We have performed an RCT of cross-linked versus non cross-linked polyethylene with 125 patients followed for five years. The study showed a dramatic reduction of wear with the cross-linked polyethylene consistent with the in-vitro studies. Because it has been recognised that hard bearings are sensitive to edge loading we were concerned that highly cross-linked polyethylene might exhibit wear properties similar to hard bearings. We have therefore analysed the wear rate as it relates to both anteversion and tilt, to compare non cross-linked polyethylene with cross-linked polyethylene. We found that there was no relationship between tilt and ante-version on any wear indices. These data suggest that, despite having different mechanical properties to non cross-linked polyethylene, cross-linked polyethylene does not exhibit increased wear with conditions that increase edge loading

Aims. The primary outcome was investigating differences in wear, as measured by femoral head penetration, between cross-linked vitamin E-diffused polyethylene (vE-PE) and cross-linked polyethylene (XLPE) acetabular component liners and between 32 and 36 mm head sizes at the ten-year follow-up. Secondary outcomes included acetabular component migration and patient-reported outcome measures (PROMs) such as the EuroQol five-dimension questionnaire, 36-Item Short-Form Health Survey, Harris Hip Score, and University of California, Los Angeles Activity Scale (UCLA). Methods. A single-blinded, multi-arm, 2 × 2 factorial randomized controlled trial was undertaken. Patients were recruited between May 2009 and April 2011. Radiostereometric analyses (RSAs) were performed from baseline to ten years. Of the 220 eligible patients, 116 underwent randomization, and 82 remained at the ten-year follow-up. Eligible patients were randomized into one of four interventions: vE-PE acetabular liner with either 32 or 36 mm femoral head, and XLPE acetabular liner with either 32 or 36 mm femoral head. Parameters were otherwise identical except for acetabular liner material and femoral head size. Results. A total of 116 patients participated, of whom 77 were male. The median ages of the vE-PE 32 mm and 36 mm groups were 65 (interquartile range (IQR) 57 to 67) and 63 years (IQR 56 to 66), respectively, and of the XLPE 32 mm and 36 mm groups were 64 (IQR 58 to 66) and 61 years (IQR 54 to 66), respectively. Mean total head penetration was significantly lower into vE-PE acetabular liner groups than into XLPE acetabular liner groups (-0.219 mm (95% confidence interval -0.348 to -0.090); p = 0.001). There were no differences in wear according to head size, acetabular component migration, or PROMs, except for UCLA. There were no cases of aseptic loosening or failures requiring revision at long-term follow-up. Conclusion. Significantly lower wear was observed in vE-PE acetabular liners than in XLPE acetabular liners. No difference in wear was observed between different head size or PROMs except for the UCLA at ten years. Cite this article: Bone Joint J 2023;105-B(10):1052–1059

We present minimum 20 year results of a randomized, prospective double blinded trial (RCT) of cross-linked versus conventional polyethylene (PE), using a computer assisted method of PE wear measurement. After Ethics Committee approval, 122 patients were enrolled into an RCT comparing Enduron (non cross-linked PE) and highly cross-linked Marathon PE (DePuy, Leeds, UK). Other than the PE liners, identical components were used, a Duraloc 300 metal shell with one screw, a 28mm CoCr femoral head and a cemented Charnley Elite femoral stem. All patients were followed with anteroposterior (A∼P) and lateral radiographs at 3 days, 6 weeks, 3 months, 6 months, 1, 2, 3, 4, 5, 10 and 20 years. PE wear was measured with PolyMig, which has a phantom validated accuracy of ± 0.09mm. At minimum 20 year follow-up, 47 patients had died, 5 of which had been revised prior to their death. Another 32 patients were revised and alive, leaving 43 patients unrevised and alive (15 Enduron, 28 Marathon). No patients were lost to follow-up, but 2 were not able to be radiographed (dementia), leaving 41 patients (15 Enduron, 26 Marathon) available for PE wear measurement. After the bedding-in period, Enduron liners had a wear rate of 0.182 mm/year, and Marathon liners had a wear rate of 0.028 mm/year. At 20 years follow-up, 37 patients had required revision. Patients with conventional PE had three times the revision rate (28/37) of those who received XLPE (9/37). This is the longest term RCT showing substantially improved clinical and radiological results when XLPE is used as the bearing surface

