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

Introduction. Currently, there is a focus on the development of novel materials to articulate against cartilage. Such materials should either eliminate or delay the necessity of total joint replacement. While cobalt-chromium (CoCr) alloy is still a material of choice and used for hemi-arthroplasties, spacers, and repair plugs, alternative materials are being studied. Pyrolytic carbon (PyC) is a biocompatible material that has been available since the 1980s. It has been widely and successfully used in small joints of the foot and the hand, but its tribological effects in direct comparison to cobalt-chromium (CoCr) remain to be investigated. Methods. A four station simulator (Figure 1), mimicking joint load and motion, was used for testing. The simulator is housed in an incubator, which and provides the necessary environmental conditions for cartilage survival. Articular cartilage disks (14mm in diameter) were obtained from the trochleas of six to eight months old steer for testing and free-swelling controls. Disks (n=8 per material) were placed in porous polyethylene scaffolds within polypropylene cups and mounted onto the simulator to articulate against 28mm balls of either PyC or CoCr. Each ball was pressed onto the cartilage disk with 40N. In order to allow fluidal load support, the contact migrated over the biphasic cartilage with a 5.2 mm excursion. Concomitantly, the ball oscillated with ±30° at 1 Hz. Testing was conducted for three hours per day over 10 days in Mini ITS medium. Media samples were collected at the end of each three hour test. Upon test commencement, media was pooled (days 1, 4, 7, 10) and analyzed for proteoglycans/sGAGs and hydroxyproline. In addition, total material release into media was estimated by determining the dry weight increase of media samples. For this purpose, 1 ml aliquots of fresh and test media were dialyzed, lyophilized and weighed on a high precision balance. Disk morphology and cell viability were histologically examined. Results. During each day of testing, cartilage control, CoCr and PyC samples released an average of 0.236, 0.253, re 0.268 mg/mL of glycol-proteins into the medium. After running-in (day 1), the increase was highly linear (R. 2. >0.99) and similar for all three testing conditions. Proteoglycan/GAG (Figure 2) and hydroxyproline release (Figure 3) were also similar for both materials (p=0.46 re. p=0.12), but significantly different from control (p<0.01). Histological and cell viability images support the hypothesis of superficial zone damage of the cartilage disks for both materials. Cell viability was not different from control (p>0.33). Discussion. The performance of PyC and CoCr was comparable using this in vitro simulation model, however appears not optimal. The observed surface fibrillation may lead to tissue breakdown in the long-term. The wear mechanism has yet to be elucidated but appears to be of adhesive nature. The lack of proteins in the medium might have suppressed boundary lubrication and thus may have played a role in the non-optimal performance of these materials. In summary, a live tissue model of articular cartilage found no difference comparing pyrolytic carbon with the current clinical gold standard CoCr

A well-fixed uncemented acetabular component is most commonly removed for chronic infection, malposition with recurrent dislocation, and osteolysis. However, other cups may have to be removed for a broken locking mechanism, a bad “track record”, and for metal-on-metal articulation problems. Modern uncemented acetabular components are hemispheres which have 3-dimensional ingrowth patterns. Coatings include titanium or cobalt-chromium alloy beads, mesh, and now the so-called “enhanced coatings”, such as tantalum trabecular metal, various highly porous titanium metals, and 3-D printed metal coatings. These usually pose a problem for safe removal without fracture of the pelvis or creation of notable bone deficiency. Preoperative planning is essential for safe and efficient removal of these well-fixed components. Strongly consider getting the operative report, component “stickers”, and contacting the implant manufacturer for information. There should a preoperative check list of the equipment and trial implants needed, including various screwdrivers, trial liners, and a chisel system. The first step in component removal is excellent 360-degree exposure of the acetabular rim, and this can be accomplished by several approaches. Then, the acetabular polyethylene liner is removed; a liner that is cemented into a porous shell can be “reamed out” using a specific device. Following this, any central or peripheral screws are removed; broken or stripped screw heads add an additional challenge. A trial acetabular liner is placed, and an acetabular curved chisel system is used. There are two manufacturers of this type of system. Both require the known outer acetabular diameter and the inner diameter of the trial liner. With the curved chisel system and patience, well-fixed components can be safely removed, and the size of the next acetabular component to be implanted is usually 4mm larger than the one removed. There are special inserts for removal of monobloc metal shells. Remember that removal of these well-fixed components is more difficult in patients compared to models, and is just the first step of a successful acetabular revision

