Influence of particulate and dissociated metal-on-metal hip endoprosthesis wear on mesenchymal stromal cells in vivo and in vitro

Biocompatibility and Antibacterial Potential of Tetrahedral Amorphous Carbon (ta-C) Coatings on CoCrMo Alloy for Articulating Implant Surfaces

Premature implant failure, a critical concern in biomedical applications, is often attributed to poor biocompatibility and vulnerability to bacterial colonization. These issues are addressed by creating an endoprosthetic material with natural biocompatibility and antibacterial properties. In this in vitro study, the relaxed and unrelaxed tetrahedral amorphous carbon (ta-C) coatings were examined, both fabricated by the improved patented Pulsed Laser Deposition (PLD) technology. The chemical composition, surface roughness, hardness, topography, and wettability were analyzed. The ta-C surfaces were incubated by MM6 cells, E. coli and S. capitis bacteria for 24 h. PCR assessed the inflammatory response in MM6 cells, while fluorescence microscopy quantified adhering bacteria, and scanning electron microscopy examined local adhesion behavior. The results demonstrate comparable carbon phase composition, wettability properties, and hardness for both relaxed and unrelaxed ta-C. However, relaxed ta-C coating exhibited significantly fewer defects in terms of both quantity and quality, along with an antibacterial effect against E. coli. This suggests that the relaxed ta-C coating could contribute to the development of an endoprosthesis, preventing adverse biological reactions and implant-related infections, thus improving the longevity of the prosthesis.

Prosthetic Metals: Release, Metabolism and Toxicity

The development of metallic joint prostheses has been ongoing for more than a century alongside advancements in hip and knee arthroplasty. Among the materials utilized, the Cobalt-Chromium-Molybdenum (Co-Cr-Mo) and Titanium-Aluminum-Vanadium (Ti-Al-V) alloys are predominant in joint prosthesis construction, predominantly due to their commendable biocompatibility, mechanical strength, and corrosion resistance. Nonetheless, over time, the physical wear, electrochemical corrosion, and inflammation induced by these alloys that occur post-implantation can cause the release of various metallic components. The released metals can then flow and metabolize in vivo, subsequently causing potential local or systemic harm. This review first details joint prosthesis development and acknowledges the release of prosthetic metals. Second, we outline the metallic concentration, biodistribution, and elimination pathways of the released prosthetic metals. Lastly, we discuss the possible organ, cellular, critical biomolecules, and significant signaling pathway toxicities and adverse effects that arise from exposure to these metals.

Cobalt and Chromium Ions Impair Macrophage Response to Staphylococcus aureus Infection

Cobalt-chromium-molybdenum (CoCrMo) alloys are routinely used in arthroplasty. CoCrMo wear particles and ions derived from arthroplasty implants lead to macrophage-driven adverse local tissue reactions, which have been linked to an increased risk of periprosthetic joint infection after revision arthroplasty. While metal-induced cytotoxicity is well characterized in human macrophages, direct effects on their functionality have remained elusive. Synchrotron radiation X-ray microtomography and X-ray fluorescence mapping indicated that peri-implant tissues harvested during aseptic revision of different arthroplasty implants are exposed to Co and Cr in situ. Confocal laser scanning microscopy revealed that macrophage influx is predominant in patient tissue. While in vitro exposure to Cr3+ had only minor effects on monocytes/macrophage phenotype, pathologic concentrations of Co2+ significantly impaired both, monocyte/macrophage phenotype and functionality. High concentrations of Co2+ led to a shift in macrophage subsets and loss of surface markers, including CD14 and CD16. Both Co2+ and Cr3+ impaired macrophage responses to Staphylococcus aureus infection, and particularly, Co2+-exposed macrophages showed decreased phagocytic activity. These findings demonstrate the immunosuppressive effects of locally elevated metal ions on the innate immune response and support further investigations, including studies exploring whether Co2+ and Cr3+ or CoCrMo alloys per se expose the patients to a higher risk of infections post-revision arthroplasty.

Cold physical plasma treatment optimization for improved bone allograft processing

In musculoskeletal surgery, the treatment of large bone defects is challenging and can require the use of bone graft substitutes to restore mechanical stability and promote host-mediated regeneration. The use of bone allografts is well-established in many bone regenerative procedures, but is associated with low rates of ingrowth due to pre-therapeutic graft processing. Cold physical plasma (CPP), a partially ionized gas that simultaneously generates reactive oxygen (O2) and nitrogen (N2) species, is suggested to be advantageous in biomedical implant processing. CPP is a promising tool in allograft processing for improving surface characteristics of bone allografts towards enhanced cellularization and osteoconduction. However, a preclinical assessment regarding the feasibility of pre-therapeutic processing of allogeneic bone grafts with CPP has not yet been performed. Thus, this pilot study aimed to analyze the bone morphology of CPP processed allografts using synchrotron radiation-based microcomputed tomography (SR-µCT) and to analyze the effects of CPP processing on human bone cell viability and function. The analyzes, including co-registration of pre- and post-treatment SR-µCT scans, revealed that the main bone morphological properties (total volume, mineralized volume, surface area, and porosity) remained unaffected by CPP treatment if compared to allografts not treated with CPP. Varying effects on cellular metabolic activity and alkaline phosphatase activity were found in response to different gas mixtures and treatment durations employed for CPP application. It was found that 3 min CPP treatment using a He + 0.1% N2 gas mixture led to the most favourable outcome regarding a significant increase in bone cell viability and alkaline phosphatase activity. This study highlights the promising potential of pre-therapeuthic bone allograft processing by CPP prior to intraoperative application and emphasizes the need for gas source and treatment time optimization for specific applications.

