Introduction. Acetabular component loosening has been one of the factors of revision of total hip arthroplasty (THA). Inadequate mechanical fixation or load transfer may contribute to this loosening process. Several reports showed the load transfer in the acetabulum by metal components. However, there is no report about the influence of the joint surface on the load transfer. We developed a novel acetabular cross-linked polyethylene (CLPE) liner with graft biocompatible phospholipid polymer(MPC) on the surface. The MPC polymer surface had high lubricity and low friction. We hypothesized the acetabular component with MPC polymer surface (MPC-CLPE) may reduce load transfer in the acetabulum compared to that of the by CLPE acetabular component without MPC. Methods. We fixed the three cement cup with MPC-CLPE (Group M; sample No.1–3) and three cement cup with CLPE (Group C; sample No.4–6) placed in the synthetic bone block with bone cement with a 0.10mm thick arc-shaped piezoresistive force sensor, which can measure the dynamic load transfer(Tekscan K-scan 4400; Boston). (Fig 1) A hip simulator (MTS Systems Corp., Eden Prairie, MN) was used for the load transfer test performed according to the ISO Standard 14242-1. Both groups had same inner and outer diameter s of 28 and 50mm, respectively. A Co–Cr alloy femoral head with a diameter of 28 mm (K-MAXs HH-02; KYOCERA Medical Corp.) was used as the femoral component. A biaxial rocking motion was applied to the head/cup interface via an offset bearing assembly with an inclined angle of +20. Both the loading and motion were synchronized at 1 Hz. According to the double-peaked Paul-type physiologic hip load, the applied peak loads were 1793 and 2744 N described in a previous study. The simulator was run 3 cycles. We recorded both the peak of the contact force and the accumulation of the six times load in total. Secondly, we calculated the mean change of the load transfer. We used the Student t-test. P value < 0.05 was used to determine statistical significance. We used EZR for statistical analysis. Results. The mean of total accumulation of the load transfer in the group M is significantly lower than that of in the group C. (7037±508 N vs 11019±1290 N, P<0.0001). The peak of load in the group M was also significantly lower than that in the group C. (1024±166 N vs 1557±395 N) (Fig 2)The mean of the change of the load transfer in the group M is significantly lower than that of in the group C. (2913±112 N vs 4182±306 N) (Fig 3). Conclusion. The acetabular component with MPC surface could reduce and prevent the radical load transfer change toward to the acetabulum compared to CLPE acetabular component without MPC. For any figures or tables, please contact the authors directly

Background

Bioresorbable materials offer the potential of developing fracture fixation plates with similar mechanical properties to bone thereby minimizing stress shielding and obviating the need for implant removal.

INTRODUCTION

The menisci play a fundamental biomechanical role in the knee and also help in the maintaining of the articular homeostasis; thus, either a lesion or the complete absence of the menisci can invalidate the physiological function of the knee causing important damages, even at long term. Unfortunately, meniscal tears are often found during the ordinary orthopaedic practice while the regenerative potential of this kind of tissue is very low and limited to its peripheral-vascularized part; this is why the majority of these common arthroscopic findings are not reparable and often the surgeon is almost forced to perform a partial, subtotal or even total meniscectomy, regardless of the well-known consequences of this kind of surgery.

Biodegradable metals as orthopaedic implant materials receive substantial scientific and clinical interest. Marketed cardiovascular products confirm good biocompatibility of iron. Solid iron biodegrades slowly in vivo and has got supra-physiological mechanical properties as compared to bone and porous implants can be optimized for specific orthopaedic applications. We used Direct Metal Printing (DMP)3 to additively manufacture (AM) scaffolds of pure iron with fine-tuned bone-mimetic mechanical properties and improved degradation behavior to characterize their biocompatibility under static and dynamic 3D culture conditions using a spectrum of different cell types. Atomized iron powder was used to manufacture scaffolds with a repetitive diamond unit cell design on a ProX DMP 320 (Layerwise/3D Systems, Belgium). Mechanical characterization (Instron machine with a 10kN load cell, ISO 13314: 2011), degradation behavior under static and dynamic conditions (37ºC, 5% CO2 and 20% O2) for up of 28 days, with μCT as well as SEM/energy-dispersive X-ray spectroscopy (EDS) (SEM, JSM-IT100, JEOL) monitoring under in vivo-like conditions. Biocompatibility was comprehensively evaluated using a broader spectrum of human cells according to ISO 10993 guidelines, with topographically identical titanium (Ti-6Al-4V, Ti64) specimen as reference. Cytotoxicity was analyzed by two-way ANOVA and post-hoc Tukey's multiple comparisons test (α = 0.05). By μCT, as-built strut size (420 ± 4 μm) and porosity of 64% ± 0.2% were compared to design values (400 μm and 67%, respectively). After 28 days of biodegradation scaffolds showed a 3.1% weight reduction after cleaning, while pH-values of simulated body fluids (r-SBF) increased from 7.4 to 7.8. Mechanical properties of scaffolds (E = 1600–1800 MPa) were still within the range for trabecular bone, then. At all tested time points, close to 100% biocompatibility was shown with identically designed titanium (Ti64) controls (level 0 cytotoxicity). Iron scaffolds revealed a similar cytotoxicity with L929 cells throughout the study, but MG-63 or HUVEC cells revealed a reduced viability of 75% and 60%, respectively, already after 24h and a further decreased survival rate of 50% and 35% after 72h. Static and dynamic cultures revealed different and cell type-specific cytotoxicity profiles. Quantitative assays were confirmed by semi-quantitative cell staining in direct contact to iron and morphological differences were evident in comparison to Ti64 controls. This first report confirms that DMP allows accurate control of interconnectivity and topology of iron scaffold structures. While microstructure and chemical composition influence degradation behavior - so does topology and environmental in vitro conditions during degradation. While porous magnesium corrodes too fast to keep pace with bone remodeling rates, our porous and micro-structured design just holds tremendous potential to optimize the degradation speed of iron for application-specific orthopaedic implants. Surprisingly, the biological evaluation of pure iron scaffolds appears to largely depend on the culture model and cell type. Pure iron may not yet be an ideal surface for osteoblast- or endothelial-like cells in static cultures. We are currently studying appropriate coatings and in vivo-like dynamic culture systems to better predict in vivo biocompatibility

