Aims

We conducted a prospective study of a delta ceramic total hip arthroplasty (THA) to determine the rate of ceramic fracture, to characterise post-operative noise, and to evaluate the mid-term results and survivorship.

Two types of ceramic materials currently used in total hip replacements are third generation hot isostatic pressed (HIPed) alumina ceramic (commercially known as BIOLOX®forte, CeramTec) and an alumina matrix composite material consisting of 75% alumina, 24% zirconia, and 1% mixed oxides (BIOLOX®delta, CeramTec). The aim of this study is to compare BIOLOX delta femoral heads to BIOLOX forte femoral heads revised within 2 years in vivo. Ceramic bearings revised at one center from 1998 to 2010 were collected (61 bearings). BIOLOX delta heads (n=11) revised between 1–33 months were compared to BIOLOX forte femoral heads with less than 24 months in vivo (n=20). The surface topography of the femoral heads was measured using a chromatically encoded confocal measurement machine (Artificial Hip Profiler, RedLux Ltd.). The median time to revision for BIOLOX delta femoral heads was 12 months, compared to 13 months for BIOLOX forte femoral heads. Sixteen out of 20 BIOLOX forte femoral heads and 6 out of 11 BIOLOX delta femoral heads had edge loading wear. The average volumetric wear rate for BIOLOX forte was 0.96 mm3/yr (median 0.13 mm3/yr), and 0.06 mm3/yr (median 0.01 mm3/yr) for BIOLOX delta (p=0.03). There was no significant difference (p>0.05) in age, gender, time to revision or femoral head diameter between the two groups. Early results suggest less volumetric wear with BIOLOX delta femoral heads in comparison to BIOLOX forte femoral heads

In 2020 almost 90% of femoral heads for total hip implants in Germany were made of ceramic. Nevertheless, the cellular interactions and abrasion mechanisms in vivo have not been fully understood until now. Metal transfer from the head-neck taper connection, occurring as smear or large-area deposit, negatively influences the surface quality of the articulating bearing. In order to prevent metal transfer, damage patterns of 40 Biolox delta ceramic retrievals with CoC and CoPE bearings were analysed. A classification of damage type and severity for each component (n=40) was done according to an established scoring system. To investigate the physical properties, the surface quality was measured using confocal microscopy, quantitative analysis of phase composition were performed by Raman spectroscopy and qualitative analysis of metal traces was done by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). The periprosthetic tissue was analysed for abrasion particles with SEM and EDX. Both bearing types show different damage patterns. Dotted/ drizzled metal smears were identified in 82 % of CoC (n=16) and 96 % of CoPE (n=24) bearings. Most traces on the ceramic heads were identified in the proximal area while they were observed predominantly in the distal area for the ceramic inlays. The identified marks are similar to those of metallic bearings. Metallic smears lead to an increase of up to 30 % in the monoclinic crystalline phase of the ceramic. The roughness increases by up to six times to Ra=48 nm. Ceramic and metallic wear particles from the articulating surfaces or head neck taper junctions were found in the periprosthetic tissue. Damage patterns on CoC hip implants seem to be similar to those of metallic implants. More detailed analysis of CoC implants are needed to understand the described damage patterns and provide advice for prevention

Introduction. The bearing surfaces of ceramic-on-ceramic (CoC) total hip replacements (THR) show a substantially lower wear rate than metal-on-polyethylene (MoP) THR in-vitro. However, revision rates for CoC THR are comparable with MoP. Our hypothesis that an explanation could be adverse reaction to metal debris (ARMD) from the trunnion led us to investigate the wear at both the bearing surfaces and the taper-trunnion interface of a contemporary CoC THR in an in-vitro study. Methods. Three 36mm CoC hips were tested in a hip simulator for 5 million cycles (Mc). BIOLOX. ®. delta ceramic femoral heads were mounted on 12/14 titanium (Ti6Al4V) trunnions. Wear of femoral heads, acetabular liners and trunnions was determined gravimetrically using the analytical balance. Roughness measurements (Sa) were taken on the articulating surfaces (pre and post-test) and on the trunnion surfaces (worn and unworn). Furthermore, Energy Dispersive X-ray Spectroscopy (EDX) was used to identify and quantify the wear debris present in the lubricant using scanning electron microscope (SEM). Results and Discussion. The total volumetric wear was 0.25 mm. 3. for CoC joints and 0.29 mm. 3. for titanium trunnions. The total wear volume of the titanium trunnions was in agreement with an explant study (Kocagoz et al, 2016, CORR) which quantified the volumetric material loss from retrieved trunnions with the total wear ranging from 0.0–0.74 mm. 3. The Sa values, pre-and post-test, for heads were 0.003 ± 0.002 and 0.004 ± 0.001 µm and for liners were 0.005 ± 0.001 and 0.005 ± 0.001 µm. Pre-and post-test measurements for Sa of heads (p = 0.184) and liners (p = 0.184) did not show a statistically significant change. The Sa of the trunnions on the unworn and worn areas showed a statistically significant decrease from 0.558 ± 0.060 to 0.312 ± 0.028 µm respectively (p < 0.001). Analysis of wear debris within the lubricant confirmed the presence of titanium. A recent clinical study (Matharu et al, 2016, BMC Musc Dis) found more ARMD in CoC hips than MoP hips. This is despite there being fewer metallic components in a CoC hip than a MoP hip. This in vitro study has shown that one source of metal debris in a CoC hip is the taper-trunnion junction. Conclusion. An explanation for wear related failures in ceramic-on-ceramic hip arthroplasty, despite the low wear arising at the articulating surfaces, may now exist; namely that titanium wear particles are generated from the trunnion. No other long-term hip simulator studies have measured wear at the taper-trunnion junction

