Abstract. Background. Oxidized zirconium (OxZr) has been introduced as an alternative bearing for femoral components in Total Knee Arthroplasty (TKA). It has a ceramic-like zirconium oxide outer layer with a low coefficient of friction. Early studies have found OxZr TKA to have a low incidence of early failure in young high demand patients. Currently no study has reported on the outcome of these implants beyond ten years. Objectives. The purpose of our study was to present an in-depth 15-year survival analysis of cemented Profix II OxZr TKA. Study Design & Methods. Data was collected prospectively and survival analysis undertaken with multiple strict end points. Complication rates were recorded and patient reported outcomes were measured. Results. 617 Profix II OxZr TKAs were performed over four years. Forty-nine patients underwent reoperation. Aseptic tibial loosening was the most common cause of failure (32.7%) on average occurring 2.8 years post primary procedure. There was one recorded failure due to loosening of the zirconium femoral component. Revision rate at 15-years was 6.38%. Cumulative survivorship was 91.52% with failure considered to be reoperation for any reason. WOMAC score improved in 86% of patients by year 1. The average score improved by 21.2 points and met the standard for minimum clinically important difference. Conclusions. This study presents the first 15-year survival analysis of cemented Profix II OxZr TKA. Our data supports current literature on the long-term survivorship of oxidised zirconium total knee replacements

While Oxidized Zirconium (OxZr) femoral heads matched with highly cross-linked polyethylene (XLPE) have demonstrated the lowest rate of revision compared to other bearing couples in the Australian National Joint Registry, it has been postulated that these results may, in part, be due to the fact that a single company offers this bearing option with a limited combination of femoral and acetabular prostheses. The purpose of this study was to assess clinical and radiographic outcomes in a matched cohort of total hip replacements (THR) utilizing an identical cementless femoral stem and acetabular component with either an Oxidized Zirconium (OxZr) or Cobalt-Chrome (CoCr) femoral heads at a minimum of 10 years follow-up. We reviewed our institutional database to identify all patients whom underwent a THR with a single cementless femoral stem, acetabular component, XLPE liner and OxZr femoral head with a minimum of 10 years of follow-up. These were then matched to patients who underwent a THR with identical prosthesis combinations with CoCr femoral head by gender, age and BMI. All patients were prospectively evaluated with WOMAC, SF-12 and Harris Hip Score (HHS) preoperatively and postoperatively at 6 weeks, 3 months, 1 and 2 years and every 2 years thereafter. Charts and radiographs were reviewed to determine the revision rates and survivorship (both all cause and aseptic) at 10 years for both cohorts. Paired analysis was performed to determine if differences exist in patient reported outcomes. There were 208 OxZr THRs identified which were matched with 208 CoCr THRs. There was no difference in average age (OxZr, 54.58 years, CoCr, 54.75 years), gender (OxZr 47.6% female, CoCr 47.6% female), and average body max index (OxZr, 31.36 kg/m2, CoCr, 31.12 kg/m2) between the two cohorts. There were no significant differences preoperatively in any of the outcome scores between the two groups (WOMAC (p=0.449), SF-12 (p=0.379), HHS(p=0.3718)). Both the SF12 (p=0.446) and the WOMAC (p=0.278) were similar between the two groups, however the OxZr THR cohort had slightly better HHS compared to the CoCr THR cohort (92.6 vs. 89.7, p=0.039). With revision for any reason as the end point, there was no significant difference in 10 years survivorship between groups (OxZr 98.5%, CoCr 96.6%, p=0.08). Similarly, aseptic revisions demonstrated comparable survivorship rates at 10 year between the OxZr (99.5%) and CoCr groups (97.6%)(p=0.15). Both THR cohorts demonstrated outstanding survivorship and improvement in patient reported outcomes. The only difference was a slightly better HHS score for the OxZr cohort which may represent selection bias, where OxZr implants were perhaps implanted in more active patients. Implant survivorship was excellent and not dissimilar for both the OxZr and CoCr groups at 10 years. Therefore, with respect to implant longevity at the end of the first decade, there appears to be no clear advantage of OxZr heads compared to CoCr heads when paired with XLPE for patients with similar demographics. Further follow-up into the second and third decade may be required to demonstrate if a difference does exist

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

The purpose of this study was to precisely measure the 10-year polyethylene wear rate of primary total hips using Radiostereometric analysis (RSA) comparing Oxidized Zirconium (OxZi) to cobalt chrome (CoCr) femoral heads articulating with highly cross-linked polyethylene (XLPE). RSA was performed on 46 patients who underwent total hip arthroplasty − 23 who received OxZi femoral heads and 23 who received CoCr heads in combination with XLPE at a minimum of 10 years follow-up. All patients had identical THR systems implanted except for the femoral head utilized. The Centre Index method was utilised to assess total wear rates (from index surgery until final evaluation) using a dedicated RSA Software program (UmRSA Digital Measure v.2.2.1). In addition, the Martell technique was used to subtract head penetration occurring in the first 1–2 years (i.e. bedding-in phase) to allow calculation of the ‘steady state’ wear rates. There were no significant differences in demographics (i.e age, BMI, gender) between the groups. The average time from surgery of the RSA examinations was 11.7 and 12.6 years for the CoCr and OxZi groups respectively. Using the Centre Index Method to calculate total head penetration, wear rates were slightly higher in the OxZi group (0.048 +/− 0.021mm/year) compared to the CoCr group (0.035 +/− 0.017mm/year) with no statistical difference between the groups (p= 0.02). After correction for the bedding-in period, there was no statistically significant difference in mean ‘steady-state’ wear rate between OxZi (0.031 +/− 0.021mm/year) and CoCr (0.024 +/− 0.019mm/year) at 10 year follow up (p= 0.24). A comparison of preoperative and postoperative SF12, HHS, and WOMAC scores showed no statistical difference between the groups. RSA demonstrated the 10 year in-vivo wear rates of both bearing combinations to be well below the threshold for osteolysis. There was no significant difference between either the total or ‘steady-state’ wear rates of the OxZi and CoCr groups at 10 years

