In vitro and in vivo activation of polymorphonuclear leukocytes in response to particulate debris

Hyaluronic acid-British anti-Lewisite as a safer chelation therapy for the treatment of arthroplasty-related metallosis

Cobalt-containing alloys are useful for orthopedic applications due to their low volumetric wear rates, corrosion resistance, high mechanical strength, hardness, and fatigue resistance. Unfortunately, these prosthetics release significant levels of cobalt ions, which was only discovered after their widespread implantation into patients requiring hip replacements. These cobalt ions can result in local toxic effects-including peri-implant toxicity, aseptic loosening, and pseudotumor-as well as systemic toxic effects-including neurological, cardiovascular, and endocrine disorders. Failing metal-on-metal (MoM) implants usually necessitate painful, risky, and costly revision surgeries. To treat metallosis arising from failing MoM implants, a synovial fluid-mimicking chelator was designed to remove these metal ions. Hyaluronic acid (HA), the major chemical component of synovial fluid, was functionalized with British anti-Lewisite (BAL) to create a chelator (BAL-HA). BAL-HA effectively binds cobalt and rescues in vitro cell vitality (up to 370% of cells exposed to IC50 levels of cobalt) and enhances the rate of clearance of cobalt in vivo (t1/2 from 48 h to 6 h). A metallosis model was also created to investigate our therapy. Results demonstrate that BAL-HA chelator system is biocompatible and capable of capturing significant amounts of cobalt ions from the hip joint within 30 min, with no risk of kidney failure. This chelation therapy has the potential to mitigate cobalt toxicity from failing MoM implants through noninvasive injections into the joint.

Aseptic and septic prosthetic joint loosening: Impact of biomaterial wear on immune cell function, inflammation, and infection

The success of total joint replacements has led to consistent growth in the use of arthroplasty in progressively younger patients. However, more than 10 percent of patients require revision surgeries due to implant failure caused by osteolytic loosening. These failures are classified as either aseptic or septic and are associated with the presence of particulate wear debris generated by mechanical action between implant components. Aseptic loosening results from chronic inflammation caused by activation of resident immune cells in contact with implant wear debris. In contrast, septic loosening is defined by the presence of chronic infection at the implant site. However, recent findings suggest that subclinical biofilms may be overlooked when evaluating the cause of implant failure, leading to a misdiagnosis of aseptic loosening. Many of the inflammatory pathways contributing to periprosthetic joint infections are also involved in bone remodeling and resorption. In particular, wear debris is increasingly implicated in the inhibition of the innate and adaptive immune response to resolve an infection or prevent hematogenous spread. This review examines the interconnectivity of wear particle- and infection-associated mechanisms of implant loosening, as well as biomaterials-based strategies to combat infection-related osteolysis.

pH and metal concentration of synovial fluid of osteoarthritic joints and joints with metal replacements

BACKGROUND

Due to degradation and metal dissolution during articulation of metal joint replacements the chemical periprosthetic environment may change. The aim was to establish whether metal replacements cause the local changes in pH and elevated metal concentrations.

METHODS

pH was measured on samples from 167 patients: native hip and knee osteoarthritic joints, joints with hip and knee replacements revised for aseptic or septic reasons. pH of synovial fluid and periprosthetic tissue was measured perioperatively using a microelectrode and pH indicator papers for removed metal components. Metal concentrations were measured in 21 samples using inductively coupled plasma mass spectrometry.

RESULTS

The mean pH value of synovial fluid at native osteoarthritic joints (n = 101) was 7.78 ± 0.38. The mean pH value of synovial fluid at revision aseptic operation (n = 58) was 7.60 ± 0.31, with statistically significant difference (p = 0.002) compared to native osteoarthritic joints. The mean pH value of synovial fluid at revision septic operation (n = 8) was 7.55 ± 0.25, with statistically significant difference (p = 0.038) compared to native osteoarthritic joints. Measurements in tissue and at stems were not reliable. In the majority of samples taken at revision increased levels of cobalt and chromium were measured.

CONCLUSION

A small but statistically significant difference was observed in the pH of synovial fluid between natural joints with degenerative diseases and joints treated with metal replacements. Based on the increased metal levels we expected the value of pH to be lower, but the influence of metal ions is counteracted by the buffering capacity of human body. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2507-2515, 2017.

