The effect of an advanced porous surface morphology on the mechanical performance of an uncemented femoral knee prosthesis was investigated. Eighteen implants were inserted and then pushed-off from nine paired femurs (Left legs: advanced surface coating; right legs: Porocoat® surface coating as baseline). Bone mineral density (BMD) and anteroposterior dimension were measured, which both were not significantly different between groups. The insertion force was not significantly different, but push-off force was significantly higher in the advanced surface coating group (P = 0.007). BMD had direct relationship with the insertion force and push-off force (p < 0.001). The effect of surface morphology on implant alignment was very small. We suggest that the surface properties create a higher frictional resistance thereby providing a better inherent stability of implants featuring the advanced surface coating

Introduction

Recently, the combination of press-fit acetabular cup with ceramic articulation is a widely used for implanting cementless acetabular components and has been shown to provide good initial stability. However, these methods may lead to elevating stresses, changing in the bearing geometries, and increasing wear due to deformation of the cup and insert. In addition, there is a potential for failure of ceramic inserts when a large ball head was used because it should be assembled with shallow thickness of the acetabular cup. For risk reduction of it, we applied direct metal tooling (DMT) based on 3D printing for porous coating on the cup. Due to its capability of mechanical strength, DMT coated cup could be feasible to provide better stability than conventional coating. Therefore, we constructed laboratory models for deformation test simulating an press-fit situation with large ceramic ball head to evaluate stability of the DMT coated cup compared with conventional coated cup.

Title. Longitudinal Intravital Imaging to Quantify the “Race for the Surface” Between Host Immune Cell and Bacteria for Orthopaedic Implants with S. aureus Colonization in a Murine Model. Aim. To assess S. aureus vs. host cell colonization of contaminated implants vis intravital multiphoton laser scanning microscopy (IV-MLSM) in a murine model. Method. All animal experiments were approved by IACUC. A flat stainless steel or titanium L-shaped pin was contaminated with 10. 5. CFU of a red fluorescent protein (RFP) expressing strain of USA300LAC, and surgically implanted through the femur of global GFP-transgenic mice. IV-MLSM was performed at 2, 4, and 6 hours post-op. Parallel cross-sectional CFU studies were performed to quantify the bacteria load on the implant at 2,4,6,12,18 and 24 hours. Results. 1) We developed a high-fidelity reproducible IV-MLSM system to quantify S. aureus and host cell colonization of a bone implant in the mouse femur. Proper placement of all implants were confirmed with in vivo X-rays, and ex vivo photos. We empirically derive the ROI during each imaging session by aggregating the imaged volume which ranges from (636.4um × 636.4um × 151um) = 0.625 +/- 0.014 mm. 3. of bone marrow in a global GFP-transgenic mouse. 2) IV-MLSM imaging acquisition of the “race for the surface”.In vitro MPLSM images of implants partially coated with USA300LAC (RFP-MRSA) were verified by SEM image. Results from IV-MLSM of RFP-MRSA and GFP. +. host cell colonization of the contaminated implants illustrated the mutually exclusive surface coating at 3hrs, which to our knowledge is the first demonstration of “the race for the surface” between bacteria and host cells via intravital microscopy. 3) Quantifying the “race for the surface” with CFU verification of S. aureus on the implant. 3D volumetric rendering of the GFP. +. voxels and RFP+ voxels within the ROI were generated in Imaris. The voxel numbers suggeste that the fight for the surface concludes ∼3hrs post-infection, and then transitions to an aggressive MRSA proliferation phase. The results of WT control demonstrate a significant increase in CFU by 12hrs post-op for both stainless steel (P<0.01) and titanium (P<0.01). Conclusions. We developed IV-MLSM to quantify the “Race for the Surface” between host cells and contaminating S. aureus in a murine femur implant model. This race is remarkably fast, as the implant surface is completely covered with 3hrs, peak bacterial growth on the implant occurs between 2 and 12 hours and is complete by 12hrs

INTRODUCTION. Reaming of the acetabular cavity prior to cementless cup implantation aims to create a defined press-fit between implant and bone. The goal is to achieve full implant seating with the desired press-fit to reduce the risk of early cup loosening and the risk of excessive cup deformation. Current research concentrated on the spherical deviations of the reamed cavity compared to the reamer size, but the direct relationship between nominal press-fit, reamer geometry, cavity shape and bone-implant contact has not yet been investigated. The aim of this study was to determine the influence of the reaming process, the surface coating, and the implantation force on the achieved press-fit situation. METHODS. Fresh-frozen porcine acetabulae (n = 20) were prepared and embedded. Hemispherical reamers were used and the last reaming step was performed using a vertical drilling machine to ensure a proper alignment of the cavity axis. A hand-guided 3D laser scanner was used (HandySCAN 700, Creaform) to determine the reamer geometry and the cavity shape. Press-fit cups with two different surface coatings (Ø44 mm, Porocoat/Gription, DePuy Synthes) were implanted using a drop tower. The Porocoat cup was implanted with impacts from lower drop heights (low implantation force) and press-fits of 1 mm and 2 mm. The Gription cup, exhibiting a rougher surface, was implanted with low and high implantation forces and a press-fit of 1 mm. Bone-implant contact was analysed by the registration of the cup and cavity surface models, scanned prior to implantation, to the scan of the implanted cup. The cup surface was divided in areas with and without contact to the surrounding cavity. Overhang indicates that there was no adjacent cavity surface surrounding the implanted cup. The transition between contact and a gap at the cup dome was defined as contact depth and used as indicator for the cup seating. RESULTS. The peripheral cavity diameter was on average 0.94 ± 0.29 mm smaller than the reamer diameter due to the sub-hemispherical distribution of the cutting blades. This led to an increased effective press-fit in the peripheral area of the cavity. The contact area between cup and bone increased with the implantation force (p = 0.008) and ranged from 13.1 % to 27.8 %. The contact depth was larger for the smoother Porocoat coating (p = 0.008), a press-fit of 2 mm (p = 0.008) and a higher implantation force (p = 0.008). DISCUSSION. This study shows that, assuming similar implantation forces, an increased surface roughness of the cup coating increases the risk of an insufficient cup seating. For a given press-fit, higher implantation forces would be necessary to fully seat the cup in order to enhance the bone-implant contact. Implantation of a cup without a defined nominal press-fit could increase the contact area; however a high reaming accuracy and an increased friction coefficient of the cup coating are required to compensate for a reduction in initial fixation strength caused by reduced radial compressive forces. For any figures or tables, please contact authors directly

