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. 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

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

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

Introduction:. The management strategy regarding optimally addressing polyethylene wear with a well-fixed acetabular shell remains controversial. The purpose of the present study was to document outcomes of cementation of a highly cross-linked polyethylene (PE) liner into a well-fixed acetabular metal shell in 36 hips. Materials & Methods:. We identified 37 patients (39 hips) who had undergone revision THA by cementation of a highly cross-linked PE liner into a well-fixed metal shell between June 2004 and April 2009. Of these patients, one (1 hip) died before the end of the 3-year evaluation and another was lost to follow-up. Thus, the study cohort consisted of 35 patients (36 hips). There were 23 males (24 hips) and 12 female (12 hips) patients with a mean age at time of revision surgery of 57.6 years (range, 38–79 years). All operations were performed by a single surgeon using only one type of liner. Clinical and radiographic evaluation was performed at a mean of 6.1 years (range, 3–8 years) postoperatively. Results:. Mean Harris hip score improved from 58.1 (range, 39–81 points) preoperatively to 91.3 (range, 45–100 points) postoperatively (p < 0.001). Of the 36 hips, 29 (80.1%) had an excellent result, 6 (16.7%) a good result, and 1 (2.8%) a poor result. The patient with a poor clinical result had aseptic cup loosening with a greater trochanteric fracture at 2 years postoperatively and was treated by acetabular cup revision and internal fixation of the fracture. However, no case of PE liner dislodgement from the cement or of dissociation of the PE-cement construct from the metal shell was encountered. At last follow-up, no new osteolytic lesion was identified and previous osteolytic lesions filled with bone graft were completely or partially incorporated. Other complications included 1 incomplete peroneal nerve palsy and 1 dislocation. Conclusions:. The results of this study and previous reports demonstrated that cementation of highly cross-linked PE liner into well-fixed metal shell could provide good midterm durability

Background. The advent of highly cross-linked polyethylene has resulted in improved wear rates and reduced osteolysis with at least intermediate follow-up when compared to conventional polyethylene. However, the role of alternative femoral head bearing materials in decreasing wear is less clear. The purpose of this study was to determine in-vivo polyethylene wear rates across ceramic, Oxinium, and cobalt chrome femoral head articulations. Methods. A review of our institutional database was performed to identify patients who underwent a total hip arthroplasty using either ceramic or oxidized zirconium (Oxinium) femoral head components on highly cross-linked polyethylene between 2008 and 2011. These patients were then matched on implant type, age, sex and BMI with patients who had a cobalt chrome bearing implant during the same time period. RSA analysis was performed using the center index method to measure femoral head penetration (polyethylene wear). Secondary quality of life outcomes were collected using WOMAC and HHS Scores. Paired analyses were performed to detect differences in wear rate (mm/year) between the cobalt chrome cohorts and their matched ceramic and Oxinium cohorts. Additional independent group comparisons were performed by analysis of variance with the control groups collapsed to determine wear rate differences between all three cohorts. Results. A total of 75 patients underwent RSA analysis. 20 patients with a ceramic femoral head component and 16 patients with an Oxinium femoral head component along with the same number of matched patients with cobalt chrome femoral head component were included in the analysis. The time in vivo for the Oxinium (5.17 +/− 0.96 years), Oxinium matched cohort (5.13 +/− 0.72 years), ceramic (5.15 +/− 0.76 years) and ceramic matched cohort (5.36 +/− 0.63 years) were comparable. The demographics of all bearing surface cohorts were similar. The paired comparison between the Oxinium and cobalt chrome cohorts (0.32 vs. 0.28 mm/year, p=0.427) and ceramic vs cobalt chrome cohorts (0.28 vs. 0.22 mm/year, p=0.202) did not demonstrate a significant difference in wear rate. The independent groups analysis revealed a significantly higher wear rate of Oxinium (0.33 mm/year) compared to cobalt chrome (0.24 mm/year) (p = 0. 038). There were no differences in HHS and WOMAC scores between the Oxinium and cobalt chrome cohorts (HHS: p = 0.71, WOMAC: p=0.08) or the ceramic and cobalt chrome cohorts (HHS: p=0.15, WOMAC: p =023). Conclusion. This study presents evidence of a greater wear rate (mm/year) of the Oxinium femoral head component compared to a cobalt chrome femoral head component. This difference was not demonstrated in the ceramic femoral head component. Despite this difference, there were no clinical differences as measured by the HHS and WOMAC. Future research should focus on factors that may contribute to the higher wear rate seen in the Oxinium cohort. Level of Evidence – Level II. Disclosures - Institutional support provided by Depuy, Stryker, and Smith and Nephew