Introduction

The continued improvement of ceramic materials for total hip arthroplasty led to the development of Zirconia and Zirconia toughened Alumina materials such as BIOLOX® delta. Zirconia exists in a tetragonal phase in new ceramic heads and can transform to a monoclinic phase in response to loading giving the material improved fracture toughness. It is known that surface transformation occurs in this material under hydrothermal conditions (i.e. in vivo condition), and ISO standards recommend parts are artificially aged prior to testing to include any effect of surface transformation on new designs. Accelerated aging procedures have been used to predict the amount of phase transformation that will occur in vivo, but validation of these models requires the study of retrieved hip joints. Here 26 BIOLOX® delta retrievals are analysed to determine the degree of phase transformation that occurs in vivo. The levels of phase transformation measured are compared with those predicted based on accelerated aging tests.

Introduction

There is interest in minimally invasive solutions that reduce osteoarthritic symptoms and restore joint mobility in the early stages of cartilage degeneration or damage. The aim of the present study was to evaluate the Biolox®delta alumina-zirconia composite as a counterface for articulation against live cartilage in comparison to the clinically relevant CoCrMo alloy using a highly controlled in vitro ball-on-flat articulation bioreactor that has been shown to rank materials in accord with clinical experience.

Introduction. Hip replacements are falling short of matching the life expectancy of coxarthritis patients, due to implanting THR in younger patients and due to increasingly active patients. The most frequently implanted hip prostheses use cross linked (XL) polyethylene (PE) on metal bearings in the USA and most of the Western world. Concerns remain in the long term around the potential of wear debris-induced aseptic loosening. Thus exploring lower-wearing alternative bearings remains a major research goal. PEEK (poly-ether-ether-ketone) is a thermoplastic polymer with enhanced mechanical properties. This study compared the wear of PEEK to the wear of cross linked polyethylene, when sliding against cobalt chrome (CoCr) metallic counterfaces, and compared the wear of carbon-fibre reinforced (CFR)-PEEK to cross linked polyethylene when sliding against metallic and ceramic counterfaces under different contact stresses within the hip joint. Methods. The following materials were studied: unfilled PEEK (OPTIMA, Invibio) and CFR-PEEK (MOTIS, Invibio) against either high carbon (HC) CoCr or Biolox Delta ceramic plates. The comparative control material was a moderately cross-linked PE (Marathon, DePuy Synthes). A simple geometry wear study was undertaken. A rotational motion of ±30° across a sliding distance of ±28 mm (cross shear of 0.087), and contact pressures of 1.6 or 4 MPa were applied. The lubricant was 25% (v/v) bovine serum and the wear test was conducted for 1 million cycles at 1 Hz. Wear was assessed gravimetrically. A validated soak control method was used to adjust for serum absorption-induced mass changes during the wear test. Surface profilometry was assessed pre and post wear test. Results. Unfilled PEEK produced a six-fold higher wear factor than XL PE against HC Co Cr (p value <0.0001). CFR-PEEK vs. Biolox Delta produced a two-fold lower wear factor than XL PEvs. HC Co Cr (p value = 0.003). CFR-PEEK vs. Biolox Delta had the lowest wear factor among all studied combinations. The wear of CFR-PEEK vs. HC CoCr was higher than XL PEvs. HC CoCr (Figure 1). The counterface surfaces were scratched when articulating against CFR-PEEK. This was more evident on CoCr plates, with the average surface roughness increasing from 0.005 µm to 0.32 µm (p value = 0.0048). This might explain the accelerated wear in the CFR-PEEK vs. HC CoCr combinations. Higher contact pressures led to a 30 % reduction in the wear factor of CFR-PEEK vs. Biolox Delta combination (p value = 0.048), while no significant impact was noted against HC CoCr (Figure 2). Conclusions. The injection moulded carbon fibre reinforced PEEK vs. Biolox Delta ceramic generated significantly lower wear compared with XL PE (even under higher contact pressures). CFR-PEEK vs. Biolox Delta may lead to longer lasting hip replacements, and will be the subject of further investigations