Surface coatings have been introduced to total joint orthopaedics over the past decades to enhance osseointegration between metal implants and bone. However, complications such as aseptic loosening and infection persist. Inadequate osseointegration remains a complication associated with implants that rely on osseointegration for proper function. This is particularly challenging with implants having relatively flat and small surface areas that have high shear loading, such as noncemented uni and total condylar knee tibial trays. Faster osseointegration can enhance recovery as a result of improved load distribution and a more stable bone-implant interface. Traditionally noncemented porous bone ingrowth coatings on knee, hip and shoulder implants are typically texturised by thermal plasma spray coating, sintered metal bead coatings, or 3-D additive manufactured structures that provide porous surface features having the rough texture with pore sizes on the order of 150 to 300 micrometers. These surfaces are often further chemically enhanced with hydroxyapatite (HA) deposition. This provides macro-mechanical (millimeter scale) and micro-mechanical (micrometer scale) bone remodeling into the implant surface. However, at the nanoscale and cellular level, these surfaces appear relatively smooth. More recent studies are showing the importance of controlling the macro, micro, and the nano (nanometer scale) surface topographies to enhance cell interaction. In vitro and in vivo research shows surfaces with nanoscale features in the metal substrate result in enhanced osseointegration, greater bone-implant contact area and pullout force, and potentially bactericidal. One surface modification treatment technique of particular promise is nano-texturing via electrochemical anodization to bio-mimicking TiO2 nanotube arrays that are superimposed onto existing porous surface microstructures to further enhance the already known bone ingrowth properties of these porous structures by superimposing onto the existing microstructure arrays of nanotubes approximately 100 nanometers in outside diameter and 300–500 nanometers in height. In an ovine model, 3-D printed Direct Metal Laser Deposition (DMLS) additive manufactured porous Ti-6Al-4V implant with and without TiO2 nanotube array nano-texturing were compared to similar sized implants with commercially available sintered beads with HA coating and additive manufactured cobalt chrome implants. The average bond strength was significantly higher (42%) when the implants were nano-texturised and similarly stronger (53%) compared to HA coated sintered bead implants. Histology confirms over 420% more direct bonded growth of new bone from 0.5mm to 1.0mm deep into the porosity on the implants when the same implants are nano-texturised. Nano-texturing also changes the surface of the implant to repel methicillin-resistant staphylococcus aureus (MRSA) in an in vivo rabbit model limiting biofilm formation on the porous surface compared with non-treated porous surfaces. Since nano-texturizing only modifies the nano-morphology of the surface and does not add antibiotics or other materials to the implant, these animal studies shows great promise that nano-texturizing the TiO2 coating may not only enhance osseointegration, but also repels bacteria from porous implant surfaces. As such, we believe nano-texturing of porous implants will be the next advancement in surface coating technology

Introduction. Cementless total knee arthroplasty (TKA) implants use an interference fit to achieve fixation, which depends on the difference between the inner dimensions of the implant and outer dimensions of the bone. However, the most optimal interference fit is still unclear. A higher interference fit could lead to a superior fixation, but it could also cause bone abrasion and permanent deformation during implantation. Therefore, this study aims to investigate the effect of increasing the interference fit from 350 µm to 700 µm on the primary stability of cementless tibial implants by measuring micromotions and gaps at the bone-implant interface when subjected to two loading conditions. Methods. Two cementless e.motion® tibial components (Total Knee System, B. Braun) with different interference fit and surface coating were implanted in six pairs of relatively young human cadaver tibias (47–60 years). The Orthoload peak loads of gait (1960N) and squat (1935N) were applied to the specimens with a custom made load applicator (Figure 1A). The micromotions (shear displacement) and opening/closing gaps (normal displacement) were measured with Digital Image Correlation (DIC) in 6 different regions of interest (ROIs - Figure 1B). Two General Linear Mixed Models (GLMMs) were created with micromotions and interfacial gaps as dependent variables, bone quality, loading conditions, ROIs, and interference fit implants as independent variables, and the cadaver specimens as subject variables. Results. No significant difference was found for the micromotions between the two interference fit implants (gait p=0.755, squat p=0.232), nor for interfacial gaps (gait p=0.474, squat p=0.269). In contrast, significant differences were found for the ROIs in the two dependent variables (p < 0.001). The micromotions in the anterior ROIs (AM and AL) showed fewer micromotions for the low interference fit implant (Figure 2). More closing gaps (negative values) were seen for all ROIs (Figure 3), except in AM ROI during squat, which showed opening gaps (positive values). The posterior ROIs (PM and PL) showed more closing than seen in the anterior ROIs (AM and AL) for both loading configurations. Discussion. The results presented here demonstrate that increasing the interference fit from 350 µm to 700 µm does not affect the micromotions at the implant-bone interface of tibial TKA. While micromotions values were all below the threshold for bone ingrowth (40 µm), closing gaps were quite substantial (∼−150 µm). Since cementless e.motion® TKA components with an interference fit of 350 µm had shown a survival rate of 96.2% after 8.3 years postoperatively, interfacial gaps can be expected to be within a threshold value that can guarantee good primary stability. Moreover, increasing the interference fit to 700 µm can be considered a good range for an interference fit. For any figures or tables, please contact the authors directly