Cytokine secretion from human peripheral blood mononuclear cells cultured in vitro with metal particles

The failure of implanted medical devices can be associated with changes in the production of cytokines by cells of the immune system. Cytokines released by peripheral blood mononuclear cells upon contact with metal particles were quantified to understand their role in implantation intergration and their importance as messengers in the recruitment of T-lymphocytes at the implantation site. Opsonization was utilised to understand the influence of serum proteins on particle-induced cytokine production and release. Different metal compositions were used in the particulate format, Titanium (Ti), Titanium alloy (Ti6Al4V), and Stainless Steel 316L (SS), and were cultured in vitro with a mixed population of monocytes/macrophages and lymphocytes. The cells were also exposed to an exogenous stimulant mixture of phytohemagglutinin-P and interferon-gamma (IFN-γ) and opsonized particles with human serum. Interleukins, IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IFN-γ, and tumor necrosis factor-alpha (TNF-α) were investigated using enzyme-linked immunosorbent assay as they are an indicator of the inflammation evoked by particulate metals. It has been experimentally evidenced that metal particles induced higher amounts of IL-6 and IL-1 but very low amounts of TNF-α. T-lymphocyte activation was evaluated by the quantification of IL-2 and IFN-γ levels. The results showed that nonopsonized and opsonized metal particles did not induce the release of increased levels of IL-2 and IFN-γ.

Free Radical Production in Immune Cell Systems Induced by Ti, Ti6Al4V and SS Assessed by Chemiluminescence Probe Pholasin Assay

The oxidative burst of human blood cells in the presence of different metal materials was investigated using chemiluminescence assay. Commercial pure titanium (Ti), titanium alloy (Ti6Al4V), and stainless steel 316L (SS) in particulate form with <20 μm in size were used. The effect of particulate materials opsonisation on the upregulation of the respiratory burst production by blood cells was also assessed. The largest chemiluminescence response was achieved after simultaneous injection of the stimulants fMLP+PMA. Moreover, Ti and SS induced a greater inflammatory reaction compared to Ti6Al4V, since the respiratory burst mounted was higher for both materials after opsonisation treatment. These results suggest that in vitro chemiluminescence response and respiratory burst measurements proved to be composition and treatment dependent.

A five to seven year follow-up comparing computer-assisted vs freehand TKR with regard to clinical parameters

PURPOSE

Computer-assisted knee surgery has become established in routine clinical practice. Still, there is no study investigating midterm clinical outcome after five to seven years postoperatively. We aimed to test the hypothesis that there is no difference either for subjective [Western Ontario and McMaster Universities (WOMAC) scores] or for objective (Knee Society Score, degree of flexion) criteria between computer-assisted total knee replacement (TKR) and freehand TKR after 5.6-7.3 years.

METHODS

We performed a matched-pair analysis; 100 patients who received a primary TKR were investigated after a median follow-up of 6.25 years. Group A was operated on with the support of a computer system, while surgery on patients in group B was performed with the freehand technique. We determined WOMAC Score, Knee Society Score and degree of flexion.

RESULTS

Overall we found similar results for WOMAC Score [group A: 42.98 (SD 13.80); group B: 41.54 (SD 15.01; p = 0.62)], Knee Society Score [group A: 168.20 (SD 21.94); group B: 166.60 (SD 21.44; p = 0.71)] and range of motion [group A: 106° (SD 9.19); group B 107° (SD 7.44; p = 0.62)].

CONCLUSIONS

No significant differences in midterm clinical outcome were found after TKR performed in the freehand vs computer-assisted technique.

Two year follow-up comparing computer assisted versus freehand TKR on joint stability, muscular function and patients satisfaction

Computer assisted (CAS) knee surgery has been established in clinical routine. There is still no study that investigates clinical outcome. Fifty patients who received a primary total knee replacement 2 years before were investigated. These patients were divided into two groups of matched-pairs; group A was operated in the freehand technique and group B with support of a computer system. We compared Womac score, Knee Society score, range of motion, leg alignment, knee stability and isokinetic muscle strength. We found similar results for WOMAC, Knee Society score and isokinetic muscle force. Stability and range of motion revealed slightly better values for the CAS group. A statistically significant difference could only be demonstrated for postoperative leg alignment. Two years after freehand versus computer assisted TKR we found slightly better values for range of motion and ligamentous stability. Only postoperative leg alignment was statistically better in the CAS group.

