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

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

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

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

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

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

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

We report the medium term outcome of a 15 degrees face-changing acetabular cup in THA due to secondary OA in DDH. We analysed 28 Hips in 26 patients who underwent THA between May 2007and September 2009. There were 20 females and 6 males with a mean age of 52 yrs (range 33–68yrs). All patients received a cementless Exceed Advanced Bearing Technology 15° Face-changing cup (Biomet) with a ceramic liner through a posterior approach. A cementless or a cemented femoral stem, with 28 or 32mm Biolox Delta ceramic head, was used in all cases. All patients started full weight-bearing the next day. The average clinical and radiological follow-up was for 50 months (range 36–76 months). The mean Harris Hip Score improved to 94 and the Oxford Hip Score improved to 44. There was 100% survivorship of the hip joint for both components. Post-operative radiographs revealed integration of the cup with no signs of loosening or osteolysis. The mean covered acetabular lip inclination angle was 51 degrees (range 43–61)and the true inclination angle of the bearing was 36 degrees (range 28–46). The clinical results support the use of the cementless 15 degrees face-changing acetabular cup in the dysplastic acetabulum

To discuss the rationale, selection criteria, indications, and results of using large diameter ceramic heads in revision hip arthroplasty. We routinely use Biolox family of ceramic heads and acetabular liners in patients undergoing revision total hip replacements. We present our experience in using ceramic articular bearings over the last 20 years and the switch to larger diameter ceramic heads. We also present our rationale for using a large diameter ceramic head instead of a large metal head. We reviewed a total of 689 revision arthroplasties over this time period and we report the outcome of large bearing couples with case examples in primary and revision scenarios. Furthermore we compared a subset of patients (110) with large diameter ceramic heads – Biolox Delta 36mm to patients who had metal on metal (large head 42 mm and above) bearing couples. The performance of the ceramic bearing couples will be discussed along with the functional outcome of these patients. We found no difference in the functional, clinical sports activities (UCLA and Tegner scores) between patients who had large metal bearing couples and large ceramic couples. Complication rate was less with the ceramic bearing revision arthroplasties, as was patient satisfaction. Ceramic bearing couples have stood the test of time and have demonstrated an excellent long term wear properties. The recent introduction of the large diameter couples proves to be an excellent alternative if not the first choice in young, complex primary and revision case scenarios

Cemented Total Hip Arthroplasty gives good results for 10 or more years, but is too often complicated by a combination of mechanical loosening, wear debris and osteolysis. Patients require an implant which will last the rest of their life. Cemented hips may not survive and a better alternative is needed. Furlong hydroxyapatite ceramic coated (HAC) implants have been used for more than 19 years and to date there are 2248 primary hip arthroplasties. Fixation of the implants with HA ceramic is entirely satisfactory; histological studies from post-mortem specimens have confirmed that there is good cancellous bone fixation to the HA. The hydroxyapatite behaves like bone and is replaced by creeping substitution. This results in a Perfect Fit with no intervening fibrous tissue. Fixation is therefore maintained. Aseptic loosening is rare; eleven components. Polythene wear is a problem. Those patients with ceramic/polythene couples who have now reached about 15 years since surgery are showing wear of the liner evidenced by eccentricity of the ceramic head in the liner. Three of these have completely destroyed the liner and the titanium shell. Ceramic/ceramic bearings do not seem to wear, although there have been occasional fractures of alumina. For the last two years Biolox Delta, a stronger compound ceramic material, has been available from Ceramtec. There are no reports of any fractures. Patients who have a life expectancy of more than 10 or 15 years should be fitted with an HA coated implant with ceramic bearing surfaces. This may provide the answer for the long-lasting hip prosthesis