Introduction. Pin-tract infections are a common problem in orthopaedic surgery, which limits the time an external fixator or Taylor spatial frame can be applied to a patient. The purpose of our study is to evaluate the ability of a novel implant surface coating — cationic steroid antibiotic (CSA)-44 — to delay or prevent the onset of these infections. This coating mimics endogenous antimicrobial peptides of the innate immune system and has been shown to effectively eradicate biofilms as well as prevent infection and stimulate healing of open, contaminated fractures. Methods. Surgeries were performed on 20 animals (outbred; Sprague-Dawley strain rats). Each animal received both CSA-coated and standard-of-care titanium pins, with pins randomized to the fifth or sixth vertebrae prior to surgeries. Animals were also randomized to either “Imaging” (imaging analysis) or “Infection” (microbiological analysis) cohorts. Surgeons were blinded to pin types and analyses cohorts. Digital images of pin sites were collected weekly over 12 weeks, and then graded by two orthopaedic surgery residents according to an established Likert scale. Graders were blinded to animal numbers, pin types, and timepoints (Figure 1). For the infection analysis cohort, four specimens per site were subjected to microbiological analysis from each site (i.e. pin, superficial skin swab, deep skin swab, sonicated bone). Each specimen was processed on three different microbiological plates (i.e. BAP, CAN, MAC) using standardized techniques. Imaging analysis was performed by dissecting vertebrae en bloc with pin retained, followed by fixation in 10% neutral buffered formalin for 72 hours. Following a graded ethanol series and storage in 70% ethanol, specimens were scanned with microcomputed tomography (µCT). Statistical analyses were performed to compare pin site appearance (chi-square testing) as well as total bacterial colony counts within each plate cohort and imaging data (Kruskal-Wallis testing); for all tests, significance was set at α=0.05. Results. Weekly digital images of each pin site were collected, graded, and then averaged (Figure 2). Statistical analysis showed no significant difference in pin appearance between the control and CSA pin cohorts at any timepoints. For the infection analysis cohort, bacterial colonies were counted on BAP, CAN, and MAC plates, followed by bacteria species identification (Figure3). Statistical analysis showed no significant difference in total bacterial colony counts between the control and CSA pin cohorts in any of the plate groups. For the imaging cohort, post-processing and subsequent data and statistical analyses are ongoing. Discussion. No significant differences were found between the control and CSA pin cohorts, with respect to pin appearance during the 12-week study or total bacterial colony counts on three plates, indicating that the control and CSA pins performed equivalently. Imaging analysis is ongoing. Although the environmentally-acquired infection model in an outbred rat strain was used to replicate the onset of pin tract infections in human populations, many animals showed Grade 1 or 2 pin site appearances at the 12-week endpoint. A follow-on study is underway using a direct bacterial seeding model. For any figures or tables, please contact the authors directly

Patellar fractures account for approximately 1% of all fractures. Open reduction and internal fixation is recommended to restore extensor continuity and articular congruity. However, complications such as nonunion and symptomatic hardware, still exist. Furthermore, there is a risk of re-fracturing of the healed bone during the removal of the implants. Magnesium (Mg), a biodegradable metal, has elastic moduli and compressive yield strength that are comparable to those of natural bone. Our previous study showed that released Mg ions enhanced fracture healing. However, Mg-based implants degrade rapidly after implantation and lead to insufficient mechanical strength to support the fracture. Microarc oxidation (MAO) is a metal surface coating that reduces corrosion. We hypothesized that Mg pins, with or without MAO, would enhance fracture healing radiologically, mechanically, and histologically, while MAO would decrease degradation of Mg pins. Patellar fracture was performed on forty-eight 18-week-old female New Zealand White rabbits according to established protocol. Briefly, the patella is osteotomized transversely and a tunnel (1.1mm) was drilled longitudinally through the two bone fragments. A pin (1 mm, stainless steel, Mg, or MAO-Mg) was inserted into the tunnel. The reduced construct was stabilized with a figure-of-eight band wire (⊘ 0.6 mm stainless steel wire). Cast immobilization was applied for 6 weeks. The rabbits were euthanized at week 8 and 12 post-operation. Microarchitecture and mechanical properties of the repaired patella were analyzed with microCT and tensile testing respectively. Histological sections of the repaired patella were stained. To evaluate the effect of the MAO treatment on degradation rate of Mg pin, the volume of the Mg pins in the patella was measured with microCT. At week 8, both Mg and Mg-MAO showed higher ratio of bone volume to tissue volume (BV/TV) than the control while there was no significant different between Mg and Mg-MAO. At week 12, Control, Mg, and Mg-MAO groups showed enlarged patella when compared to the normal patella. Tissue volume (TV) and bone volume (BV) of the patella in Mg and Mg-MAO were larger than those in the Control group. However, the Control had higher ratio of bone volume to tissue volume (BV/TV), TV density, and BV density than Mg and Mg-MAO. Tensile testing showed that the mechanical properties of the repaired patella (failure load, stiffness, ultimate strength, and energy-to-failure) of Mg and Mg-MAO were higher than that of the control at both week 8 and week 12. Histological analysis showed that there was significant new bone formation in the Mg and Mg-MAO group compared with the Control group at week 8 and 12. The degradation rate of the MAO-coated Mg pins was significantly slower than those without MAO at week 8 but no significant difference was detected at week 12. Mechanical, microarchitectural, and histological assessments showed that Mg pins, with or without MAO, enhanced fracture healing of the repaired patella compared to the Control. MAO treatment enhanced the corrosion resistance of the Mg pins at the early time point

