Polycrystalline Diamond Coating on Orthopedic Implants: Realization and Role of Surface Topology and Chemistry in Adsorption of Proteins and Cell Proliferation.

Polycrystalline diamond has the potential to improve the osseointegration of orthopedic implants compared to conventional materials such as titanium. However, despite the excellent biocompatibility and superior mechanical properties, the major challenge of using diamond for implants, such as those used for hip arthroplasty, is the limitation of microwave plasma chemical vapor deposition (CVD) techniques to synthesize diamond on complex-shaped objects. Here, for the first time, we demonstrate diamond growth on titanium acetabular shells using the surface wave plasma CVD method. Polycrystalline diamond coatings were synthesized at low temperatures (∼400 °C) on three types of acetabular shells with different surface structures and porosities. We achieved the growth of diamond on highly porous surfaces designed to mimic the structure of the trabecular bone and improve osseointegration. Biocompatibility was investigated on nanocrystalline diamond (NCD) and ultrananocrystalline diamond (UNCD) coatings terminated either with hydrogen or oxygen. To understand the role of diamond surface topology and chemistry in the attachment and proliferation of mammalian cells, we investigated the adsorption of extracellular matrix proteins and monitored the metabolic activity of fibroblasts, osteoblasts, and bone-marrow-derived mesenchymal stem cells (MSCs). The interaction of bovine serum albumin and type I collagen with the diamond surfaces was investigated by confocal fluorescence lifetime imaging microscopy (FLIM). We found that the proliferation of osteogenic cells was better on hydrogen-terminated UNCD than on the oxygen-terminated counterpart. These findings correlated with the behavior of collagen on diamond substrates observed by FLIM. Hydrogen-terminated UNCD provided better adhesion and proliferation of osteogenic cells, compared to titanium, while the growth of fibroblasts was poorest on hydrogen-terminated NCD and MSCs behaved similarly on all tested surfaces. These results open new opportunities for application of diamond coatings on orthopedic implants to further improve bone fixation and osseointegration.

Strength of side-to-side and step-cut repairs in tendon transfers: biomechanical testing of porcine flexor tendons.

The aim of the study was to compare side-to-side with step-cut repairs to determine how much of the width it is possible to remove and still keep the repair strong enough to start active mobilization. Porcine flexor tendons were used to create side-to-side, one-third step-cut and half step-cut repairs. There were 15 repairs in each group. The tensile properties of the constructs were measured in a biomechanical testing machine. All repairs failed by the sutures splitting the tendon longitudinally. The maximum load and stiffness were highest in the side-to-side group. Our findings suggest that the half step-cut repair can withstand the forces exerted during active unrestricted movement of the digits in tendons of this size. The advantage of the step-cut repair is reduced bulkiness and less friction, which might compensate for the difference in strength.

Cementing technique for primary knee arthroplasty: a scoping review.

Background and purpose - The optimal cementing technique for primary total knee arthroplasty (TKA) remains unclear. We therefore performed a scoping review based on available studies regarding cementation technique in primary TKA and unicondylar knee arthroplasty (UKA).Patients and methods - A search in 3 databases identified 1,554 studies. The inclusion criteria were literature that studied cementing technique in primary TKA or UKA. This included cement application methods, full or surface cementing, applying cement to the bone and/or prosthesis, stabilization of the implant during curing phase, bone irrigation technique, drilling holes in the bone, use of suction, and the timing of cementation. 57 studies met the inclusion criteria.Results - The evidence was unanimously in favor of pulsatile lavage irrigation, drying the bone, and drilling holes into the tibia during a TKA. All studies concerning suction recommended it during TKA cementation. 7 out of 11 studies favored the use of a cement gun and no studies showed that finger packing was statistically significantly better than using a cement gun. There is evidence that full cementation should be used if metal-backed tibial components are used. Applying the cement to both implant and bone seems to give better cement penetration.Interpretation - There are still many knowledge gaps regarding cementing technique in primary TKA. There seems to be sufficient evidence to recommend pulsatile lavage irrigation of the bone, drilling multiple holes, and drying the bone before cementing and implant insertion, and applying cement to both implant and on the bone.

Strength of Pulvertaft modifications: tensile testing of porcine flexor tendons.