Introduction. Oxidized zirconium (OxZr) is used as a ceramic surface for femoral components in total knee arthroplasty (TKA). The aim of this study was to investigate its performance by examining retrieved femoral components and their corresponding PE inserts in matched comparison with conventional chrome/cobalt/molybdenum alloy (CrCoMo). Methods. 11 retrieved posterior stabilized (PS) TKA with an OxZr femoral component were included. From a cohort of 56 retrieved TKA with CrCoMo femoral components, pairs were matched according to duration of implantation, patient age, reason for revision, and BMI. The retrieved tibial polyethylene (PE) inserts were analyzed for wear using the Hood classification. Femoral components were optically viewed at 8–32x magnification and screened for scratching, pitting, delamination, and striation. Profilometry was performed to measure surface roughness of the OxZr components using a non-contact white light profiler. Results. The prostheses were in situ for a mean of 18.5±10.6 (OxZr) and 19.5±14.3 (CrCoMo) months (p=0.41). None of these cases were revised for problems directly related to the use of OxZr. There was one reaction to the implant in the CrCoMo group. The average wear of the tibial PE inserts was significantly lower with OxZr components (41.5±16.8 vs. 60.1±22.0, p=0.01). The average wear score in the visual analysis of the femoral components was significantly lower for the OxZr (1.6±1.3 vs. 9.5±0.6, p=0.005). Discussion and Conclusion. Femoral components made of OxZr are less sensitive to in vivo wear damage than those of CrCoMo. PE inlays show significantly less in vivo wear damage in combination with an OxZr femoral component

Oxidized Zirconium (OxZr), metallic zirconium alloy oxidized to form a ceramic surface, was developed as an alternative bearing material to cobalt-chrome (CoCr) alloy for improvements in roughening resistance, frictional behavior, and biocompatibility without a risk of brittle fracture. Knee simulator testing without intentional addition of abrasives demonstrated that the ultra-high molecular weight polyethylene (UHMWPE) wear rate was 85% less with OxZr than with CoCr femorals. The relative performance of articulating materials can change when tested under abrasive conditions, so test protocols were investigated with abrasives added directly to the simulator test lubricant. Testing was conducted on a six-station, four-axis, physiological knee simulator. OxZr and CoCr medium-sized, cruciate-retaining, femoral components were tested against UHMWPE tibial inserts sterilized by ethylene oxide. Alumina powder was mixed into 50% bovine serum lubricant at a concentration of 0.2 mg/cm3. Tests were conducted with different powder sizes in the range of 0.3 to 150 μm. Measurements included tibial insert weight and femoral surface roughness. The lubricant in CoCr tests became opaque with gray debris while the femoral condyles became scratched. In contrast, the lubricant in OxZr tests remained normal (as in tests without abrasives), and femoral condyle scratching was much less severe. Despite these obvious effects, the UHMWPE wear produced by each material did not increase appreciably over that of tests without abrasives, with OxZr maintaining a wear rate about 85% less than for CoCr. It was noted that the scratches were aligned, or became realigned, with the translation motion and had little evidence of the swirls or cross-hatching often observed on retrieved components. Previous testing indicates that UHMWPE wear increases significantly only if scratches are oblique to the sliding direction. Thus, a test technique that produces scratches with more clinically relevant orientations is needed for a performance comparison between femoral materials under abrasive conditions

Introduction. In Total Hip Arthroplasty (THA), polyethylene wear reduction is key to implant longevity. Oxidized Zirconium (OxZi) unites properties of a ceramic bearing surface and metal head, producing less wear in comparison to standard Cobalt-Chromium (CoCr) when articulating with Cross-linked polyethylene (XLPE) in vitro. This study investigates in vivo polyethylene (PE) wear, outcomes and complications for these two bearing couples in patients at 5 year follow-up. Methods. 400 patients undergoing THA across four institutions were prospectively randomised into three groups. Group I received a cobalt-chrome (CoCr) femoral head/ cross-linked polyethylene (XLPE) liner; Group II received an OxZi femoral head/ ultrahigh molecular weight polyethylene (UHMWPE) liner; Group III received an OxZi femoral head/XLPE liner. All bearing heads were 32 mm. Linear wear rate was calculated with Martell computer software. Functional outcome and complications were recorded. Results. At median follow-up of 3.7 years, implant survivorship was 98% across all groups with no difference in SF-36, WOMAC, pain score or complications (p > 0.05). After the first 12 months of creep, rate of linear wear over 3 years was 0.07 mm for Group I, 0.16 mm for Group II, and 0.03 mm/year for Group III. A significant difference was detected when using UHMWPE (p = 0.012) but not when using XLPE (P = 0.75). Conclusion. At midterm follow-up, an XLPE acetabular liner is more important in reducing wear than the femoral head bearing. There is a trend towards lower wear when coupling OxZi rather than CoCr with XLPE; further long-term analysis is recommended to observe this pattern