Biocompatibility testing of simulated total joint arthoplasty articulation debris

Surface characterization was performed to evaluate the surface condition of an uncoated cobalt alloy disc (control), and discs with medium and thick boron coatings for total joint articulating surfaces. Discs were characterized by scanning electron microscopy before and after dissolution studies. Chemical analyses of elemental transfer to the solution were assessed to evaluate the surface stability of the new coating. An in vivo biocompatibility study for particulates [of boron (B), titanium alloy (Ti), cobalt alloy (Co), and combinations of B + Ti and B + Co] was performed using a rat air pouch model. The inflammatory reactions to particulates were evaluated histologically and histochemically. No physical alteration was seen in the discs after the dissolution studies, and the elemental transfer to the dissolution solution was minimal. The cytokines, tumor necrosis factor (TNFalpha), and histology results from these simulated debris showed similar and moderate level responses magnitudes for the boron and mixtures and the primary alloy particulates. The conclusion from this initial study was that assessments of the coated discs showed physical properties similar to control. Also results from the in vivo studies of simulated wear debris from boron coatings on titanium and cobalt alloys demonstrated biocompatibility profiles that were mild to moderate and similar to prior analyses of wear debris products in synovial pouch models.

Bone response to endosseous titanium implants surface-modified by blasting and chemical treatment: A histomorphometric study in the rabbit femur

This study evaluated the effects of the addition of oxide structure with submicron-scale porous morphology on the periimplant bone response around titanium (Ti) implants with microroughened surfaces. Hydroxyapatite-blasted Ti implants with (experimental) and without (control) a porous oxide structure produced by chemical treatment were investigated in a rabbit femur model. Surface characterizations and in vivo bone response at 4 and 8 weeks after implantation were compared. The experimental implants had submicron-scale porous surface structure consisted of anatase and rutile phase, and the original R(a) values produced by blasting were preserved. The histomorphometric evaluation demonstrated statistically significantly increased bone-to-implant contact (BIC) for experimental implants, both in the three best consecutive threads (p < 0.01) and all threads (p < 0.05) at 4 weeks. There was no remarkable difference in the BIC% or bone area percentage between the two groups at 8 weeks. The porous Ti oxide surface enhanced periimplant bone formation around the Ti implants with microroughened surfaces at the early healing stage. Based on the results of this study, the addition of crystalline Ti oxide surface with submicron-sized porous morphology produced by chemical treatment may be an effective approach for enhancing the osseointegration of Ti implants with microroughened surfaces by increasing early bone-implant contact.

Microvasculatory reaction of skeletal muscle to Ti-15Mo in comparison to well-established titanium alloys

Beta-titanium alloys such as Ti-15Mo are increasingly utilized for orthopaedic implant applications because of their excellent corrosion resistance and low elastic modulus. Particularly in osteosynthesis, where the biomaterial stands in direct contact to soft tissue, undesirable biologic reactions may have severe consequences especially in the vulnerable state of trauma and added iatrogenic damage to the microvascular system. In a comparative study we therefore assessed in vivo nutritive perfusion and leukocytic response of striated muscle to the biomaterials Ti-15Mo, Ti-6Al-4V and Ti-6Al-7Nb, thereby drawing conclusions on their short term inflammatory potential. Utilizing the well established skinfold chamber preparation in the hamster and intravital fluorescence microscopy, we could not demonstrate any significant discrepancies between the three alloys. All metals induced an initial moderate inflammatory response in skeletal muscle microcirculation. While recuperation of animals treated with Ti-15Mo and Ti-6Al-7Nb was prompt, we documented a slightly more sluggish recovery of Ti-6Al-4V treated animals. A gross toxicity was not observed for any of the alloys. Conclusively, Ti-15Mo, Ti-6Al-4V and Ti-6Al-7Nb induce an only transient inflammatory answer of the striated muscle microvascular system. Our results indicate that on the microvascular level the tested bulk Ti-alloys do not cause enduring biologic impairment in muscle.