The advent of highly cross-linked polyethylene has resulted in improved wear rates and reduced osteolysis with at least intermediate follow-up when compared to conventional polyethylene. However, the role of alternative femoral head bearing materials in decreasing wear is less clear. The purpose of this study was to determine in-vivo polyethylene wear rates across ceramic, Oxinium, and cobalt chrome femoral head articulations. A review of our institutional database was performed to identify patients who underwent a total hip arthroplasty using either ceramic or oxidised zirconium (Oxinium) femoral head components on highly cross-linked polyethylene between 2008 and 2011. These patients were then matched on implant type, age, sex and BMI with patients who had a cobalt chrome bearing implant during the same time period. RSA analysis was performed using the centre index method to measure femoral head penetration (polyethylene wear). Secondary quality of life outcomes were collected using WOMAC and HHS Scores. Paired analyses were performed to detect differences in wear rate (mm/year) between the cobalt chrome cohorts and their matched ceramic and Oxinium cohorts. Additional independent group comparisons were performed by analysis of variance with the control groups collapsed to determine wear rate differences between all three cohorts. A total of 68 patients underwent RSA analysis. Fifteen patients with a ceramic femoral head component and 14 patients with an Oxinium femoral head component along with the same number of matched patients with cobalt chrome femoral head component were included in the analysis. The time in vivo for the Oxinium (5.17 +/− 0.96 years), Oxinium matched cohort (5.13 +/− 0.72 years), ceramic (5.15 +/− 0.76 years) and ceramic matched cohort (5.36 +/− 0.63 years) were comparable. The demographics of all bearing surface cohorts were similar. The paired comparison between the Oxinium and cobalt chrome cohorts (0.33 vs. 0.29 mm/year, p=0.284) and ceramic vs cobalt chrome cohorts (0.26 vs. 0.20 mm/year, p=0.137) did not demonstrate a significant difference in wear rate. The independent groups analysis revealed a significantly higher wear rate of Oxinium (0.33 mm/year) compared to cobalt chrome (0.24 mm/year) (p = 0. 038). There were no differences in HHS and WOMAC scores between the Oxinium and cobalt chrome cohorts (HHS: p = 0.71, WOMAC: p=0.08) or the ceramic and cobalt chrome cohorts (HHS: p=0.15, WOMAC: p=023). This study presents evidence of a greater wear rate (mm/year) of the Oxinium femoral head component compared to a cobalt chrome femoral head component. This difference was not demonstrated in the ceramic femoral head component. Despite this difference, there were no clinical differences as measured by the HHS and WOMAC. Future research should focus on factors that may contribute to the higher wear rate seen in the Oxinium cohort

Irradiated, thermally stabilized, highly cross-linked UHMWPE bearings have demonstrated superior wear performance and improved in vitro oxidation resistance compared with terminally gamma-sterilized bearings, yet retrieval analysis reveals unanticipated in vivo oxidation in these materials. There has been little evidence to date that oxidation in these materials is leading to degradation of mechanical properties, but since oxidation has previously been shown to cause chain scission in other materials, there is the potential for oxidation to cause decreased molecular weight and crosslink density. The aim of this study was to determine whether measured in vivo oxidation in highly cross-linked tibial bearings corresponds with a decreasing crosslink density. Retrieval analysis for three tibial bearing materials reveals that crosslink density is decreasing following in vivo duration, and that the change in crosslink density is strongly correlated with oxidation. The results suggest that oxidation in highly cross-linked materials is causing chain scissions that may impact the material properties. If the correlation between oxidation and duration continues, then as longer duration, more oxidized devices are retrieved there is a potential for measurable mechanical property changes