Background and aim. Arthroplasty registries and consecutive series indicate significantly worse results of conventional metal-on-polyethylene total hip arthroplasty (THA) in patients younger than 50 years compared to older patients, with inferior clinical outcomes and 10-year survivorship ranging between 70 and 90%. At our institution, patients under 50 needing a THA receive either a metal-on-metal hip resurfacing (MoMHRA) or a ceramic-on-ceramic (CoC)THA. In order to evaluate the outcome of these options at minimum 10 years, we conducted a retrospective review of all MoMHRA and CoCTHA with more than 10 years follow-up implanted in patients under 50. Methods. From a single surgeon patients’ prospective database, we identified all consecutive THA performed before May 2005 in patients under 50. All patients are contacted by phone and asked to present for a clinical exam and patient reported outcome questionnaires, standard radiographs and metal ion measurements unless the hip arthroplasty has been revised. Complications and reasons for revision are noted. Kaplan-Meier survivorship is analysed for the whole cohort and sub-analysis is performed by type hip arthroplasty, gender, diagnosis and component size. Results. We identified 773 hip arthroplasties in 684 patients under 50 years performed by a single surgeon between 1997 and May 2005. There are 626 MoMHRA, all Birmingham Hip Resurfacings (BHR) in 561 patients (65 bilateral BHR), 135 CoCTHA in 111 patients (24 bilateral CoC) and 12 Metasul MoMTHA in 12 patients. In the BHR group, there are 392 males (70%) (42 bilateral) and 169 females (30%) (23 bilateral). Mean age at surgery was 40.8 years (median 42 years; range 16–50 years). In 33 cases, a BHR dysplasia cup was used (23 in females). Mean follow-up is 11.5 years (median 11 years; range 10–17 years). In the Metasul MoMTHA, there are 8 males and 4 females. Mean age at surgery was 40.4 years (range 20–50 years). All THA were non-cemented and head size was 28mm in all cases. Mean follow-up is 16.8 years (median 17.5 years; range 12–19 years). In the CoCTHA group, there are 71 males (64%) (17 bilateral) and 40 females (36%) (7 bilateral). Mean age at surgery was 38.2 years (median 39 years; range 16–50 years). In 21 cases, the CoCTHA was a revision of a former hip replacement: 15 THA revisions and 6 hip resurfacing revisions. Three types non-cemented acetabular components were used and 7 types femoral stems (5 non-cemented; 2 cemented). Ceramic heads and inlays were Biolox forte in 128 cases and Biolox delta in 7. Head size was 28mm in 125, 32mm in 7 and 36mm in 3. Mean follow-up is 14.9 years (median 15 years; range 10–18 years). Discussion. Patients under 50 needing a hip arthroplasty often present with more complex anatomic abnormalities or bone damage as in congenital dysplasia, avascular necrosis, traumatic osteoarthritis or rheumatic diseases. Besides, the worse results with conventional THA in young patients may be related to a higher activity level. We present the outcome and survivorship of MoMHRA and CoCTHA in patients under 50 at more than 10 years postop

The problem associated with ceramic on ceramic total hip replacement (THR) is audible noise. Squeaking is the most frequently documented sound. The incidence of squeaking has been reported to wide range from 0.7 to 20.9%. Nevertheless there is no study to investigate on incidence of noise in computer assisted THR with ceramic on ceramic bearing. The purpose of this study was to determine the incidence and risks factors associated with noise. We retrospectively reviewed 200 patients (202 hips) whom performed computer assisted THR (Orthopilot, B. Braun, Tuttlingen, Germany) with ceramic on ceramic bearing between March 2009 and August 2012. All procedures underwent uncemented THR with posterior approach by single surgeon. All hips implanted with PLASMACUP and EXIA femoral stem (B. Braun, Tuttlingen, Germany). All cases used BIOLOX DELTA (Ceramtec, AG, Plochingen, Germany) ceramic liner and head. The incidence and type of noise were interviewed by telephone using set of questionnaire. Patient's age, weight, height, body mass index, acetabular cup size, femoral offset size determined from medical record for comparing between silent hips and noisy hips. The acetabular inclination angle, acetabular anteversion angle, femoral offset, hip offset were reviewed to compare difference between silent hips and noisy hips. The audible noise was reported for 13 hips (6.44%). 5 patients (5 hips) reported click (2.47%) and 8 patients (8 hips) squeaked (3.97%). The mean time to first occurrence of click was 13.4 months and squeak was 7.4 months after surgery. Most common frequency of click was less than weekly (60%) and squeak was 1–4 times per week (50%). Most common activity associated with noise was bending; 40% in click and 75% in squeaking. No patients complained for pain or social problem. Moreover, no patient underwent any intervention for the noise. The noise had not self-resolved in any of the patients at last follow up. Age, weight, height and BMI showed no statistically significant difference between silent hips and click hips. In addition, there was also same result between silent hips and squeaking hips. Acetabular cup insert size and femoral offset stem size the results showed that there was no statistically significant difference between silent hips and click hips, also with squeaking hips. Acetabular inclination, angle acetabular anteversion angle, femoral offset, hip offset the results shown that only acetabular anteversion angle differed significantly between silent hips (19.94±7.78 degree) and squeaking hips (13.46±5.54 degree). The results can conclude that incidence of noise after ceramic on ceramic THR with navigation was 6.44 %. Squeaking incidence was 3.97% and click incidence was 2.47%. The only associated squeaking risk factor was cup anteversion angle. In this study, squeaking hip had cup anteversion angle significant less than silent hip