This study reports the ten-year polyethylene liner wear rates, incidence of osteolysis, clinical outcomes and complications of a three-arm, multicentre randomised controlled trial comparing Cobalt-Chrome (CoCr) and Oxidised Zirconium (OxZr) femoral heads with ultra-high molecular weight polyethylene (UHMWPE) versus highly cross-linked polyethylene (XLPE) liners in total hip arthroplasty (THA).

Patients undergoing THA from four institutions were prospectively randomised into three groups. Group A received a CoCr femoral head and XLPE liner; Group B received an OxZr femoral head and XLPE liner; and Group C received an OxZr femoral head and UHMWPE liner. Blinded observers recorded predefined outcomes in 262 study patients at regular intervals for ten years following THA.

At ten years follow-up, increased linear wear rates were recorded in group C compared to group A (0.133 ± 0.21 mm/yr vs 0.031 ± 0.07 mm/yr respectively, p<0.001) and group B (0.133 ± 0.21 mm/yr vs 0.022 ± 0.05 mm/yr respectively, p<0.001). Patients in group C were associated with increased risk of osteolysis and aseptic loosening requiring revision surgery compared with group A (7/133 vs 0/133 respectively, p=0.007) and group B (7/133 vs 0/135 respectively, p=0.007). There was a non-significant trend towards increased liner wear rates in group A compared to group B (0.031 ± 0.07 mm/yr vs 0.022 ± 0.05 mm/yr respectively, p=0.128). All three groups were statistically comparable preoperatively and at ten years follow-up when measuring normalised Western Ontario and McMaster Universities Osteoarthritis Index(p=0.410), short-form-36 (p = 0.465 mental, p = 0.713 physical), and pain scale scores (p=0.451).

The use of UHMWPE was associated with progressively increased annual liner wear rates after THA. At ten years follow-up, this translated to UHMWPE leading to an increased incidence of osteolysis and aseptic loosening requiring revision THA, compared with XLPE. Femoral heads composed of OxZr were associated with a non-significant trend towards reduced wear rates compared to CoCr, but this did not translate to any differences in osteolysis, functional outcomes, or revision surgery between the two treatments groups.

Purpose

The success of total knee replacement (TKR) surgery can be attributed to improvements in TKR design, instrumentation, and surgical technique. Over a decade ago oxidized zirconium (OxZr) femoral components were introduced as an alternative bearing surface to cobalt-chromium (CoCr), based on strong in-vitro evidence, to improve the longevity of TKR implants. Early reports have demonstrated the clinical success of this material however no long-term comparative studies have demonstrated the superiority of OxZr implants compared to a more traditional CoCr implant. This study aims to compare long-term survivorship and outcomes in OxZr and CoCr femoral components in a single total knee design.

This study reports the ten-year outcomes of a three-arm, multicentre randomised controlled trial comparing Cobalt-Chrome (CoCr) and Oxidised Zirconium (OxZr) femoral heads with ultra-high molecular weight polyethylene (UHMWPE) versus highly cross-linked polyethylene (XLPE) liners in total hip arthroplasty (THA).

Patients undergoing THA from four institutions were prospectively randomised into three groups. Group A received a CoCr femoral head and XLPE liner; Group B received an OxZr femoral head and XLPE liner; and Group C received an OxZr femoral head and UHMWPE liner. The outcomes of 262 study patients were analysed at ten years follow-up.

At ten years, increased linear wear rates were recorded in group C compared to group A (0.133 ± 0.21 mm/yr vs 0.031 ± 0.07 mm/yr respectively, p<0.001) and group B (0.133 ± 0.21 mm/yr vs 0.022 ± 0.05 mm/yr respectively, p<0.001). Patients in group C had increased risk of osteolysis and aseptic loosening requiring revision surgery compared with group A (7/133 vs 0/133 respectively, p=0.007) and group B (7/133 vs 0/135 respectively, p=0.007). There was a non- significant trend towards increased liner wear rates in group A compared to group B (0.031 ± 0.07 mm/yr vs 0.022 ± 0.05 mm/yr respectively, p=0.128). All three groups were statistically comparable preoperatively and at ten years follow-up from a clinical score perspective.

The use of UHMWPE was associated with progressively increased annual liner wear rates. At ten years follow-up, this translated to an increased incidence of osteolysis and aseptic loosening requiring revision, compared with XLPE. Femoral heads composed of OxZr were associated with a non-significant trend towards reduced wear rates compared to CoCr, but this did not translate to any differences in osteolysis, functional outcomes, or revision surgery between the two treatments groups.