Introduction. Highly cross-linked (HXL) polyethylene has demonstrated clinical advantages as a wear resistant acetabular bearing material in total hip arthroplasty (THA) [1]. In vitro wear testing has predicted a tenfold reduction in the wear rate of HXL polyethylene, as compared to its conventional, non-HXL counterpart [2]. To date, radiographic studies of head penetration represent the state-of-the-art in determining clinical wear of polyethylene hip liners [3]. However, as the amount of wear drops to very low levels, it becomes important to develop a precise and reliable method for measuring wear, facilitating a comparison of clinical results to expectations. This study focuses on locating and quantifying the maximum linear wear of retrieved acetabular poly liners using a coordinate measuring machine (CMM). Specifically, HXL liners are compared to a baseline of conventional, non-HXL bearings. Methods. An IRB-approved retrieval laboratory received 63 HXL acetabular bearing retrievals from 5 manufacturers with in vivo durations of 1.01–14.85 years. These were compared with 32 conventional, non-HXL controls (including gas plasma, gamma-barrier and EtO) from 3 manufacturers with in vivo durations of 1.03–20.89 years. Liners were mounted in a tripod of axial contacts with the liner face positioned in a vertical plane. Each bearing was scanned with a CMM dual-probe head, with one horizontal probe scanning the articular surface and the other scanning the non-articular, sequentially. Surface-normal wall thickness values along each latitude were calculated using a custom developed algorithm (Figure 1). Because the liners are axially symmetric as manufactured, deviation in wall thickness at a given latitude represents linear wear [4]. Results. Total wear penetration for the HXL liners ranged from 0.02 to 1.03 mm, and for the conventional, non-HXL controls ranged from 0.07 to 6.85 mm. The HXL liners had an average linear wear rate of 0.02 mm/year, compared to 0.20 mm/year for the conventional, non-HXL controls (Figure 2). The direction of maximum wear, as measured in degrees from the cup pole, ranged from 8.32 to 73.86 degrees. Differences in wear rates as a function of crosslinking dose, as well as presence/absence of a lip can be identified. Discussion. This wear measurement study of retrievals is the first application of a novel CMM technique to locate and quantify wear in HXL liners compared to conventional polyethylene controls. The study confirms the expectations of a tenfold reduction in wear rates that were based on in vitro testing [2]. The results are consistent with those of radiographic studies that have documented lower wear of HXL polyethylene in the hip compared to conventional polyethylene [3]. However, the current technique offers higher precision and reliability, and eliminates the large proportion of negative wear measurements common amongst radiographic methods. A sufficient number of liners have been measured to begin to differentiate wear between different radiation doses

Introduction. Vitamin-E (VE, dl-α-tocopherol) is a powerful antioxidant for highly cross-linked polyethylene (XLPE). It was previously reported that VE-stabilized XLPE succeeded in retaining no measurable oxidation even after accelerated aging tests combined with cyclic loading or lipid absorption. Thus, VE-stabilized XLPE is nowadays recognized worldwide as one of the new standard materials in total hip arthroplasty (THA). However, the effects of such VE addition on physical behavior of polyethylene remain to be fully elucidated by contrast to the clear statement of its chemical role (i.e., the enhanced oxidation resistance) in the published literature. In this presentation, we shall attempt to provide those missing notations and to explore the microstructural and biomechanical role of VE in XLPE acetabular liner on the molecular scale. Methods. The two different types of XLPE acetabular liners, VE-blended and VE-free (no VE-blended) component (n=3 for each sample), were investigated by means of laser-scanning confocal polarized micro-Raman spectroscopy. In both components, the cross-linking was achieved by electron-beam irradiation with a total dose of 300kGy in vacuum. Raman spectroscopy offers non-destructive, contactless, and high-resolution analyses of polymer morphologies. In this study, we performed an in-depth profiling of crystalline and non-crystalline phase (i.e., amorphous and intermediate phase between crystalline and amorphous regions) percentages and degree of molecular orientation in the above two liners before and after introducing the 10% plastic deformation via uniaxial compression loading at room temperature. These results were also compared to the morphological analyses under the same compression conditions performed on the virgin conventional polyethylene (Virgin liner) without radiation crosslinking as well as VE blending. Results. In the deformed state, Virgin and VE-blended liner showed a pronounced development of the surface crystalline texture. On the other hand, deformation-induced texturing occurred at much less extent in VE-free liner. According to the results of phase percentages, there was no crystallinity change in VE-blended liner by contrast to the marked increase of crystallinity in Virgin and VE-free liner after compression deformation. Alternatively, amorphous-to-intermediate phase transition was confirmed in VE-blended liner. Discussion/Conclusion. We found molecular rearrangement and phase transitions in crystalline and non-crystalline phase as a reconstruction process after plastic deformation in the investigated samples, which can be deeply related to their wear and mechanical properties. The morphological comparisons between Virgin and VE-free liner suggested that the intermolecular cross-linked networks in polyethylene highly restricted the molecular chain mobility as evidenced by few texture evolutions in VE-free liner. On the other hand, the comparisons between VE-free/-blended liner indicated that the presence of VE might promote molecular chain mobility even in the cross-linked structure, resulting in the significant surface texturing. These physical and structural aspects of VE blending would imply the possibility of the increased micromechanical wear through the strain-softening and weakening phenomena due to the molecular reorientation during in-vivo service. However, in other words, wear resistance of VE-blended liner might be further maximized by the more rigid control of molecular movements