Bone marrow from periacetabular osteotomies as a novel source for human mesenchymal stromal cells

BACKGROUND

Bone marrow-derived mesenchymal stromal cells (BM-MSCs) are used in regenerative medicine and related research involving immunomodulatory, anti-inflammatory, anti-fibrotic and regenerative functions. Isolation of BM-MSCs from samples obtained during total hip arthroplasty (THA) is routinely possible. Advanced age and comorbidities of the majority of patients undergoing THA limit their applicability. Our study aimed to evaluate the potential of bone marrow obtained during periacetabular osteotomy (PAO) as a novel source of BM-MSCs from young donors by analyzing cell yield and cell characteristics.

METHODS

Bone samples were obtained from the anterior Os ilium or superior Os pubis during PAO and from the femoral cavity during primary THA. Isolation of bone marrow-derived mononuclear cells (BM-MNCs) was performed by density gradient centrifugation. The samples from PAO and THA patients were compared in terms of BM-MSC yield, colony formation and the proportion of BM-MSCs within the BM-MNC population using flow cytometry analysis. The cells were characterized based on the expression of BM-MSC-specific surface markers. The functionality of the cells was compared by quantifying post-thaw viability, metabolic activity, proliferation capacity, senescence-associated beta galactosidase (SA-β-gal) expression, trilineage differentiation potential and major secretome proteins.

RESULTS

Isolation of BM-MNCs was possible in a reliable and reproducible manner when using bone from PAO containing more than 0.24 g bone marrow. PAO patients were younger than patients of the THA group. Bone obtained during PAO contained less bone marrow and led to a lower BM-MSC number after the first cell culture passage compared to BM-MSCs obtained during THA. BM-MSCs from PAO samples are characterized by a higher proliferation capacity. This results in a higher yield in cell culture passage two, when normalized to the sample weight. BM-MSCs from PAO patients showed increased secretion of TGF-β1, TIMP2, and VEGF upon osteogenic differentiation. BM-MSCs from PAO and THA patients revealed similar results regarding the onset of SA-β-gal expression and trilineage differentiation capacity.

CONCLUSIONS

We suggest that bone obtained during PAO is a promising novel source for BM-MSCs from young donors. Limited absolute cell yield due to low sample weight must be considered in early cell culture passages and might be critical for the range of clinical applications possible for BM-MSCs from this source. The higher proliferation capacity and increased growth factor secretion of BM-MSCs from young donors may be beneficial for future regenerative cell therapies, in vitro models, and tissue engineering.

Bone and Soft Tissue Reaction to Co(II)/Cr(III) Ions Stimulation in a Murine Calvaria Model: A Pioneering in vivo Study

Metal ions released during wear and corrosion of the artificial knee/hip joints are considered to contribute to aseptic implant failure. However, there are few convincing in vivo studies that demonstrate the effects of metal ions on bone and soft tissue. This study examined the in vivo effects of Co(II)/Cr(III) ions on mouse calvaria and the supra-calvaria soft tissue in an original mouse model. With the implantation of a helmet-like structure, we set up a subcutaneous cavity on the calvaria in which Co(II) Chloride or Cr(III) Chloride solutions were administered respectively. A layer of interface membrane formed on the calvaria along with the implantation of the helmet. The administered Cr(III) ions accumulated in the interface membranes while Co(II) disseminated into the circulation. Accumulated Cr(III) and related products induced local massive macrophage infiltration and skewed the bone metabolic balance. At last, we revealed that lymphocyte aggregates, which are the pathologic hallmark of human periprosthetic tissue, could be caused by either Co(II) or Cr(III) stimulation. These in vivo results may shed light on the effects and pathogenic mechanism of the Co(II)/Cr(III) ions released from the joint prosthesis. STATEMENT OF SIGNIFICANCE: Macrophage infiltration and lymphocyte aggregates are hallmarks of human joint periprosthetic tissue. We chronically administered Co(II)/Cr(III) ions on mouse calvaria and reproduced these two histopathologic hallmarks on mouse tissue based on an implanted helmet-like structure. Our results reveal that Cr(III) ions are locally accumulated and are effective in inducing macrophage infiltration and they can be phagocytosed and stored. However, the lymphocytes aggregates could be induced by both Co(II), Cr(III) and other unspecific inflammatory stimuli.