Oxidized zirconium (Oxinium) and highly cross-linked polyethylene (HXLPE) were developed with the purpose of minimizing wear, and subsequent osteolysis, in Total Hip Arthroplasty (THA). However, few articles have been published on long-term results of Oxinium on highly cross-linked polyethylene. The purpose of this investigation is to report minimum 10-year HXLPE wear rates and the clinical outcome of patients in this group and compare this population to a control group of cobalt chrome and ceramic. One hundred forty THAs were performed for 123 patients using an Oxinium head with an HXLPE liner. Ninety-seven had 10 years of clinical follow-up (avg. 14.5). Harris Hip Scores (HHS) were collected preoperatively and at the most recent follow-up. Radiographs of 85 hips were available for a minimum 10-year follow-up (avg. 14.5) and used to calculate wear using PolyWare software. Control groups of cobalt chrome and ceramic articulation on HXLPE with a minimum 10-year follow-up were studied. Clinical follow-up of the Oxinium group showed a statistical improvement compared to preoperative and was similar to the control group of patients. Radiographic evaluation found the linear and volumetric wear rates for the Oxinium group of 0.03 mm/year (range 0.00–0.08) and 3.46 mm. 3. /year (range 1.0 to 15.0) respectively. There was no statistically significant difference in linear or volumetric wear rate between the groups (P-value 0.92 and 0.55 respectively). None of these patients underwent revision of their hip for any reason. Oxinium on highly cross-linked polyethylene has performed exceptionally with wear rates comparable to those of cobalt chrome or ceramic on HXLPE

Aims. Limited implant survival due to aseptic cup loosening is most commonly responsible for revision total hip arthroplasty (THA). Advances in implant designs and materials have been crucial in addressing those challenges. Vitamin E-infused highly cross-linked polyethylene (VEPE) promises strong wear resistance, high oxidative stability, and superior mechanical strength. Although VEPE monoblock cups have shown good mid-term performance and excellent wear patterns, long-term results remain unclear. This study evaluated migration and wear patterns and clinical and radiological outcomes at a minimum of ten years’ follow-up. Methods. This prospective observational study investigated 101 cases of primary THA over a mean duration of 129 months (120 to 149). At last follow-up, 57 cases with complete clinical and radiological outcomes were evaluated. In all cases, the acetabular component comprised an uncemented titanium particle-coated VEPE monoblock cup. Patients were assessed clinically and radiologically using the Harris Hip Score, visual analogue scale (pain and satisfaction), and an anteroposterior radiograph. Cup migration and polyethylene wear were measured using Einzel-Bild-Röntgen-Analyze software. All complications and associated treatments were documented until final follow-up. Results. Clinical assessment showed persistent major improvement in all scores. On radiological assessment, only one case showed a lucent line (without symptoms). At last follow-up, wear and migration were below the critical thresholds. No cup-related revisions were needed, indicating an outstanding survival rate of 100%. Conclusion. Isoelastic VEPE cups offer high success rates and may prevent osteolysis, aseptic loosening, and the need for revision surgeries in the long term. However, longer follow-up is needed to validate our findings and confirm the advantages offered by this cup. Cite this article: Bone Jt Open 2024;5(10):825–831

Aims. Radiostereometric analysis (RSA) is the most accurate radiological method to measure in vivo wear of highly cross-linked polyethylene (XLPE) acetabular components. We have previously reported very low wear rates for a sequentially irradiated and annealed X3 XLPE liner (Stryker Orthopaedics, USA) when used in conjunction with a 32 mm femoral heads at ten-year follow-up. Only two studies have reported the long-term wear rate of X3 liners used in conjunction with larger heads using plain radiographs which have poor sensitivity. The aim of this study was to measure the ten-year wear of thin X3 XLPE liners against larger 36 or 40 mm articulations with RSA. Methods. We prospectively reviewed 19 patients who underwent primary cementless THA with the XLPE acetabular liner (X3) and a 36 or 40 mm femoral head with a resultant liner thickness of at least 5.8 mm. RSA radiographs at one week, six months, and one, two, five, and ten years postoperatively and femoral head penetration within the acetabular component were measured with UmRSA software. Of the initial 19 patients, 12 were available at the ten-year time point. Results. The median proximal, 2D, and 3D wear rates calculated between one and ten years were all less than 0.005 mm/year, with no patient recording a proximal wear rate of more than 0.021 mm/year. Importantly, there was no increase in the wear rate between five and ten years. Conclusion. The very low wear rate of X3 XLPE liners with larger articulations remains encouraging for the future clinical performance of this material. Cite this article: Bone Jt Open 2023;4(11):839–845