Objectives. The purpose of this study was to evaluate in vivo biocompatibility of novel single-walled carbon nanotubes (SWCNT)/poly(lactic-co-glycolic acid) (PLAGA) composites for applications in bone and tissue regeneration. Methods. A total of 60 Sprague-Dawley rats (125 g to 149 g) were implanted subcutaneously with SWCNT/PLAGA composites (10 mg SWCNT and 1gm PLAGA 12 mm diameter two-dimensional disks), and at two, four, eight and 12 weeks post-implantation were compared with control (Sham) and PLAGA (five rats per group/point in time). Rats were observed for signs of morbidity, overt toxicity, weight gain and food consumption, while haematology, urinalysis and histopathology were completed when the animals were killed. Results. No mortality and clinical signs were observed. All groups showed consistent weight gain, and the rate of gain for each group was similar. All groups exhibited a similar pattern for food consumption. No difference in urinalysis, haematology, and absolute and relative organ weight was observed. A mild to moderate increase in the summary toxicity (sumtox) score was observed for PLAGA and SWCNT/PLAGA implanted animals, whereas the control animals did not show any response. Both PLAGA and SWCNT/PLAGA showed a significantly higher sumtox score compared with the control group at all time intervals. However, there was no significant difference between PLAGA and SWCNT/PLAGA groups. Conclusions. Our results demonstrate that SWCNT/PLAGA composites exhibited in vivo biocompatibility similar to the Food and Drug Administration approved biocompatible polymer, PLAGA, over a period of 12 weeks. These results showed potential of SWCNT/PLAGA composites for bone regeneration as the low percentage of SWCNT did not elicit a localised or general overt toxicity. Following the 12-week exposure, the material was considered to have an acceptable biocompatibility to warrant further long-term and more invasive in vivo studies. Cite this article: Bone Joint Res 2015;4:70–7

A novel injectable hydrogel based on DNA and silicate nanodisks was fabricated and optimized to obtain a suitable drug delivery platform for biomedical applications. Precisely, the hydrogel was designed by combining two different type of networks: a first network (type A) made of interconnections between neighboring DNA strands and a second one (type B) consisting of electrostatic interactions between the silicate nanodisks and the DNA backbone. The silicate nanodisks were introduced to increase the viscosity of the DNA physical hydrogel and improve their shear-thinning properties. Additionally, the silicate nanodisks were selected to modulate the release capability of the designed network. DNA 4% solutions were heated at 90°C for 45 seconds and cooled down at 37°C degree for two hours. In the second step, the silicate nanodisks suspension in water at different concentrations (0.1 up to 0.5%) were then mixed with the pre-gel DNA hydrogels to obtain the nanocomposite hydrogels. Rheological studies were carried out to investigate the shear thinning properties of the hydrogels. Additionally, the hydrogels were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron microscopy. The hydrogels were loaded with the osteoinductive drug dexamethasone and its release was tested in vitro in phosphate buffer pH 7.4. The drug activity upon release was tested evaluating the osteogenic differentiation of human adipose derived stem cells (hASCs) in vitro through analysis of main osteogenic markers and quantification of alkaline phosphatase activity and calcium deposition. Finally, the hydrogels were tested in vivo and injected into cranial defects in rats to assess their biocompatibility and bone regeneration potential. The inclusion of the silicate nanodisks increased the viscosity of the hydrogels and the best results were obtained with the highest concentration of the nanoclay (0.5%). The hydrogels possessed shear-thinning properties as demonstrated by cyclic strain sweep tests and were able to recover their original storage modulus G' upon removal of strain. Such improvement in the injectable properties of the formulated hydrogels was mainly attributed to the formation of electrostatic interactions between the silicate nanodisks and the phosphate groups of the DNA backbone as confirmed by XPS analysis of the O, N, and P spectra. Additionally, laponite was able to sustain the release of the osteoinductive drug dexamethasone which was instead completely released from the DNA-based hydrogels after a week. The drug after being released was still active and promoted the osteogenic differentiation of hASCs as confirmed by ALP expression and expression of main osteogenic markers including ALP and COLA1. Finally, the gels proved to be biocompatible in vivo when injected into cranial defects and promoted bone formation at the periphery of the defect after a month post-treatment. A novel injectable shear-thinning DNA-based hydrogel was characterized and tested for its drug delivery properties. The hydrogel can promote the sustain release of a small molecule like dexamethasone and be biocompatible in vitro and in vivo. Due to these promising findings, the designed system could find also applicability for the delivery of growth factors or other therapeutic molecules