Noninfectious tissue interactions at periprosthetic interfaces

The success of hip arthroplasty is based on modern materials in addition to the continuous development of surgical techniques and clinical experience gained over six decades. The biocompatible implant materials used in hip arthroplasty can be textured or coated with biomimetic surfaces to ensure durable component ingrowth and moderate host response. Material integrity plays a critical role in the durability of the stable interface between implant components and periprosthetic tissues. Inflammation at the interfaces due to the release of degradation products from the implant materials is one of the causes of hip arthroplasty failure. This review summarizes the implant materials currently used in hip arthroplasty, their preclinical testing and the postoperative neogenesis of periprosthetic tissues, and the interactions of periprosthetic bone and the implant materials at the periprosthetic interfaces.

[Particle disease and its effects on periarticular tissue]

Particle disease is the condition caused by wear debris on surrounding tissues and influences the well-being of arthroplasty patients. This condition is multifactorial due to the type of bearing couple, head size and implant position. Subsequent periprosthetic osteolysis and soft tissue reactions, can lead to revision THA surgery. The periprosthetic synovial membrane (synovial-like interface membrane, SLIM) is used in diagnostics when the cause of implant failure is uncertain. Detailed analysis of synovial fluid and bone marrow could improve the diagnostic procedure and strengthen the cases for revision surgery and the underlying biology. A large number of research approaches on this topic have evolved and continue to be utilized in the clinic.

Scaffold Guided Bone Regeneration for the Treatment of Large Segmental Defects in Long Bones

Bone generally displays a high intrinsic capacity to regenerate. Nonetheless, large osseous defects sometimes fail to heal. The treatment of such large segmental defects still represents a considerable clinical challenge. The regeneration of large bone defects often proves difficult, since it relies on the formation of large amounts of bone within an environment impedimental to osteogenesis, characterized by soft tissue damage and hampered vascularization. Consequently, research efforts have concentrated on tissue engineering and regenerative medical strategies to resolve this multifaceted challenge. In this review, we summarize, critically evaluate, and discuss present approaches in light of their clinical relevance; we also present future advanced techniques for bone tissue engineering, outlining the steps to realize for their translation from bench to bedside. The discussion includes the physiology of bone healing, requirements and properties of natural and synthetic biomaterials for bone reconstruction, their use in conjunction with cellular components and suitable growth factors, and strategies to improve vascularization and the translation of these regenerative concepts to in vivo applications. We conclude that the ideal all-purpose material for scaffold-guided bone regeneration is currently not available. It seems that a variety of different solutions will be employed, according to the clinical treatment necessary.

[Postoperative outcomes and survival rates after aseptic revision total hip arthroplasty : What can patients expect from revision surgery?]

BACKGROUND

In 2020, more than 14,000 aseptic revision procedures for total hip arthroplasty (THA) were registered in Germany. Patient expectations of revision hip arthroplasty are not substantially different from expectations of primary hip replacement.

OUTCOME

However, revision surgery is associated with increased complication rates and a higher proportion of dissatisfied patients. In particular, poorer postoperative function and mobility as well as increased pain levels following revision THA have been described compared to the outcome after primary THA. Quality of life and return-to-work can also be impaired.

SURVIVAL RATE

Implant survival is influenced by age, BMI, and comorbidities of the patients, but also by the size and complexity of bone defects, the extent of periprosthetic soft tissue compromise and the choice of revision implant(s). In addition, the number of previous revision surgeries inversely correlates with the survival rates. Previous revisions have been shown to be associated with increased risks of aseptic loosening, instability and periprosthetic infection.

Clinical Outcomes, Metal Ion Levels, Lymphocyte Profiles, and Implant Survival Following Five Different Bearings of Total Hip Arthroplasty: A Mean 10-year Follow-up Study

BACKGROUND

Different bearings have been used in total hip arthroplasty (THA), but the long-term performance is still controversial. The purpose of this study was to investigate whether there are differences when comparing THAs with 5 different bearings at a long-term follow-up of more than 10 years.

METHODS

From January 2010 to May 2012, 101 THA patients (134 hips) were divided into metal-on-metal group (MoM, 31 hips), metal-on-polyethylene group (MoP, 23 hips), ceramic-on-metal group (CoM, 21 hips), ceramic-on-ceramic group (CoC, 33 hips), and ceramic-on-polyethylene group (CoP, 26 hips). The mean follow-up period was 10.3 years. The Harris hip score (HSS), Western Ontario and McMaster Universities Osteoarthritis Index scores (WOMAC), range of motion (ROM), blood cell count, and liver-kidney function were measured. Serum and urine metal ion levels were measured using high-resolution inductively coupled plasma-mass spectrometry (ICP-MS) and a blood lymphocytes analysis was counted by flow cytometry.

RESULTS

No difference was observed in the HSS, WOMAC, ROM, blood cell count, or liver-kidney function among any of the 5 groups. Metal ion levels were significantly elevated in metal-containing bearings. Flow cytometry showed that no differences were found. Revision was performed due to pseudotumor in 3 patients. The implant survival rate was 96.7% and 93.3% for the MoM and CoC groups, which was significantly lower compared with other groups.