INTRODUCTION. Ceramic-on-ceramic hip resurfacing offers a bone conserving treatment for more active patients without the potential metal ion risks associated with resurfacing devices. The Biolox Delta ceramic material has over 15 years of clinical history with low wear and good biocompatibility but has been limited previously in total hip replacement to 48mm diameter bearings [1]. Further increasing the diameter for resurfacing bearings and removing the metal shell to allow for direct fixation of the ceramic cup may increase the wear of this material and increase the risk of fracture. METHODS. Eighteen implants (ReCerf™, MatOrtho, UK; Figure1) were wear tested; six were ⊘40mm (small) and twelve ⊘64mm (large). All small and six large implants were tested under ISO 14242 standard conditions for 5 million cycles (mc) at 30° inclination (45° clinically). The six remaining large implants were tested under microseparation conditions in which rim contact was initiated during heel strike of the gait cycle for 5mc. Cups were orientated at 45° inclination (60° clinically) to allow for separation of the head and cup with a reduced 50N swing phase load and a spring load applied to induce a 0.5mm medial-superior translation of the cup. Wear was determined gravimetrically at 0.5mc, 1mc and every mc after. RESULTS. Wear was low in both standard and microseparation tests, less than 1mm. 3. cumulatively over 5mc (Figure 2). Standard conditions showed a run-in wear phase over the first mc followed by negligible wear in both diameters. The run-in wear significantly increased from 0.2mm. 3. /mc in the 40mm diameter bearings to 0.5mm. 3. /mc with the larger diameter implants. Under microseparation conditions, there was low wear over the first mc, increasing to 0.28mm. 3. /mc between 1–3mc. The wear rate reduced to 0.11mm. 3. /mc from 3=5mc. Stripe wear was evidenced on the microseparated components. There were no incidences of fracture or squeaking. DISCUSSION. Biolox Delta is known for its low wear rates but published results have only reported testing up to ⊘36mm [2]. Increasing the diameter to 64mm showed increased wear compared to smaller diameters but this was only significant over the first mc suggesting similar performance long term. Microseparation testing of these large sized bearings doubled the cumulative wear produced over 5mc but wear measured was still much lower than other bearing combinations. Wear of metal-on-metal resurfacing implants under these high angle, microseparation conditions has been reported up to 10.5mm. 3. /mc [3], significantly higher than any wear rate reported in the current study. Despite the 3mm wall thickness, no fracture of the cup occurred but stripe wear was observed in the ceramic components. SIGNIFICANCE. Biolox Delta ceramic is appropriate for use in larger diameters without excessive wear or damage to the bearings. The improved biocompatibility of the material may allow for hip resurfacing to be offered to more patients than currently available. For any figures or tables, please contact the authors directly

Background. The CoCrMo large bearings had shown a high failure rate, because of metal ion and particle release. Alumina matrix composite (AMC) ball heads have shown to mitigate such phenomena. The aim of this study was to investigate the leaching properties of AMC clinically as well as experimentally. Methods. Two patient groups were compared: a control group (n=15) without any implant (Controls) and 15 Patients with unilateral treatment with Biolox delta ceramic-on-ceramic (CoC). Whole-blood samples of Controls and Patients (after 3 and 12 months from treatment with CoC) were measured by means of trace element analysis using a HR-ICPMS. The leaching behaviour of BIOLOX delta was also analysed in-vitro: five Biolox delta heads and five CoCrMo heads were immersed in serum for seven days at 37°C. Aluminium, cobalt, chromium and strontium were detected based on HR-ICPMS. Results. In Patients, most elements remained below the limit of detection (LoD), except for aluminium and strontium. The aluminium values of Controls were below the LoD (27.2μg/L). The values of Patients after three months show a median of 34.2μg/L and after 12 months 37.1μg/L (p=0,510). Strontium ranged from 39.7μg/L of Controls and 79.6μg/L and 70.7μg/L of Patients, after three and twelve months, respectively. This difference was not statistically significant (p=0,322). The leaching experiments showed high amounts of cobalt (177.3μg/L) and chromium (4.2μg/L) released by CoCrMo. Ceramic heads didn't show any significant release. Conclusions. The current study revealed that there was no significant increase of any element in patients with CoC bearings. Metal heads released high values of cobalt in leaching test. As this release occurred even without any joint articulation, as shown in the experiments, surface corrosion seems to be a relevant mechanism in the ion release of metal bearings. A limitation of the study is that Controls differed from Patients within the clinical trial. Level of evidence. III