Aim. A novel anti-infective biopolymer implant coating was developed to prevent bacterial biofilm formation and allow on-demand burst release of anti-infective silver (Ag) into the surrounding of the implant at any time after surgery via focused high-energy extracorporeal shock waves (fhESW). Method. A semi-crystalline Poly-L-lactic acid (PLLA) was loaded with homogeneously dissolved silver (Ag) applied onto Ti6Al4V discs. A fibroblast WST-1 assay was performed to ensure adequate biocompatibility of the Ag concentration at 6%. The prevention of early biofilm formation was investigated in a biofilm model with Staphylococcus epidermidis RP62A after incubation for 24 hours via quantitative bacteriology. In addition, the effect of released Ag after fhESW (Storz DUOLITH SD1: 4000 impulses, 1,24 mJ/mm. 2. , 3Hz, 162J) was assessed via optical density of bacterial cultures (Escherichia coli TG1, Staphylococcus epidermidis RP62A, Staphylococcus aureus 6850) and compared to an established electroplated silver coating. The amount of released Ag after the application of different intensities of fhESW was measured and compared to a control group without fhESW via graphite furnace atomic absorption spectrometry (GF-AAS), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Results. The coating with 6% Ag reduced Staphylococcus epidermidis biofilm formation by 99.7% (mean±SD: 2.1×10^5 ± 3,9×10^5 CFU/µL) compared to uncoated controls (6.8×10^7 ± 4.9×10^7 CFU/µL); (p=0.0001). After applying fhESW the commercially available electroplated silver coating did not prevent the growth of all tested bacterial strains. Bacterial growth is delayed with 4% Ag and completely inhibited with 6% Ag in the novel coating, except for a small increase of S. aureus after 17 hours. SEM and EDS confirmed a local disruption of the coating after fhESW. Conclusions. This novel anti-infective implant coating has the potential to prevent bacterial biofilm formation. The on-demand burst release of silver via fhESW could be an adjunctive in the treatment of implant related infection and is of particular interest in the concept of single stage revision surgery

Introduction. Humans Functions (locomotion, protection of organs, reproduction) require a strong support system (bones). The ‘Osteostasis’ is the ability of maintaining the bone structure, its mechanical characteristics and function. Five principles are required for an efficient bone system:. Basic Requirements:. 1) Stability and 2) Function. Repair System (like house building in desert or sea):. 3) Roads (vessels), 4) Materials (calories, proteins), 5) Workers (bone cells). Analysis of bone problems through these principles bring to optimised treatments. Materials & Methods. Measurements (>700 lengthening, 32-year follow-up, Full WB Albizzia/G-Nails FWBAG): Bone-DEXA, WB conditions, muscle, fat, etc. Principle-1. Solid bone replacement with a 100% biocompatible and reliable FWBAG with sports (POD0). Principle-2. Bone, Muscle & neural integrity for function Principle-3. Vascular flow lesions induce non-healing (arteriography). Muscle activity accounts for 90% of bone blood flow, ×10 by sports. Required: Checks (arteriography) and treatments (training). Principle-4. Food (NRV Kcal × 2–3, 20–25% proteins). Principle-5. Maintain bone cells and increase them. Suppress ‘opening’, ‘venting’, ‘drainages’. Results. Principle1. Nail fracture (1.2%), nail dysfunction (0%) with FWBAG. Principle2. Intensive sports preop and from POD0 - Principle3. Increased preop vascular supply & muscle force, postop resistance sports fasten recovery. Wheel-chair or low activity decreases healing. Principle4. 6–9 cm circumference loss (non WB-nails or no proper training); 0 cm circumference loss (gain <10 cm) with intense resistance training + high calory intake. - Principle5. Bone cells preservation (no opening, IM saw, increasing bone cells) allow Healing Index down to 8D/cm. Conclusions. The ‘5P’ allow reaching treatment targets by optimisation of problem solving, maintaining Osteostasis. What would I like or tolerate for me? How can I reach it? Full WB and sports from POD0 was a target 38 years-ago, still not enforced by most of us. Resistance sports, high-calory intake suppress muscle loss and fasten healing, thanks to muscle blood flow and the ‘5P’