CONCLUSIONS

Metal ion levels were elevated significantly in metal-containing bearings, especially in MoM THA patients. The implant survival rate was significantly lower in CoC and MoM THAs, which was mainly due to pseudotumor formation.

LEVEL OF EVIDENCE

Therapeutic Level II.

Analytical and toxicological aspects of nanomaterials in different product groups: Challenges and opportunities

The widespread integration of engineered nanomaterials into consumer and industrial products creates new challenges and requires innovative approaches in terms of design, testing, reliability, and safety of nanotechnology. The aim of this review article is to give an overview of different product groups in which nanomaterials are present and outline their safety aspects for consumers. Here, release of nanomaterials and related analytical challenges and solutions as well as toxicological considerations, such as dose-metrics, are discussed. Additionally, the utilization of engineered nanomaterials as pharmaceuticals or nutraceuticals to deliver and release cargo molecules is covered. Furthermore, critical pathways for human exposure to nanomaterials, namely inhalation and ingestion, are discussed in the context of risk assessment. Analysis of NMs in food, innovative medicine or food contact materials is discussed. Specific focus is on the presence and release of nanomaterials, including whether nanomaterials can migrate from polymer nanocomposites used in food contact materials. With regard to the toxicology and toxicokinetics of nanomaterials, aspects of dose metrics of inhalation toxicity as well as ingestion toxicology and comparison between in vitro and in vivo conclusions are considered. The definition of dose descriptors to be applied in toxicological testing is emphasized. In relation to potential exposure from different products, opportunities arising from the use of advanced analytical techniques in more unique scenarios such as release of nanomaterials from medical devices such as orthopedic implants are addressed. Alongside higher product performance and complexity, further challenges regarding material characterization and safety, as well as acceptance by the general public are expected.

Effects of HSD11B1 knockout and overexpression on local cortisol production and differentiation of mesenchymal stem cells

Exogenous glucocorticoids increase the risk for osteoporosis, but the role of endogenous glucocorticoids remains elusive. Here, we describe the generation and validation of a loss- and a gain-of-function model of the cortisol producing enzyme 11β-HSD1 (HSD11B1) to modulate the endogenous glucocorticoid conversion in SCP-1 cells — a model for human mesenchymal stem cells capable of adipogenic and osteogenic differentiation. CRISPR-Cas9 was successfully used to generate a cell line carrying a single base duplication and a 5 bp deletion in exon 5, leading to missense amino acid sequences after codon 146. These inactivating genomic alterations were validated by deep sequencing and by cloning with subsequent capillary sequencing. 11β-HSD1 protein levels were reduced by 70% in the knockout cells and cortisol production was not detectable. Targeted chromosomal integration was used to stably overexpress HSD11B1. Compared to wildtype cells, HSD11B1 overexpression resulted in a 7.9-fold increase in HSD11B1 mRNA expression, a 5-fold increase in 11β-HSD1 protein expression and 3.3-fold increase in extracellular cortisol levels under adipogenic differentiation. The generated cells were used to address the effects of 11β-HSD1 expression on adipogenic and osteogenic differentiation. Compared to the wildtype, HSD11B1 overexpression led to a 3.7-fold increase in mRNA expression of lipoprotein lipase (LPL) and 2.5-fold increase in lipid production under adipogenic differentiation. Under osteogenic differentiation, HSD11B1 knockout led to enhanced alkaline phosphatase (ALP) activity and mRNA expression, and HSD11B1 overexpression resulted in a 4.6-fold and 11.7-fold increase in mRNA expression of Dickkopf-related protein 1 (DKK1) and LPL, respectively. Here we describe a HSD11B1 loss- and gain-of-function model in SCP-1 cells at genetic, molecular and functional levels. We used these models to study the effects of endogenous cortisol production on mesenchymal stem cell differentiation and demonstrate an 11β-HSD1 dependent switch from osteogenic to adipogenic differentiation. These results might help to better understand the role of endogenous cortisol production in osteoporosis on a molecular and cellular level.

Evaluating the Performance of 3D-Printed PLA Reinforced with Date Pit Particles for Its Suitability as an Acetabular Liner in Artificial Hip Joints

Off-the-shelf hip joints are considered essential parts in rehabilitation medicine that can help the disabled. However, the failure of the materials used in such joints can cause individual discomfort. In support of the various motor conditions of the influenced individuals, the aim of the current research is to develop a new composite that can be used as an acetabular liner inside the hip joint. Polylactic acid (PLA) can provide the advantage of design flexibility owing to its well-known applicability as a 3D printed material. However, using PLA as an acetabular liner is subject to limitations concerning mechanical properties. We developed a complete production process of a natural filler, i.e., date pits. Then, the PLA and date pit particles were extruded for homogenous mixing, producing a composite filament that can be used in 3D printing. Date pit particles with loading fractions of 0, 2, 4, 6, 8, and 10 wt.% are dispersed in the PLA. The thermal, physical, and mechanical properties of the PLA–date pit composites were estimated experimentally. The incorporation of date pit particles into PLA enhanced the compressive strength and stiffness but resulted in a reduction in the elongation and toughness. A finite element model (FEM) for hip joints was constructed, and the contact stresses on the surface of the acetabular liner were evaluated. The FEM results showed an enhancement in the composite load carrying capacity, in agreement with the experimental results.