Aims. Ceramic-on-ceramic (CoC) bearings in total hip arthroplasty (THA) are commonly used, but concerns exist regarding ceramic fracture. This study aims to report the risk of revision for fracture of modern CoC bearings and identify factors that might influence this risk, using data from the National Joint Registry (NJR) for England, Wales, Northern Ireland and the Isle of Man. Patients and Methods. We analysed data on 223 362 bearings from 111 681 primary CoC THAs and 182 linked revisions for bearing fracture recorded in the NJR. We used implant codes to identify ceramic bearing composition and generated Kaplan-Meier estimates for implant survivorship. Logistic regression analyses were performed for implant size and patient specific variables to determine any associated risks for revision. Results. A total of 222 852 bearings (99.8%) were CeramTec Biolox products. Revisions for fracture were linked to seven of 79 442 (0.009%) Biolox Delta heads, 38 of 31 982 (0.119%) Biolox Forte heads, 101 of 80 170 (0.126%) Biolox Delta liners and 35 of 31 258 (0.112%) Biolox Forte liners. Regression analysis of implant size revealed smaller heads had significantly higher odds of fracture (chi-squared 68.0, p < 0.001). The highest fracture risk was observed in the 28 mm Biolox Forte subgroup (0.382%). There were no fractures in the 40 mm head group for either ceramic type. Liner thickness was not predictive of fracture (p = 0.67). Body mass index (BMI) was independently associated with revision for both head fractures (odds ratio (OR) 1.09 per unit increase, p = 0.031) and liner fractures (OR 1.06 per unit increase, p = 0.006). . Conclusions. We report the largest independent study of CoC bearing fractures to date. The risk of revision for CoC bearing fracture is very low but previous studies have underestimated this risk. There is good evidence that the latest generation of ceramic has greatly reduced the odds of head fracture but not of liner fracture. Small head size and high patient BMI are associated with an increased risk of ceramic bearing fracture. Cite this article: Bone Joint J 2017;99-B:1012–19

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

Ceramic-on-ceramic total hip replacements (THRs) have shown low wear volumes in standard gait hip simulator studies. 1. However clinical reports have indicated a variation in wear rates and formation of stripe wear on the ceramic femoral heads. 2. The aim of this study was to investigate the influence of different clinical conditions such as cup inclination angle and microseparation (head offset deficiency) on the wear of ceramic-on-ceramic THRs. The six station Leeds II hip joint simulator was used to investigate the wear of size 28mm ceramic-on-ceramic bearing couples. The alumina matrix composite ceramic material (AMC, Biolox Delta, CeramTec AG, Germany) was used in this study. The lubricant used was 25% bovine serum. The study was carried out for a total of five million cycles; the first two million cycles under standard gait conditions and a further three million cycles under microseparation conditions. During microseparation, a lateral movement of 0.5mm was applied to the cup relative to the head during the swing phase of the gait cycle. 3. Three of the cups were mounted to provide a clinical angle of 55°, which is referred to as the ‘standard’ condition; and the other three cups were mounted to provide a clinical angle of 65°, which is referred to as the ‘steep angle’ condition. These combinations provided four different testing conditions: standard, steep cup angle, microseparation, and combination of steep cup angle and microseparation conditions. Volumetric wear was determined gravimetrically and statistical analysis was performed using One Way ANOVA (significance at p< 0.05). Increasing the cup inclination angle from 55° to 65° had no significant effect on the wear rate in Biolox Delta ceramic-on-ceramic THRs under both standard (p> 0.42) and microseparation (p> 0.55) conditions. Under standard gait conditions, the mean wear rate for both cup inclination angles was very low at 0.05 mm3/million cycles. The introduction of microseparation to the standard gait cycle significantly increased the mean wear rates (p< 0.01) to 0.13 mm3/ million cycles for the ‘standard’ cup inclination angle of 55° and 0.11 mm3/million cycles for the ‘steep’ cup inclination angle of 65°. A stripe of wear on the head also formed, with corresponding superior rim wear on the cup. For comparison, the steady state wear rate of HIPed third generation alumina ceramic (Biolox Forte) under microseparation conditions was 1.3 mm3/million cycles [. 4. ]. In conclusion, increasing the cup inclination angle by 10° had no influence on the wear rate of Biolox Delta ceramic-on-ceramic bearings. The introduction of microseparation conditions significantly increased the wear rate and resulted in stripe-like wear on the femoral head, which has previously been observed on retrieved ceramic prosthesis. However, these wear rates were still low, and were ten times lower than those previously reported for Biolox Forte