Introduction. Highly cross-linked ultrahigh molecular weight polyethylene (UHMWPE) is the most common bearing surface used in total joint arthroplasty due to its excellent wear resistance. While radiation cross-linking is currently used, cross-linking using a cross-linking agent such as a peroxide can also be effective with improved oxidative stability, which can be achived by an antioxidant such as vitamin E. The peroxide cross-linking behavior of UHMWPE in the presence of vitamin E was unknown. We investigated the cross-linking behavior and the clinically relevant mechanical and wear properties of peroxide cross-linked, vitamin E-blended UHMWPE. Materials and Methods. Medical grade UHMWPE (GUR1050) was blended with vitamin E and the peroxide (2,5-Dimethyl-2,5-di(t-butylperoxy)hexyne-3 or P130) before compression molding. Various vitamin E (0.1, 0.2, 0.3, 0.5, 0.6, 0.8 and 1.0 wt%) and peroxide concentrations (0.5, 1 and 1.5 wt%) were studied. The cross-link density was calculated as previously described (Oral 2010). The wear rate was determined using a custom-designed pin-on-disc wear tester against CoCr polished discs at 2 Hz and a rectangular path of 5 × 10 mm in undiluted bovine serum (Bragdon 2001). Tensile mechanical properties were determined using Type V dogbones according to ASTM D638. Oxidative stability was determined using oxidation induction testing (Braithwaite 2010). Double-notching and IZOD impact testing was performed according to ASTM D256. Samples prepared with vitamin E concentrations of 0.3 wt% and above and P130 concentrations of 0.5 and 1 wt% were also terminally gamma sterilized. Controls were 150-kGy irradiated vitamin E blends of UHMWPE. Results and Discussion. The cross-link density of peroxide cross-linked UHMWPEs were higher than the irradiated controls at a given vitamin E concentration (For example 250, 301 and 355 mol/dm3 for 0.5, 1 and 1.5 wt% peroxide cross-linked UHMWPE compared to 217 mol/dm3 for 150 kGy irradiated UHMWPE; Figure 1). The cross-link density dependence of wear was similar to radiation cross-linked UHMWPE, resulting in clinically relevant wear rates of 0.5 to 1.5 mg/MC. While the cross-link density of radiation cross-linked UHMWPE became saturated at vitamin E concentrations above 0.3 wt% (Oral 2008), this was not observed in peroxide cross-linked UHMWPE (Figure 2), suggesting more efficient cross-linking in the presence of the antioxidant. The impact strength was 30% higher for the peroxide cross-linked UHMWPEs at the comparable wear rate compared to irradiated controls (72 vs. 56 kJ/m2). The oxidation induction time of all peroxide cross-linked UHMWPEs (up to 57 min) was higher than that of the 0.1 wt% vitamin E-blended, 150-kGy irradiated UHMWPE (6 min). Gamma sterilization of peroxide cross-linked vitamin E blends decreased wear (0.5 wt% peroxide in Figure 3). Thus, peroxide concentration for cross-linking can be reduced if terminal sterilization is used. The mechanical properties and the oxidative stability of the material were not significantly affected by gamma sterilization. Significance. Peroxide cross-linking enabled good wear resistance for high vitamin E concentration blends of UHMWPE (>0.3 wt%), previously not possible by irradiation. Peroxide cross-linking of vitamin E-blended UHMWPE can provide a one-step, cost-effective method to manufacture wear resistant total joint implants with improved oxidative stability

The 2021 Australian Orthopaedic Association National Joint Replacement Registry report indicated that total shoulder replacement using both mid head (TMH) length humeral components and reverse arthroplasty (RTSA) had a lower revision rate than stemmed humeral components in anatomical total shoulder arthroplasty (aTSA) - for all prosthesis types and diagnoses. The aim of this study was to assess the impact of component variables in the various primary total arthroplasty alternatives for osteoarthritis in the shoulder. Data from a large national arthroplasty registry were analysed for the period April 2004 to December 2020. The study population included all primary aTSA, RTSA, and TMH shoulder arthroplasty procedures undertaken for osteoarthritis (OA) using either cross-linked polyethylene (XLPE) or non-cross-linked polyethylene (non XLPE). Due to the previously documented and reported higher revision rate compared to other anatomical total shoulder replacement options, those using a cementless metal backed glenoid components were excluded. The rate of revision was determined by Kaplan-Meir estimates, with comparisons by Cox proportional hazard models. Reasons for revision were also assessed. For a primary diagnosis of OA, aTSA with a cemented XLPE glenoid component had the lowest revision rate with a 12-year cumulative revision rate of 4.7%, compared to aTSA with cemented non-XLPE glenoid component of 8.7%, and RTSA of 6.8%. The revision rate for TMH was lower than aTSA with cemented non-XLPE, but was similar to the other implants at the same length of follow-up. The reason for revision for cemented aTSR was most commonly component loosening, not rotator cuff deficiency. Long stem humeral components matched with XLPE in aTSA achieve a lower revision rate compared to shorter stems, long stems with conventional polyethylene, and RTSA when used to treat shoulder OA. In all these cohorts, loosening, not rotator cuff failure was the most common diagnosis for revision