Aim. Several local antibiotic-eluting drug delivery systems have been developed to treat bacterial bone infections. However, available systems have significant shortcomings, including suboptimal drug-release profiles with a burst followed by subtherapeutic release, which may lead to treatment failure and selection for drug resistance. Here, we present a novel injectable, biocompatible, in situ-forming depot, termed CarboCells, which can be fine-tuned for the desired antibiotic-release profile. The CarboCell technology has flexible injection properties that allow surgeons to accurately place antibiotic-eluting depots within and surrounding infectious sites in soft tissue and bones. The CarboCell technology is furthermore compatible with clinical image-guided injection technologies. These studies aimed to determine the therapeutic potential of CarboCell formulations for treatment of implant-associated osteomyelitis by mono- and dual antimicrobial therapy. Methods. The solubility and stability of several antibiotics were determined in various CarboCell formulations, and in vitro drug release was characterized. Lead candidates for antimicrobial therapy were selected using a modified semi-solid biofilm model with 4-day-matured Staphylococcus aureus biofilm (osteomyelitis-isolate, strain S54F9). Efficacy was investigated in a rat implant-associated osteomyelitis model established in the femoral bone by intraosseous implantation of a stainless-steel pin with 4-day-old in vitro-matured S. aureus biofilm. CarboCells were injected subcutaneously at the femur, and antimicrobial efficacy was evaluated 7 days post-implantation. Lead formulations were subsequently tested in a well-established translational implant-associated tibial S. aureus osteomyelitis pig model. Infection was established for 7 days before revision surgery consisting of debridement, washing, implantation of a new stainless-steel pin, and injection of antibiotic-releasing CarboCells into the debrided cavity and in the surrounding bone- and soft-tissue. Seven days post-revision, pigs were euthanized, and samples were collected for microbial and histopathological evaluation. Results. Lead antimicrobial agents were soluble in high concentrations and were stable in CarboCell formulations. Three combinations completely eradicated bacteria in the in vitro semi-solid biofilm model. In the rat osteomyelitis model, CarboCell formulations of the lead combinations also eradicated bacteria in bone and implant in several rats and significantly reduced infection in all treated rats. In the pig model, CarboCell antimicrobial monotherapy demonstrated promising therapeutic efficacy, including complete eradication of infection in bone and implants in several pigs and significantly reduced bacterial burden in others. Conclusions. Using the CarboCell technology for antimicrobial delivery exert substantial loco-regional efficacy. The attractive sustained high-dose antibiotic release profile combined with the flexible injection technology allows surgeons to accurately place effective drug-eluting depots in key areas not accessible to competing technologies

Aim. Antibacterial activity of coatings based on metal and metal oxide nanoparticles (NPs) often depends on materials and biotic targets resulting in a material-specific killing activity of selected Gram-positive and Gram-negative bacteria, including drug-resistant strains. In this perspective, the NPs loading amount, the relative elemental concentration inside the nanogranular building blocks and the deposition method are of paramount importance when the goal is to widen the antimicrobial spectrum, but at the same time to avoid high levels of metal content to limit undesired toxic effects. Aim of the present study was evaluation of the antimicrobial properties of two multielement nanogranular coatings composed of Titanium-Silver and Copper and of Magnesium-Silver and Copper. Method. Ti-Ag-Cu and Mg-Ag-Cu NPs were deposited on circular cover glasses (VWR) by Supersonic Cluster Beam Deposition. Biofilm-producer strains of Staphylococcus aureus (methicillin susceptible and resistant), Staphylococcus epidermidis (methicillin susceptible and resistant), Escherichia coli (fully susceptible and producer of extended spectrum beta lactamases), and Pseudomonas aeruginosa (susceptible and multidrug-resistant) were selected. The abilities of the selected strains to adhere, colonize and produce biofilm on the discs coated with Ti-Ag-Cu or Mg-Ag-Cu NPs were compared to uncoated circular cover glasses which were used as growth control. Cytotoxicity was also evaluated in order to assess the biocompatibility of the newly synthesized NPs. Results. In comparison to uncoated controls, both coatings showed significant anti-adhesive properties against S. aureus, S. epidermidis, and E. coli. Reduction in adhesion to Mg-Ag-Cu coated discs was observed also for P. aeruginosa isolates, although differences vs uncoated controls did not reach statistical significance. Biofilm formation was reduced on discs coated with Mg-Ag-Cu compared to Ti-Ag-Cu and, again, coatings had a milder effect on P. aeruginosa, probably due to its exceptional capability of attachment and matrix production. These results were confirmed by the evaluation of bacterial colonization on nanoparticles-coated discs by means of confocal laser scanning microscopy. A viability of 95.8% and 89.4% of cells cultured in the presence of Ti-Ag-Cu and Mg-Ag-Cu discs, respectively, when compared to negative controls was observed, thus excluding cytotoxic effects on eukaryotic cells. Conclusions. The newly synthesized Ti-Ag-Cu and Mg-Ag-Cu coatings are able to limit bacterial adhesion colonization and biofilm production, thus highlighting the safe use of multi-element families of NPs as new strategies against bacterial attachment to the surface of biomedical implants. However, further studies addressing activity against P. aeruginosa and including a wide number of isolates are warranted