Synchrotron-based characterization of arthroprosthetic CoCrMo particles in human bone marrow

Particles released from cobalt-chromium-molybdenum (CoCrMo) alloys are considered common elicitors of chronic inflammatory adverse effects. There is a lack of data demonstrating particle numbers, size distribution and elemental composition of bone marrow resident particles which would allow for implementation of clinically relevant test strategies in bone marrow models at different degrees of exposure. The aim of this study was to investigate metal particle exposure in human periprosthetic bone marrow of three types of arthroplasty implants. Periprosthetic bone marrow sections from eight patients exposed to CoCrMo particles were analyzed via spatially resolved and synchrotron-based nanoscopic X-ray fluorescence imaging. These analyses revealed lognormal particle size distribution patterns predominantly towards the nanoscale. Analyses of particle numbers and normalization to bone marrow volume and bone marrow cell number indicated particle concentrations of up to 1 × 10¹¹ particles/ml bone marrow or 2 × 10⁴ particles/bone marrow cell, respectively. Analyses of elemental ratios of CoCrMo particles showed that particularly the particles' Co content depends on particle size. The obtained data point towards Co release from arthroprosthetic particles in the course of dealloying and degradation processes of larger particles within periprosthetic bone marrow. This is the first study providing data based on metal particle analyses to be used for future in vitro and in vivo studies of possible toxic effects in human bone marrow following exposure to arthroprosthetic CoCrMo particles of different concentration, size, and elemental composition. Graphical abstract.

Biocompatible Gas Plasma Treatment Affects Secretion Profiles but Not Osteogenic Differentiation in Patient-Derived Mesenchymal Stromal Cells

Cold physical plasma (CPP), a partially ionized gas that simultaneously generates reactive oxygen and nitrogen species, is suggested to provide advantages in regenerative medicine. Intraoperative CPP therapy targeting pathologies related to diminished bone quality could be promising in orthopedic surgery. Assessment of a clinically approved plasma jet regarding cellular effects on primary bone marrow mesenchymal stromal cells (hBM-MSCs) from relevant arthroplasty patient cohorts is needed to establish CPP-based therapeutic approaches for bone regeneration. Thus, the aim of this study was to derive biocompatible doses of CPP and subsequent evaluation of human primary hBM-MSCs’ osteogenic and immunomodulatory potential. Metabolic activity and cell proliferation were affected in a treatment-time-dependent manner. Morphometric high content imaging analyses revealed a decline in mitochondria and nuclei content and increased cytoskeletal compactness following CPP exposure. Employing a nontoxic exposure regime, investigation on osteogenic differentiation did not enhance osteogenic capacity of hBM-MSCs. Multiplex analysis of major hBM-MSC cytokines, chemokines and growth factors revealed an anti-inflammatory, promatrix-assembling and osteoclast-regulating secretion profile following CPP treatment and osteogenic stimulus. This study can be noted as the first in vitro study addressing the influence of CPP on hBM-MSCs from individual donors of an arthroplasty clientele.

Molybdenum trioxide enhances viability, osteogenic differentiation and extracellular matrix formation of human bone marrow-derived mesenchymal stromal cells

BACKGROUND

Metals and their ions allow specific modifications of the biological properties of bioactive materials that are intended for application in bone tissue engineering. While there is some evidence about the impact of particles derived from orthopedic Cobalt-Chromium-Molybdenum (Co-Cr-Mo) alloys on cells, there is only limited data regarding the influence of the essential trace element Mo and its ions on the viability, osteogenic differentiation as well as on the formation and maturation of the primitive extracellular matrix (ECM) of primary human bone marrow-derived stromal cells (BMSCs) available so far.

METHODS

In this study, the influence of a wide range of molybdenum (VI) trioxide (MoO₃), concentrations on BMSC viability was evaluated via measurement of fluorescein diacetate metabolization. Thereafter, the impact of three non-cytotoxic concentrations of MoO₃ on the cellular osteogenic differentiation as well as on ECM formation and maturation of BMSCs was assessed.

RESULTS

MoO₃ had no negative influence on BMSC viability in most tested concentrations, as viability was in fact even enhanced. Only the highest concentration (10 mM) of MoO₃ showed cytotoxic effects. Cellular osteogenic differentiation, measured via the marker enzyme alkaline phosphatase was enhanced by the presence of MoO₃ in a concentration-dependent manner. Furthermore, MoO₃ showed a positive influence on the expression of relevant marker genes for osteogenic differentiation (osteopontin, osteocalcin and type I collagen alpha 1) and on the formation and maturation of the primitive ECM, as measured by collagen deposition and ECM calcification.