Polyimide (MP-1, MMATech, Haifa, Israel), is a high performance aerospace thermoplastic used for its lubricity, stability, inertness and radiation resistance. A wear resistant thin robust bearing is needed for total hip arthroplasty (THR). After independent laboratory testing, in 2006, the author used the material as a bearing in two Reflection (Smith and Nephew, USA) hip surgeries. The first, a revision for polyethylene wear, survives with no evidence of wear, noise, new osteolysis or complications related to the MP-1 bearing after 16 yrs. The second donated his asymptomatic MP-1 hip at 6.5yrs for post-mortem examination. There were no osteoclasts, cellular reaction bland in contrast to that of polyethylene. In 2013 a clinical study with ethical committee approval was started using a Biolox Delta (Ceramtec, Germany) head against a polyimide liner in 97 patients. MMATech sold all liners, irradiated: steam 52:45. Sixteen were re-machined in New Zealand. Acetabular shells were Delta PF (LIMA, Italy). The liner locked by taper. The cohort consisted of 46:51 M:F, and ages 43 to 85, mean 65. Ten received cemented stems. For contralateral surgery, a ceramic or polyethylene liner was used. Initial patients were lower demand, later, more active patients, mountain-biking and running. All patients have on-going follow up, including MP-1 liner revision cases. There has been no measurable wear, or osteolysis around the acetabular components using weight-bearing radiographs. Squeaking within the first 6 weeks was noted in 39 number of cases and subtle increase in palpable friction, (passive rotation at 50 degrees flexion), but then disappeared. There were 6 revisions, four of which were related to cementless Stemsys implants (Evolutis, Italy) fixed distally with proximal linear lucencies in Gruen zones 1 and 7, and 2 and 6. No shells were revised and MP-1 liners were routinely changed to ceramic or polyethylene. The liners showed no head contact at the apex, with highly polished contact areas. There were no deep or superficial infections, but one traumatic anterior dislocation at 7 years associated with 5 mm subsidence of a non-collared stem. The initial squeaking and increased friction was due to the engineering of the liner / shell composite as implanted, not allowing adequate clearance for fluid film lubrication and contributed to by shell distortion during impaction. The revised bearings were “equatorial” rather than polar, and with lack of wear or creep this never fully resolved. Where the clearance was better, function was normal. The “slow” utilization was due to my ongoing concern with clearances not being correct. The revision of 4 Stemsys stems, tribology issues may have contributed, but non “MP-1” / Stemsys combinations outside this study have shown the same response, thought to be due to de-bonding of the hydroxyapatite coating. With correct engineering and clearances, a 3.6 mm thick MP-1 bearing, a surface Ra<0.5, steam sterilized, shows no appreciable wear, and with confidence, can be used as a high performance THR bearing

Introduction. Concerns regarding UHMWPE wear particle induced osteolysis in total hip replacement (THR, [1]) have led to alternative materials to be sought. Carbon-fibre reinforced poly-ether-ether-ketone (CFR-PEEK) has shown reduced wear in hip and knee configurations compared with conventional polyethylene [2-4]. The aim of this study was to investigate the wear performance of a ceramic-on-CFR PEEK THR through a simulator study. Methodology. Five 36mm diameter Biolox Delta heads were paired with extruded CFR-PEEK cups and tested in a hip wear simulator (Simulator Solutions, UK) for 10 million cycles (Mc). Tests were performed in a Prosim hip simulator, which applied a twin peak loading cycle, with a peak load of 3kN. Flexion-extension of −15 to +30 degrees was applied to the head and internal-external rotation of +/− 10 degrees was applied to the cup, components were mounted anatomically. The lubricant was 25% (v/v) calf serum supplemented with 0.03% (w/v) sodium azide. Wear was assessed gravimetrically at several intervals adjusted for moisture uptake using loaded and unloaded soak controls. Results. The volumetric wear of the CFR-PEEK cups was calculated from weight loss, corrected for fluid uptake by a mean value of the loaded and unloaded soak controls. The CFR-PEEK bearings exhibited step-like wear behaviour throughout the study (Figure 1), with periods of ‘higher’ wear rate (between 0.4mm–1.4mm. 3. /Mc) and periods of a ‘lower’ wear rate (less than 0.4mm. 3. /Mc), a phenomenon that has previously been observed with this material [3]]). Discussion. The wear of a novel ram-extruded CFR-PEEK cup, articulating with a Biolox Delta ceramic head was assessed through a 10Mc experimental wear study. The mean wear rate over the period of the study was very low, with less than 1mm. 3. /Mc measured. The wear rates observed in this study are comparable with reported wear rates for 36mm diameter hard-on-hard bearings [5], and lower than wear rates measured for a highly cross-linked polyethylene bearing [6]. The wear rates reported in this study are lower than those previously reported [3], however, as CFR-PEEK operates within a boundary lubrication regime, the reduced head diameter in the present study would result in reduced sliding distance and lower surface wear

