prevent metallic wear. Nevertheless, PE-wear can lead to periprosthetic osteolysis followed by aseptic loosening of the implant. Based on high creep and wear resistance carbon-fibre-reinforced polyether ether ketones (CFR-PEEKs) could provide an alternative material to ultra-high-molecular-weight polyethylene (UHMWPE) for this bearing type. MethodsFlexion bushings of four different materials were investigated (CFR-PEEK pitch fibres, CFR-PEEK PAN fibres, virgin PEEK without carbon fibres and UHMWPE) using a bushing tester. For determination of the polymeric and metallic wear, gravimetric measurements and particle analyses were performed. ResultsThe polymeric wear rates of CFR-PEEK PAN (6.657 ± 0.714 mg/106 cycles) and CFR-PEEK pitch (32.085 ± 2.748 mg/106 cycles) were significantly higher compared to the polymeric wear rates of virgin PEEK (0.764 ± 0.283 mg/106 cycles) or UHMWPE (−0.015 ± 0.011 mg/106 cycles) (p < .001). In addition, the metallic wear rates were significantly higher when using bushings made of CFR-PEEK PAN (3.373 ± 0.214 mg/106 cycles) and CFR-PEEK pitch (3.604 ± 0.355 mg/106 cycles), than when using bushings made of virgin PEEK (0.177 ± 0.049 mg/106 cycles) or UHMWPE (0.031 ± 0.011 mg/106 cycles) (p < .001). The mean particle size of the two CFR-PEEK groups was significantly smaller compared to the virgin PEEK and UHMWPE group (p < .001). ConclusionAccording to these results, the clinical use of CFR-PEEK in combination with CoCr could lead to higher wear rates and this should be avoided. Virgin PEEK may still be considered as an alternative to UHMWPE to use it for flexion bushings in a hinged knee joint.

Ten-year follow-up study of three alternative bearing surfaces used in total hip arthroplasty in young patients: a prospective randomised controlled trial.

We present the ten-year data of a cohort of patients, aged between 18 and 65 years (mean age 52.7 years; 19 to 64), who underwent total hip arthroplasty. Patients were randomised to be treated with a cobalt-chrome (CoCr) femoral head with an ultra-high molecular weight polyethylene (UHMWPE), highly cross-linked polyethylene (XLPE) or ceramic-on-ceramic (CoC) bearing surface. A total of 102 hips (91 patients) were randomised into the three groups. At ten years, 97 hips were available for radiological and functional follow-up. Two hips (two patients) had been revised (one with deep infection and one for periprosthetic fracture) and three were lost to follow-up. Radiological analysis was performed using a validated digital assessment programme to give linear, directional and volumetric wear of the two polyethylene groups. There was a significantly reduced rate of steady-state linear wear with XLPE (0.07 mm/yr) compared with UHMWPE (0.37 mm/yr) (p = 0.001). Volumetric wear was also significantly reduced in the XLPE group (29.29 mm3/yr) compared with the UHMWPE group (100.75mm3/yr) (p = 0.0001). There were six patients with UHMWPE who had non-progressive osteolysis and none in the XLPE group. All three bearing groups had significant improvements in 12-item short form health survey scores, Western Ontario and McMaster Universities Osteoarthritis Index score and Harris Hip Score. However, the improvement in HSS was significantly less in the UHMWPE group (p = 0.0188) than in the other two groups. At ten years, the rates of volumetric and linear wear in the XLPE group remain low and predominantly below the estimated threshold for osteolysis (1 mm/yr). The rate of linear wear in the XLPE group was three times less than in the UHMWPE group at five-year follow-up and five times less at ten years. The rate of volumetric wear was also three times less in the XLPE group at ten years. While CoC also performs well, XLPE at ten years remains a safe and excellent bearing option in young patients, with low rates of wear and no evidence of osteolysis. Cite this article: Bone Joint J 2017;99-B:1590-5.