INTRODUCTION

One of the recent advances in the hard-on-hard hip arthroplasty is the development of a new material of diffusion hardened oxidised zirconium (DHOxZr). The DHOxZr material consists of a ceramic layer on the top surface which is supported by a thick oxygen diffusion hardened (DH) zone underneath. With the desired properties of metal substrate, ceramic surface and a gradient structure of the oxygen diffusion zone, the DHOxZr-on-DHOxZr bearing combination is expected to produce low wear and minimal metal ions. This can possibly address the concerns associated with metal hypersensitivity associated with metal on metal bearings and fracture risk associated with ceramics. The aim of this study was to evaluate the wear of DHOxZr-on-DHOxZr as a possible hard on hard bearing combination in hips.

Femoral components with an oxidized zirconium-niobium (OxZr) gradient ceramic surface (Oxinium, Smith & Nephew, Memphis, TN) were introduced as an alternative to cobalt-chromium (CoCr) alloy femoral components for the purpose of PE wear reduction in total knee replacements [1]. In the present study, the surface damage and clinical performance of both CoCr alloy and OxZr femoral components were investigated. By matching CoCr alloy and OxZr femoral components for clinical factors, as done by Heyse et al. [2], the surface damage on retrieved CoCr alloy and OxZr femoral component was assessed. Twenty-six retrieved cobalt-chromium (CoCr) alloy femoral components were matched with twenty-six retrieved oxidized zirconium (OxZr) femoral components for implantation period, body-mass index, patient gender, implant type (cruciate ligament retaining/substituting), and polyethylene insert thickness. Detailed surface profilometry was performed on retrieved femoral condyles in areas that had not been damaged by gouging [3] with the specific purpose of investigating the in vivo wear behaviour of undamaged OxZr surface. In addition, the cumulative survivorships were calculated for patients who had received CoCr alloy or OxZr femoral components from our orthopaedic database. In order to identify factors that affect the clinical performance of CoCr alloy and OxZr femoral components, the findings from the retrieval analysis and the survivorship analysis were combined. The Rp, Rpm, and Rpk-values for the retrieved CoCr alloy femoral components were found significantly higher than the Rp, Rpm, and Rpk-values for the retrieved OxZr femoral components (p ≤ 0.031). The roughness parameters values (Ra, Rq, Rz, Rp, Rpm, Rpk, Rv, and Rsk) for the retrieved CoCr alloy femoral components were found significantly higher than the values of the new, never implanted CoCr alloy femoral components (p ≥ 0.001). The surface roughness was higher on the medial condyles than the lateral condyles of the retrieved CoCr alloy femoral components; such a difference was not observed on the retrieved OxZr femoral components. The OxZr bearing surface appeared to protect the femoral components from abrasive wear in vivo. At 8.5-years follow up, the cumulative survivorship for the CoCr alloy femoral components (98%) was not found to be statistically significantly different (p = 0.343, Breslow test) from the OxZr femoral components (97.5%). Therefore, OxZr femoral components appeared to possess low wear characteristics and could be particularly suitable for younger, heavier patients to ensure long-term durability.

Although total knee arthroplasty (TKA) has been a reliable procedure providing durable pain relief, polyethylene (PE) wear remains a major limitation of the long-term success of TKA. One potential method of lowering PE wear in TKA is to use oxidized zirconium (OxZr)-bearing surface. Although wear simulating testing of an OxZr counter surface of femoral component produced less PE wear and fewer particles than did cobalt-chrome (Co-Cr) counter surface of femoral component [1–4], this finding has not been demonstrated in vivo to our knowledge.

We measured in vivo PE wear by isolating and analyzing PE wear particles in synovial fluid from wellfunctioning TKA [5]. The purpose of the current study was to determine the size, shape, and amount of PE wear particles isolated from synovial fluid of patients who underwent a bilateral simultaneous TKA prosthesis, but different materials of femoral components.

We performed a bilateral simultaneous TKA in 100 patients (200 knees) who received an OxZr femoral component in one knee and a Co-Cr femoral component in the other. Mean age was 55.6 (44–60) years. Synovial fluid was obtained from 28 patients (56 knees) who had undergone a simultaneous bilateral TKA under completely sterile conditions at one or two years after the operation. Randomization to an OxZr or Co-Cr femoral component was accomplished with use of a sealed study number envelope, which was opened in the operating room before the skin incision had been made. After the opening the randomization envelope, the first knee received prosthesis indicated by the envelope (OxZr or Co-Cr component) and the contralateral (second TKA) knee received the other prosthesis (OxZr or Co-Cr component).

All operations were performed by one surgeon using the same design of total knee prosthesis: Genesis II (Smith and Nephew, Memphis, Tennessee). Only the material of the femoral component differed between two groups. The preoperative diagnosis was osteoarthritis in all patients. Preoperative and post operative KS and HSS knee scores, KS functional scores and UCLA activity scores were evaluated.

The amount of polyethylene wear particles in the aspirated synovial fluid sample was analyzed by thermogravimetic analysis (TGA) using a TGA instrument (TGA/SDTA 84le model, Mettler Toledo CO., Greifensee, Switzerland). The weight of the sample solution was measured before and after removing the organic content by heating the sample solution. The sample solution was casted onto petri dishes. The petri dish was covered and kept in a dry oven at 60°C for 2 days. While the sample solution was kept in a dry oven for 2 days, a small hole was made on the cover of the petri dish to allow water to evaporate slowly for 2 days. After this procedure, the cover of petri dish was removed and TGA sample was dried at 60°C for another 2 days. After the sample was completely dried out, the dried sample was measured using analytical balance.