Introduction. Radiation cross-linked UHMWPEs were developed to address osteolysis-induced joint arthroplasty failure by improving wear resistance and reducing associated particulate debris. Introduced clinically fifteen years ago, they are the primary bearing surface in use with excellent clinical outcomes and wear resistance. First generation materials sought to maintain oxidative stability by reducing or eliminating free radicals through thermal treatments, while second generation aimed to further balance oxidation resistance and improve mechanical properties through sequential irradiation and annealing or the incorporation of an antioxidant. Recent reports have identified lipid absorption and cyclic loading as potential in vivo oxidation-inducing mechanisms. In this on-going retrieval study, we report on the current status of oxidative stability in these two generations of UHMWPE bearings. Materials & Methods. Six types of highly cross-linked UHMWPE hip and knee bearings (Table 1) were surgically-retrieved and collected under IRB approval. Standard material analysis was performed on cross-sections of loaded and unloaded bearing surfaces of the components. Thin sections (150 µm thickness) were extracted in boiling hexanes under reflux for 16 hours followed by vacuum drying for 24 hours. FTIR was used to evaluate oxidation and calculated from post-hexane absorbance spectra by normalizing the area under 1740 cm. −1. (1680–1780 cm. −1. ) to the area under 1370 cm. −1. (1330–1390 cm. −1. ), per ASTM F2102-13. Gravimetric swelling of regional cross-sectional blocks (1–2 mm. 3. ) for 2 hours in 130°C boiling xylenes was used to assess cross-link density, per ASTM 2214. Results. Irradiated and melted retrievals all showed detectable (OI>0.1) subsurface oxidation in the articular surface of retrievals (Fig 1). Behavior between materials types differed: 47% of Longevity acetabular liners (MOI=0.14±0.19; Table 2) showed detectable oxidation as opposed to 19% in Marathon retrievals (MOI=0.07±0.08), both with comparable sample sizes and in vivo durations. We saw no concomitant change in the cross-link density, except in one case where OI>1.0. Sequentially irradiated and annealed (X3) retrievals showed the highest incidence of detectable oxidation (76%), highest average maximum oxidation (0.35±0.39), signs of oxidative embrittlement and a loss of cross-link density which correlated with decreasing oxidation (R. 2. =0.30; p-value=0.000016). Oxidation was in both loading regions of X3 knees, while Prolong knees were observed to have oxidation solely at the articular surface. Antioxidant-stabilized E1 retrievals showed low detectable oxidation values (MOI=0.11±0.03) in both regions without change in cross-link density. Discussion. Throughout the first decade of service, irradiated and melted UHMWPE retrievals showed subsurface oxidation, but with little to no impact on material properties. Detectable oxidation and embrittlement were identified in sequentially irradiated and annealed retrievals at shorter time points. Residual free radicals and pre-implantation shelf oxidation, as a result of air permeable packaging, are potential factors behind the higher oxidation at earlier time points. Antioxidant-stabilized retrievals showed no change in their oxidative behavior with the lowest oxidation and variability in this very short 0–3 year follow-up. Continued analysis is needed to understand the second decade of behavior along with longer-term follow-up with patients to understand if these changes could affect clinical outcomes through oxidation-induced changes in material or mechanical properties

Current implant designs and materials provide a high grade of quality and safety, but aseptic implant loosening is still the main reason for total hip revision. Highly cross-linked polyethylene (HX-PE) is used successfully in total hip replacements (THR) since several years. The good wear properties lead to a reduction of wear debris and may contribute to a longer survival time of the THRs. Furthermore, thin HX-PE liner allows the use of larger femoral heads associated with a decreased risk of dislocation and an improved range of motion. However, the cross-linking process is associated with a loss of mechanical properties of the polyethylene material which compromise the use of thin HX-PE liner in terms of high stress situations. The aim of the present study was the experimental wear analysis of HX-PE liner under steep acetabular cup position. Furthermore, a finite element analysis (FEA) was performed in order to calculate the stress within the HX-PE material in case of steep cup position under physiological loading. Experimental wear testing was performed for 5 Mio load cycles, using highly cross-linked polyethylene (HX-PE) acetabular liner combined with 44 mm ceramic femoral heads at a standard position of the acetabular cup (30° inclination) according to ISO 14242 as well as at 60° cup inclination. The wall thickness of the HX-PE liner was 3.8 mm. A hip wear simulator, according to ISO 14242 (EndoLab GmbH, Rosenheim, Germany), was used and wear was determined gravimetrically. Moreover, finite element models of the THR system at standard and steep cup position was created by Abaqus/CAE (Dessault Systemes Providence, USA). Using the finite element software Abaqus (Dessault Systemes Providence, USA) the total hip implants were physiologically loaded with maximum force of the gait cycle (3.0 kN). Thereby, the stresses within the HX-PE material were analysed. The average gravimetrical wear rates of the HX-PE liners at standard implant position (30°) and 60° cup inclination showed small wear amounts of 3.15 ± 0.32 mg and 1.92 ± 1.00 mg per million cycles, respectively. The FEA revealed a clear increase of stresses at the HX-PE liner with respect to steep cup position (von Mises stress of 8.78 MPa) compared to ISO standard implant position (von Mises stress of 5.70 MPa). The wear simulator tests could not demonstrate significant differences of gravimetrical wear amount of HX-PE liners under steep hip cup position compared to standard implant position. The small contact surface between the femoral head and the SX-PE liner during the wear testing may lead to the low wear rate of the misaligned acetabluar cup. Moreover, the FEA showed that the effect of a misaligned acetabular cup on the stresses within the polyethylene liner can be critical. Although an increase of wear could not be detected a steeper acetabular cup position using thin HX-PE liners should be avoided due to higher stresses preventing implant failure in clinical application