Purpose:. Although short term outcomes of reverse total shoulder arthroplasty (rTSA) have been promising, long-term success may be limited due to complications, including scapular notching. Scapular notching has been explained primarily as a mechanical erosion, however, generation of wear debris may lead to further biologic changes contributing to the severity of scapular notching. Highly cross-linked ultra-high molecular weight polyethylene (UHMWPE) has been used routinely in constrained joint applications such as total hip arthroplasty for reduction of wear debris particles. Although rTSA shares similarity in design conformity, conventional UHMWPE remains the gold standard. Methods:. A commercially available hip simulator was converted to a 12-station rTSA wear simulator. Conventional and highly cross-linked UHMWPE humeral liners were subjected to 5,000,000 cycles of alternating abduction-adduction and flexion-extension loading profiles. Every 250,000 cycles, liners were evaluated with gravimetric wear measurements and test serum was collected for morphological characterization of wear particles. Results:. Highly cross-linked UHMWPE liners (36.5 ± 10.0 mm. 3. /million cycle) exhibited significantly lower volumetric wear rates compared to conventional UHMWPE liners (83.6 ± 20.6 mm3/million cycle) (p < 0.001) (Figure 1). The flexion-extension loading profile exhibited significantly higher wear rates for both conventional (p < 0.001) and highly cross-linked UHMWPE (p < 0.001) compared to the abduction-adduction loading profile. Highly cross-linked wear particles had an equivalent circle diameter significantly smaller than wear particles from conventional UHMWPE (p < 0.001) (Figure 2). Highly cross-linked wear particles were also significantly less fibrillar than conventional UHMWPE particles with respect to particle aspect ratio (p < 0.001) and particle roundness (p < 0.001). Conclusion:. This is the first study to examine the effect of cross-linked PE in a rTSA wear simulation. Highly cross-linked UHMWPE liners significantly reduced UHWMPE wear and subsequent particle generation. More favorable wear properties with the use of highly cross-linked UHMWPE may lead to increased rTSA device longevity and fewer complications but must be weighed against the impact of reduced mechanical properties

Introduction. Radiation cross-linked UHMWPE is preferred in total hip replacements due to its wear resistance [1]. In total knees, where stresses are higher, there is concern of fatigue damage [2]. Antioxidant stabilization of radiation cross-linked UHMWPE by blending vitamin E into the polymer powder was recently introduced [3]. Vitamin E greatly hinders radiation cross-linking in UHMWPE [4]. In contrast peroxide cross-linking of UHMWPE is less sensitive to vitamin E concentration [5]. In addition, exposing UHMWPE to around 300°C, increases its toughness by inducing controlled chain scission and enhanced intergranular diffusion of chains, simultaneously [6]. We present a chemically cross-linked UHMWPE with high vitamin E content and improved toughness by high temperature melting. Methods and Materials. Medical grade GUR1050 UHMWPE was blended with vitamin E and with 2,5-Di(tert-butylperoxy)-2,5-dimethyl-3-hexyne or P130 (0.5% Vitamin-E and 0.9% P130). The mixed powder was consolidated into pucks. The pucks were melted for 5 hours in nitrogen at 300, 310 and 320°C. One set of pucks melted at 310°C was accelerated aged at 70°C at 5 atm. oxygen for 2 weeks. Tensile mechanical properties were determined using ASTM D638. Izod impact toughness was determined using ASTM D256 and F648. Wear rate was determined using a bidirectional pin-on-disc (POD) tester with cylindrical pins of UHMWPE against polished CoCr discs in undiluted, preserved bovine serum. Results. The vinyl index increased as a function of temperature (Fig 1a). Cross-link density steadily decreased and impact strength increased with increasing vinyl index (Fig 1b). The ultimate tensile strength (UTS) was not affected by HTM (Table 2). Impact strength was significantly improved for all treatment temperatures (P<0.05) and wear was significantly increased only for the sample melted at 320°C (Table 2). Discussion. High temperature melting (HTM) was shown to increase toughness of UHMWPEs presumably due to controlled chain scissioning and increased intergranular diffusion of chains [6]. For radiation cross-linked UHMWPE, it was shown that an increase in elongation-at-break and impact strength could be obtained without sacrificing wear resistance up to an elongation of about 500% [7]. This vitamin E-blended, peroxide cross-linked, high temperature melted UHMWPE has very high oxidation resistance due to its high antioxidant content, high wear resistance due to cross-linking and much improved toughness, representing an optimum joint replacement surface. For figures/tables, please contact authors directly.

Introduction. Highly cross-linked polyethylene has been introduced to decrease osteolysis secondary to polyethylene wear debris generation, but there are few long-term data on revision total hip arthroplasty using highly cross-linked polyethylene liners. The purpose of this study was to report the long-term radiographic and clinical outcomes of a highly cross-linked polyethylene liner in revision total hip arthroplasty. Materials & Methods. We analyzed 63 revision total hip arthoplasties that were performed in 63 patients using a highly cross-linked polyethylene liner between April 2000 and February 2005. Of these, nine died and four were lost to follow-up before the end of the 10-year evaluation. Thus, the final study cohort consisted of 50 patients (50 hips). There were 26 males and 24 females with a mean age at time of revision total hip arthoplasty of 53 years (range, 27–75 years). Mean duration of follow-up was 11 years (range, 10–14 years). Results. Mean Harris hip score improved from 44 points preoperatively to 85 points at final follow-up. No radiographic evidence of osteolysis was found in any hip. One hip required re-revision surgery for acetabular cup loosening at 6.5 years postoperatively. One required re-revision with a constrained liner because of recurrent dislocation. Three sustained deep infections requiring additional surgical procedures. Kaplan-Meier survivorship with an end point of re-revision for any reason was 91.0% and for aseptic cup loosening was 97.9% at 11 years (Figs. 1 and 2). Conclusions. At a minimum of 10 years, the highly cross-linked polyethylene liners showed excellent clinical performance and implant survivorship, and were not associated with osteolysis in our group of patients with revision total hip arthoplasties