CONCLUSION

MoO₃ is considered as an attractive candidate for supplementation in biomaterials and qualifies for further research.

In silico assessment of collateral eddy current heating in biocompatible implants subjected to magnetic hyperthermia treatments

Purpose: Bearing partially or fully metallic passive implants represents an exclusion criterion for patients undergoing a magnetic hyperthermia procedure, but there are no specific studies backing this restrictive decision. This work assesses how the secondary magnetic field generated at the surface of two common types of prostheses affects the safety and efficiency of magnetic hyperthermia treatments of localized tumors. The paper also proposes the combination of a multi-criteria decision analysis and a graphical representation of calculated data as an initial screening during the preclinical risk assessment for each patient.Materials and methods: Heating of a hip joint and a dental implant during the treatment of prostate, colorectal and head and neck tumors have been assessed considering different external field conditions and exposure times. The Maxwell equations including the secondary field produced by metallic prostheses have been solved numerically in a discretized computable human model. The heat exchange problem has been solved through a modified version of the Pennes' bioheat equation assuming a temperature dependency of blood perfusion and metabolic heat, i.e. thermorregulation. The degree of risk has been assessed using a risk index with parameters coming from custom graphs plotting the specific absorption rate (SAR) vs temperature increase, and coefficients derived from a multi-criteria decision analysis performed following the MACBETH approach.Results: The comparison of two common biomaterials for passive implants - Ti6Al4V and CoCrMo - shows that both specific absorption rate (SAR) and local temperature increase are found to be higher for the hip prosthesis made by Ti6Al4V despite its lower electrical and thermal conductivity. By tracking the time evolution of temperature upon field application, it has been established that there is a 30 s delay between the time point for which the thermal equilibrium is reached at prostheses and tissues. Likewise, damage may appear in those tissues adjacent to the prostheses at initial stages of treatment, since recommended thermal thresholds are soon surpassed for higher field intensities. However, it has also been found that under some operational conditions the typical safety rule of staying below or attain a maximum temperature increase or SAR value is met.Conclusion: The current exclusion criterion for implant-bearing patients in magnetic hyperthermia should be revised, since it may be too restrictive for a range of the typical field conditions used. Systematic in silico treatment planning using the proposed methodology after a well-focused diagnostic procedure can aid the clinical staff to find the appropriate limits for a safe treatment window.

Preclinical In Vitro Assessment of Submicron-Scale Laser Surface Texturing on Ti6Al4V

Loosening of orthodontic and orthopedic implants is a critical and common clinical problem. To minimize the numbers of revision surgeries due to peri-implant inflammation or insufficient osseointegration, developments of new implant manufacturing strategies are indicated. Ultrafast laser surface texturing is a promising contact-free technology to modify the physicochemical properties of surfaces toward an anti-infectious functionalization. This work aims to texture Ti6Al4V surfaces with ultraviolet (UV) and green (GR) radiation for the manufacturing of laser-induced periodic surface structures (LIPSS). The assessment of these surface modifications addresses key aspects of topography, morphology and chemical composition. Human primary mesenchymal stromal cells (hMSCs) were cultured on laser-textured and polished Ti6Al4V to characterize the surfaces in terms of their in vitro biocompatibility, cytotoxicity, and metal release. The outcomes of the in vitro experiment show the successful culture of hMSCs on textured Ti6Al4V surfaces developed within this work. Cells cultured on LIPSS surfaces were not compromised in terms of their viability if compared to polished surfaces. Yet, the hMSC culture on UV-LIPSS show significantly lower lactate dehydrogenase and titanium release into the supernatant compared to polished. Thus, the presented surface modification can be a promising approach for future applications in orthodontics and orthopedics.

Metal-Specific Biomaterial Accumulation in Human Peri-Implant Bone and Bone Marrow

Metallic implants are frequently used in medicine to support and replace degenerated tissues. Implant loosening due to particle exposure remains a major cause for revision arthroplasty. The exact role of metal debris in sterile peri-implant inflammation is controversial, as it remains unclear whether and how metals chemically alter and potentially accumulate behind an insulating peri-implant membrane, in the adjacent bone and bone marrow (BM). An intensively focused and bright synchrotron X-ray beam allows for spatially resolving the multi-elemental composition of peri-implant tissues from patients undergoing revision surgery. In peri-implant BM, particulate cobalt (Co) is exclusively co-localized with chromium (Cr), non-particulate Cr accumulates in the BM matrix. Particles consisting of Co and Cr contain less Co than bulk alloy, which indicates a pronounced dissolution capacity. Particulate titanium (Ti) is abundant in the BM and analyzed Ti nanoparticles predominantly consist of titanium dioxide in the anatase crystal phase. Co and Cr but not Ti integrate into peri-implant bone trabeculae. The characteristic of Cr to accumulate in the intertrabecular matrix and trabecular bone is reproducible in a human 3D in vitro model. This study illustrates the importance of updating the view on long-term consequences of biomaterial usage and reveals toxicokinetics within highly sensitive organs.