Removing well-fixed components can be difficult. It can be required in instances of infection, malalignment, instability and polyethylene wear. Success requires patience, skill and the use of correct instruments. Using too much force or haste will result is excessive bone loss and a more difficult reconstruction. One's goal should be to save bone and save time. The surgeon must be familiar with the implants to know if any special techniques will be required to deal with modularity of the tibial polyethylene, surface coatings and geometry of pegs and stems. The usual steps are to remove the tibial liner if modular, followed by removal of the femoral component, then tibial component. Thin osteotomes are used to loosen the cement prosthesis or bone prosthesis interfaces to be able to remove the implants and not lose bone in the process. Removal of cement mantles around long-stemmed femoral and tibial components can be facilitated by femoral cortical window osteotomies and tibial crest osteotomies

INTRODUCTION. The restoration of the anatomical hip rotation center (HRC) has a major influence on the longevity of hip prostheses. Deviations from the HRC of the anatomical joint after total hip arthroplasty (THA) can lead to increased hip joint forces, early wear or loosening of the implant. The contact conditions of acetabular press-fit cups after implantation, including the degree of press-fit, the existence of a polar gap and cup orientation, may affect the HRC restoration, and therefore implant stability. The aim of this study was to determine the influence of acetabular press-fit, polar gap and cup orientation on HRC restoration during THA. METHODS. THAs were performed by an experienced orthopaedic surgeon in full cadaveric models simulating real patient surgery (n=7). Acetabular cups with a Porocoat™ (n=3) and Gription™ surface coating (n=4) were implanted (DePuy Synthes, Leeds, UK). Computed tomography (CT) scans prior to surgery, as well as after reaming and implantation of press-fit cups were used to calculate the HRC displacement. After aligning the pelves in the anterior pelvic plane, 3D reconstruction of the HRC at each stage was performed by fitting spheres to the femoral head, the reamed cavity and the inserted cup. 3D surface models of the cups were generated using a laser scanner and were registered to the CT images. The effective press-fit was calculated using the diameters of spheres, fitted to the cavity prior to cup insertion and to the outer cup coating. The polar gap was defined as the difference between the outer cup surface and the subchondral bone at the cup pole. Anteversion and abduction angles were calculated as difference between the cup planes and the sagittal and transverse plane, respectively. RESULTS. A medial (6.4±1.6mm), superior (5.1±1.5mm) and posterior (3.0±1.4mm) displacement of the HRC after reaming was measured. A significant inferior shift of the HRC could be measured after cup implantation (p=0.043). No significant influence of the coating design on the HRC shift could be observed. The shift of the HRC back towards the anatomical HRC was highly correlated to the degree of polar gap (R. 2. =0.928, p<0.001) and a trend towards an association with effective press-fit was observed (R. 2. =0.536, p=0.061). The cup angles had no influence on the shift of the HRC, but a high variability in cup anteversion (20.7° to 61.8°) was observed. DISCUSSION. The study suggests that increasing the press-fit and polar gap improves the restoration of the anatomical HRC. Since increasing the degree of press-fit could also lead to higher stresses and an increased fracture risk, future work will study how the acetabular contact conditions influence both primary implant stability and fracture risk, in order to establish an optimal HRC reconstruction to maximize implant longevity

Introduction. The accumulation of proteins and bacteria on implant surfaces is a critical concern in the biomedical field, especially with respect to the potential of biofilm formation on implant surfaces. Material surface wettability is often used as a predictor of potential colonization of specific bacterial strains. Surface roughness has also been shown to have a strong relationship with biofilm formation, as rougher surfaces tend to have a stronger affinity to harbor bacterial colonies. The modification of implant surfaces to impart a biofilm resistant layer can come at the expense of increasing surface roughness however, and it is therefore important to determine how the variables of wettability and roughness are affected by any new surface coating technologies. In the current work, a novel CoBlast (C) process that impregnates alumina (A) at 50 μm grit (5) or 90 μm grit (9) sizes, with the possible addition of polytetrafluoroethylene (P) onto titanium surfaces, combined with a plasma coating process called BioDep, that coats the surface with chitosan (X) with the possible addition of vancomycin (V), were evaluated for wettability and surface roughness to determine their potential as biofilm resistant treatments on implants. Materials and Methods. N=65 titanium alloy samples (n=5 for 13 sample modification types as described above and in the figure legends below) were analyzed for surface roughness and wettability. Following cleaning in ethanol, roughness testing (Ra, Rq, Rt and Rz, Wyko NT-2000 optical profilometer @ 28.7× magnification, FOV of 164×215 μm) at 5 different surface locations per specimen, and contact angle analysis was performed (2 μL water drops, KRUSS EasyDrop). Statistical differences between groups was determined using ANOVA. Results and Discussion. Figure 1a summarizes the roughness results, with significant roughening being observed with between surface blanks and all surface modification techniques, especially the CoBlasted 90 μm grit treatments. As expected, wettability (shown in Figure 1b) was significantly affected by PTFE modifications and also by the introduction chitosan and vancomycin. Conclusions. As can be seen from these results, changing the coating of a material can change the surface topography and the wettability of the surface, which can be beneficial for different applications. The results from this work show that the CoBlast and BioDep processes significantly affect both wettability and roughness, and that the benefits and potential drawbacks of each must be considered when assessing their potential for biofilm resistance. PTFE-coated samples would be best used when wanting to prevent a hydrophobic substance from binding to the material, while the alumina-coated or blank samples would be best used to prevent a hydrophilic substance from binding. In the future, nonpolar liquid wettability will be assessed to better mimic in-vivo conditions and to determine surface energy to be able to make better conclusions about the relationship between surface roughness and wettability. For any figures or tables, please contact the authors directly