TGA was used to determine the weight change profiles of polyethylene subject to heating under a nitrogen atmosphere. The nitrogen flow rate was kept constant at 50mL per minute. TGA data were taken at heating rate as 5°C per minute in the temperature range of 20° to 1000°C. The weight loss data were recorded as a function of time and temperature using special software in computer. When the temperature reached to the point of decomposition of the sample, the sample started to lose weight. By calculating the weight of the sample around the temperature which led to start to decomposition, real amount of polyethylene in the sample was measured. The size and shape of PE particles were examined using scanning electron microscopy (JSH-6360A model, Jeol Co., Tokyo, Japan). The samples were coated using a platinum sputtering machine for 20 sec.

ANOVA, nonparametric chi square test, nonpaired t-test and Mann-Whitney U-test were used for statistical analyses. Differences of P< 0.05 were considered statistically significant.

Mean preoperative KS (27.5 vs 27.2 points) scores, HSS (51.1 vs 51.2 points) knee scores, KS functional scores (55.4 vs 55.4 points) and UCLA activity scores (2.8 vs 2.8 point) were not significantly different between two groups. Mean postoperative KS (93 vs 92 points), HSS knee scores (90 vs 89 points), KS functional scores (78 vs 78 points), and UCLA activity scores (7.8 vs 7.8) were not significantly different. Mean weight of the polyethylene particles was 0.0219 g (SD, 0.0058) in the Co-Cr femoral component groups and it was 0.0214 g (SD, 0.005) in the OxZr group. This difference was not significant (P=0.711139, paired t-test). The size of particles was not different between the two groups. Also, shape of particles was not different between the two groups.

Under the condition and the duration of this study in this specific group of patients, TKA with OxZr or Co-CR femoral knee component had excellent clinical and radiographic outcomes with no osteolysis. While the wear simulator test in vitro demonstrated significant decrease in PE particles in the knees with an OxZr femoral component, our study in vivo revealed that total particle weight, size, and shape of PE wear particles were similar in the knees with an OxZr femoral component and in those with a Co-Cr femoral component.

Introduction

Large diameter femoral heads offer increased range of motion and reduced risk of dislocation. However, their use in total hip arthroplasty has historically been limited by their correlation with increased polyethylene wear. The improved wear resistance of highly crosslinked UHWMPE has led a number of clinicians to transition from implanting traditionally popular sizes (28mm and 32 mm) to implanting 36 mm heads. Desire to further increase stability and range of motion has spurred interest in even larger sizes (> 36 mm). While the long-term clinical ramifications are unknown, in-vivo measurements of highly crosslinked UHMWPE liners indicate increases in head diameter are associated with increased volumetric wear [1]. The goal of this study was to determine if this increase in wear could be negated by using femoral heads with a ceramic surface, such as oxidized Zr-2.5Nb (OxZr), rather than CoCrMo (CoCr). Specifically, wear of 10 Mrad crosslinked UHMWPE (XLPE) against 36 mm CoCr and 44 mm OxZr heads was compared.

Introduction. The development of new bearing surfaces for total joint replacement is constantly evolving. Oxidized zirconium (Oxinium) has been introduced for use in total hip arthroplasty (THA) and total knee arthroplasty (TKA). One of the most common causes of failure of THA is aseptic loosening secondary to polyethylene wear debris. The aetiology of wear is multifactorial and includes adhesive, abrasive, third-body and fatigue wear mechanisms. Oxidized zirconium is a relatively new material that features an oxidized ceramic surface chemically bonded to a hard metallic substrate. This material possesses the reduced polyethylene wear characteristics of a ceramic, without the increased risk of implant fracture While short-term results of oxidized zirconium in THA have been reported, there have been no reports on retrieved highly cross linked PE articulating with Oxinium headsObjectives:. Objectives. The purpose of this study was to compare matched pairs of retrieved highly cross-linked polyethylene (XLPE) acetabular liners with OxZr and CoCr articulation. The liners were examined for evidence of wear damage, including articular surface damage, impingement, screw-hole creep, and rim cracks. Materials and Methods. Four retrieved highly cross-linked polyethylene (XLPE) acetabular liners with 32mm OxZr femoral heads were identified and matched to four retrieved highly cross-linked polyethylene (XLPE) acetabular liners with 32mm CoCr femoral heads by duration of implantation, patient age, and body mass index. Visual damage grading of the articular surface was performed by two independent graders by direct visualization and by light stereomicroscopy. The articular surfaces were subjectively graded for abrasion, burnishing, cracking, delamination, pitting, plastic deformation, third body debris, and scratching using a 0 to 3 scale as described by Hood et al. Liners were divided into quadrants with the elevated rim, when present, to the left and the quadrants labeled in a clockwise fashion beginning in the upper left hand corner. When an elevated rim was not present, liners were divided into quadrants based on the ocation of the etchings. Each quadrant was scored separately. Results. The retrieved components showed predominantly abrasion and burnishing primarily in zones 1 and 2 representing the supero-anterior and supero- posterior regions in the liner. The mean damage score for the Oxinium group was 17.3 vs 23.3 in the CoCr group. The mean time in vivo for the oxinium group was 7.1 yrs vs 4.5 yrs for the CoCr group. Interestingly, the damage scores in zones 3 and 4 were very similar in both groups representing the infero post and anterior portions on the liner. Conclusion. The development of new bearing surfaces for total joint replacement is constantly evolving and will continue to do so as polyethylene wear and osteolysis continue to be a major problem in the long-term survival of total hip arthoplasties. CoCr roughens significantly more in situ compared with OxZr components. Despite the small number of retrieved implants in our study, OxZr demonstrated lower damage on XLPE liners when compared to the CoCr group. Longer-term studies will be necessary to establish the overall clinical fatigue performance of highly crosslinked liners with newer bearing surfaces such as OxZr