The aim of the study was to present two new modifications of the Pulvertaft weave, allowing a higher number of weaves without the need for a longer overlap. The mechanical properties were measured and compared with the traditional technique. Forty-five pairs of porcine flexor tendons were randomized to a Pulvertaft repair with three weaves, a Double Pulvertaft and Locking Pulvertaft repairs. In the last two repairs one of the tendons in each repair was split in two before weaving. A difference in the maximum stiffness was observed between the three groups (p = 0.024). All repairs failed by the sutures being sheared through the tendons splitting the tendon fibres longitudinally. The two modifications were both stronger than the Pulvertaft weave and provide an alternative when a strong connection is needed and a longer overlap is impossible.

The effect of blood protein adsorption on cellular uptake of anatase TiO2 nanoparticles.

Protein adsorption onto nanoparticles (NPs) in biological fluids has emerged as an important factor when testing biological responses to NPs, as this may influence both uptake and subsequent toxicity. The aim of the present study was to quantify the adsorption of proteins onto TiO2 NPs and to test the influence on cellular uptake. The surface composition of the particles was characterized by thermal analysis and by X-ray photoelectron spectroscopy. The adsorption of three blood proteins, ie, human serum albumin (HSA), γ-globulins (Glbs), and fibrinogen (Fib), onto three types of anatase NPs of different sizes was quantified for each protein. The concentration of the adsorbed protein was measured by ultraviolet-visible spectrophotometry using the Bradford method. The degree of cellular uptake was quantified by inductivity coupled plasma mass spectroscopy, and visualized by an ultra-high resolution imaging system. The proteins were adsorbed onto all of the anatase NPs. The quantity adsorbed increased with time and was higher for the smaller particles. Fib and Glbs showed the highest affinity to TiO2 NPs, while the lowest was seen for HSA. The adsorption of proteins affected the surface charge and the hydrodynamic diameter of the NPs in cell culture medium. The degree of particle uptake was highest in protein-free medium and in the presence HSA, followed by culture medium supplemented with Glbs, and lowest in the presence of Fib. The results indicate that the uptake of anatase NPs by fibroblasts is influenced by the identity of the adsorbed protein.

Role of physicochemical characteristics in the uptake of TiO2 nanoparticles by fibroblasts.

The relation between the physico-chemical properties of nanoparticles (NPs) and the degree of cellular uptake is incompletely elucidated. In this study, we investigated the influence on the cellular uptake of a wide range of fully characterized TiO2 NPs. L929 fibroblasts were exposed for 24 h to clinically relevant concentrations of nano-TiO2 and the degree of their association was assessed by ultrahigh resolution imaging microscopy (URI), scanning (SEM) and transmission (TEM) electron microscopy, as well as inductivity coupled plasma-mass spectroscopy (ICP-MS). The role of actin polymerization, a central feature of active internalization, was also studied and the results indicated that the internalization of TiO2 NPs involves a combination of actin-dependent uptake of large agglomerates as well as non actin-dependent uptake of small agglomerates. SEM and TEM revealed that the agglomerates of all NPs types were attached to the cellular membrane as well as internalized and confined inside cytoplasmic vesicles. URI and ICP-MS demonstrated that the particle association with cells was dose-dependent. The highest association was observed for spherical particles having mixed anatase-rutile crystallographic phase and the lowest for spindle-shaped rutile particles. ICP-MS revealed that the association was size-dependent in the order 5>10>40 nm for anatase spherical nanoparticles.

Is there still a place for the cemented titanium femoral stem? 10,108 cases from the Norwegian Arthroplasty Register.

BACKGROUND AND PURPOSE: Despite the fact that there have been some reports on poor performance, titanium femoral stems intended for cemented fixation are still used at some centers in Europe. In this population-based registry study, we examined the results of the most frequently used cemented titanium stem in Norway. PATIENTS AND METHODS: 11,876 cases implanted with the cemented Titan stem were identified for the period 1987-2008. Hybrid arthroplasties were excluded, leaving 10,108 cases for this study. Stem survival and the influence of age, sex, stem offset and size, and femoral head size were evaluated using Cox regression analyses. Questionnaires were sent to the hospitals to determine the surgical technique used. RESULTS: Male sex, high stem offset, and small stem size were found to be risk factors for stem revision, (adjusted RR = 2.5 (1.9-3.4), 3.3 (2.3-4.8), and 2.2 (1.4-3.5), respectively). Patients operated in the period 2001-2008 had an adjusted relative risk (RR) of 4.7 (95% CI: 3.0-7.4) for stem revision due to aseptic stem loosening compared to the period 1996-2000. Changes in broaching technique and cementing technique coincided with deterioration of the results in some hospitals. INTERPRETATION: The increased use of small stem sizes and high-offset stems could only explain the deterioration of results to a certain degree since the year 2000. The influence of discrete changes in surgical technique over time could not be fully evaluated in this registry study. We suggest that this cemented titanium stem should be abandoned. The results of similar implants should be carefully evaluated.