Introduction. Biological fixation through bone ingrowth and ongrowth to implants can be achieved with a variety of surface treatments and technologies. This study evaluated the effect of two different three dimensional surface coatings for CoCr where porosity was controlled through the use of different geometry of CoCr beads in the sintering process. Methods. Test specimens in Group A were coated with conventional spherical porous-bead technology. The porous coating technology used on Group B was a variation of the conventional porous-bead technology. Instead of spherical beads, cobalt-chromium particles in irregular shapes were sieved for a particular size range, and were sintered onto the specimen substrate using similar process as Group A. The geometry and the size variation of the particles resulted in a unique 3D porous structure with widely interconnected pores. Three implants were placed bicortically in the tibia. Two implants were placed in the cancellous bone of the medial distal femur and proximal tibia bilaterally with 4 implantation conditions (2 mm gap, 1 mm gap line-to-line, and press fit). Animals were euthanized at 4 or 12 weeks for standard mechanical, histological and histomorphometric endpoints. Results. Shear strength increased with time for both groups (P<0.001). While no difference was detected between groups at the 4 week time point, the difference was statistically significant at 12 weeks with the irregular shaped beads using in the coating in group B providing a shear strength that outperformed the standard spherical beads. Histomorphometry revealed new bone ingrowth into the porous domains of both implant groups improved with time (P<0.001). Significantly greater (P<0.05) new bone integration was observed with the irregular shaped beads in the cortical as well as cancellous sites at 4 and 12 weeks (Figure 1). Discussion. Significant improvements can be made in the fixation strength of three dimensional CoCr coatings. This holds true in cortical implantation as well as different cancellous implantation scenarios. Material chemical composition of both coating and substrate conforms to ASTM F75 standard. The conventional sintered porous-bead technology in Group A provided a multi-layer porous structure at the bone implant interface has been well-established for the clinical use on TKA implants for over 15 years. This type of coating usually produces an average porosity of 30% to 40%, and an average pore size of 150 µm to 250 µm. The porous coating technology used on Group B was a variation of the conventional porous-bead technology. Instead of spherical beads, cobalt-chromium particles in irregular shapes were sieved for a particular size range, and were sintered onto the specimen substrate using similar process as Group A. Due to the geometry and the size variation of the particles, a true 3D porous structure with widely interconnected pores can be formed. Microstructure analysis on femoral implants showed that this coating technology is able to provide an average porosity of 50% to 70%, and an average pore size of 200 µm to 450 µm. This technology also produces a rougher coating surface appearance which could also play a potential role in the overall performance

INTRODUCTION. Systemic levels of metal ions are surrogate markers of in-vivo wear of metal-on-metal hip resurfacings (MoMHRA). The wear-related generation of metal ions is associated with component size and positioning but also with design specific features such as coverage angle, clearance, metallurgy and surface technology. OBJECTIVES. The objective of the study was to investigate whether a hip resurfacing design (ACCIS) with TiNb engineered bearing surfaces would generate less chromium (Cr) and cobalt (Co) ions during and after the run-in phase of wear and whether Ti ions could be detected indicating wear of the coating. METHODS. Whole blood and serum Cr, Co and Ti levels were measured at 3, 6, 12, 24 and 60 months (ICP-MS). RESULTS. The Cr and Co levels were virtually untraceable during the running-in phase till 1 year. After that, there was a significant increase at the 2 years interval and further at the 5 years interval for both Cr and Co. Overall mean 5 years concentrations of Cr 4.8 μg/l (range 0.5–10.5 µg/L) and Co 4.3 μg/l (range 0.7–12.1µg/l)) had evolved above the established acceptable upper limits (Cr < 4.6 μg/l - Co < 4.0μg/l). 1. Elevated whole blood Ti levels were demonstrated in all patients (mean levels of 9.16 μg/l, 12.54 μg/l and 9.17 μg/l at 3,6 and 12 months respectively) with a peak level at 6 months although there was no statistical difference between the measurements at 3, 6, 12 and 24 months. DISCUSSION. These findings correspond with a release of Ti ions from the TiNb surface during the running-in phase. The whole blood Ti levels were higher compared to whole blood Ti levels in the literature for uncemented grit-blasted acetabular and femoral MoMTHA components and Ti plasma spray coated MoMHRA acetabular components. In those reports, the Ti release is due to passive corrosion from non-articulating surfaces (acetabular and/or femoral fixation surfaces) and is thus likely to be less elevated compared to release due to articulating surface wear as with the ACCIS HRA. A remarkable finding was the continuous elevation of Cr and Co ion levels after the TiNb coating seems to have been worn off. This may be due to a change in clearance as the head is slightly migrating into the cup because of the worn-off coating at the cup-head contact area. CONCLUSION. The ACCIS design has no traceable Cr and Co ions in the running in phase because of its TiNb ceramic surface coating that prevents Cr and Co release. Once the coating is worn off, which only happens at the patch area of friction, a release of Co and Cr ions starts. Although TiNb coating allegedly protects the CoCrMo surface from corrosion by acting as a seal, Cr and Co ions continued to increase at 5 years indicating further wear possibly as a result of change in clearance