Inactivation of a subpopulation of human neutrophils by exposure to ultrahigh-molecular-weight polyethylene wear debris

Polymorphonuclear neutrophils, a first line of defence against invading microbial pathogens, may be attracted by inflammatory mediators triggered by ultrahigh-molecular-weight polyethylene (UHMWPE) wear particles released from orthopaedic prostheses. Phagocytosis of UHMWPE particles by neutrophils may indirectly compromise their phagocytic-bactericidal mechanisms, thus enhancing host susceptibility to microbial infections. In an in vitro assay, pre-exposure of purified human neutrophils to UHMWPE micrometre- and submicrometre-sized wear particles interfered with subsequent Staphylococcos aureus uptake in a heterogeneous way, as assessed by a dual label fluorescence microscopic assay that discriminated intracellular rhodamine-labelled UHMWPE particles from fluorescein isothiocyanate-labelled S. aureus. Indeed, a higher percentage (44%) of neutrophils having engulfed UHMWPE particles lost the ability to phagocytize S. aureus, compared with UHMWPE-free neutrophils (<3%). Pre-exposure of neutrophils to UHMWPE wear particles did not impair but rather stimulated their oxidative burst response in a chemoluminescence assay. The presence of UHMWPE wear particles did not lead to significant overall consumption of complement-mediated opsonic factors nor decreased surface membrane display of neutrophil complement receptors. In conclusion, engulfment of UHMWPE wear particles led to inactivation of S. aureus uptake in nearly half of the neutrophil population, which may potentially impair host clearance mechanisms against pyogenic infections.

Genetic susceptibility to total hip arthroplasty failure--positive association with mannose-binding lectin

Mannose-binding lectin (MBL) may be involved in the biologic cascade of events initiated by wear debris and bacterial infection around loosened total hip arthroplasties (THAs). Individual responses to such stimuli may be dictated by genetic variation caused by single nucleotide polymorphisms (SNPs). We performed a case-control study on 4 MBL SNPs using case patients (n = 91) with aseptic loosening or deep infection (n = 71). Control subjects (n = 150) had clinically and radiologically well-fixed THAs for more than 10 years. Frequency of the C allele (P = .001) and that of the genotype C/C (P = .004) for the -550 SNP were associated with aseptic failure. The codon 54 SNP G allele (P = .012) and G/G genotype (P = .027) frequencies were associated with aseptic failure as well. In the septic group, the frequency of the C allele (P = .01) and that of the genotype C/C (P = .05) for the -550 SNP were significant. Failure of THAs may be under genetic influence to candidate susceptibility genes such as MBL.

Abriebpartikel

The aseptic prosthetic loosening of hip and knee prosthesis is the most important cause of implant insufficiency. Bone loss as a result of the biological effect of wear particles is the main cause of such loosening. Wear particles develop their biological activity along different cellular pathways, above all via macrophages, foreign body giant cells as well as fibroblasts of the periprosthetic membrane. These cells induce particle-dependent bone resorption by means of proinflammatory cytokines, such as IL-1beta, TNF-alpha, IL-6 and PGE2. These factors induce the activation of osteoclasts as well as the suppression of osteoblasts. Neutrophil granulocytes and lymphocytes do not play an important role in the process of aseptic loosening. The different wear particles, such as ultra-high molecular weight polyethylene, metal particles, ceramic particles and polymethylmethacrylate can be morphologically recognized very easily. From the clinical point of view, the differentiation between acute or chronic implant infection and particle induced prosthetic loosening is very important, with the histomorphological differential diagnosis between septic and aseptic loosening and their combination being the key clinicopathological factor.