Highly cross-linked polyethylene (HXLPE) has decreased wear and revision rates in total hip replacement (THR) at a long-term. However, the effect of HXLPE manufacturing characteristics on femoral head penetration has not been clearly defined yet. We report this single-institution study to investigate the clinical and radiological results of different HXLPE liners in THR. In this retrospective cohort analysis of our prospective database, we identified 904 THRs performed between 2000 and 2013. Seven different HXLPE liner types were assessed: remelted (3), annealed (2), sequentially annealed (1) and vitamin E-infused (1). The linear femoral head penetration rate was measured at six weeks, one year, and annually thereafter, using the Roman Software v1.70 package. Thirty hips were revised for the following reasons: aseptic loosening (11), dislocation (12), periprosthetic femoral fracture (6), and infection (1). No hip was revised for wear or osteolysis. 741 THRs were evaluated for a mean follow-up of 15 years (range, 10 to 20). The mean total penetration 15 years after THR was 0.17 mm in the sequentially annealed, and 0.16 mm in the vitamin E-infused groups, whereas it was 0.26 mm in the melted 95 kGy, 0.27 mm in the melted 5 Mrad and 0.25 mm in the melted 100 kGy groups (p=0.001). From one to 15 years after surgery, the mean wear was 0.206 mm in cups with an acetabular inclination greater than 50º and 0.105 mm in those placed between 35º and 50º (p<0.001). Although HXLPE characteristics can result in a different wear performance in patients undergoing THR at a mean follow-up of 15 years, the clinical results are excellent. The position of the acetabular component can influence on the femoral head penetration of modern HXLPEs. Nevertheless, these patients should continue to be monitored to detect future problems

Introduction. Technological advances in the processing of polyethylene have led to improved survivorship of total hip arthroplasty. The purpose of this study was to determine if a second generation highly cross-linked polyethylene could improve upon wear rates compared to conventional and first generation cross-linked polyethylene in patients undergoing primary total hip arthroplasty. Methods. Linear and volumetric wear rates of a second generation highly cross-linked polyethylene were evaluated following primary total hip arthroplasty. There were 44 patients with an average age of 68.6 years and mean follow-up of 5.3 years. Patients were evaluated at six weeks, one, two and five years. Wear rates were determined from digitized AP Pelvis radiograph by an independent observer using Martell's software. Acetabular inclination and femoral head size were also evaluated to determine variability in wear rates. Results. The mean linear wear rate for the entire group was 0.015mm/year (±0.055). There was a 64% decrease in linear wear rate when compared to a first generation highly cross-linked polyethylene from the same institution. There was a 90% decrease in wear rate compared to conventional polyethylene. There were no differences in the linear wear rate between the 32mm vs. larger head sizes (36mm and 40mm). However, there was a 30% increase in volumetric wear rate with larger head sizes. The mean wear rate in patients with cup inclination less than 45 degrees was 0.006mm/year compared with 0.024mm/year for those with an inclination greater than 45 degrees. The amount of linear wear was increased by 4 times in patients with a cup inclination of greater than 45 degrees. There was no evidence of any osteolysis in this group of patients. Conclusion. Our data with a mean follow-up of 5.3 years, using a second generation highly cross-linked polyethylene, demonstrates a dramatic decrease in incidents of linear wear compared to conventional polyethylene and first generation highly cross-linked polyethylene (Figure 1). Of concern is the higher volumetric wear rate noted with larger head sizes and increased linear wear rates with cup inclination angles of greater than 45 degrees. Despite improvements in wear rates using a second generation highly cross-linked polyethylene, cup orientation and choice of head size play significant roles in implant survivorship