Despite the increasing availability of bone grafting materials, the regeneration of large bone defects remains a challenge. Especially infection prevention while fostering regeneration is a crucial issue. Therefore, loading of grafting material with antibiotics for direct delivery to the site of need is desired. This study evaluates the concept of local delivery using in vitro and in vivo investigations. We aim at verifying safety and reliability of a perioperative enrichment procedure of demineralized bone matrix (DBM) with gentamicin. DBM (DBMputty, DIZG, Germany) was mixed with antibiotic using a syringe with an integrated mixing propeller (Medmix Systems, Switzerland). Gentamicin, as powder or solution, was mixed with DBM at different concentrations (25 −100 mg/g DBM), release and cytotoxicity was analyzed. For in vivo analysis, sterile drill hole defects (diameter: 6 mm, depth: 15 mm) were created in diaphyseal and metaphyseal bones of sheep (Pobloth et al. 2016). Defects (6 – 8 per group and time point) were filled with DBM or DBM enriched with gentamicin (50 mg/g DBM) or left untreated. After three and nine weeks, defect regeneration was analyzed by µCT and histology. The release experiments revealed a burst release of gentamicin from DBM independent of the used amount, the sampling strategy, or the formulation (powder or solution). Gentamicin was almost completely released after three days in all set-ups. Eluates showed an antimicrobial activity against S. aureus over at least three days. Eluates had no negative effect on viability and alkaline phosphatase activity of osteoblast-like cells (partially published Bormann et al. 2014). µCT and histology of the drill hole defects revealed a reduced bone formation with gentamicin loaded DBM. After nine weeks significantly less mineralized tissue was detectable in metaphyseal defects of the gentamicin group. Histological evaluation revealed new bone formation starting at the edges of the drill holes and growing into the center over time. The amount of DBM decreased over time due to the active removal by osteoclasts while osteoblasts formed new bone. Using this mixing procedure, loading of DBM was fast, reliable and possible during surgical setting. In vitro experiments revealed a burst and almost complete release after three days, antimicrobial activity and good biocompatibility of the eluates. Gentamicin/DBM concentration was in the range of clinically used antibiotic-loaded-cement for prophylaxis and treatment in joint replacement (Jiranek et al. 2006). The delayed healing seen in vivo was unexpected due to the good biocompatibility found in vitro. A reduced healing was also seen in spinal fusion where DBM was mixed with vancomycin (Shields et al. 2017), whereas DBM with gentamicin or DBM/bioactive glass with tobramycin had no negative effect on osteoinductivity or femur defect healing, respectively (Lewis et al. 2010, Shields et al. 2016). In conclusion, loading of DBM with gentamicin showed a proper antibiotic delivery over several days, covering the critical phase shortly after surgery. Due to the faster and complete release of the antibiotic compared to antibiotic loaded cement, the amount of antibiotic should be much lower in the DBM compared to cement

Aim. Silver is known for its excellent antimicrobial activity, including activity against multiresistant strains. The aim of the current study was to analyze the biocompatibility and potential influence on the fracture healing process a silver-coating technology for locking plates compared to silver-free locking plates in a rabbit model. Methods. The implants used in this study were 7-hole titanium locking plates, and plasma electrolytic oxidation (PEO) silver coated equivalents. A total of 24 rabbits were used in this study (12 coated, 12 non-coated). An osteotomy of the midshaft of the humerus was created with an oscillating saw and the humerus stabilized with the 7 hole locking plates with a total of 6 screws. X-rays were taken on day 0, week 2, 4, 6, 8, and 10 for continuous radiographical evaluation of the fracture healing. All animals were euthanized after 10 weeks and further assessment was performed using X-rays, micro-CT, non-destructive four-point bending biomechanical testing and histology. Furthermore, silver concentration was measured in the kidney, liver, spleen and brain. Results. X-rays showed normal undisturbed healing of the osteotomy in all animals without any differences between the two groups over the entire X-ray analysis over 10 weeks (Figure 1). Callus formation was observed up to week 4 to 5 followed by callus remodeling after 6 weeks indicating physiological fracture healing pattern in both the silver and in the silver free group. Micro CT analysis revealed overall tissue (callus and cortical bone) volume as well as tissue density to be comparable between the two groups. Mechanical testing showed comparable stiffness with an average stiffness relative to contralateral bones of 75.7 ± 16.1% in the silver free control group compared to 69.7 ± 18.5% (p-value: 0.46). Histology showed no remarkable difference in the analysis of the healed osteotomy gap or in the surrounding soft tissue area. Silver content was found to be close to baseline values without differences between the two groups. Conclusions. This study shows that the presented antimicrobial silver surface modification for locking plates has a good biocompatibility without any negative influence on the fracture healing processes compared to the silver free control group. This allows for further clinical investigation of this silver technology for locking plates in fracture patients with an elevated infection risk, e.g. in patients with open fractures. For any figures or tables, please contact the authors directly