Currently, different techniques to evaluate the biocompatibility of orthopaedic materials, including two-dimensional (2D) cell culture for metal/ceramic wear debris and floating 2D surfaces or three-dimensional (3D) agarose gels for UHMWPE wear debris, are used. Moreover, cell culture systems evaluate the biological responses of cells to a biomaterial as the combined effect of both particles and ions. We have developed a novel cell culture system suitable for testing the all three type of particles and ions, separately. The method was tested by evaluating the biological responses of human peripheral blood mononuclear cells (PBMNCs) to UHMWPE, cobalt-chromium alloy (CoCr), and Ti64 alloy wear particles. Methods. Clinically relevant sterile UHMWPE, CoCr, and Ti64 wear particles were generated in a pin-on-plate wear simulator. Whole peripheral blood was collected from healthy human donors (ethics approval BIOSCI 10–108, University of Leeds). The PBMNCs were isolated using Lymphoprep (Stemcell, UK) and seeded into the wells of 96-well and 384-well cell culture plates. The plates were then incubated for 24 h in 5% (v/v) CO. 2. at 37°C to allow the attachment of mononuclear phagocytes. Adherent phagocytes were incubated with UHMWPE and CoCr wear debris at volumetric concentrations of 0.5 to 100 µm. 3. particles per cell for 24 h in 5% (v/v) CO. 2. at 37°C. During the incubation of cells with particles, for each assay, two identical plates were set up in two configurations (one upright and one inverted). After incubation, cell viability was measured using the ATPlite assay (Perkin Elmer, UK). Intracellular oxidative stress was measured using the DCFDA-based reactive oxygen species detection assay (Abcam, UK). TNF-α cytokine was measured using sandwich ELISA. DNA damage was measured by alkaline comet assay. The results were expressed as mean ± 95% confidence limits and the data was analysed using one-way ANOVA and Tukey-Kramer post-hoc analysis. Results and Discussion. Cellular uptake of UHMWPE, CoCr and Ti64 particles was confirmed by optical microscopy. PBMNCs incubated with UHMWPE particles did not show any adverse responses except the release of significant levels of TNF-α cytokine at 100 µm. 3. particles per cell, when in contact with particles. PBMNCs incubated with CoCr wear particles showed adverse responses at high particle doses (100 µm. 3. particles per cell) for all the assays. Moreover, cytotoxicity was observed to be a combined effect of both particles and ions, whereas oxidative stress and DNA damage were mostly caused by ions. Ti64 wear particles did not show any adverse responses except cytotoxicity at high particle doses (100 µm. 3. particles per cell). Moreover, this cytotoxicity was mostly found to be a particle effect. In conclusion, the novel cell culture system is suitable for evaluating the biological impact of orthopaedic wear particles and ions, separately

Between April 2008 and February 2012, we implanted 159 large-diameter MOM stemmed THA with head diameters of 38–50mm. There were 6–38mm, 22–40mm, 42–42mm, 42–44mm, 24–46mm, 13–48mm, 4–50mm, 5–52mm, and one-54mm heads implanted in 138 patients (21 males and 117 females). The pre-operative diagnoses included: 120 OAs, 12 IONs, 4 femoral neck fractures, one RA, and one post-traumatic OA. Their ages were 40–86 years (avg. 63.6 yrs). Follow up was 4 to 67 months post implantation (avg. 40.4 months). All implants were manufactured by one company (Wright Medical Technology, Arlington, TN, USA). The stems were of a standard titanium-aluminum alloy, either 44 ANCA-FIT or 115 PROFEMUR Z non-cemented stems. Acetabular components were all CONSERVE PLUS cobalt-chromium monoblock shells. Heads were also fabricated out of cobalt-chromium alloy, with modular junctions. Patients with complaints of groin pain and/or swelling or hip instability underwent MRI examination in order to detect the presence of fluid collections or soft tissue masses. The statistical correlation between abnormal findings on MRI and age, gender, head diameter, component position and duration post-surgery was performed. 35 hips in 31 patients (22.0%) were found to have either a fluid collection or “pseudotumor” on MRI. These were in 5 males and 26 female patients. According to Hart's MRI classification, they were classified 21 hips in Type 1, twelve hips in Type 2, and two hips in Type 3 (Fig. 1, 2 and 3). 8 hips in 8 patients who had any pseudotumors were undergone revision THA (Fig. 4, 5 and 6). All hips had corrosions at head-neck taper junctions (Fig. 7). There was no difference in age between these two groups of patients (63.7 vs. 63.6 yrs.), but a significant difference in duration from the time of implantation of two groups (23.9 vs. 44.8 months). There appeared to be no significant difference between the mean head diameter of the two groups, 43.2mm and 44.0mm respectively. There was no statistical difference between the two groups with regard to implant orientation: cup inclination 18–70 degrees (41.8 vs. 43.6 degrees); cup anteversion −13–49 degrees (15.1 vs. 14.7 degrees); stem anteversion 2–48 degrees (20.1 vs. 23.3 degrees); and stem offset 17.5–56.2mm (38.2 vs. 37.8mm). Furthermore, according to Lewinnek's safe zone, there was no difference in cup orientation between the two groups (Fig. 8). When we investigated the types of modular neck, the hips having any pesudotumors tended to have long or varus necks. In this study, it is important to emphasize that the appearance of symptoms and development of a pseudotumor occurred early after a MOM THA in some patients. Also it will be important to subject all patients to MRI examination to evaluate the possibility of “silent” fluid collections and pseudotumors. In large-diameter head metal-on-metal stemmed THAs, femoral stems having long or varus neck may contribute to head-neck junction failure