Introduction. Significant reduction in the wear of current orthopaedic bearing materials has made it challenging to isolate wear debris from simulator lubricants. Ceramics such as silicon nitride (SiN), as well as ceramic-like surface coatings on metal substrates have been explored as potential alternatives to conventional implant materials. Current isolation methods were designed for isolating conventional metal, UHMWPE and ceramic wear debris. The objective of this study was to develop methodology for isolation and characterisation of modern ceramic or ceramic-like coating particles and metal wear particles from serum lubricants under ultra-low wearing conditions. Sodium polytungstate (SPT) was used as a novel density gradient medium due to its properties, such as high water solubility, the fact that it is non-toxic and acts as a protein denaturant, coupled with a large density range of 1.1–3.0 g/cm3 in water. Methods. SiN nanoparticles (<50nm nanopowder, Sigma-Aldrich) and clinically relevant cobalt-chromium wear debris were added to 25% (v/v) bovine serum lubricant at concentrations of 0.03 and 0.3 mm3/ million cycles. The particles were isolated by a newly developed method using SPT gradients. The sample volume was reduced by centrifuging the lubricant at 160,000 g for 3 h at 20°C. Then, re-suspended pellet was digested twice with 0.5 mg/ml proteinse K for 18 hours at 50°C in the presence of 0.5% (w/v) SDS. Particles were then isolated from partially hydrolysed proteins by density gradient ultracentrifugation at 270,000 g for 4 h using SPT gradients [Figure 1]. At the end of centrifugation, particles were pelleted at the bottom of the centrifuge tube, leaving protein fragments and other impurities suspended higher up the tube. Isolated particles were then washed with pyrogen free water, dispersed by sonication and filtered through 15 nm polycarbonate membrane filters for SEM and EDX analysis. Results and Discussion. The morphology and size distribution of the SiN and cobalt-chromium particles was not altered after isolation [Figure 2] [Figure 3]. The mode size of the SiN particles was 30–40 nm, while the mode size of cobalt-chromium particles was 10–20 nm [Figure 3]. Unlike current isolation methods, the present study developed a highly sensitive method which uses cost effective commercially available reagents and components. Furthermore, the particles are recovered in solution and can be readily analysed using commercial size analysers, prior to use in cell studies. This study also confirmed the aggregation characteristics of silicon nitride particles in aqueous medium as observed in previous studies. The above method may also be used to isolate wear debris of materials that have density higher than 1.6 g/cm3. This includes the majority of ceramics, metals and ceramic-like coatings used in TJR components such as alumina, zirconia toughened alumina, titanium, chromium nitride coating, titanium nitride coating and chromium carbon nitride coating. Conclusions. The new isolation method successfully isolated silicon nitride nanoparticles and cobalt-chromium wear debris from serum lubricant at ultra-low concentrations of 0.03 mm3/million cycles. Acknowledgements. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. GA-310477 LifeLongJoints

Introduction. Achieving durable implant–host bone fixation is the major challenge in uncemented revision hip arthroplasty when significant bone stock deficiencies are encountered. The purpose of this study was to develop an experimental model which would simulate the clinical revision hip scenario and to determine the effects of alendronate coating on porous tantalum on gap filling and bone ingrowth in the experimental model. Methods. Thirty-six porous tantalum plugs were implanted into the distal femur, bilaterally of 18 rabbits for four weeks. There were 3 groups of plugs inserted; control groups of porous tantalum plugs (Ta) with no coating, a 2nd control group of porous tantalum plugs with micro-porous calcium phosphate coating, (Ta-CaP) and porous tantalum plugs coated with alendronate (Ta-CaP-ALN). Subcutaneous fluorochrome labelling was used to track new bone formation. Bone formation was analysed by backscattered electron microscopy and fluorescence microscopy on undecalcified histological sections. Results. The relative increase in mean volume of gap filling, bone ingrowth and total bone formation was 124%, 232% and 170% respectively in Ta-CaP-ALN compared with the uncoated porous tantalum (Ta) controls, which was statistically significant. The contact length of new bone formation on porous tantalum implants in Ta-CaP-ALN was increased by 700% (8-fold) on average compared with the uncoated porous tantalum (Ta) controls. Discussion. Alendronate coated porous tantalum significantly modulated implant bioactivity compared with controls. This study has demonstrated the significant enhancement of bone-implant gap filling and bone ingrowth, which can be achieved by coating porous tantalum with alendronate. It is proposed that, when faced with the clinical problem of revision joint replacement in the face of bone loss, the addition of alendronate as a surface coating would enhance biological fixation of the implant and promote the healing of bone defects