Summary. Four highly cross-linked UHWMPEs except vitamin E-stabilised explants. Introduction. The development of both first and second generation highly cross-linked material focused on stabilizing radiation-induced free radicals as the sole precursor to oxidative degradation; however, secondary in vivo oxidation mechanisms have been identified in both conventional and highly cross-linked UHMWPE, induced by absorbed lipids and cyclic mechanical load. Retrieval studies are reporting in vivo oxidation highly cross-linked retrievals with up to ten year in vivo durations. Preclinical aging tests did not predict these in vivo material changes. With only a decade of these materials in clinical use, retrieval studies are limited to mid-term follow-up. In vitro studies face a challenge in effectively replicating the precise in vivo conditions that lead to this loss of oxidation resistance. In this study, we bypass replicating these in vivo variables by examining surgically-retrieved components, thereby testing material that has been affectively “pre-conditioned” by their in vivo service. After a preliminary post-operative analysis, we subjected retrievals to accelerated aging tests in order to predict the extent to which their oxidative stability had been uniquely compromised in vivo. Patients & Methods. Twenty-four highly cross-linked retrievals of four manufacturing methods (n=6 each of Longevity™, Prolong™, X3™ and E1™) and in vivo durations (1–4 years) were analyzed post-operatively and after accelerated aging (70°C, 5atm O. 2. for 2 weeks; ASTM F2003). Never-implanted components (n=1) of each material type were also aged. Infrared microscopy was used to evaluate lipid absorption, oxidation (per ASTM F2102-01ε1) and hydroperoxide levels after 16 hrs of nitric oxide staining for oxidation potential, and gravimetric swelling analysis assessed cross-link density (ASTM F2214). Results. All retrievals contained absorbed lipids penetrating below both loaded (penetration depth=1.3 ± 0.5 mm) and unloaded (0.6 ± 0.2 mm) surfaces. Each material type subset contained retrievals with and without detectable oxidation after in vivo service (Max OI=0.01–0.94). After aging, all post-irradiation thermally-treated, highly cross-linked retrievals, regardless of initial lipid levels or oxidation, showed oxidative degradation, demonstrated by subsurface oxidative peaks (MOI=0.30–2.63), increased hydroperoxides (3–5X), and decreased cross-link density (−34–90%). In contrast, vitamin E-stabilised retrievals showed below MOI<0.2 with no significant loss of cross-link density. Never-implanted controls for each material type showed no oxidative changes after accelerated aging. Discussion/Conclusion. Accelerating aging after in vivo service has shown oxidative instability characterised by high oxidation and material property loss in the three highly cross-linked materials without an incorporated antioxidant. This oxidative degradation took place regardless of post-operative oxidation levels, indicating that even without detectable oxidation the material had undergone changes during in vivo service, as compared to the lack of oxidative response in never-implanted controls. These findings also suggest that the presence of an antioxidant may be able to slow down and/or stabilise in vivo mechanisms compromising long-term oxidative stability and increase the longevity of highly cross-linked UHMWPE materials

Although autografts represent the gold standard for anterior cruciate ligament (ACL) reconstruction, tissue-engineered ACLs provide a prospect to minimize donor site morbidity and limited graft availability. This given study characterizes the ligamentogenesis in embroidered poly(L-lactide-co-ε-caprolactone) (P(LA-CL)) / polylactic acid (PLA) constructs using a dynamic nude mice xenograft model. (P(LA-CL))/PLA scaffolds remained either untreated (co) or were functionalized by gas fluorination (F), collagen foam cross-linked with hexamethylene diisocyanate (HMDI) (coll), or gas fluorination combined with the foam (F+coll). Cell free constructs or those seeded for 1 week with lapine ACL ligamentocytes were implanted into nude mice for 12 weeks. Following explantation, biomechanical properties, cell vitality and content, histopathology of scaffolds (including organs: liver, kidney, spleen), sulphated glycosaminoglycan (sGAG) contents and biomechanical properties were assessed. Implantation of the scaffolds did not negatively affect mice weight development and organs, indicating biocompatibility. All scaffolds maintained their size and shape for the duration of the implantation. A high cell viability was detected in the scaffolds prior to and following implantation. Coll or F+coll scaffolds seeded with cells yielded superior macroscopic properties when compared to the controls. Mild signs of inflammation (foreign-body giant cells, hyperemia) were limited to scaffolds without collagen. Microscopical score values and sGAG content did not differ significantly. Although remaining stable in vivo, elastic modulus, maximum force, tensile strength and strain at Fmax were significantly lower in the in vivo compared to the samples cultured 1 week in vitro, but did not differ between scaffold subtypes, except for a higher maximum force in F+coll compared with F samples (in vivo). Scaffold functionalization with fluorinated collagen foam provides a promising approach for ACL tissue engineering. (shared first authorship). Acknowledgement: The study was supported by DFG grants SCHU1979/9-1 and SCHU1979/14-1

Aims: Hipsimulator tests with highly cross-linked PE shows excellent results after 20 million cycles. Since March 99 we implanted hips with the Fitmore-Cup, Durasul-Inlay and an anatomical stem. In vivo investigations with 300 hips with highly cross-linked PE are introduced. Methods:. We used three methods to test the highly cross-linked PE in vivo: With Polyware-edge-detection we measured the penetration-rate of the Durasul ball-head. With electron scan microscopy we measured the wear rate in 5 retrierals. Histological examination of the periprosthetic tissue in 5 retrievals were done. Results: 1. The linear penetration rate after 1 year is 0,42 mm and after 2 years 0,096 mm. 2. Surface investigation shows no wear in the 5 retrieval cases. 3. Histological examination revealed extremely low depostion of smallest polyethylene particules. Conclusions:Now we have 3 years clinical experience with highly cross-linked PE. 3D-penetration results are as expected: we see no significant difference between conventional-PE and highly cross-linked PE (bedding in and creep). Surface investigation confirm the plastic deformation and the wear resistence of highly cross-linked PE. Histological examination shows ultra low depostion of PE particles and confirm the excellent in vitro results with highly cross-linked PE. The clinical investigation will be continued