The Relationship Between Polyethylene Wear and Periprosthetic Osteolysis in Total Hip Arthroplasty at 12 Years in a Randomized Controlled Trial Cohort

BackgroundPolyethylene acetabular components are common in hip arthroplasty. Highly cross-linked polyethylene (HXLPE) has lower wear than ultra-high molecular weight polyethylene (UHMWPE). Evidence suggests that wear particles induce inflammation causing periprosthetic osteolysis contributing to implant loosening with wear rates of 0.05 mm/y were considered safe. We aimed to compare incidence and volume of periacetabular osteolysis between HXLPE and UHMWPE using computed tomography. MethodsInitially, 54 hips in 53 patients were randomized to HXLPE or UHMWPE acetabular liner. At 10 years, 39 hips in 38 patients remained for the radiostereometric analysis' demonstrating significantly lower wear in the HXLPE group. At 12 years, 14 hips in 13 patients were lost to follow-up leaving 25 hips for computed tomography assessment. Images were reconstructed to detect osteolysis and where identified, areas were segmented and volumized. ResultsOsteolysis was observed in 8 patients, 7 from the UHMWPE group and only 1 from the HXLPE group (Fisher exact, P = .042). There was no correlation between the amount of polyethylene wear and osteolysis volume; however, the radiostereometric analysis-measured wear rate in patients with osteolysis from both groups was significantly higher than overall average wear rate. ConclusionThis data demonstrates lower incidence of periacetabular osteolysis in the HXLPE group of a small cohort. Although numbers are too low to estimate causation, in the context of lower wear in the HXLPE group, this finding supports the hypothesis that HXLPE may not elevate osteolysis risk, and hence does not suggest that HXLPE wear particles are more biologically active than those generated by earlier generations of polyethylene.

Does vitamin E-blended polyethylene reduce wear in primary total hip arthroplasty: a blinded randomised clinical trial.

Some data indicate that first-generation highly cross-linked polyethylene (HXLPE) can oxidise in vivo and is associated with reduced mechanical properties. To overcome these limitations, a natural anti-oxidant vitamin E has been added to HXLPE to preserve the mechanical properties and decrease oxidative degradation whilst conserving high wear resistance. We hypothesised that after a minimal threeyears of follow-up the use of vitamin E-blended HXLPE would result in lower radiographic wear when compared with ultra-high molecular weight polyethylene (UHMWPE). One hundred patients were randomised to receive hybrid total hip arthroplasty (THA) using a monoblock cementless acetabular component made either of UHMWPE or vitamin E-blended HXLPE. All other parameters were identical in both groups. Complete follow-up was available for 74 of these patients. Femoral head penetration was measured using a validated computer-assisted method. The median creep measured 0.111mm (range, -0.576 - +0.444mm) in the vitamin E-blended group versus 0.170mm (range, -0.861 - +0.884mm) in the UHMWPE group (difference of medians, 0.059; p = 0.046). The median steady state penetration rate was -0.008mm/year (range, -0.88 - +0.64mm/year) in the vitamin E-blended group versus 0.133mm/year (range, -0.84 - +0.85mm/year) in the UHMWPE group (difference of medians 0.141, p = 0.043). This study demonstrated that femoral head penetration was lower when using vitamin E-blended HXLPE when compared with UHMWPE, with a steady-state penetration rate far below the osteolysis threshold. Longer-term follow-up is needed to warrant whether wear reduction will generate less occurrence of osteolysis and aseptic loosening.

Elevated cytokine expression of different PEEK wear particles compared to UHMWPE in vivo

Due to their mechanical properties, there has been growing interest in poly-ether-ether-ketone (PEEK) and its composites as bearing material in total and unicompartmental knee arthroplasty. The aim of this study was to analyze the biological activity of wear particles of two different (pitch and PAN) carbon-fiber-reinforced- (CFR-) PEEK varieties in comparison to ultra-high-molecular-weight-polyethylene (UHMWPE) in vivo. The authors hypothesized no difference between the used biomaterials. Wear particle suspensions of the particulate biomaterials were injected into knee joints of Balb/c mice, which were sacrificed after seven days. The cytokine expression (IL-1β, IL-6, TNF-α) was analyzed immunohistochemically in the synovial layer, the adjacent bone marrow and the articular cartilage. Especially in the bone marrow of the two CFR-PEEK varieties there were increased cytokine expressions compared to the control and UHMWPE group. Furthermore, in the articular cartilage the CFR-PEEK pitch group showed an enhanced cytokine expression, which could be a negative predictor for the use in unicondylar knee systems. As these data suggest an increased proinflammatory potential of CFR-PEEK and its composites in vivo, the initial hypothesis had to be refuted. Summarizing these results, CFR-PEEK seems not to be an attractive alternative to UHMWPE as a bearing material, especially in unicompartmental knee arthroplasty.