INTRODUCTION. Resurfacing prostheses are implanted by impaction onto the prepared femoral head. Ceramic resurfacings can be proposed as an alternative to metal implants, combining bone conservation with mitigation of sensitivity reaction risks. With low wall-thickness required for bone conservation, their strength must be verified. This study aimed to assess a ceramic resurfacing prosthesis' strength under surgical loads using a computational model, tuned and verified with physical tests. METHODS. Tests were conducted to obtain baseline impact data (Fig1 left). Ø58mm DeltaSurf prostheses (Finsbury Development Ltd., UK), made from BIOLOX Delta (CeramTec AG, Germany) ceramic were cemented onto 40pcf polyurethane foam stubs (Sawbone AG, Sweden) attached to a load cell (Instron 8874, Instron Corp., USA). Ten repeatable 2ms. −1. slide hammer impacts were applied with a 745g mass. The reaction force at the bone stub base was recorded, and the cumulative impulse was calculated by integrating reaction force over time. A half-plane symmetry model was developed using LS-DYNA (ANSYS Inc., USA) explicit dynamic FE analysis software (Fig1, right). The bone stub was constrained, and the mallet was given an initial velocity of 2.0m/s. Outputs were the impact reaction force at the bone stub base, the impact duration and the peak tensile prosthesis stress. First, the model was solved representing the experimental setup, to fit damping parameters. Then the damped model was used to predict the peak prosthesis stresses under more clinically representative loads from a 990g mallet. The smallest (Ø40mm) and largest (Ø58mm) prosthesis heads in the size range were analysed, with two impact directions: along the prosthesis axis, and with the impactor inclined at 10°. RESULTS AND DISCUSSION. The experimental tests gave a mean peak impact force of 4.70kN (S.D.0.11kN), an impact duration of 1.1ms (S.D.0.06ms) and a total impulse of 2.88Ns (S.D. 0.017Ns). The damped basic FE model gave a peak impact force of 7.0kN, an impact duration of 0.70ms and a total impulse of 2.88Ns. The model overestimated the measured peak impact force by 49% and underestimated the impact duration by 36% (Fig. 2), but was in close agreement with the measured cumulative impulse (Fig3). The peak force and impulse results were consistent with surgical and cadaveric test measurements [1,2]. Comparison with a similar computational analysis [3] suggest that this study's stiff polyurethane foam stub represents a worse case than bone, with a similar overall impulse but a higher peak force and lower impact duration. The model therefore represents a conservative case, which is beneficial in pre-clinical analysis. With the surgical impact model, peak prosthesis stresses of 42.5MPa and 68.7MPa were predicted for the Ø40mm head with axial and inclined impaction respectively. For the Ø58mm head, the peak stresses were 20.0MPa (axial) and 27.9MPa (inclined). Stresses were highest with inclined loading, which stressed the prosthesis stem root. The maximum stress predicted was 6% of the 1150MPa material strength [4], indicating that the prosthesis strength should be sufficient to sustain surgical impaction loads