Purpose. Cross-linking of polyethylene greatly reduces its wear rate in hip simulator studies. We conducted a systematic review and meta-analysis of randomized controlled trials comparing cross-linked to conventional polyethylene liners for total hip arthroplasty to determine if there is a clinical reduction of: 1) wear rates, 2) radiographic osteolysis, and 3) need for total hip revision. Method. A systematic search of MEDLINE, EMBASE, and COCHRANE databases was conducted from inception to May 2010 for all trials involving the use of cross-linked polyethylene for total hip arthroplasty. Eligibility for inclusion in the review was: use of a random allocation of treatments; a treatment arm receiving cross-linked polyethylene and a treatment arm receiving conventional polyethylene for total hip arthroplasty; and use of radiographic wear as an outcome measure. Eligible studies were obtained and read in full by two co-authors who then independently applied the Checklist to Evaluate a Report of a Nonpharmacological Trial to each study. Pooled mean differences were calculated for the following continuous outcomes: bedding-in, linear wear rate, three dimensional linear wear rate, volumetric wear rate, and total linear wear. Pooled risk ratios were calculated for radiographic osteolysis and revision hip arthroplasty. Results. The literature search strategy identified 194 potential studies of which 12 met inclusion criteria. All studies reported a significant reduction in radiographic wear with cross-linked polyethylene. Pooled mean differences for linear wear rate, three dimensional linear wear rate, volumetric wear rate, and total linear wear were all significantly reduced for cross-linked polyethylene. The risk ratio for radiographic osteolysis was 0.40 (95% C.I. of 0.27 to 0.58; p<0.01; I2=0%), favoring cross-linked polyethylene. There were no significant differences in need for revision total hip arthroplasty or amount of bedding-in. Conclusion. Cross-linked polyethylene liners demonstrate reduced radiographic wear and osteolysis up to 8 years after implantation. Follow up is not long enough to show a difference in need for revision total hip arthroplasty. Cross-linked polyethylene should be considered for young patients undergoing total hip arthroplasty

Summary Statement. In the most recent type of highly cross-linked UHMWPE, stabilised by vitamin E, the majority of this anti-oxidant cannot be leached out. Even more, the vitamin E molecules are grafted to the UHMWPE polymer backbone by an ether bond. Introduction. Today, highly cross-linked, vitamin E stabilised UHMWPE is clinically accepted as bearing material in joint replacements. Little is known about the chemistry of this antioxidant in the polymer after irradiation. The present investigation presents a model for the chemical nature of the trapping of vitamin E in PE. Method. UHMWPE type GUR 1020 (Ticona GmbH, Kelsterbach/Germany) was blended with 0.1 % vitamin E (Merck KGaA, Darmstadt/Germany), compression moulded at Mathys Ltd Bettlach in-house and cross-linked with γ-irradiation dose of nominally 100 kGy. To assess the extent of vitamin E leachable out, three 0.3 mm sections were cut from the centre of the samples. By extraction in heptane for 48 h at 98 °C, this amount of vitamin E trapped in the polymer was determined by Fourier transform infrared spectroscopy (FTIR) as relative vitamin E index (RVEI). The nature of the extracted substances was analysed by GC-MS. For solids, many of modern spectroscopic methods are not applicable. Therefore, 0.1 % vitamin E were dissolved in two model hydrocarbons (cyclohexane and n-octane) and irradiated at the same 100 kGy γ-dose. In order to determine the chemical bond vitamin E – hydrocarbon after irradiation, these liquid solution samples were analysed by different spectroscopic methods, such as GC-MS, MALDI-TOF-SIMS, HPLC and NMR. Results. Extraction experiments showed that only 23 % of the vitamin E could be extracted by heptane after irradiation whereas from a non-irradiated control sample, all vitamin E was extracted. GC-MS confirmed that the extracted vitamin E was chemically unchanged. Analysing the model hydrocarbons after irradiation, the GC-MS-chromatogram of the cyclohexane solution showed a single peak of the formal cyclohexene adduct of vitamin E. Illustrates this adduct, cyclohexyl-6-O-α-tocopherolether. Contrariwise, the same analysis of the n-octane solution revealed three formal octane adducts. By preparing references substances these three peaks could be attributed to ethers of vitamin E bonded at three different, but chemically equivalent CH. 2. positions on the eight carbon atom chain of n-octane. The single mass peak of the cyclohexane solution arises from the six chemically equivalent carbon atoms in this cyclic hydrocarbon. The 100 kGy γ-dose transformed 76 % of the vitamin E in the n-octane solution to the corresponding ethers and 68 % of the vitamin E in the cyclohexane to cyclohexyl ether. Therefore we postulate that in highly cross-linked, vitamin E stabilised UHMWPE the vitamin E is grafted to the polymer carbon backbone by an ether bond at the phenolic OH group of the vitamin E molecule. Conclusion. Upon irradiation, vitamin E is grafted to the UHMWPE polymer backbone to a large amount. This portion of antioxidant cannot leach out. Therefore, vitamin E stabilised HXLPE is protected from oxidation and ageing by a chemically grafted, quasi internal antioxidant