Due to increased life expectancy of human population, the amount of total knee replacements (TKR) is expected to increase. TKR reached a high grade of quality and safety, but most often it fail because of aseptic implant loosening caused by polyethylene (PE) wear debris. Wear is generated at the articulating surfaces, e.g. caused by three body particles, like bone fragments or bone cement particles. The aim of this experimental study was to compare the wear of tibial PE inserts combined with metallic and ceramic femoral components at three body wear situation induced by polymethylmethacrylate (PMMA) and zirconia (ZrO2) particles from the bone cement. Wear testing was performed for 5 Mio load cycles, using tibial standard PE inserts combined with the same CR femoral component, in two different materials, Cobalt Chromium (CoCrMo) and Biolox delta ® ceramic (Multigen Plus Knee System, Lima Corporate, Italy). A knee wear simulator, according to ISO 14243 (EndoLab GmbH, Rosenheim, Germany), was used to carry out the tests. The tests were performed in temperature-controlled test chambers at 37 °C, containing calf serum with a protein content of 30 g/l. Polymethylmethacrylate (PMMA) and zirconia (ZrO2) bone cement particles (Palacos R ®) were manufactured to a size of 30 μm. The three body particles were added at all stations onto the articulating surface of the tibial PE insert (7mg per condyle) at every 500,000 cycles. Wear was determined gravimetrically and the surfaces of tibial inserts were analysed by scanning electron microscope (SEM) after finishing the 5 million cycles. Furthermore, roughness of the PE insert surfaces and the articulating surfaces of the different femoral components were detected and the PE wear particles were analysed by SEM. The average gravimetrical wear rates of the tibial PE inserts in combination with CoCr and Biolox delta ® ceramic femoral components amounted to 6.4 ± 0.9 mg and 2.6 ± 0.4 mg per million cycles, respectively. Beside bone cement particles on the articulating surface of the PE inserts, polished surfaces and scratches were detected by SEM. In comparison to the untreated surfaces of the PE inserts at both material pairings the surface roughness at the articulating areas showed deep scratches and polished regions. Analyses of the metallic femoral components showed scratches at the articulating surfaces, none on ceramics. The present study pointed out the effect of femoral component material in an abrasive three body wear situation on the wear properties of TKR. The wear simulator tests showed that wear of PE inserts under three body wear conditions, in combination with ceramic femoral components, was significantly lower than with metallic femoral components. With regard to anti-allergic properties, ceramic femoral components are promising products for TKR

INTRODUCTION. Ceramics are excellently suited for applications in arthroplasty, mainly total hip, knee and shoulder replacement. As the most prominent representative of this demanding type of material, BIOLOX. ®. delta is widely used and very successful in the market for more than 10 years. The ability of zirconia phase transformation (t-ZrO. 2. →m-ZrO. 2. ) in zirconia-platelet toughened alumina (ZPTA) ceramics is an indispensable prerequisite for their excellent mechanical properties. The degree of stabilization of the zirconia tetragonal phase at body temperature is essential for the desired toughening mechanism. Y. 2. O. 3. is the most widely used t-ZrO. 2. chemical stabilizer; also microstructure and grain size contribute to t-ZrO. 2. phase stabilization. Stabilization must be achieved such that no material degradation will occur in body environment, i.e. in aqueous liquid (synovia), which is known to potentially trigger phase transformation at the surface of ceramic components. In this study, it is shown how phase stabilization in BIOLOX. ®. delta as a reference material is excellently balanced by means of optimal mechanical performance and environmental stability. OBJECTIVES. To assess the influence of t-ZrO. 2. chemical stabilization on ZPTA properties, in terms of fracture toughness (i.e. the ability to resist crack extension), wear resistance and environmental stability. METHODS. Three ZPTA compositions with increasing yttria content (Y. 2. O. 3. /ZrO. 2. 2–4mol%) were produced and compared to the reference. Hardness and fracture toughness were assessed by Vickers indentation method. A micro scratch tester (CSM Instruments, Peseux Switzerland) loaded with a Rockwell C diamond tip with 50µm radius was used to assess the scratch resistance of the ceramic compositions. The scratch load was linearly increased from 0 to 30N, which simulates extremely heavy local wear conditions. The morphology and depth of the scratches as well as local damage has been analysed with a laser microscope (Olympus LEXT-OLS4000) and scanning electron microscope (Hitachi S4700). The hydrothermal aging resistance was measured by autoclaving the compositions up to 150 hours at 134°C and 2.2bar and the monoclinic zirconia volume fraction measured by XRD using the Garvie formula at each time interval (i.e. 0, 10, 50, 100 and 150h). Surface roughness after hydrothermal ageing was also evaluated by atomic force microscopy. RESULTS. As expected, t-ZrO. 2. stabilization improved with increasing yttria content. Consequently, hydrothermal aging resistance increased and fracture toughness decreased strongly to almost monolithic alumina values. The scratch resistance performances also decreased showing gradually lower critical load Lc1, where grain pull-out phenomenon appeared earlier with the higher zirconia stabilization composition. The materials kept almost the same hardness (about 18GPa). Surface roughness also remained unchanged for all compostions, even in extreme hydrothermal conditions. CONCLUSIONS. Higher tetragonal zirconia stabilization leads to the suppression of zirconia phase transformation toughening and consequently of low temperature degradation; annihilating almost all the improvements of ZPTA over the monolithic alumina material. It was demonstrated that the best performance is achieved by properly triggering the tetragonal zirconia transformation. This result is explaining the successful performance of BIOLOX. ®. delta bearing couples already observed in the clinical setting