The image of exocytosis during neutrophils and macrophages phagocytic activities in inflammation of mammary gland triggered by experimental Staphylococcus aureus infection

The experiments were carried out in five clinically normal virgin heifers. Before the experimental infection and at 24, 48, 72 and 168 h after the infection, respective mammary glands were rinsed with phosphate buffered saline. Neutrophils as well as macrophages underwent a classic exocytosis accompanied by translocation of lysosomal granules. The granules filled the protuberances of the plasmalemma and after the protuberances separated from the cell, they entered the extracellular space in the shape of round bodies of different sizes. After exocytosis, neutrophils displayed a smaller nucleus/cytoplasm ratio, a greater chromatin density of the nucleus, and an overall smaller size. Macrophages phagocytosed bacteria and/or neutrophils with and without signs of apoptosis (early and late apoptotic respectively) and neutrophils after exocytosis. Macrophages underwent cytolysis that was accompanied by extrusion of granules, phagosomes and phagolysosomes containing phagocytosed bacteria or neutrophils. Confluences were formed in which the process of digestion continued. Apoptosis of neutrophils gradually appeared and intensified in resolution of inflammation. The macrophages contributed to the inactivation of bacterial noxa as well as of histotoxic contents of neutrophils. Nevertheless, macrophages often underwent cytolysis at the site of inflammation.

[Advances in soft tissue management in total knee arthroplasty. The use of imageless navigation systems]

Computer aided surgery has become established in the clinical routine over the past years. There are some very good studies which show that navigation optimizes reconstruction of the leg axis in total knee replacement. The question of why outliers occur in spite of navigation has to be asked. It is clear that total knee replacement is not only a bony procedure, but the soft tissues have an immense influence on postoperative stability of the prosthesis over the full range of movement. Current navigation systems allow visualization of the leg axis and size of the extension and flexion gap, and support the surgeon during soft tissue management. The current paper shows how the anatomic approach and the position of the patella influence soft tissue tension and support the surgeon during release of soft tissues in severe leg axis deformities.

Two-year follow-up on joint stability and muscular function comparing rotating versus fixed bearing TKR

Mobile and fixed bearing in total knee replacement are still discussed controversially. In a retrospective, matched-pair study, we investigated 40 patients with computer-assisted (BrainLAB) primary total knee replacement (PFC Sigma, DePuy) performed two years before. Twenty patients each received a mobile bearing and a fixed bearing. We compared Womac Score, Knee Society Score, postoperative ROM, fluoroscopic measurement of knee stability in flexion and extension and isokinetic muscle strength using a Biodex-3 dynamometer. Both groups showed similar results concerning WOMAC Score (total rotating bearing: 23.05; fixed bearing: 22.57), KSS (rotating bearing: 174.89; fixed bearing: 176.1). Isokinetic muscle force demonstrated statistically significant superior results for knee flexion in the rotating bearing group. Medio-lateral stability revealed statistically significant superior results for the rotating bearing compared to fixed bearing in extension (P>0.05). In flexion only lateral stability was superior (P>0.05). Two-year clinical follow-up after computer-assisted total knee replacement resulted in good clinical outcome with high patient satisfaction. Statistically significant better values for the rotating platform group were found for the medio-lateral stability in extension and the peak flexion torque.

Short-term microvascular response of striated muscle to cp-Ti, Ti-6Al-4V, and Ti-6Al-7Nb

Due to excellent mechanical properties and good corrosion resistance, titanium-aluminium-vanadium (Ti-6Al-4V) and titanium-aluminium-niobium (Ti-6Al-7Nb) are extensively used for orthopedic surgery. Concern has been voiced concerning the implications of the constituent vanadium in Ti-6Al-4V on the surrounding environment. Particularly in osteosynthesis where the alloys stand in direct contact to skeletal muscle, undesirable biologic reactions may have severe consequences. In a comparative study, we assessed in vivo nutritive perfusion and leukocytic response of striated muscle to the metals Ti-6Al-4V, Ti-6Al-7Nb, and commercially pure titanium (cpTi), thereby drawing conclusions on their short-term inflammatory potential. In 28 hamsters, utilizing the dorsal skinfold chamber preparation and intravital microscopy, we quantified primary and secondary leukocyte-endothelial cell interaction, leukocyte extravasation, microvascular diameter change, and capillary perfusion in collecting and postcapillary venules of skeletal muscle. A manifest discrepancy between the metals concerning impact on local microvascular parameters was not found. All metals induced an only transient and moderate inflammatory response. Only a slight increase in leukocyte recruitment and a more sluggish recuperation of inflammatory parameters in animals treated with Ti-6Al-4V compared to the other two metals suggested a minor, overall not significant discrepancy in biocompatibility. Gross toxicity of bulk Ti-6Al-4V on surrounding tissue could not be found. Conclusively, the commonly used biomaterials Ti-6Al-4V, Ti-6Al-7Nb, and cpTi induce an only transient inflammatory answer of the skeletal muscle microvascular system. Our results indicate that on the microvascular level the tested bulk Ti-alloys and cpTi do not cause adverse biologic reactions in striated muscle.