Statement of Purpose:. The wear rate of Ultra High Molecular Weight Polyethylene (UHMWPE) in joint replacements has been correlated to both contact area and contact stress in the literature, [1], [2]. In both publications and our experiment, UHMWPE articulated with a polished surface of cobalt-chromium alloy was evaluated using a Pin-On-Disk (POD) apparatus (AMTI) implementing bi-directional movement. In publication [1], volumetric wear was independent of normal load and dependent upon increasing contact area. The results demonstrated that increasing contact stress decreased wear rates twofold. In publication [2], at maximum cross-shear, wear was proportional to nominal contact area and wear factors normalized to area are more appropriate than load based wear factors. In both studies, the contact surface areas of the POD pins were reduced by decreasing the diameters of the POD Pins. In our experiment, the contact area was dependent on textured POD Pin 390 (T390) which had low wear [3]. T390 reduced the normal POD contact area from 71 mm. 2. to 8.26 mm. 2. Hydroxylapatite (HA) particles were introduced to the serum to simulate third body wear debris. We hypothesized that the normal POD Pins would have greater wear rates than the textured POD Pins. A measurement of 0.14 mg HA particles per 250 mL of serum was used for each test 0.33 million cycles. Methods:. The GUR 1020 resin XLK POD Pins were gamma irradiated to 50 kGy in a vacuum package and then remelted. Three (3) T390 POD pins and nine (9) untextured XLK POD Pins were used. Three untextured XLK POD Pins were tested against three T390 POD pins. The other six (6) untextured XLK POD Pins were used as soak controls. Each pin articulated against a polished, high carbon wrought CoCr metal alloy counterface (ASTM F1537; diameter = 38.1 mm; thickness = 12.7 mm). Wear rate tests were for 1.98 million cycles. In order to perform the t-test analysis, the wear rates for each pin were given by the slope of the linear regression line through the individual data points (cycle count, cumulative wear), excluding the (0, 0) point. Results:. The probability for the means between the T390 POD pins and the untextured XLK POD Pins was *p = 0.009. T390 wear rates were statistically significant as compared to the untextured XLK POD Pin wear rates. The T390 POD Pin is illustrated in Figure 1. Figures 2 and 3 summarize the wear rates between T390 POD Pins and the untextured POD Pins with and without HA particles. Conclusions:. The wear rates between T390 and untextured POD pins did not take into account that the POD pins were not cleaned using a solution to remove potentially embedded HA particles. The follow-on experiment will use a special cleaning method to remove all HA particles after each test cycle