We aimed to demonstrate the clinical safety of a novel anatomic cementless ceramic hip resurfacing device. Concerns around the safety of metal on metal arthroplasty have made resurfacing less attractive, while long term function continues to make the concept appealing. Biolox Delta ceramic is now used in more than 50% of all hip arthroplasties, suggesting that it's safety profile is acceptable. We wondered if a combination of these concepts might work?. The preclinical testing of anatomic hip resurfacing device developed by our group was presented last year. A twenty patient safety study was designed. Patients had to be between the ages of 18 and 70. The initial size range was restricted to femoral heads between 46 and 54, representing the common sizes of hip resurfacing. The primary outcomes were clinical safety, PROMs and radiological control. Secondary outcomes include CTRSA and metal ion levels. 20 patients were recruited, aged 30–69. 7 were women and 13 were men. There were no operative adverse events in their operations undertaken between September 2017 and February 2018. One patient had a short episode of atrial fibrillation on the second postoperative day, and no other complications. At three months the median oxford hip score had risen from 27 (range 14–38) to 46 (31–48). Cobalt and chromium levels were almost undetectable at 3 months. Fixation appeared satisfactory in all patients, with no migration detected in either component. CTRSA is in process. The initial safety of a novel cementless ceramic resurfacing device is demonstrated by this data. The 10 year, 250 case efficacy study will continue in 5 other European centres

Introduction. Lipped liners have the potential to decrease the rate of revision for instability after total hip replacement since they increase the jumping distance in the direction of the lip. However, the elevated lip also may reduce the Range of Motion and may lead to early impingement of the femoral stem on the liner. It is unclear whether the use of a lipped liner has an impact on the level of lever-out moments or the contact stresses. Therefore, the aim of the current study was to calculate these values for lipped liners and compare these results to a conventional liner geometry. Materials and Methods. 3D Finite Element studies were conducted comparing a ceramic lipped liner prototype and a ceramic conventional liner both made from BIOLOX. ®. delta. The bearing diameter was 36 mm. To apply loading, a test taper made of titanium alloy was bonded to a femoral head, also made from BIOLOX. ®. delta. Titanium was modeled with a bilinear isotropic hardening law. For the bearing contact a coefficient of friction of both 0.09 or 0.3 was assumed to model a well and poorly lubricated system. Frictionless contact was modeled between taper and liner. Pre-load was varied between 500 N and 1500 N and applied along the taper axis. While keeping pre-load constant, lever-out force was applied perpendicular to the taper axis until subluxation occurred. Liners were fixed at the taper region. Lever-out moment, equivalent plastic strain and von Mises stress of the taper, bearing contact area and contact area between taper and liner was evaluated. Results. With increasing pre-load, larger lever-out moment, equivalent plastic strain, contact area between taper and liner and bearing contact area was found for both liner designs. However, von Mises stresses were nearly constant but slightly exceeded yield strength of titanium. For all evaluated parameters almost no differences were found between the liner designs. Lever-out moments were comparable for both designs ranging from 4.5–10.5 Nm for the lipped liner and 4.4–10.2 Nm for the conventional liner. The increase of the coefficient of friction strongly affected lever-out moments, equivalent plastic strain and contact area between taper and liner. The other parameters were not affected by varying the coefficient of friction. Discussion. This study did not find significant differences in the lever-out behavior of the lipped acetabular liner compared to the conventional liner design. The inner geometry of the lipped liner is comparable to the conventional liner inner geometry. Therefore, contact area showed no significant differences and contact mechanics are identical in the current setup leading to similar results of both liner designs. For both designs small plastic deformations in the contact point of the taper were found at the contact region between liner and taper. However, the investigated mechanical parameters did not differ between the two investigated liner types. For any figures or tables, please contact authors directly