Systemic Effects of Metals Released from Arthroplasty Implants – a Brief Summary

In recent years, increasing concern has been raised regarding potential systemic toxicity of metals released from arthroplasty implants. A lack of valid metal thresholds for human (organ) toxicity and the prospect of multi-decade survival of modern hip and knee replacements pose special challenges. Indeed, evidence of systemic effects of metals released from such implants is largely missing. Systemic cobalt exposure has repeatedly been associated with cardiotoxic and neurotoxic effects, and also with thyroid dysfunction. The toxic potential of chromium is considered less pronounced. Yet, in arthroplasty there is usually a co-exposure to chromium and cobalt which complicates evaluation of element-specific effects. Toxicity of titanium dioxide nanoparticles has been subject to debate among international regulatory authorities. Their wide use in a variety of products in everyday life, such as toothpaste, cosmetics and food colorants, hampers the assessment of an arthroplasty-induced systemic titanium exposure. To date there is no clear evidence for systemic complications due to titanium dioxide released from arthroplasty implants. Release of further metals such as tantalum, niobium, nickel, vanadium and zirconium from hip and knee replacement implants has been described occasionally, but systemic effects of respective long-term exposure scenarios are unknown. Generally, the characterization of all released metals regarding their chemical and physical specifications is critical for the evaluation of potential systemic risks. Systematic studies investigating the accumulation of metals relevant in arthroplasty in different organs/organ systems and the biological consequences of such accumulations are urgently needed.

Local Cellular Responses to Metallic and Ceramic Nanoparticles from Orthopedic Joint Arthroplasty Implants

Over the last decades, joint arthroplasty has become a successful treatment for joint disease. Nowadays, with a growing demand and increasingly younger and active patients accepting these approaches, orthopedic surgeons are seeking implants with improved mechanical behavior and longer life span. However, aseptic loosening as a result of wear debris from implants is considered to be the main cause of long-term implant failure. Previous studies have neatly illustrated the role of micrometric wear particles in the pathological mechanisms underlying aseptic loosening. Recent osteoimmunologic insights into aseptic loosening highlight the important and heretofore underrepresented contribution of nanometric orthopedic wear particles. The present review updates the characteristics of metallic and ceramic nanoparticles generated after prosthesis implantation and summarizes the current understanding of their hazardous effects on peri-prosthetic cells.

PM2.5 collecting in a tire manufacturing plant affects epithelial differentiation of human umbilical cord derived mesenchymal stem cells by Wnt/β-catenin pathway

Mesenchymal stem cells (MSCs) can differentiate into pulmonary epithelial cells by Wnt/β-catenin pathway and promote lung repair. However, whether fine particulate matter (PM_2.5) could affect Wnt pathway and finally reduce the ability of MSCs to differentiate into epithelial cells is still unknown. This study aimed to investigate whether PM_2.5 could inhibit the epithelial differentiation of human umbilical cord-derived MSCs cells (hUCMSCs) and the related underlying mechanism. hUCMSCs were incubated with different concentrations of PM_2.5. Then, the cell viability, reactive oxygen species level, and single-cell sphere formation were assessed. The underlying mechanism of PM_2.5 in epithelial differentiation of hUCMSCs was further evaluated by co-culturing hUCMSCs with A549 cells. Our results demonstrated that PM_2.5 exposures could affect the expressions of β-catenin and lung epithelial markers (zonula occludens-1 (ZO-1); cytokeratins 5 and 19) in the co-cultured hUCMSCs. The Wnt/β-catenin pathway is involved in regulating the epithelial differentiation of MSCs. As expected, co-treatment with Wnt3a, which is the activator of the Wnt pathway, attenuated the downregulation of lung epithelial markers (ZO-1; cytokeratins 5 and 19) and paracrine factors (keratinocyte growth factor and hepatocyte growth factor) caused by PM_2.5. Altogether, these results demonstrated that PM_2.5 could affect the epithelial differentiation of hUCMSCs via the Wnt/β-catenin pathway.

Multi-Parameter Analysis of Biobanked Human Bone Marrow Stromal Cells Shows Little Influence for Donor Age and Mild Comorbidities on Phenotypic and Functional Properties

Heterogeneous populations of human bone marrow-derived stromal cells (BMSC) are among the most frequently tested cellular therapeutics for treating degenerative and immune disorders, which occur predominantly in the aging population. Currently, it is unclear whether advanced donor age and commonly associated comorbidities affect the properties of ex vivo-expanded BMSCs. Thus, we stratified cells from adult and elderly donors from our biobank (n = 10 and n = 13, mean age 38 and 72 years, respectively) and compared their phenotypic and functional performance, using multiple assays typically employed as minimal criteria for defining multipotent mesenchymal stromal cells (MSCs). We found that BMSCs from both cohorts meet the standard criteria for MSC, exhibiting similar morphology, growth kinetics, gene expression profiles, and pro-angiogenic and immunosuppressive potential and the capacity to differentiate toward adipogenic, chondrogenic, and osteogenic lineages. We found no substantial differences between cells from the adult and elderly cohorts. As positive controls, we studied the impact of in vitro aging and inflammatory cytokine stimulation. Both conditions clearly affected the cellular properties, independent of donor age. We conclude that in vitro aging rather than in vivo donor aging influences BMSC characteristics.