INTRODUCTION. There is great potential for the use of computational tools within the design and test cycle for joint replacement devices. The increasing need for stratified treatments that are more relevant to specific patients, and implant testing under more realistic, less idealised, conditions, will progressively increase the pre-clinical experimental testing work load. If the outcomes of experimental tests can be predicted using low cost computational tools, then these tools can be embedded early in the design cycle, e.g. benchmarking various design concepts, optimising component geometrical features and virtually predicting factors affecting the implant performance. Rapid, predictive tools could also allow population-stratified scenario testing at an early design stage, resulting in devices which are better suited to a patient-specific approach to treatment. The aim of the current study was to demonstrate the ability of a rapid computational analysis tool to predict the behaviour of a total hip replacement (THR) device, specifically the risk of edge loading due to separation under experimental conditions. METHODS. A series of models of a 36mm BIOLOX. ®. Delta THR bearing (DePuy Synthes, Leeds, UK) were generated to match an experimental simulator study which included a mediolateral spring to cause lateral head separation due to a simulated mediolateral component misalignment of 4mm. A static, rigid, frictionless model was implemented in Python (PyEL, runtime: ∼1m), and results were compared against 1) a critically damped dynamic, rigid, FE model (runtime: ∼10h), 2) a critically damped dynamic, rigid, FE model with friction (µ = 0.05) (runtime: ∼10h), and 3) kinematic experimental test data from a hip simulator (ProSim EM13) under matching settings (runtime: ∼6h). Outputs recorded were the variation of mediolateral separation and force with time. RESULTS/DISCUSSION. The low cost PyEL model successfully replicated experimental trends in maximum separation with changing swing phase load. PyEL provided a good estimate of the high separation values which resulted from lower swing phase loads, but overestimated the separation resulting from higher swing phase loads. The separation verses time curve of the dynamic rigid FE (with and without friction) closely matched that of the PyEL model. Inertia caused a small delay when moving into and out of the cup (peak delay ∼0.025s). Therefore there was no substantial advantage to the more costly dynamic finite element models as a predictive design tool for hard-on-hard bearings

Introduction and Aims. There are many surgical, implant design and patient factors that should be considered in preclinical testing of hip replacement which are not being considered in current standards. The aim of this study was to develop a preclinical testing method that consider surgical positioning, implant design and patient factors and predict the occurrence and severity of edge loading under the combination of such conditions. Then, assess the safety and reliability of the implant by predicting the wear, deformation and damage of the implant bearings under worst case conditions. Methods. Ceramic-on-ceramic (CoC, 36mm, BIOLOX. ®. delta, Pinnacle. ®. , DePuy Synthes, UK) and metal-on polyethylene (MoP, 36mm, Marathon®, Pinnacle. ®. , DePuy Synthes, UK) bearings were used for this study on multi-station multi-axis hip joint simulators. Two factors were varied, cup inclination angles (45° and 65°) and translational mismatch between the femoral head and acetabular cup (0, 2, 3 and 4 (mm)). Under each condition for both CoC and MoP bearings, three million cycles of gait cycle testing were completed with wear, deformation and/or damage measurements completed at one million cycle intervals. Other outputs of the study were the level of dynamic separation between the femoral head and acetabular cup during gait, the maximum force at the rim during edge loading when the head was sliding back to the cup confinement. Means and 95% confidence limits were determined and statistical analysis were done using one way ANOVA with significance taken at p<0.05. Results. As the level of mismatch and the cup inclination angle increased, the magnitude of dynamic separation and the force at the rim increased. The level of dynamic separation and the force on the rim correlated with the wear of CoC bearings (R= 0.96). For polyethylene, steeper inclination angle did not significantly increase the wear (p>0.05) however, edge loading under 4mm translational mismatch and steep cup inclination angle did (p<0.01). The combined wear and deformation of the polyethylene liners at the rim increased under larger levels of dynamic separation. Conclusions. The magnitude of dynamic separation and force at the rim were predictive of the severity of edge loading. These parameters can be measured using short term testing (500 cycles). This will determine the effect of variations in surgical positioning, implant design and patient factors on the occurrence and severity of edge loading. Then, the wear, deformation and/or damage on hip replacement bearings can be determined using longer term simulator testing under selected conditions. The short term tests do not only help identify worst case scenarios but may identify the boundary of surgical position under which the implants performance may be considered acceptable. A new approach for preclinical testing of hip replacement was developed:. Stage 1: Short biomechanical tests. : assess the occurrence and severity of edge loading conditions where the outputs are:. Magnitude of medial-lateral dynamic separation. Maximum force under edge loading. Stage 2: Wear assessment. : assess the tribological performance of hip replacement under selected conditions where the outputs are:. Wear rates. Deformation and/or damage on the bearing surface