Hip resurfacing remains a safe and effective option according to registry data. Results in women were less reliable, in part owing to soft tissue impingement. Biolox Delta ceramic bearing couples are now in widespread use with very low complication rates. We set about merging these three elements to develop a novel hip resurfacing arthroplasty. Contours of both acetabular and femoral components were generated from biometric data, adapted to the constraints of ceramic machining, to ensure that radii blended from the bearing surface avoiding any sharp boundaries. Plasma spray coating with titanium and hydroxyapatite direct onto ceramic was developed and tested using shear, tensile and taber abrasion testing. Wear testing was carried out to 5 million cycles according to the ASTM. Destructive testing was carried out in a variety of test conditions and angles. Cadaveric testing demonstrated stability using a single use disposable instruments for both conventional and patient specific procedures. Very low dose CT enabled the entire interface to be observed as the Ceramic is radiolucent, enhancing migration analysis, which will be undertaken at 4 intervals to confirm stability. Functional scores and gait analysis will be used in the safety study. The CE study recruitment is underway, with first in human trials starting in summer 2017. PMA submission will follow the safety study. Commercial release of the device in Europe is unlikely before 2019, and in the USA may not be until 2027. The path to novel device development in 2017 is very costly in time and money

INTRODUCTION. Hip resurfacing offers a more bone conserving solution than total hip replacement (THR) but currently has limited clinical indications related to some poor design concepts and metal ion related issues. Other materials are currently being investigated based on their successful clinical history in THR such as Zirconia Toughened Alumina (ZTA, Biolox Delta, CeramTec, Germany) which has shown low wear rates and good biocompatibility but has previously only been used as a bearing surface in THR. A newly developed direct cementless fixation all-ceramic (ZTA) resurfacing cup offers a new solution for resurfacing however ZTA has a Young's modulus approximately 1.6 times greater than CoCr - such may affect the acetabular bone remodelling. This modelling study investigates whether increased stress shielding may occur when compared to a CoCr resurfacing implant with successful known clinical survivorship. METHODS. A finite element model of a hemipelvis constructed from CT scans was used and virtually reamed to a diameter of 58mm. Simulations were conducted and comparisons made of the ‘intact’ acetabulum and ‘as implanted’ with monobloc cups made from CoCr (Adept®, MatOrtho Ltd, UK) and ZTA (ReCerf ™, MatOrtho Ltd. UK) orientated at 35° inclination and 20° anteversion. The cups were loaded with 3.97kN representing a walking load of 280% for an upper bound height patient with a BMI of 35. The cup-bone interface was assigned a coulomb slip-stick function with a coefficient of friction of 0.5. The percentage change in strain energy density between the intact and implanted states was used to indicate hypertrophy (increase in density) or stress shielding (decrease in density). RESULTS. Implanting both cups changed the strain distribution observed in the hemipelvis, Figure 1. The change in strain distribution was similar between materials and indicated a similar response from the bone, Figure 2. In both implanted cases, the inferior peri-acetabular bone around the implant indicated a reduction in bone strain. The bone remodelling distribution charts show that regardless of threshold remodelling stimulus level (75% in elderly, 50% in younger patients) the CoCr and ZTA cups were expected to produce the same bone response with only a small percentage of the bone in the hemipelvis indicating stress shielding or hypertrophy, Figure 3. DISCUSSION. Currently only metal cups are used for cementless fixation but improvements in design and technology have made it possible to engineer a thin-walled, direct fixation, all-ceramic cup. Both CoCr and ZTA are an order of magnitude greater than the Young's modulus of cortical bone altering the bone strain but changing the material from CoCr to a stiffer ZTA did not change the expected bone remodelling response. Given the clinical history of metal cups without loosening due to bone remodelling, the study indicates that a ZTA cup should not lead to increased stress shielding and is potentially suitable for as a cementless cup for both resurfacing and THR. SIGNIFICANCE. An all-ceramic cup is unlikely to lead to increased stress shielding around the acetabulum due to the change in material. For any figures or tables, please contact the authors directly