Introduction. The wear performances of polyethylene in THA are influenced at a great extent by the manufacturing process. During the past decade, highly cross-linked materials have been developed with encouraging results in terms of wear, whereas another body of the literature has indicated potential catastrophic failures related to reduced fatigue properties and oxidation due to lipids adsorption and fatigue mechanism. Also, each of the materials available on the market has its own processing characteristics. Therefore, a specific evaluation is necessary for each of them. The aim of this retrospective study was to evaluate the wear properties of metal-back sockets using a first generation highly cross-linked PE in a consecutive series of primary THAs. Materials. Between August 2005 and December 2007, 80 patients (80 hips) with a mean age of 62.7 ± 8.9 years were included. All patients had a 28mm CoCr femoral head articulating with a highly cross-linked insert (Highcross®, Medacta SA) that was 100 Mrads gamma radiated, remelted at 150°C, and ethylene oxide sterilized. The primary criterion for evaluation was linear head penetration measurement using the Martell system, performed by an investigator trained to this technique. Also, steady state wear was calculated. Functional results were evaluated according to WOMAC score. Results. At the minimum of 5-year follow-up, complete data were available for analysis in 67 patients at a mean follow-up of 5.5 years (5.0 to 6.8). At the latest follow-up, the mean femoral head penetration measured 0.07 ± 0.23 mm/year (median of 0.09). The steady state penetration from one year onward representing wear was −0.03 ± 0.25 mm/year (median of 0.01). The WOMAC score significantly increased from 16.5 ± 5.93 preoperatively to 4.12 ± 5.5 at the latest follow-up (Mann-Whitney, p < 0.001). No case of polyethylene insert fracture was recorded, and no hip had signs of periprosthetic osteolysis on the acetabular or femoral side. Discussion and conclusion. The minimal 5-year results of this retrospective study indicate that this highly cross-linked and remelted polyethylene had a low wear rate. The use of highly cross-linked inserts seem to be safe option provided that a minimal thickness of polyethylene is preserved. Longer-term results are needed to warrant that these mid-term data will generate less occurrence of osteolysis and aseptic loosening

Background. Cross-linked polyethylene has much less wear than conventional polyethylene and can used in a more bone conserving thickness of 4 mm. We have used it for hip resurfacing since 2001. Questions/Purposes. This study evaluated the effectiveness of a highly cross-linked polyethylene acetabular component for hip resurfacing in patients under age 50. I posed 5 questions: (1) What are the functional results, (2) What are the complications, (3) What is the 10-year implant survivorship, (4) What is the femoral head penetration into the polyethylene, and (5) What is the bone conservation?. Participants and Methods. There were 160 resurfacing procedures (144 participants) using a 2 piece acetabular shell and a cobalt chromium femoral component (fig. 1). Participants averaged 43 years of age at the time of surgery (range, 23 – 49.5 years) and 70% were women. Inclusion criteria were patients with adequate acetabular bone and a high enough head-neck ratio so that the reconstruction would not violate the femoral neck cortices or medial acetabular wall. The largest cross-linked polyethylene available was 49 mm so only patients with smaller femoral geometries were included. The Harris, WOMAC, and UCLA hip scores were used to assess pain, activity, and function and participants were asked about their satisfaction with the procedure. Digital radiography and computed tomographic scans were used to evaluate femoral head penetration and osteolysis. Removed polyethylene liners were analyzed. Results. The median follow-up was 11.5 years (range, 10 – 14 years). One participant was lost to follow-up and 1 died. The mean Harris Hip Score was 95 and 95% of the participants rated the results of their procedure as excellent. The average UCLA activity score was 8. One patient underwent successful revision surgery for acetabular loosening. Four participants underwent successful revision to a total hip replacement because of femoral neck fracture (2), femoral loosening, or infection. The Kaplan-Meier survivorship was 96%. There were no revisions for polyethylene wear and there were no instances of osteolysis. The medial acetabular wall thickness averaged 7.3 mm (range, 1.5 mm – 14.9 mm). The mean inclination angle was 39°. The mean femoral head penetration was 0.05 mm/year (range, .028 – .09 mm/year). Conclusions. Hip resurfacing with a highly cross-linked polyethylene acetabular component is a reliable procedure at mid-term follow-up. The rate of polyethylene wear is below the osteolytic threshold of .1 mm/yr. The preservation of both acetabular and femoral bone is reasonable even in comparison to thin metal shells available for metal-on-metal resurfacing and total hip replacement. The functional results are comparable to those of metal-on-metal resurfacing without the concerns of a metal bearing couple. The procedures are demanding and patient selection is critical to the success of the procedure. Although long-term follow-up is needed to determine if implant survivorship with highly cross-linked polyethylene acetabular components will equal that of metal-on-metal prostheses, the low rate of femoral head penetration suggests that many years of use in young highly active participants are possible