Background. Wear and osteolysis are major contributors, which limit the durability of total hip Arthroplasty (THA) and ultimately cause it to fail. Efforts were made to decrease wear by highly cross-linked polyethylene (HXLPE) and using ceramic bearings. Questions/Purposes. The purpose of this study is to analyze and compare the five year performance of large sized (32mm and 36mm) ceramic and metal heads on X3 HXLPE (Stryker, Mahwah, NJ, USA). Materials and Methods. One hundred and twenty near-consecutive patients that underwent primary THA between January 2006 and December 2009 for osteoarthritis with five-year radiographic and clinical follow-up were identified from our institutional review board-approved prospective database. All patients received a non-cemented THA with larger femoral head (32 or larger) on X3 HXLPE, either a ceramic (n=60) or metal (n=60). Linear and volumetric wear was measured using the computer-assisted Roman software. Results. At final follow up, the mean wear rates were not significantly different (p=0.63): 0.018 ± 0.06 mm/yr and 0.021 ± 0.06 mm/yr for ceramic-on-X3 and metal-on-X3, respectively. When negative values were considered zero as worst-case scenario, wear rates for ceramic-on-X3 and metal-on-X3 HXLPE groups were 0.032 ± 0.04 mm/yr and 0.041 ± 0.05 mm/yr, respectively (P=0.55). Mean volumetric wear rates were also statistically similar: 68.56 mm3/y and 79.96 mm3/y for the ceramic-on-X3 and metal-on-X3 HXLPE groups respectively (p=0.78); when negatives were considered zeroes, they were 121.42 mm3/y and 164.63 mm3/y, respectively (p=0.20). Patients with ceramic heads were significantly younger (p <0.01), more active (p<0.01) and had better clinical scores than those with metal heads. Conclusions. Large ceramic and metal heads on HXLPE have excellent durability at minimum 5 years followup without any statistical significant difference in linear or volumetric wear rates

Introduction. Wear and osteolysis are major contributors which limit the durability of total hip arthroplasty (THA) and ultimately cause it to fail. Efforts were made to decrease the wear by highly cross-linked polyethylene (HXLPE) and using ceramic bearings. The purpose of this study is to analyze the five year performance of large sized (32mm and 36mm) ceramic and metal heads on X3 HXLPE (Stryker, Mahwah, NJ). Materials and Method. From Jan 2006 to June 2008, 81 consecutive patients with minimum 5 year radiographic and clinical followup were identified from out institutional prospective database. 51 non-cemented THA (45 patients) had ceramic on HXLPE (CoX3) group and 30 hips (29 patients) had metal on HXLPE (MoX3) group. Mean age was 36 ± 8 years (36–76) and 50 ± 9 years (51–86) in ceramic and metal group, respectively. Wear rates were measured on an anteroposterior weight-bearing pelvis radiographs using the computer-assisted Roman software. Results. The mean WOMAC, PAQ, HSS and UCLA scores for CoX3 and MoX3 groups at final follow-up were 13.2 ± 17.3, 10.1 ± 14.4, 36.4 ± 5.3 and 5.9 ± 1.8 and 16.5 ± 17.8, 17.1 ± 17.2, 31.6 ± 10.5 and 5.3 ± 1.6, respectively. At the final follow up, the mean wear rates were 0.022 ± 0.06 mm/yr and 0.022 ± 0.05 mm/yr for CoX3 and MoX3 groups, respectively. This was not statistically significant (p=0.8). When negative values were considered zero, wear rates for CoX3 and MoX3 groups were 0.037 ± 0.04 mm/yr and 0.033 ± 0.04 mm/yr, respectively (p=0.6). Radiographic analysis does not reveal any incidence of osteolysis or loosening in both groups. Discussion and Conclusion. The five year wear rate of large diameter metal and ceramic femoral heads on HXLPE bearing demonstrated excellent similar wear rates. Longer follow-ups are required to assess superiority of one bearing over another