Introduction. Total knee arthroplasty has become an established operation. Cemented fixation of the components has given satisfactory results and is accepted as the gold standard. Cement failure with aseptic loosening, however, is a possible long term complication. This is particularly important in view of the increasing number of younger patients who can benefit from this procedure. Hence the attraction of using implants fixed by direct osseointegration of bone into the implant, by passing the potential weak link of the cement. Objectives. The objective of this study was to determine the mid-term clinical, radiological and functional outcomes after navigated cementless and cemented implantation of total knee arthroplasties without patella resurfacing done by a single surgeon. Methods. A mixed patient cohort of 97 consecutive patients who received a navigated e.motion((BBraun Aesculap, Tuttlingen) mobile bearing knee was invited for follow up after a minimum of 5 years. All the procedures were navigated using the Orthopilot(system. The uncemented components were manufactured with a surface coating of plasma sprayed titanium with a pore size between 50 to 200(m to facilitate osteointegration (Plasmapore(). 63 patients followed the invitation and thereof 46 knees were cementless and were reviewed clinically and radiologically. The Knee Society Score (KSS), clinical (KSKS) and functional (KSFS), the Oxford knee score (OKS), complications and revisions were assessed. A radiological determination of potential radiolucencies was done. Results. In the cementless knees, there was a statistically significant improvement in the KSS (KSFS/KSKS) from an average preoperative 74 (36/39) to 185 (90/94) points after an average of 61 months follow-up. The range of motion showed a statistically significant increase from 94° to 110°. The average Oxford score in these patients showed a statistically significant improvement from 45 to 17 points. (p<0.05). All results slightly deteriorated during the period between 2 and 5 years after the index operation. Radiographic examination showed no instances of osteolysis. There were no radiolucent lines adjacent to the femoral implants and none along the coated areas of the tibial implants. For all 97 patients (71 uncemented knees) there was a total of 24(19) complications, 2(2) reoperations and 4(3) revisions. None of the adverse and serious adverse events was prosthesis related. The overall survival rate was 95.9% (cementless: 95.7%). The number of cemented knees was too small for statistical analysis. Conclusion. The Navigated cementless floating platform e.motion total knee replacement gave good clinical and functional results in the medium term. Radiographs showed excellent osteointegration of the implants. These results compared favourably with historical results of both cementless and cemented knees. The survival rate is not significantly different for hybrid (96.1%) and cementless TKA (95.7%) but longer-term follow up results with controls have to be assessed in the future

Cementless biologic fixation surfaces on total joint replacement devices, such as those used in total hip and knee procedures, have evolved over the decades. Historically, various surfaces to allow bone ingrowth or ongrowth have been applied as a coating to a pre-formed solid metal substrate. As shown in Figure 1, from left to right, representative coating surfaces include sintered beads, diffusion-bonded fiber metal, and plasma sprayed titanium. In certain applications, tantalum porous metal (Fig 1, left) can be used without a solid metal substrate, but its most widespread usage is in a modular acetabular cup design with the porous metal diffusion-bonded to a solid metal substrate similar to other coatings. Each of these examples of biologic fixation surfaces has limitations. With comparatively low porosity, bead, fiber metal and plasma spray coatings are simply a surface enhancement onto a rigid machined, forged or cast metal substrate. Furthermore, the thermal process to apply the coatings can adversely affect the mechanical properties of the metal substrate. Released in the 1990's, tantalum porous metal is considered a ‘highly porous metal’ with twice the porosity of the applied surface coatings. With that greater porosity comes lower strength that requires engineers to make standalone tantalum porous metal shapes more bulky. The chemical deposition process to produce tantalum porous metal shapes has also limitations on geometry possibilities. Where bonding the tantalum porous metal to a solid metal substrate is necessary for adequate strength, that diffusion bonding process pressure can diminish the surface coefficient of friction necessary for initial stability. A new class of manufacturing processing, referred to as ‘additive manufacturing’, allows engineers to create unique porous configurations. These configurations can be fabricated with beneficial properties to a specific implant application. One such enabling additive manufacturing process is called direct metal laser sintering (DMLS). This process utilizes a laser that travels over a fine powder bed. The laser path is determined by a program that mimics a computer model. Where the laser contacts the powder bed, the powder consolidates. Layer by layer, a scaffold porous metal is fabricated. Figure 2 shows a titanium alloy porous metal structure produced by DMLS. This formed biomaterial has 65% porosity, a high coefficient of friction, low stiffness, and strength that is 2 to 3 times that of tantalum porous metal. From a design versatility perspective, with greater strength, relatively thinner and more bone conserving geometries can be developed. When a solid metal surface interface to secure a modular polymer bearing is required, the DMLS process can produce the solid surface and the porous metal at the same time. With no secondary bonding thermal cycle needed, the construct's mechanical integrity is not compromised. Advancing biologic fixation necessitates bone conserving implant designs that have the properties to achieve immediate mechanical stability and longer term bone ingrowth. This novel use of DMLS in this particular porous metal geometry allows engineers to meet those criteria