Cross-linked ultra-high-molecular weight polyethylene liner and ceramic femoral head in total hip arthroplasty: a prospective study at 5 years follow-up

Recent data indicate that enhanced wear resistance can be obtained with new cross-linked ultra-high-molecular weight polyethylene (CL-UHMWPE) liners, in comparison with previous-generation liners. The current prospective, cohort study was undertaken to analyse whether the use of a new CL-UHMWPE (Rexpol) results in a lower wear rate than ultra-high-molecular weight polyethylene (UHMWPE) in a group of similar patients undergoing total hip arthroplasty (THA). This study provides the first clinical data with this particular CL-UHMWPE. Between January 2001 and December 2001, patients underwent THA with biconical threaded cups and ceramic femoral heads using either a CL-UHMWPE liner (n = 50) or a regular UHMWPE liner (n = 57). At the time of the final 5-year evaluation, there were 48 patients available in the CL-UHMWPE and 54 patients available in the UHMWPE group. After a mean 5.6 years follow-up, there were no significant differences between the groups in Harris Hip Score outcomes. However, there was a 69.1% decrease in wear at 5 years for the CL-UHMWPE group in comparison with the UHMWPE group (p < 0.01). The use of CL-UHMWPE significantly reduced the risk of polyethylene wear in patients undergoing THA with biconical threaded cups and ceramic femoral heads. Further follow-up is needed to determine how this will influence long-term outcomes.

The Seven-Year Wear of Highly Cross-Linked Polyethylene in Total Hip Arthroplasty

The use of highly cross-linked polyethylene is now commonplace in total hip arthroplasty. Hip simulator studies and short-term in vivo measurements have suggested that the wear rate of highly cross-linked polyethylene is significantly less than that of conventional ultra-high molecular weight polyethylene. However, long-term data to support its use are limited. The aim of this study was to compare the intermediate-term steady-state wear of highly cross-linked polyethylene compared with that of conventional ultra-high molecular weight polyethylene acetabular liners in a prospective, double-blind, randomized controlled trial with use of radiostereometric analysis. Fifty-four patients were randomized to receive hip replacements with either conventional ultra-high molecular weight polyethylene acetabular liners (Zimmer) or highly cross-linked polyethylene liners (Longevity; Zimmer). All patients received a cemented, collarless, polished, tapered femoral component (CPT; Zimmer) and an uncemented acetabular component (Trilogy; Zimmer). Clinical outcomes were assessed and the three-dimensional penetration of the head into the socket was determined for a minimum of seven years. Linear regression was used to calculate the steady-state wear rate following the creep-dominated penetration seen during the first year. At a minimum of seven years postoperatively, the mean total femoral head penetration was significantly lower in the highly cross-linked polyethylene group (0.33 mm; 95% confidence interval [CI], ±0.10 mm) than it was in the ultra-high molecular weight polyethylene group (0.55 mm; 95% CI, ±0.10 mm) (p = 0.005). The mean steady-state wear rate of highly cross-linked polyethylene was 0.005 mm/yr (95% CI, ±0.015 mm/yr), compared with 0.037 mm/yr (95% CI, ±0.019 mm/yr) for conventional ultra-high molecular weight polyethylene (p = 0.007). No patient in the highly cross-linked polyethylene group had a wear rate above the osteolysis threshold of 0.1 mm/yr, compared with 9% of patients in the ultra-high molecular weight polyethylene group. This study demonstrates that highly cross-linked polyethylene has a significantly lower steady-state wear rate compared with that of conventional ultra-high molecular weight polyethylene. Longer-term follow-up is required to determine if this will translate into improved clinical performance and longevity of these implants.