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. Titanium and its alloys are attractive biomaterials attributable to their desirable corrosion, mechanical, biocompatibility and osseointegration properties. Ti6Al4V alloy in particular remains a prominent biomaterial used in Total Hip Arthroplasty (THA) today. This is partly due to biocompatibility and stress shielding issues with CoCrMo alloys, resulting in its increasing side-lining from the THA construct. For several decades now, research efforts have been dedicated to understanding wear, corrosion and surface degradation processes in implant materials. Only recently have researchers shown interest in understanding the subsurface implications of fretting and the role it plays on implant fracture. The purpose of this study was to utilise advanced microscopy and spectroscopy techniques to characterise fretting-induced subsurface transformations in Ti6Al4V. This makes mapping specific regions that are most prone to wear and fatigue failures at the modular taper interface of THA probable. Thus, informing a proactive approach to component design and material selection. Method. A ball-on-flat configuration was utilised in this study to achieve a Hertzian point contact for a CoCrMo – Ti6Al4V material combination. Four fretting displacement amplitudes were assessed: ±10, ±25, ±50 and ±150 µm. An initial contact pressure of 1 GPa was used for all fretting tests in this study and each fretting test lasted 6000 cycles at a frequency of 1 Hz. The simulated physiological solution consisted of Foetal Bovine Serum (FBS) diluted to 25% with Phosphate Buffered Saline (PBS) and 0.03% Sodium Azide (SA) balance. The temperature was kept at ∼37°C. Subsurface transformations in the Ti6Al4V alloy was characterised using the Transmission Electron Microscopy (TEM) to obtain high resolution micrographs. The samples were prepared using a FIB-SEM. Bright-field, dark-field and selected area electron diffraction (SAED) patterns were all captured using a scanning TEM (STEM) and Energy Dispersed X-Ray spectroscopy (EDX) mapping was carried out. Results. At both ±10 and ±25 µm displacement, a stick fretting regime was realised. Subsurface transformation in the Ti6Al4V alloy was characterised as strain-induced orientation. At ±50 µm, a mixed fretting regime was realised, TEM and SAED micrographs as well as EDX spectroscopy identified complex but distinctive structures at the surface and subsurface of the Ti6Al4V alloy. This included a CoCrMo-rich fine particulate, mechanically mixed structure, an amorphous-transformed Ti6Al4V structure and a highly refined nano-crystalline Ti6Al4V structure. At ±150 µm, a full gross slip regime was realised and Ti6Al4V alloy was characterised mainly by subsurface cracks, formation and refinement of nano-crystalline structures. Conclusion. The degree of subsurface recrystallization within Ti6Al4V alloy was observed to be energy dependent. However, the manifestation of the dissipated energy was dependent on the contact condition. The interwoven relationship between energy dissipation, contact condition and mechanisms of clinical failure in Ti6Al4V was consolidated into a map (Figure 1). The map is intended to provide users with an indication of the failure modes to expect for an implant material subjected to specific tribocorrosion conditions. For any figures or tables, please contact the authors directly

Introduction. Silicon nitride (SiN) is a recently introduced bearing material for THR that has shown potential in its bulk form and as a coating material on cobalt-chromium (CoCr) substrates. Previous studies have shown that SiN has low friction characteristics, low wear rates and high mechanical strength. Moreover, it has been shown to have osseointegration properties. However, there is limited evidence to support its biocompatibility as an implant material. The aim of this study was to investigate the responses of peripheral blood mononuclear cells (PBMNCs) isolated from healthy human volunteers and U937 human histiocytes (U937s) to SiN nanoparticles and CoCr wear particles. Methods. SiN nanopowder (<50nm, Sigma UK) and CoCr wear particles (nanoscale, generated in a multidirectional pin-on-plate reciprocator) were heat-treated for 4 h at 180°C and dispersed by sonication for 10 min prior to their use in cell culture experiments. Whole peripheral blood was collected from healthy donors (ethics approval BIOSCI 10–108, University of Leeds). The PBMNCs were isolated using Lymphoprep® as a density gradient medium and incubated for 24 h in 5% (v/v) CO2at 37°C to allow attachment of mononuclear phagocytes. SiN and CoCr particles were then added to the phagocytes at a volume concentration of 50 µm3 particles per cell and cultured for 24 h in RPMI-1640 culture medium in 5% (v/v) CO2 at 37°C. Cells alone were used as a negative control and lipopolysaccharide (LPS; 200ng/ml) was used as a positive control. Cell viability was measured after 24 h by ATPLite assay and tumour necrosis factor alpha (TNF-α) release was measured by sandwich ELISA. U937s were co-cultured with SiN and CoCr particles at doses of 0.05, 0.5, 5 and 50 µm3 particles per cell for 24h in 5% (v/v) CO2 at 37 C. Cells alone were used as a negative control and camptothecin (2 µg/ml) was used as a positive control. Cell viability was measured after 0, 1, 3, 6 and 9 days. Results from cell viability assays and TNF-α response 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. At a high volume concentration of particles (50µm3 per cell), SiN did not affect the viability of PBMNCs, while CoCr significantly reduced the viability over a 24 h period [Figure 1A]. Similarly, SiN particles had no effect on the viability of U937s up to 9 days with a range of particle doses (0.05–50 µm3 per cell) [Figure 2A]. In contrast, CoCr particles significantly reduced the viability of U937s after 6 days [Figure 2B]. Additionally, CoCr particles caused significantly elevated levels of pro-inflammatory cytokine TNF-α, whereas no inflammation was associated with SiN particles [Figure 1B]. Conclusion. This study has demonstrated the in-vitro biocompatibility of SiN nanoparticles. Therefore, SiN is a promising orthopaedic bearing material not only due to its suitable mechanical and tribological properties, but also due to its biocompatibility. 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. 3-D Printing with direct metal tooling (DMT) technology was innovatively introduced in the field of surface treatment of prosthesis to improve, moreover to overcome the problems of plasma spray, hopefully resulting in opening the possibility of another page of coating technology. We presumed such modification on the surface of Co-Cr alloy by DMT would improve the ability of Co-Cr alloys to osseointegrate. Method. We compared the in vitro and in vivo ability of cells to adhere to DMT coated Co-Cr alloy to that of two different types of surface modifications: machined and plasma spray(TPS). We performed energy-dispersive x-ray spectroscopy and scanned electron microscopy investigations to assess the structure and morphology of the surfaces. Biologic and morphologic responses to osteoblast cell lines of human were then examined by measuring cell proliferation, cell differentiation (alkaline phosphatase activity), and avb3 integrin. The cell proliferation rate, alkaline phosphatase activity, and cell adhesion in the MAO group increased in comparison to those in the machined and grit-blasted groups. Results. The cell proliferation rate, alkaline phosphatase activity, and cell adhesion in the DMT group increased in comparison to those in the machined and TPS groups. Cell proliferation, alkaline phosphatase activity, migration, and adhesion were increased in DMT group compared to the two other groups. Human Osteoblast cells on DMT-coated surface were strongly adhered, and proliferated well compared to those on the other surfaces. Discussion. The surface modifications of DMT coating enhanced the biocompatibility (proliferation and migration of osteoblastlike cells) of Co-Cr alloy. This process is not unique to Co-Cr alloy; it can be applied to many metals to improve their biocompatibility, thus allowing a broad range of materials to be used for cementless implants