Introduction. Bearing surfaces of metal-on-metal (MoM) hip resurfacing devices and total hip replacements (THRs) are a known source of metallic debris. Further, large diameter heads and the high friction of a MoM joint are thought to lead to fretting and corrosion at the taper interface between modular components. 1. The metal debris generated can cause significant problems on the joint area. 2. This paper investigated fretting and corrosion of femoral head-neck junctions. Variables of the head-neck junction which may have an effect on fretting and corrosion were identified with the aim of determining the key drivers so that their risk on fretting and corrosion could be reduced through design. Additionally, a Chromium Nitride (CrN) coating was assessed to determine the effect on fretting and corrosion of coating the stem (male), head (female) or both trunnion interfaces. As there is currently no standard specification for a head-neck trunnion interface and trunnion designs vary significantly across the market, this work may lead to a positive change in the design and materials used in head-neck taper interfaces for all THR devices. Methods. Suitable head and stem combinations were identified to enable individual variables such as; coating, medial-lateral (M-L) offset, head offset and taper angle to be isolated (Figure 1 and Figure 2). For the coated components a 3 μm CrN coating was applied to trunnion using electron beam physical vapour deposition (Tecvac, Cambridge, UK). Fretting and corrosion testing was carried out in accordance with ASTM F1875-98 (2009) method II procedure B. 3. following assembly of the components under a 2 kN load. Results. For the majority of the testing the CrN coating reduced the fretting and corrosion. Tests showed that increasing the M-L offset decreased the dynamic current but increased the static current. The results also demonstrated that increasing the head offset increases the fretting and corrosion. Taper angle did not appear to significantly alter either fretting or corrosion. Discussion. There are many peer reviewed papers regarding fretting and corrosion observed in vivo and the consequence of this on the patient. 4,5,6. To the author's knowledge this systematic identification of individual variables accountable for damaged caused to the taper junction is the first of its kind. Previous issues have been identified with CrN coatings. 7. , however the coating used here has already been shown to be very durable as a bearing surface coating under long term tests. 8. The results presented here are therefore encouraging as they also demonstrate that both fretting and corrosion can be reduced by the addition of a CrN coating to trunnion surfaces. The M-L offset results indicated that fretting may have different root causes to corrosion, as different trends were seen for dynamic and static currents. Increasing the head length increased fretting and corrosion, while altering the taper angle had no significant effect. Further work is therefore required to establish additional trends to enable design optimisation

Purpose of the study. to verify, after a period of 5 years, that no particular complication overshadows the benefits of a large diameter metal-on-metal articulation in combination with a conventional femoral stem with regard to stability and functional result. Patients and methods. Between October 2003 and May 2005, 100 hips in 99 patients were treated with an uncemented Emeraude stem and a Durom Resurfacing Cup made from cobalt-chrome with high carbon content. Mean age at time of surgery was 60 years. 80 of the operated patients were reviewed after a follow-up of 5 years and two months: the results are expressed according to Merle d'Aubigné and Harris, by means of the UCLA and the WOMAC scores. The radiographs were reviewed by independent observers. The patients underwent a chrome and cobalt test in whole blood. Of the 20 patients lost to follow-up, 13 had died, 1 could no longer be located, 1 had been revised because of a peri-prosthetic fracture and the remaining 5 were unable to show up for the follow-up examination. A telephone interview and the WOMAC did not reveal any complication in their cases. Results. The mean Merle d'Aubigné and Harris scores increase from 9.8 to 16.3 and from 37.4 to 79.9, respectively. The UCLA score improves from 4.2 to 6.5. The corrected WOMAC is 77.2%. But the results after 1 year show a distinct difference between the first 30 patients (Harris score of 58.2) and the subsequent patients (Harris score of 82.4). The radiographic analysis does not show any migration; the observed radiolucencies, whether around the fixation wings or at the level of the surface coating, are not progressive; mean cup inclination is 52°. The mean values for chrome are 1.95 μg/l and for cobalt 2 μg/l. Discussion and conclusion. This study confirms the relevance of this concept with regard to stability (no dislocations) and functional result, and reveals no particular complication. The less good clinical results are to be attributed to the pain previously noted in the first 30 cases, before our technical experience led us to impact an undersized cup in respect to the last used rasp. This technique enables a better centering of the cup, ensures that the latter does not protrude nor expose it to excessive equatorial compression, which seems to cause pain. We have no doubt that it is this technical modification that has spared us the complications that have led some of our colleagues to abandon this type of implant

Introduction. The initial mechanical stability of cementless femoral stems in total hip arthroplasty is an important factor for stable biological fixation. Conversely, insufficient initial stability can lead to stem subsidence, and excessive subsidence can result in periprosthetic femoral fracture due to hoop stress. The surface roughness of stems with a surface coating theoretically contributes to initial mechanical stability by increasing friction against the bone, however, no reports have shown the effect of surface roughness on stability. The purpose of this study was to evaluate the effect of differences in surface roughness due to different surface treatments with the same stem design on the initial stability. Materials and Methods. Proximally titanium plasma-sprayed femoral stems (PS stem) and proximally grit-blasted stems (GB stem) were compared. The stem design was identical with an anatomic short tapered shape for proximal fixation. The optimum size of PS stem based on 3D templating was implanted in one side of 11 pairs of human cadaveric femora and the same size of GB stems was implanted in the other side. After implantation, the specimens were fixed to the jig of a universal testing machine in 25cm of entire length so that the long axis of the femur was positioned at 15-degrees adduction to the vertical. Vertical load tests were conducted under 1 mm/minute of displacement-controlled conditions. After 200 N of preload to eliminate the variance in the magnitude of press-fit by manual implantation, load was applied until periprosthetic fracture occurred. Results. The same size of PS or GB stem was successfully implanted in all 11 pairs without fracture. The distances of subsidence until fracture occurred were 2.2±1.2 mm in the PS stem and 2.5±1.1 mm in the GB stem and no significant difference was detected. The load applied for 1 mm of subsidence was 792±478 N in the PS stem and 565±431 N in the GB stem and there was a significant difference between the two groups. The load at fracture was 3037±1563 N in the PS stem and 2614±1484 N in the GB stem and there was a significant difference between the groups. Discussion. A significantly larger load was applied for 1 mm of subsidence in the PS stem compared to the GB stem. This suggests that the plasma-spray porous-coated surface had a less slippery interface than the grit-blasted surface. Both femora of a pair fractured at the same level of hoop stress that was induced by the same amount of stem subsidence but at significantly different loads. The fact that the load at fracture in the PS stem was significantly larger than that in the GB stem was due to differences in shear stress caused by different levels of friction. The scratching effect against the femoral canal due to the rougher surface of the plasma-spray porous-coating works advantageously for initial mechanical stability