Metallic shedding, surface finish changes, and extensive femoral osteolysis in the loose Spectron EF stem

The addition of a proximal rough surface finish in the satin finish Spectron stem (Spectron EF) reportedly does not alter its clinical performance. However, we have revised 15 Spectron EF stems because of aseptic loosening and extensive femoral osteolysis at early and intermediate-term followup, raising a question as to its safety. We sought to determine which interface has aseptic failure, the presence of massive femoral osteolysis, and the consequences of loosening at the implant-cement interface in the implant's surface finish. Fifteen patients with aseptic loosening of a proximal rough surface-finished Spectron EF stem at intermediate-term followup (Group A) were compared with seven patients having revisions of the same stem for infection or recurrent dislocation but without loosening (Group B). Radiographs for Group A showed debonding at the cement-implant interface and stem subsidence in 13 hips, and severe femoral osteolysis in seven, including two pathologic periprosthetic fractures. During revision surgery, all 13 subsided stems showed a metallic stained pseudomembrane and metallic shedding with polishing of the stem surface. None of the patients in Group B who had revision surgery had these changes. Aseptic failure of the Spectron EF stem was characterized by debonding, subsidence, and metallic shedding with concomitant massive femoral osteolysis and metallosis, which is similar to conditions reported for loose, rough cemented stems, but has not been reported for the satin finish Spectron stem.

LEVEL OF EVIDENCE

Therapeutic study, Level III (retrospective comparative study). See the Guidelines for Authors for a complete description of levels of evidence.

The effects of titanium and polymethylmethacrylate particles on osteoblast phenotypic stability

Wear particles generated following total joint arthroplasty interact with cells at the periprosthetic margin and induce an inflammatory response that contributes to osteolysis, aseptic loosening, and implant failure. This study examined the long-term effects of particles from two commonly implanted materials, titanium (Ti) and polymethylmethacrylate (PMMA), on cell viability and metabolism over a 21-day time course, using the human osteoblast-like cell line MG-63. Addition of particles was not associated with increased cell death or nitric oxide production at the particle concentration chosen. Collagen production was increased with exposure to titanium particles, whereas alkaline phosphatase and osteocalcin expression remained unchanged following exposure to both types of particles. The data show that titanium but not PMMA particles shifts bone cell metabolism to preferentially produce fibrous tissue rather than bone.

Human defensin 5 expression in intestinal metaplasia of the upper gastrointestinal tract

BACKGROUND

Upper gastrointestinal tract intestinal metaplasia (IM) is termed Barrett's oesophagus (BO) or gastric intestinal metaplasia (GIM), depending on its location. BO and GIM are associated with chemical exposure resulting from gastro-oesophageal reflux and chronic Helicobacter pylori infection, respectively. Paneth cells (PCs), characterised by cytoplasmic eosinophilic granules, are found in a subset of IM at these sites, but histology may not accurately detect them.

AIM

To determine human defensin 5 (HD5; an antimicrobial peptide produced by PCs) expression in BO and GIM, and to investigate its association with H pylori infection.

METHODS

Endoscopic biopsies from 33 patients with BO and 51 with GIM, and control tissues, were examined by routine histology and for H pylori infection and HD5 mRNA and protein expression.

RESULTS

In normal tissues, HD5 expression was specific for PCs in the small intestine. Five patients with BE and 42 with GIM expressed HD5, but few HD5 expressing cells in IM had the characteristic histological features of PCs. Most HD5 positive specimens were H pylori infected and most HD5 negative specimens were not infected.

CONCLUSIONS

HD5 immunohistochemistry was often positive in IM when PCs were absent by conventional histology. Thus, HD5 immunohistochemistry may be superior to histology for identifying metaplastic PCs and distinguishing GIM from BO. The higher frequency of HD5 expression in GIM than in BO is associated with a higher frequency of H pylori infection, suggesting that in IM PCs may form part of the mucosal antibacterial response.