Oxidized Zirconium (Oxinium, Smith & Nephew, Inc., Memphis, TN) is a relatively new material that features an oxidized ceramic surface chemically bonded to a tough metallic substrate. This material has demonstrated the reduced polyethylene wear characteristics of a ceramic, without the increased risk of implant fracture. The purpose of the current investigation was to assess clinical outcomes following primary total hip arthroplasty with Oxinium versus Cobalt Chrome femoral heads. One hundred uncemented primary total hip arthroplasty procedures were prospectively performed in 100 patients. There were 52 males and 48 females with mean age at the time of surgery of 51 years (SD 11, range, 19–76). Using a process of sealed envelope randomization, patients were divided into 2 groups. Each group contained fifty patients. Those in group 1 received an Oxinium femoral head (OX), while those in group 2 a cobalt-chrome femoral head (CC). The current study reports clinical outcome measures for both the OX and CC groups at a minimum follow-up of 2 years postoperatively. At the time of latest follow-up, stem survival for both groups was 98%. There was a significant improvement in all clinical outcome scores between preoperative and 2 year postoperative time periods for both bearing groups (p< 0.003). There were no significant differences between bearing groups for any of the clinical outcome scores at final follow-up (p> 0.159). Mean Harris Hip Scores at 2 years postoperatively were 92 and 92.5 for OX and CC, respectively (range; 65–100 OX, 60–100 CC). For SF-12, both the Physical Component Summary Scale (PCS) and the Mental Component Summary Scale (MCS) are reported. Mean PCS scores at final follow-up were 45.2 and 49.21 for OX and CC (range; 27.1–56.7 OX, 26.3–61.8 CC). Mean MCS scores were 53.8 and 52.57 for OX and CC (range; 39.2–65.5 OX, 34.3–64 CC). Mean final WOMAC scores are reported as 84.9 and 87 for OX and CC, respectively. The current data suggest that total hip arthroplasty utilizing Oxinium femoral heads is safe and effective. Additional follow-up of the current cohort will be performed in order to fully assess mid-to long-term clinical outcomes

INTRODUCTION. The development of new bearing surfaces for total joint replacement is constantly evolving. Oxidized zirconium (Oxinium) has been introduced for use in both total hip arthroplasty (THA) and total knee arthroplasty (TKA). The aetiology of wear is multifactorial and includes adhesive, abrasive, third-body and fatigue wear mechanisms. Oxinium femoral components have demonstrated clear improvements in wear characteristics in-vitro. The purpose of this prospective study was to evaluate the mid-term (minimum 5 year) clinical and radiographic results and survivorship of the Genesis II™ knee implant system using an Oxinium femoral component. METHODS. Between January 2001 and December 2008, 382 Genesis II Oxinium (Smith & Nephew) primary total knee arthroplasties (TKA) (313 patients) were implanted at our institution. A comparison with a cohort of 317 patients (382 knees) who received a Genesis II knee implant using a ‘conventional’ cobalt-chrome (Co-Cr) femoral component was performed during the same time period. Prospective data was collected on all patients including demographics (age, BMI, diagnosis) as well as pre and postoperative clinical outcome scores (SF-12, WOMAC, and knee society clinical rating scores (KSCRS). Radiological analysis for evidence of osteolysis and loosening was performed in all patients. Comparisons were performed to determine differences between the Oxinium and Cobalt Chrome cohorts. Kaplan-Meier survival analysis was performed to show cumulative survival over time. Failure was defined as femoral component revision due to any cause. RESULTS. The mean age at time of surgery was 54.0 and 60.6 years respectively for the Oxinium and Co-Cr groups. The mean time from surgery was 8.13 +/− 2.03 years and 8.59 +/− 2.01 years for the Oxinium and Co-Cr groups respectively. Both groups demonstrated a statistically significant improvement in clinical outcome measures between pre, and post operative SF-12, WOMAC, and KSCRS scoring systems with no difference between two groups. There were a total of 15 revisions (infection: 8, stiffness: 2, aseptic loosening of patella component: 2, Aseptic loosening of the tibial component: 1, instability: 1, and one malaligned Femoral Component) in the Oxinium group. In the CoCr group there were a total of 9 revisions (Infection:5, aseptic loosening:1, instability: 1, stiffness: 1 and one patient revised for unexplained pain). Radiographically, no loosening was noted in the Oxinium group and all implants appeared well fixed. There was one case of loosening seen in the cobalt chrome group. The overall survival was 99.7 for both Oxinium and CoCr femoral components. Our study demonstrated no significant differences in validated clinical outcome scores and radiographic outcomes when comparing the Oxinium and Co-Cr femoral components. CONCLUSION. Despite the large numbers in our study, there were no statistically significant differences between Oxinium and CoCr femoral components at a minimum of five years follow up. While no clear benefits have been demonstrated, the use of an Oxinium femoral component demonstrated no adverse events at mid-term follow-up. Conventional Co-Cr femoral components remain the gold standard while long-term follow-up data is required to demonstrate the potential benefits of Oxinium