The spine is one of the most common sites of bony metastasis, with 80% of prostate, lung, and breast cancers metastasizing to the vertebrae resulting in significant morbidity. Current treatment modalities are systemic chemotherapy, such as Doxorubicin (Dox), administered after resection to prevent cancer recurrence, and systemic antiresorptive medication, such as Zolendronate (Zol), to prevent tumor-induced bone destruction. The large systemic doses required to elicit an adequate effect in the spine often leads to significant side-effects by both drugs, limiting their prolonged use and effectiveness. Recently published work by our lab has shown that biocompatible 3D-printed porous polymer scaffolds are an effective way of delivering Dox locally over a sustained period while inhibiting tumor growth in vitro. Our lab has also generated promising results regarding antitumor properties of Zol in vitro. We aim to develop 3D-printed scaffolds to deliver a combination of Zol and Dox that can potentially allow for a synergistic antitumor activity while preventing concurrent bone loss locally at the site of a tumor, avoiding long systemic exposure to these drugs and decreasing side effects in the clinical setting. The PORO Lay polymer filaments are 3D-printed into 5mm diameter disks, washed with deionized water and loaded with Dox or Zol in aqueous buffer over 7 days. Dox or Zol-containing supernatant was collected daily and the drug release was analyzed over time in a fluorescence plate reader. The polymer-drug (Dox or Zol) release was tested in vitro on prostate and lung cancer cell lines and on prostate- or lung-induced bone metastases cells. Alternatively, direct drug treatment was also carried out on the same cells in vitro. Following treatment, all cells were subject to proliferation assay (MTT and alamar blue), viability assay (LIVE/DEAD), migration assay (Boyden chamber) and invasion assay (3D gel matrix). 3D-printed scaffolds loaded with both Dox and Zol will also be tested on cells. We have established an effective dose (EC50) for prostate and lung cancer cell lines and bone metastases cells with direct treatment with Zol or Dox. We have titrated the drug loading of scaffolds to allow for a release amount of Dox at the EC50 dose over 7 days. In ongoing experiments, we are testing the release of Zol. We have shown Dox releasing scaffolds inhibit cancer cell growth in a 2D culture over 7 days using the above cellular assays and testing the scaffolds with Zol is currently being analyzed. 3D-printed porous polymers like the PORO Lay series of products offer a novel and versatile opportunity for delivery of drugs in future clinical settings. They can decrease systemic exposure of drugs while at the same time concentrating the drugs effect at the site of tumors and consequently inhibit tumor proliferation. Their ability to be loaded with multiple drugs can allow for achieving multiple goals while taking advantage of synergistic effects of different drugs. The ability to 3D-print these polymers can allow for production of custom implants that offer better structural support for bone growth

Introduction. Currently, different techniques to evaluate biocompatibility of orthopaedic materials, including two-dimensional (2D) cell culture for metal and ceramic wear debris and floating 2D surfaces or three-dimensional (3D) agarose gels for UHMWPE wear debris, are used. We have developed a single method using 3D agarose gels that is suitable to test the biocompatibility of all three types of wear debris simultaneously. Moreover, stimulation of the cells by wear particles embedded in a 3D gel better mimics the in vivo environment. Materials and Methods. Clinically relevant sterile UHMWPE and CoCr wear particles were generated using methodologies described previously [1,2]. Commercially available nanoscale and micron-sized silicon nitride (Si. 3. N. 4. ) particles (<50 nm and <1 μm, Sigma UK) were sterilised by heat treatment for 4h at 180°C. Agarose-particle suspensions were prepared by mixing warm 2% (w/v) low-melting-point agarose solution with the particles dispersed by sonication in DMEM culture media. The suspensions were then allowed to set at room temperature for 10 min in 96 well culture plates. Sub-confluent L929 murine fibroblasts were cultured on the prepared gels for up to 6 days in 5% (v/v) CO. 2. at 37°C. After incubation, the viability of cells was measured using the ATP-lite 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. The gels were observed to ensure uniform distribution of particles and migration of cells into the gel. No significant reduction in viability was observed for nanoscale and micron-sized Si. 3. N. 4. particles at low doses (0.5 μm. 3. per cell) and high doses (50 μm. 3. per cell), or for UHMWPE wear debris at high doses (100 μm. 3. per cell) [Figure1]. Moreover, the viability was significantly reduced for high doses of CoCr wear debris (50 μm. 3. per cell) and the positive control, camptothecin (2 μg.ml. −1. ) at day 6 [Figure1]. These results are consistent with the literature [2,3] and therefore validate our 3D agarose cell culture method for comparing cytotoxicity of polymer, metal and ceramic particles in a single assay, simultaneously. Conclusion. Biocompatibility ofpolymer, metal and ceramic wear debris can be tested simultaneously by using 3D particle embedded agarose gels. 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