Background. Highly cross-linked polyethylene (HCLPE) was introduced to reduce wear and osteolysis in total hip arthroplasty (THA). There is no reported data regarding wear rates and clinical performance of Crossfire HCLPE (Stryker, Mahwah, New Jersey) in young and active patients. The purpose of this prospective study is to assess minimum 10-year wear rates and survivorship of Crossfire in young and active patients. Material and Methods. Between January 2001 to December 2003, 52 consecutive THAs (43 patients; 26 males and 17 females), 55 years and younger, with an average University of California Los Angeles activity (UCLA) score of 7.3 ± 1.5 (5 – 10) at the time of surgery were prospectively followed. The mean age of patients was 47.4 ± 7.8 years old (range 24 to 55 years). Indication for surgery included osteoarthritis in all cases. All operations were performed by the senior surgeon via a posterolateral approach. All components were non-cemented SecurFit femoral stem, 28 mm Cobalt-Chromium (Co-Cr) femoral head, and Trident PSL cup with Crossfire HCLPE acetabular liner (Stryker, Mahwah, New Jersey). At minimum 10-years follow-up (mean 11.5 ± 0.94 years), wear rates were assessed using the Roman software. Hospital for Special Surgery (HSS) scores and survivorship data were analyzed. Results. Good to excellent clinical results were seen with HSS score of 38.1 ± 4.7. The mean linear wear was 0.019 ± 0.018 mm/year (range 0 to 0.082). There were no revisions for osteolysis or loosening, periprosthetic infection or dislocation in this cohort. Kaplan-Meier survivorship was 100% for all failures. Conclusion. This is the first study to demonstrate that metal on Crossfire performs very well with excellent survivorship and wear rates at a minimum 10-year follow-up in young and active patients. Oxidation concern with Crossfire has not caused any clinical problems up to 10 years

Background. Highly cross-linked polyethylene (HCLPE) was introduced to reduce wear and osteolysis in total hip arthroplasty (THA). There is no reported data regarding wear rates and clinical performance of Crossfire HCLPE (Stryker, Mahwah, New Jersey) in young and active patients. The purpose of this prospective study is to assess minimum 10-year wear rates and survivorship of Crossfire in young and active patients. Material and Methods. Between January 2001 to December 2003, 52 consecutive THAs (43 patients; 26 males and 17 females), 55 years and younger, with an average University of California Los Angeles activity (UCLA) score of 7.3 ± 1.5 (5 – 10) at the time of surgery were prospectively followed. The mean age of patients was 47.4 ± 7.8 years old (range 24 to 55 years). Indication for surgery included osteoarthritis in all cases. All operations were performed by the senior surgeon via a posterolateral approach. All components were non-cemented SecurFit femoral stem, 28 mm Cobalt-Chromium (Co-Cr) femoral head, and Trident PSL cup with Crossfire HCLPE acetabular liner (Stryker, Mahwah, New Jersey). At minimum 10-years follow-up (mean 11.5 ± 0.94 years), wear rates were assessed using the Roman software. Hospital for Special Surgery (HSS) scores and survivorship data were analyzed. Results. Good to excellent clinical results were seen with HSS score of 38.1 ± 4.7. The mean linear wear was 0.019 ± 0.018 mm/year (range 0 to 0.082). There were no revisions for osteolysis or loosening, periprosthetic infection or dislocation in this cohort. Kaplan-Meier survivorship was 100% for all failures. Conclusion. This is the first study to demonstrate that metal on Crossfire performs very well with excellent survivorship and wear rates at a minimum 10-year follow-up in young and active patients. Oxidation concern with Crossfire has not caused any clinical problems up to 10 years