Microvascular response of striated muscle to common arthroplasty-alloys: A comparativein vivo study with CoCrMo, Ti-6Al-4V, and Ti-6Al-7Nb

The impairment of skeletal muscle microcirculation by a biomaterial may have profound consequences. Due to excellent physical and corrosion characteristics, CoCrMo-, Ti-6Al-4V-, and Ti-6Al-7Nb-alloys are commonly used in orthopedic surgery. Yet concern has been raised with regard to the implications of inevitable corrosion product of these metals on the surrounding biologic environment, particularly in the case of CoCrMo. We, therefore, studied in vivo nutritive perfusion and leukocytic response of striated muscle to these alloys, thereby drawing conclusions on their inflammatory potential. In 28 hamsters, utilizing the dorsal skinfold chamber preparation and intravital microscopy, we could demonstrate that the implant material CoCrMo has a marked impact on local microvascular parameters. While the Ti-alloys Ti-6Al-4V and Ti-6Al-7Nb induced only a transient and moderate inflammatory response, the implantation of a CoCrMo sample led to a distinct and persistent activation of leukocytes combined with disruption of the microvascular endothelial integrity and marked leukocyte extravasation. Animals with Ti-alloys showed a clear tendency of recuperation, while in all but one CoCrMo-treated animals, a breakdown of microcirculation prior to the scheduled end of the experiment was observed. Overall, the alloy Ti-6Al-7Nb was tolerated slightly better than Ti-6Al-4V under the chosen test conditions, though this discrepancy was not statistically significant. Conclusively, the commonly used biomaterials Ti-6Al-7Nb and Ti-6Al-4V induce a considerably lower inflammatory response in the skeletal muscle microvascular system, compared to a CoCrMo-alloy. With a minimum of adverse host reaction, our results indicate that for this particular model Ti-alloys are better tolerated than CoCrMo implant materials.

In vitro assessment of proximal polyethylene contact surface areas and stresses in mobile bearing knees

Wear of the polyethylene (PE) insert in total knee arthroplasty remains a significant problem. The generation of biologically active wear particles may ultimately affect implant longevity through osteolysis or premature/catastrophic PE failure. The rate and pattern of wear is influenced by many factors, including component geometry and individual loading conditions, which determine the contact surface area and kinematics of the reconstructed knee. Contact areas and stresses at the proximal femoral-PE insert interface and distal PE-tibial interface contact surface areas were measured in nine mobile bearing total knee designs at 0, 30, 60, 90 and 110 degrees of flexion at 3600 N (5 x body weight) using a standardized test method. Proximal and, to a lesser degree, distal interface contact area footprints decreased significantly with increasing flexion angle based on the conformity of the designs, resulting in a corresponding increase in the mean and peak stresses.

Depleted uranium-uranyl chloride induces apoptosis in mouse J774 macrophages

Depleted uranium entering the body as a result of inhalation or embedded fragments becomes associated to a great extent with macrophages. As part of our continuing studies on the health effects of internalized depleted uranium, we investigated the effect of soluble depleted uranium-uranyl chloride on the mouse macrophage cell line, J774. Using a cytochemical staining protocol specific for uranium, we found that uranium uptake by the macrophages increased in a time-dependent manner. Treatment with 1, 10, or 100 microM depleted uranium-uranyl chloride resulted in decreased viability of the J774 cells within 24 h. Flow cytometric analysis of the treated cells with annexin V showed the translocation of phosphatidylserine from the inner face of the plasma membrane to the outer surface indicating the loss of phospholipid symmetry and the beginning of the apoptotic process. Significant differences in annexin V labeling between control cells and cells treated with 100 microM depleted uranium-uranyl chloride were apparent within 2 h. Other events associated with apoptosis, including morphological changes and DNA fragmentation, were also apparent after depleted uranium-uranyl chloride treatment. These results suggest that the uptake and concentration of soluble depleted uranium by macrophages initiates events that results in the apoptotic death of these cells.