Background. Additive manufacturing (AM) has created many new avenues for material and manufacturing innovation. In orthopaedics, metal additive manufacturing is now widely used for production of joint replacements, spinal fusion devices, and cranial maxillofacial reconstruction. Plastic additive manufacturing on the other hand, has mostly been utilized for pre-surgical planning models and surgical cutting guides. The addition of pharmaceuticals to additively manufactured plastics is novel, particularly when done at the raw material level. The purpose of this study was to prove the concept of antibiotic elution from additively manufactured polymeric articles and demonstrate feasibility of application in orthopaedics. Methods. Using patented processes, three heat-stable antibiotics commonly used in orthopaedics were combined with six biocompatible polymers (2 bioresorbable) into filament and powder base materials for fused deposition modeling (FDM) and selective laser sintering (SLS) AM processes. Raw materials of 1%, 2%, and 5% antibiotic concentrations (by mass) were produced as well as a blend of all three antibiotics each at 1% concentration. Thin disks of 25 mm diameter were manufactured of each polymer with each antibiotic at all concentrations. Disks were applied to the center of circular petri dishes inoculated with a bacterium as per a standard zone of inhibition, or Kirby-Bauer disk diffusion tests. After 72 hours incubation, the zone of inhibited bacterial growth was measured. Periprosthetic joint infection (PJI) of the knee was selected as the proof-of-concept application in orthopaedics. A series of tibial inserts mimicking those of a common TKR system were manufactured via SLS using a bioresorbable base material (Figure 1). Three prototype inserts were tested on a knee wear simulator for 333,000 cycles following ISO 14242–1:2014 to approximate 2–4 months of in vivo use between surgeries of a 2-stage procedure for PJI. Gravimetric measurement and visual damage assessment was performed. Results. Bacterial growth was inhibited to a mean diameter of 32.3 mm (FDM) and 42.2 mm (SLS) for nearly all combinations of polymers and concentrations of antibiotics. Prototype tibial inserts experienced an average of 200 mg of wear during testing and demonstrated no evidence of cracking, delamination or significant deformation (Figure 2). Conclusion. Bench-level testing of these novel antibiotic-eluting polymers demonstrates feasibility for their application in orthopaedic medicine. In particular, treatment of stubborn PJI with potential for increased and sustained antibiotic elution, patient-specific cocktailing, and maintenance of knee joint structure and function compared to existing PJI products and practices. Subsequent testing for these novel polymers will determine static and dynamic (wear-induced) antibiotic elution rates. For any figures or tables, please contact the authors directly

Structural bone allografts are a viable option in reconstructing massive bone defects in patients following musculoskeletal (MSK) tumour resection and revision hip/knee replacements. To decrease infection risk, bone allografts are often sterilised with gamma-irradiation, which consequently degrades the bone collagen connectivity and makes the bone brittle. Clinically, irradiated bone allografts fracture at rates twice that of fresh non-irradiated allografts. Our lab has developed a method that protects the bone collagen connectivity through ribose pre-treatment while still undergoing gamma-irradiation. Biomechanical testing of bone pretreated with our method provided 60–70% protection of toughness and 100% protection of strength otherwise lost with conventional irradiation. This study aimed to determine if the ribose-treated bone allografts are biocompatible with host bone. The New Zealand White rabbit (NZWr) radius segmental defect model was used, in which 15-mm critically-sized defects were created. Bone allografts were first harvested from the radial diaphysis of donor female NZWr, and treated to create 3 graft types: C=untreated controls, I=conventionally-irradiated (33 kGy), R=our ribose pretreated + irradiation method. Recipient female NZWr (n=24) were then evenly randomised into the 3 graft groups. Allografts were surgically fixed with a 0.8-mm Kirschner wire. Post-operative X-rays were taken at 2, 6, and 12 weeks, with bony healing assessed by a blinded MSK radiologist using an established radiographic scoring system. The reconstructed radii were retrieved at 12 weeks and analysed using bone histomorphometry and microCT. Kruskal-Wallis and Mann-Whitney tests were utilised to compare groups, with statistical significance when p<0.05. Radiographic analysis revealed no differences in periosteal reaction and degree of osteotomy site union between the groups at any time point. Less cortical remodeling was observed in R and I grafts compared to untreated controls at 6 weeks (p=0.004), but was no longer evident by 12 weeks. Radiographic union was achieved in all groups by 12 weeks. Histologic and microCT analysis further confirmed union at the graft-host bone interface, with the presence of mineralising callus and osteoid. Histomorphometry also showed the bridging external callus originated from host bone periosteum and a distinct cement line between allograft and host bone was present at the union site. Previous studies have shown that the presence of non-enzymatic glycation end products in bone can impair fracture healing. However, these studies investigated bony healing in the setting of diabetic states. Our findings showed that under normal conditions, ribose pretreated grafts healed at rates similar to controls via mechanisms also seen in retrieved human allografts clinically in use. These findings that grafts pretreated with our method are biocompatible with host bone in the rabbit help to further advance this technology for clinical trials