Different types of highly cross-linked polyethylene (HXLPE) have been introduced widely in acetabular cups in hip prostheses to reduce the incidence of wear debris-induced osteolysis. Also, we reported that HXLPE cups with 28-mm alumina ceramic femoral head exhibited lower wear than conventional PE cups. Recently, the combination of HXLPE cup and larger diameter femoral head is used widely to prevent dislocation. In this study, we examined the wear of HXLPE with 32-mm alumina ceramic femoral head and compared it with the wear of HXLPE with 28-mm alumina ceramic femoral head. The in vivo wear of 60 HXLPE cups (Aeonian; Kyocera Corp., Kyoto, Japan, currently Japan Medical Materials Corp., Osaka, Japan) with 28-mm alumina ceramic femoral head with clinical use for 3.1–9.1 years (mean 7.4 years) and eight HXLPE cups with 32-mm alumina ceramic femoral head used for 2.3–3.2 years (mean 2.8 years) were examined by radiographic analysis. The early wear rate for the first year of HXLPE cups with 28-mm and 32-mm alumina ceramic femoral head were 0.24±0.10 mm/year and 0.29±0.12 mm/year respectively. There was no significant difference in both femoral head groups (p>0.05). The steady wear rate after 1 year were 0.001±0.03 mm/year and −0.03±0.10 mm/year respectively. There was no significant difference either in both femoral head groups (p>0.05). These findings from this radiographic analysis suggest that the early wear rate in the first 1 year probably represents the creep deformation in bedding-in stage; and the steady wear rate after 1 year probably represents mainly the wear than of the creep deformation. By the radiographic analysis, HXLPE cups in both femoral head groups exhibited low steady wear rate. In conclusion, we expect that the combination of HXLPE cup and 32-mm diameter alumina ceramic femoral head has favorable wear properties with possibility of prevention of dislocation in long-term clinical use

Introduction. In order to reduce polyethylene wear and incidence of osteolysis, and improve the long-term durability of total hip arthroplasty (THA), highly cross-linked polyethylene was introduced for clinical use in substitution for conventional polyethylene. We performed 35 cementless THAs between December 2000 and February 2002, and cross-linked polyethylene was used in these surgeries. The purpose of this study is to research linear wear rate of these hips, and to find the risk factor for high wear rate. Patients and Methods. 32 hips (26 patients) among the 35 could be evaluated at more than 10 years postoperatively. One hip required reoperations due to infection at 8 years postoperatively, and two were lost to followup in less than 10 years. There were 2 males and 24 females, and the observation period was 11.4 years in average (range 10?13 years). The age at the time of operation was 49.4 years in average (range 24?67 years), and body mass index was 22.4 in average (15?34). We used AHFIX total hip prostheses (KYOCERA Medical Corporation) for both acetabular and femoral replacement, and 22 mm Zirconia head was used in all cases. The median cup diameter was 46 mm (range 42?50). Osteolysis and loosening of the implant was evaluated on the anteroposterior radiograph of the hip. Using software for wear measurement (Hip Analysis Suite), linear wear rate and cup inclination angle were measured. Correlation between linear wear rate and age, BMI, cup inclination angle, and cup diameter was investigated using correlation coefficient. Results. Osteolysis and loosening were not found in any cases on the final radiograph. Cup inclination angle was 44.7±4.6 degree, and linear wear rate was 0.034±0.019 mm/y in average. No statistical correlation was found between linear wear rate and age, BMI, cup inclination angle, and cup diameter. Discussion. Long-term clinical performance of cross-linked polyethylene is rarely reported, although it is considered to have excellent wear resistance, and reduces the risk of osteolysis and loosening. Linear wear rate in this series was relatively low, and osteolysis and loosening were not observed. It was demonstrated that cross-linked polyethylene had excellent wear resistance when used in combination with 22 mm zirconia head, and observed for more than 10 years

One of serious issues in total hip arthroplasty (THA) is the osteolysis which results in aseptic loosening caused by the wear particles from a polyethylene (PE) acetabular cup. In addition, oxidation degradation of PE cup resulting in the fracture or the severe wear caused by the reduction of mechanical properties in vivo is also the issue. The oxidation degradation is considered to be induced by residual free radicals generated by gamma-ray irradiation for cross-linking to reduce wear or for sterilization. In this study, (1) wear property, (2) oxidation degradation of retrieved PE and highly cross-linked PE (CLPE) cups against alumina ceramic femoral heads, and (3) the correlation between those properties were evaluated. The radiographic wear of six conventional PE cups with the mean follow-up of 19.1–23.3 years and 60 CLPE cups with the mean follow-up of 3.1–9.1 years were measured by a non-radiostereometric analysis method (Vectorworks. ®. 10.5 software package). As a retrieval analysis, 26 retrieved acetabular cups were evaluated; 16 cups were ethylene oxide gas-sterilized conventional PE cups with clinical use for 16.0–24.9 years and 10 cups were gamma-ray-sterilized CLPE cups with clinical use for 0.9–6.7 years. The linear and the volumetric wear were measured using a three-dimensional (3D) coordinate measurement machine. The shapes of unworn and worn surfaces with 15- and 30-point intervals, respectively, were measured. Oxidation degradation of the surface, sub-surface and inner for both worn and unworn parts of the retrieved cups was measured using a Fourier-transform infrared (FT-IR) spectroscopy. Oxidation indices were calculated using the peak at 1740 cm. −1. and 1370 cm. −1. according to ASTM F2012. In the radiographic analysis, the linear wear rate of CLPE cups was significantly lower than that of conventional PE cups [Fig. 1]. In the retrieval analysis, the linear wear rate of CLPE cups (mean: 0.07 mm/year) showed a 51% reduction (p = 0.002) compared to conventional PE cups (mean: 0.14 mm/year) [Fig. 2]. The retrieval and the radiographic analysis for both conventional PE and CLPE cups showed similar results (p = 0.7 and 0.1, respectively). Maximum oxidation indices for CLPE cups were similar to those of conventional PE cups regardless of the difference of clinical duration [Fig. 3]. This result is different from in vivo wear, which increases as the clinical duration. For both conventional PE and CLPE cups, the oxidation indices of subsurface were higher than those for surface. The worn parts showed higher oxidation indices than those for unworn parts. From the results, even when the free radicals were so few or absent, the oxidation degradation would be induced in vivo. In conclusion, the wear resistance for CLPE cups was greater than that for conventional PE cups from both radiographic and retrieval analyses. The in vivo oxidation degradation might not be caused by only residual free radicals. It was found that oxidation degradation of PE cups when used with alumina ceramic femoral heads is not correlated to their wear properties