Titanium particles induce the immediate early stress responsive chemokines IL-8 and MCP-1 in osteoblasts

Exposure of human osteoblasts to ultrafine titanium (Ti) particles has been shown to alter osteoblast gene expression. We previously reported that Ti particles can increase IL-6 release and suppress the gene expression of procollagens alpha1[I] and alpha1[III] in human osteoblasts. In this study, we now demonstrate that Ti particles can rapidly induce the chemotactic cytokines interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1), two immediate early stress responsive chemokines important for the activation and chemotaxis of neutrophils and macrophages, respectively. In MG-63 osteosarcoma cells and bone marrow derived primary osteoblasts Ti particles selectively increased the steady state levels of IL-8 and MCP-1 mRNA in a time and concentration dependent manner. The increased chemokine mRNA correlated with increased secretion of IL-8 and MCP-1 protein. Actinomycin D, a potent RNA polymerase II inhibitor, blocked the Ti particle induction of IL-8 and MCP-1 mRNA expression, whereas cycloheximide, which inhibits protein synthesis, failed to inhibit chemokine gene expression suggesting Ti particles directly target activation of chemokine gene transcription. Consistent with a transcriptional mechanism not involving new protein synthesis, we demonstrate that Ti particles induce the binding of the p65 and p50 subunits of the latent transcription factor NF-kappaB to the IL-8 gene promoter. Taken together, these data demonstrate that Ti particles can activate transcription of the stress responsive chemokine genes IL-8 and MCP-1 in human osteoblasts.

Impact of a nickel-reduced stainless steel implant on striated muscle microcirculation: a comparative in vivo study

The impairment of skeletal muscle microcirculation by a biomaterial may have profound consequences. With moderately good physical and corrosion characteristics, implant-quality stainless steel is particularly popular in orthopedic surgery. However, due to the presence of a considerable amount of nickel in the alloy, concern has been voiced in respect to local tissue responses. More recently a stainless steel alloy with a significant reduction of nickel has become commercially available. We, therefore, studied in vivo nutritive perfusion and leukocytic response of striated muscle to this nickel-reduced alloy, and compared these results with those of the materials conventional stainless steel and titanium. Using the hamster dorsal skinfold chamber preparation and intravital microscopy, we could demonstrate that reduction of the nickel quantity in a stainless steel implant has a positive effect on local microvascular parameters. Although the implantation of a conventional stainless steel sample led to a distinct and persistent activation of leukocytes combined with disruption of the microvascular endothelial integrity, marked leukocyte extravasation, and considerable venular dilation, animals with a nickel-reduced stainless steel implant showed only a moderate increase of these parameters, with a clear tendency of recuperation. Titanium implants merely caused a transient increase of leukocyte-endothelial cell interaction within the first 120 min, and no significant change in macromolecular leakage, leukocyte extravasation, or venular diameter. Pending biomechanical and corrosion testing, nickel-reduced stainless steel may be a viable alternative to conventional implant-quality stainless steel for biomedical applications. Concerning tolerance by the local vascular system, titanium currently remains unsurpassed.

Effect of plasma and matrix proteins on defensin-induced impairment of phagocytic killing by adherent neutrophils

Infection is too often associated with prosthetic devices. Increased susceptibility to infection at these surgical sites appears to be associated with defective local phagocytic killing. The mechanisms for neutrophil down-regulation, however, continue to be obscure. We have recently demonstrated that cytotoxic substances are released from granulocytes associated with materials. One group of releasants, the cationic human neutrophil peptide(s) (also called defensins) not only impairs the antimicrobial capacity of the granulocyte that releases it but also impairs bystander phagocytes. Because plasma or matrix proteins soon become associated with implants, we investigated the interactive effect of adding these proteins, singly and in combination, on the microbicidal effect of bystander cells. Some plasma/matrix proteins (whole plasma, albumin, fibrinogen, and fibronectin) strongly interfered with the anti-microbicidal effects generated by neutrophil-polystyrene interaction. Other proteins (vitronectin and laminin) were without effect. These results suggest that protein composition at the prosthetic implant site could have a significant effect on infectivity, depending on whether neutrophils releasants were attenuated. In the absence of attenuation, the local environment would be hostile to host defenses, permitting bacterial survival and proliferation.