[Introduction]. In 1995, Muller reported on the improvement of metal-on-metal (MOM) bearing over the existing metal-on-polyethylene (MOP) articulations which demonstrated more rapid wear together with granulomatous foreign body reactions, damage of periarticular bony and soft tissues and associated expansile psoas bursal masses. He suggested that adequate lubrication together with improved material properties and manufacturing technologies would bring to the market a superior device with greater longevity. We wish to present our experience with a modern version of a MOM bearing. [Material and Methods]. Between April 2008 and February 2012, we implanted 160 MOM THA with head diameters of 38–50 mm in 139 patients (21 males and 118 females). Their ages were 40–86 years (avg. 63.6 yrs). Follow up was 9 to 53 months post implantation (avg. 28 months). All implants were manufactured by one company (Wright Medical Technology, Arlington, TN, USA). The stems were of a standard titanium-aluminum alloy, either 45 ANCA-FIT or 115 PROFEMUR Z non-cemented stems. Acetabular components were all CONSERVE PLUS cobalt-chromium monoblock shells. Heads were also fabricated out of cobalt-chromium alloy, with modular junctions. Patients with complaints of groin pain and/or swelling or hip instability underwent MRI examination in order to detect the presence of fluid collections or soft tissue masses (Fig. 1 and 2). The statistical correlation between abnormal findings on MRI and age, gender, head diameter, component position and duration post-surgery was performed. [Results]. 27 hips in 23 patients (16.9%) were found to have either a fluid collection or “pseudotumor”. These were in 2 males and 21 female patients. There were 19 males and 97 females without complaints who did not undergo MRI examination. There was no difference in age between these two groups of patients (63.1 vs. 63.7 yrs). There was no difference in duration from the time of implantation, but there was an early presentation of symptomatic pseudotumor. There appeared to be a significant difference between the mean head diameter of the two groups, 41.8 mm and 44.2 mm respectively. There was no statistical difference between the two groups with regard to implant orientation: cup inclination 18–70 degrees (40.4 vs. 43.8 degrees); cup anteversion −13−49 degrees (14.0 vs. 15.0 degrees); stem anteversion 2–48 degrees (20.2 vs. 23.1 degrees); and stem offset 17.5–56.2 mm (38.2 vs. 37.8 mm). [Discussion]. In this study, it is important to emphasize that the appearance of symptoms and development of a pseudotumor occurred early after a MOM THA in some patients. It may represent a hypersensitivity to materials implanted. However, the possibility that this may represent a foreign body reaction to particulate debris produced by articulating surfaces much like that seen with alternative material such as MOP, reflective of wear, insufficient lubrication or other causes. In this regard, our study suffers from the limitation that serum levels of chromium and cobalt were not obtained from symptomatic patients. Nor were these patients skin tested for hypersensitivity to these materials. Also it will be important to subject all patients to MRI examination to evaluate the possibility of “silent” fluid collections and pseudotumors

Introduction. Are there really ‘conventional’ bearings, offering more security and less risk than the ‘alternative’ bearings that feature in the programme?. Alternative, when used as an adjective has 2 meanings:. offering or expressing a choice, as in several alternative plans. different from or functioning outside the usual or conventional:. eg alternative newspaper, alternative rock music, alternative medicine. This paper reviews the elements that make up the bearing couples available today in the developed world, and tests each bearing against these meanings. Materials. what are the alternatives?. The materials available today fall into the following broad families:. Metals. Stainless Steel and Cobalt-Chromium Alloy, are the dominant metals available. There is no variation in the Steel, but the characterisation of the Co-Cr does vary. Several manufacturers use different carbide content for the femoral and acetabular components, and different processes. One has been withdrawn from the market, and others may be at risk of this, although it is not the material itself that seems to be the main issue. Ceramics include alumina and zirconia ceramics. Alumina has been available unchanged for over 40 years, although delta ceramic (a zirconia toughened alumina) has only been available unchanged since 2001, making in available for 10 years. Polymers. a huge range of polyethylenes are now available, with different individual claims. All claim superior wear resistance, and oxidation resistance. More than 20 unique products are available in the EU, each with a proprietary formula giving individual characteristics. Coatings and surface treatments. these are now available today from many companies, who either ceramicise the surface of cobalt chrome or titanium with titanium nitride, or use oxinium (a proprietary product from a single company). Bearing couples. what are the alternatives Symmetric and Asymmetric bearings are currently offered. Symmetric bearings are available for Ceramic on Ceramic and Metal on Metal bearings only. Asymmetric bearings are available with metals, including metal on poly, and metal on peek. Ceramics can couple with metal or polymers. Bearing Sizes. Larger than 32mm should be considered ‘alternative’. The larger metal bearings have seen the start of crevice corrosion at the taper between titanium and Co-Cr, and even between different Co-Cr alloys. This new class of complication seems to be unique to metal femoral heads. Bearing-stem compatibility. Larger metal on metal head bearings have brought an entirely new world of complications. The choices of trunion are mainly twofold: the 12/14 tapers which differ significantly between products, and the V40 taper still used by one manufacturer. Neither was designed for use with a larger diameter head. Conclusions. The use of the word ‘alternative’ implies a ‘standard’ or conventional bearing. Ceramic bearings have changed least, have been immune from the metallosis and crevice corrosion seen with large ball Metal head whether bearing on metal or polyethylene. They also have reassuring long term results. In 2011 they should be considered the standard bearing for the young and active patient. The large diameter metal on highly cross-linked poly bearings should now be considered ‘alternative’