Introduction. In vivo, UHMWPE bearing surfaces are subject to wear and oxidation that can lead to bearing fatigue or fracture. A prior study in our laboratory of early antioxidant (AO) polyethylene retrievals, compared to gamma-sterilized and highly cross-linked (HXL) retrievals, showed them to be more effective at preventing in vivo oxidation. The current analysis expands that early study, addressing the effect of:. manufacturing-variables on as-manufactured UHMWPE;. in vivo time on these initial properties;. identifying important factors in selecting UHMWPE for the hip or knee. Methods. After our prior report, our IRB-approved retrieval laboratory received an additional 96 consecutive AO-retrievals (19 hips, 77 knees: in vivo time 0–6.7 years) of three currently-marketed AO-polyethylenes. These retrievals represented two different antioxidants (Vitamin E and Covernox) and two different delivery methods: blending-prior-to and diffusing-after irradiation cross-linking. Consecutive HXL acetabular and tibial inserts, received at retrieval, with in vivo time of 0–6.7 years (260 remelted, 170 annealed) were used for comparison with AO-retrievals. All retrievals were analyzed for oxidation and trans-vinylene index (TVI) using a Thermo-Scientific iN10 FTIR microscope. Mechanical properties were evaluated for 35 tibial inserts by uniaxial tensile testing using an INSTRON load frame. Cross-link density (n=289) was measured using a previously published gravimetric gel swell technique. Oxidation was reported as maximum ketone oxidation index (KOI) measured for each bearing. TVI was reported as the average of all scans for each material. Cross-link density and mechanical properties were evaluated as a function of both TVI and oxidation. Results. Minimal increase in oxidation was seen in these AO-retrievals, out to almost 7 years in vivo. In contrast, HXL-retrievals showed increasing KOI with time in vivo (annealed-HXL = 0.127/year, remelted-HXL = 0.036/year, p<0.001). HXL oxidation rate was higher in knees (0.091/year) than in hips (0.048/year), p<0.001. Cross-link density (XLD) correlated positively with TVI for both HXL (Pearson's correlation=0.591, p<0.001) and AO (Pearson's correlation=0.598, p<0.001) retrievals. AO-materials had higher TVI for the same or similar XLD than did HXL polyethylene. XLD correlated negatively with KOI for HXL retrievals (Pearson's correlation=−0.447, p<0.001). Mechanical properties varied by material across all materials evaluated, with tensile toughness correlating negatively with increasing TVI (Pearson Correlation=−0.795, p<0.001). Discussion. Irradiation cross-linking has been used effectively to improve wear resistance. Residual free radicals from irradiation are the target of AO-polyethylene, to prevent loss of UHMWPE XLD, resulting from in vivo oxidation of free radicals as seen in HXL retrievals, and toughness, resulting from oxidation or initial remelting. Despite different manufacturing variables, AO-polyethylene retrievals in this cohort had minimal oxidation and no change in XLD or toughness due to oxidation. However, toughness did vary with irradiation dose as did cross-link density. To achieve the same level of cross-linking as HXL-polyethylene required a higher irradiation dose in blended AO-polyethylene. AO-polyethylenes evaluated in this study had toughness that decreased with irradiation dose, but avoided loss of toughness due to remelting. Because AO-polyethylenes did not oxidize, they did not show the decrease of cross-link density, and potential loss of wear resistance, seen in HXL-polyethylene. For any figures or tables, please contact authors directly