Introduction. Wear-related osteolysis continues to be a concern in the long-term outcome and survivorship of total hip arthroplasty (THA) and there continues to be an emphasis on bearing materials that exhibit improved wear profiles. Oxidized zirconium metal (Oxinium®, Smith & Nephew) was developed to reduce the amount of polyethylene wear as compared to cobalt chromium femoral heads, without the risk of brittle fracture seen with older generation ceramics. There are a limited number of retrieval studies evaluating the performance of Oxinium in THA. The aims of this study were 1) to visually assess damage on the surface of a large number of retrieved Oxinium femoral heads, 2) to measure surface roughness of scratches on the surfaces of Oxinium femoral heads, and 3) to use scanning electron microscopy (SEM) to assess the integrity of the oxidized zirconium surface in damaged areas. BIOLOX delta (CeramTec), a ceramic alternative to Oxinium, was included in this study for comparison. Methods. From 2006 to 2013, 59 retrieved Oxinium femoral heads in THAs were collected after an average time to revision surgery of 1.64 years. The mean patient age was 61.9 years, with 32 males and 27 females. Reasons for revision surgery were recurrent dislocation (24), femoral component loosening or subsidence (13), infection (9), acetabular loosening (4), periprosthethic fracture (4), acetabular malposition (2), heterotopic ossification (2), and 1 case of leg length discrepancy. The diameters of the femoral heads were 28 mm (9), 32 mm (22), 36mm (26) and 40mm (2). Three observers visually graded surface damage on all femoral heads according to the following criteria: 1) no scratches, 2) minimal damage with one to two scratches, 3) significant damage with multiple scratches. We measured the surface roughness of retrieved Oxinium and BIOLOX delta femoral heads with an interferomic profiler, and SEM to evaluate the extent of surface effacement. Results. Oxinium femoral heads explanted for recurrent dislocation showed substantially more severe damage as compared to heads retrieved during revision surgery for other reasons (p<0.001). Eighteen of 24 heads explanted for recurrent dislocation (75%) showed gross visual evidence of substantial surface damage (grade 3), compared to only 5 of the 35 explants for non-dislocation causes (Figure 1). The surface roughness of damaged Oxinium femoral heads was significantly higher (28.6× more rough) than undamaged Oxnium and 17.7× more rough than damaged Biolox delta heads (p<0.001; Figure 2). High magnification imaging showed severe damage and effacement of the oxidized zirconium layer, exposing the metal alloy underneath (Figure 3). This was confirmed by Energy Dispersive Xray Analysis (EDXA). Discussion. This study represents the first large-scale retrieval analysis of oxidized zirconium femoral heads in THA. The results show that high impact between an acetabular shell and an Oxinium femoral head during dislocation increases the surface roughness and causes substantial effacement to the oxidized zirconium layer compared with matched modern ceramic bearings. The surface damage seen to these femoral heads is of clinical concern because it has the potential to increase the wear of polyethylene liners in THA

The use of metal on polyethylene articulations was a key development in establishing total hip arthroplasty as a successful and reproducible treatment for end stage osteoarthritis. In order to ensure implant durability in relatively younger populations, there is a need for alternative, wear resistant bearing surfaces. Oxidized Zirconium (Oxinium, Smith & Nephew, Inc., Memphis, TN) is a relatively new material that features an oxidized ceramic surface chemically bonded to a tough metallic substrate. This material has demonstrated the reduced polyethylene wear characteristics of a ceramic, without the increased risk of implant fracture. The purpose of the current investigation was to assess early clinical outcomes following primary total hip arthroplasty with Oxinium versus Cobalt Chrome femoral heads. One-hundred primary THA procedures were prospectively performed in 100 patients. There were 52 males and 48 females. Using a process of sealed envelope randomization, patients were divided into 2 groups. Group 1 consisted of fifty patients, each receiving primary THA implants with an Oxinium femoral head (OX). The mean age of each patient was 51 years (SD 10.8, Range 22–74) with 26 males and 24 females. Group 2 also consisted of 50 patients. Within this group again each patient received primary THA implants however with a cobalt-chrome femoral head (CC). Demographics were similar with mean age 51 years (SD 11.0, Range 19–76) and again 26 males and 24 females. The current study reports clinical outcome measures for both the OX and CC groups at a minimum follow-up of 2 years postoperatively. At the time of latest follow-up, stem survival for both groups was 98%. There was a significant improvement in all clinical outcome scores between preoperative and 2 year postoperative time periods for both bearing groups (p< 0.003). There were no significant differences between bearing groups for any of the clinical outcome scores at final follow-up (p> 0.159). Mean Harris Hip Scores at 2 years postoperatively were 92 and 92.5 for OX and CC, respectively (range; 65–100 OX, 60–100 CC). For SF-12, both the Physical Component Summary Scale (PCS) and the Mental Component Summary Scale (MCS) are reported. Mean PCS scores at final follow-up were 45.2 and 49.21 for OX and CC (range; 27.1–56.7 OX, 26.3–61.8 CC). Mean MCS scores were 53.8 and 52.57 for OX and CC (range; 39.2–65.5 OX, 34.3–64 CC). Mean final WOMAC scores are reported as 84.9 and 87 for OX and CC, respectively. The current data suggest that total hip arthroplasty utilizing Oxinium femoral heads is safe and effective. Additional follow-up of the current cohort will be performed in order to fully assess mid- to long-term clinical outcomes