Agglomeration and sedimentation of TiO2 nanoparticles in cell culture medium.

The physicochemical characterization of nanoparticles in suspension is a prerequisite for the adequate assessment of their potential biological effect. Little is known to date about the colloidal stability of TiO2 nanoparticles in cell culture medium. This study investigates the effect of particle concentration, ionic strength, pH, and the presence of fetal bovine serum (FBS) and human serum albumin (HSA) on the colloidal stability of TiO2 nanoparticles in RPMI cell culture medium, by sedimentation measurements, dynamic light scattering, and electrokinetic measurements (zeta-potential). TEM revealed that the particles were polydisperse, with diameters ranging from approximately 15 to approximately 350 nm. The agglomeration rate and sedimentation rate increased with particles' concentration. The size of the agglomerates at 100 mg/L TiO2 was significantly reduced, from 1620+/-160 to 348+/-13 and 378+/-15 nm, upon the addition of 10% (v/v) FBS and 1% (w/w) HSA, respectively. The isoelectric point of TiO2 in water was 2.9 and the measured zeta-potential in RPMI was -16+/-2 mV at pH 7.4. A slight increase in the zeta-potential of TiO2 in RPMI was observed upon the addition of FBS and HSA. The addition of FBS and HSA prevented high agglomeration, leading to a stable dispersion of TiO2 nanoparticles for at least 24 h, possibly due to steric stabilization of the particles.

Induction of cell death by TiO2 nanoparticles: studies on a human monoblastoid cell line.

The cellular responses to degradation products from titanium (Ti) implants are important indicators for the biocompatibility of these widely used implantable medical devices. The potential toxicity of nanoparticulate matter released from implants has been scarcely studied. The aim of this study was to investigate the potential of TiO2 nanoparticles to induce modifications characteristic for death by apoptosis and/or necrosis in U937 human monoblastoid cells. Suspensions of TiO2 nanoparticles with a diameter <100nm were prepared in RPMI cell culture medium at concentrations that covered a range (0.005-4mg/ml) corresponding to concentrations found in blood, plasma, or in tissues surrounding Ti implants. The cells were exposed to the nanoparticulate suspensions for 24 and 48h and the responses were evaluated by flow cytometry and transmission electron microscopy. TiO2 nanoparticles induced both apoptotic and necrotic modifications in U937 cells.

Blood mercury following DMPS administration to subjects with and without dental amalgam.

The use of DMPS as a diagnostic tool in patients with symptoms allegedly caused by mercury from dental amalgam fillings is disputed. We have previously shown that the mercury concentrations in urine cannot be used in such a way. In the present study, we wished to evaluate the effect on blood mercury levels (B-Hg) following intravenously injected DMPS in four groups of subjects: 19 controls without amalgam experience; 21 healthy controls with amalgam fillings; 20 patients with self-reported symptoms from existing dental amalgams; and 20 patients who had removed amalgam fillings. A single dose of DMPS (2 mg/kg) was injected. Blood samples were collected prior to the injection and after 15, 30, 120 min, and after 24 h, and mercury was analyzed by cold vapor atomic absorption spectrophotometry. All groups showed an initial drop of 24 to 30% in the blood levels, approaching baseline values (2.5-5.5 microg/l) after 2 h. The subjects with no amalgam experience had the lowest mercury values. There was no significant difference between the three groups with such experience. There were no significant differences between the two groups with amalgam fillings present. Patients with symptoms allegedly caused by amalgam were not different from the control groups. There were indications that part of the urinary mercury excreted during the first 30 min originated from blood.