Introduction. Conventional implant designs in total knee arthroplasty (TKA) are based on metal on UHMWPE bearing couples. Although this procedure is quite successful, early loosening is still a matter of concern. One of the causes for early failure is stress shielding, leading to loss of bone stock, periprosthetic bone fractures and eventually aseptic loosening of the component. The introduction of a polyetheretherketone (PEEK) on UHMWPE bearing couple could address this problem. With mechanical properties more similar to distal (cortical) bone it could allow stresses to be distributed more naturally in the distal femur. A potential adverse effect, however, is that the femoral component and the underlying cement mantle may be at risk of fracturing. Therefore, we analyzed the effect of a PEEK-Optima® femoral component on stress shielding and the integrity of the component and cement mantle, compared to a conventional Cobalt-Chromium (CoCr) alloy implant. Methods. We created a Finite Element (FE) model of a reconstructed knee in gait, based on the ISO-14243-1 standard. The model consisted of an existing cemented cruciate retaining TKA design implanted on a distal femur, and a tibial load applicator, which together with the bone cement layer and the tibial implant is referred to as the tibial construct. The knee flexion angle was controlled by the femoral construct, consisting of the femoral implant, the bone cement and the distal femur. The tibial construct was loaded with an axial force, anterior-posterior (AP) force and a rotational torque, representing the ground reaction force, soft tissue constraints and internal/external rotation of the tibia, respectively. The integrity of the femoral component and cement mantle were expressed as a percentage of their yield stress. Stress shielding in the periprosthetic femur was evaluated by the strain energy (density) in the bone and compared to a model replicating an intact knee joint. Results. Considering implant durability, the CoCr and PEEK-Optima® femoral components performed equally well, with peak stresses reaching only 12–18 percent of their respective yield stresses (Figure 1(A)). The bone cement experienced higher loads in the reconstruction with the PEEK-Optima® implant, but the principal stresses were within a safe range, with a maximum of 20 percent of the ultimate compressive load (Figure 1(B)). As anticipated, the more compliant polymer implant resulted in a strain energy magnitude and distribution similar to that of an intact knee (Figure 2,3), which could prevent the loss of bone stock on the longer term. Discussion. Our simulations indicate that the femoral implant and cement mantle are not at risk of failure during gait. Moreover, the hypothesis that stress shielding can be reduced by a polymer implant is corroborated by this model. ISO loads can be considered an underestimation and so we intend to expand the model with more comprehensive loading regimes, based on musculoskeletal simulations of gait as well as more arduous physical activities. We plan to include activities like squatting or stair ascending as they are likely to be more detrimental to the implant performance

Introduction:. The addition of neck-stem modularity of femoral components allowed for increased versatility in controlling stability, head center, and limb length in total hip arthroplasty (THA). Recent reports of neck-stem corrosion, complicated by adverse local tissue reaction, have raised concern and prompted further patient evaluation for revision arthroplasty. Methods:. This was a single center, retrospective case series of thirteen hips in twelve patients. The cohort included eight women and four men, with an average age of 69.5 years (range 50–82), who underwent primary THA with a dual-taper femoral component with a titanium alloy stem, cobalt-chromium (CoCr) alloy modular neck and CoCr alloy head. Patients were followed an average of 34.3 months postsurgical (range 24–38.5 months). Each patient underwent serologic studies including metal ion levels, and Metal Artifact Reduction Sequence (MARS) magnetic resonance imaging (MRI) or Ultrasound. All patients were then referred for fluoro-assisted hip aspiration. Four patients underwent revision surgery. Results:. Ten of thirteen hips were symptomatic at the time of evaluation. ESR and CRP were normal in all patients. Serum Cobalt was elevated in 10/12 patients, with an average serum Cobalt level 4.16 mcg/L (range 1.7–9.4). Serum Chromium levels were normal in all patients. MRI was completed in eleven of twelve patients, with abnormal findings consistent with adverse local tissue reaction in nine hips. Three hips were normal by MRI. One patient had an abnormal ultrasound. Hip aspirations were positive in nine hips, negative in three, and indeterminate in one. Asymptomatic hips (3/13) all had elevated cobalt levels, and 2/3 had positive MRI and aspirates. One patient had a normal MRI and a negative aspirate. Of ten symptomatic hips, eight had elevated cobalt. 7/10 had an abnormal MRI, 2/10 a normal MRI, and 1 abnormal Ultrasound. 5/10 had aspirates that were consistent with the MRI. One aspirate was indeterminate. Four symptomatic patients had discrepancies between MRI findings and aspiration (negative MRI with positive aspirate, or vice versa); one patient had normal labs and MRI, but a positive aspirate, and was noted to have extensive adverse local tissue reaction at revision. Discussion:. Patients with dual-taper femoral stems are at risk of neck-stem corrosion and adverse local tissue reactions. The workup of these patients should include serologic studies as well as advanced imaging with MRI or Ultrasound. Hip aspiration may be a useful adjunct in identifying underlying soft tissue destruction in patients with normal or indeterminate labs or advanced imaging