Traditional polyethylene oxidizes, wears and generates particles over time, which most probably contributes to increased risk of periprosthetic osteolysis. Even contemporary sterilization methods such as radiation and package in oxygen reduced or oxygen substituted environment do not eliminate oxidation over time. Thus, there is a need for alternative bearing in total hip replacement surgery and especially in patients with high activity and long life expectancy. All three major alternate bearings, ceramic-on-ceramic, metal-on-metal and highly crosslinked polyethylene produce major reductions in volumetric wear. The electron beam, melted highly cross-linked polyethylene has an in vivo penetration rate after the bedding in period, which is less than 8 microns per year. This is not substantially different from ceramic on ceramic or metal on metal. Therefore, the inherent risk of periprosthetic osteolysis with these alternate bearings is probably smaller than observed with conventional polyethylene. In the competition between different articulations highly cross-linked polyethylene has some advantages. The polyethylene is more adaptable than the hard bearing surfaces. This means that extended lip liners, offset liners, constrained liners and further special designs may be used. These options are not possible with any of the hard bearings. Another advantage with polyethylene is forgiveness. Impingement in hard-on-hard bearings may lead to serious complications such as chipping of the ceramics or metallosis in a metal on metal articulation. Impingement should also be avoided with use of polyethylene, but if it occurs, the consequences are often more benign at least in the short term perspective. Micro-separation results in less material damage with use of polyethylene than with the 2 other types of articulations. A few degrees of additional abduction above the geometrical limits for a particular socket is far less harmful if it is made of polyethylene compared to the situation in ceramic-on-ceramic or metal-on-metal bearings. Polyethylene is also more familiar to the majority of orthopaedic surgeons. In the operating room the cross-linked polyethylene is identical to those types of polyethylene, which have been used fore 3 to 4 decades. Finally the cost is a major factor (Harris 2004). The hard-on-hard bearings are substantially more expensive. The fracture incidence of ceramics components has decreased with improved manufacturing technology, but the risk of polyethylene fracture appears to be still smaller. On the other hand using highly cross-link polyethylene carries some risks. Particles generated from this new material are smaller with higher inflammatory response. Compared with joints including conventionally sterilised polyethylene the total particle production is, however, reduced with more than 85%, which has implications for the magnitude of the inflammatory response. The significance and importance of the irradiation and melting induced changes of the mechanical properties of the polyethylene is not known. Long term follow-up is needed to evaluate this issue. Charnley preferred small head sizes in total hip replacement because they resulted in transmittance of low frictional torque to the acetabular implant. Mueller advocated larger head sizes with improved joint stability and lower contact pressure. Large heads do, however, imply increased volumetric wear. Therefore, 32 mm heads were abandoned in the early 90ties in favour of 28 mm heads. Another consequence of using larger heads is that polyethylene liners are relatively thin. The highly cross-link polyethylene and the hard bearings can be used with bigger femoral heads, which increases the range of motion and the hip joint stability. Amorphous diamond coatings has been studied as an alternative bearing surface in the laboratory (Santavirta 2003). Such coatings may provide wear rates 104 to 105 times lower than conventional THR articulations, because of their extremely hard surface and low coefficient of friction without any corrosion paths (Santavirta et al. 1999 Lappalainen et al. 2003). Oxidized Zirconium (OxZr) is another material, which has similar advantages. Oxinium materials are the results of a process that allows thermally–driven oxygen to diffuse and transform the metallic zirconium alloy surface into a durable low-friction oxide. The Oxinium material is harder than commonly used cobalt chrome, and with only the surface changing during the manufacturing process, the rest of the implant remains metal to maintain its overall strength. OxZr provides superior abrasion resistance without the risk of brittle fracture, thereby combining the benefits of metal and ceramics. Knee simulator tests have shown that OxZr can reduce polyethylene wear substantially (Ries et al. 2002). Although promising, these two coatings still lack clinical documentation. During the last decade it has become evident that many designs of total hip arthroplasty can in patients with normal bone quality be fixed to the bone with a high degree of reproducibility. This has had the effect that younger patients have been operated on in increasing numbers. Wear and periprosthetic bone loss have remained a serious and comparatively frequent complications. The introduction of more wear resistant articulations has the potential to solve these problems making the procedure safer also among these patients. So far there is no or very scarce evidence that these articulations can be used safely during decades without complications causing progressive and often silent bone destruction resulting in difficult revisions with high morbidity. In the case of metal on metal articulations release and accumulation of ions remains a long term concern and especially if the patients will suffer from a temporary or permanent disease associated with impaired renal function. Because evidence of long term superiority of these new articulations is lacking it is of utmost importance that these new implants and materials are introduced into clinical practice in a controlled way. Careful surveillance of preclinical and gradually enlarged randomised studies followed by multicenter trials is necessary to avoid disastrous mistakes so common in the past