Local Biological Reactions and Pseudotumor-Like Tissue Formation in relation to Metal Wear in a Murine In Vivo Model

Metal wear debris and released ions (CoCrMo), which are widely generated in metal-on-metal bearings of hip implants, are also found in patients with metal-on-polyethylene bearings due to the mechanically assisted crevice corrosion of modular taper junctions, including head-neck and neck-stem taper interfaces. The resulting adverse reactions to metal debris and metal ions frequently lead to early arthroplasty revision surgery. National guidelines have since been published where the blood metal ion concentration of patients must consistently be monitored after joint replacement to prevent serious complications from developing after surgery. However, to date, the effect of metal particles and metal ions on local biological reactions is complex and still not understood in detail; the present study sought to elucidate the complex mechanism of metal wear-associated inflammation reactions. The knee joints in 4 groups each consisting of 10 female BALB/c mice received injections with cobalt chrome ions, cobalt chrome particles, and ultra-high-molecular-weight polyethylene (UHMWPE) particles or PBS (control). Seven days after injection, the synovial microcirculation and knee joint diameter were assessed via intravital fluorescence microscopy followed by histological evaluation of the synovial layer. Enlarged knee diameter, enhanced leukocyte to endothelial cell interactions, and an increase in functional capillary density within cobalt chrome particle-treated animals were significantly greater than those in the other treatment groups. Subsequently, pseudotumor-like tissue formations were observed only in the synovial tissue layer of the cobalt chrome particle-treated animals. Therefore, these findings strongly suggest that the cobalt chrome particles and not metal ions are the cause for in vivo postsurgery implantation inflammation.

Twenty common errors in the diagnosis and treatment of periprosthetic joint infection

Background

Misconceptions and errors in the management of periprosthetic joint infection (PJI) can compromise the treatment success. The goal of this paper is to systematically describe twenty common mistakes in the diagnosis and management of PJI, to help surgeons avoid these pitfalls.

Materials and methods

Common diagnostic and treatment errors are described, analyzed and interpreted.

Results

Diagnostic errors include the use of serum inflammatory biomarkers (such as C-reactive protein) to rule out PJI, incomplete evaluation of joint aspirate, and suboptimal microbiological procedures (such as using swabs or collection of insufficient number of periprosthetic samples). Further errors are missing possible sources of distant infection in hematogenous PJI or overreliance on suboptimal diagnostic criteria which can hinder or delay the diagnosis of PJI or mislabel infections as aseptic failure. Insufficient surgical treatment or inadequate antibiotic treatment are further reasons for treatment failure and emergence of antimicrobial resistance. Finally, wrong surgical indication, both underdebridement and overdebridement or failure to individualize treatment can jeopardize surgical results.

Conclusion

Multidisciplinary teamwork with infectious disease specialists and microbiologists in collaboration with orthopedic surgeons have a synergistic effect on the management of PJI. An awareness of the possible pitfalls can improve diagnosis and treatment results.

The Allergic Bone Marrow? The Immuno-Capacity of the Human Bone Marrow in Context of Metal-Associated Hypersensitivity Reactions

Arthroplasty ranks among the greatest achievements of surgical medicine, with total hip replacement termed “the operation of the century.” Despite its wide success, arthroplasty bears risks, such as local reactions to implant derived wear and corrosion products. Prevalence of allergies across Western society increases and along the number of reported hypersensitivity reactions to orthopedic implant materials. In this context the main focus is on delayed hypersensitivity (DTH). This mechanism is mainly attributed to T cells and an overreaction of the adaptive immune system. Arthroplasty implant materials are in direct contact with bone marrow (BM), which is discussed as a secondary lymphoid organ. However, the mechanisms of sensitization toward implant wear remain elusive. Nickel and cobalt ions can form haptens with native peptides to activate immune cell receptors and are therefore common T helper allergens in cutaneous DTH. The rising prevalence of metal-related allergy in the general population and evidence for the immune-modulating function of BM allow for the assumption hypersensitivity reactions could occur in peri-implant BM. There is evidence that pro-inflammatory factors released during DTH reactions enhance osteoclast activity and inhibit osteoblast function, an imbalance characteristic for osteolysis. Even though some mechanisms are understood, hypersensitivity has remained a diagnosis of exclusion. This review aims to summarize current views on the pathomechanism of DTH in arthroplasty with emphasis on BM and discusses recent advances and future directions for basic research and clinical diagnostics.

Rapid and Highly Effective Noninvasive Disinfection by Hybrid Ag/CS@MnO2 Nanosheets Using Near-Infrared Light

A bacterial infection on the surface of medical apparatus and instruments as well as artificial implants is threatening human health greatly. Antibiotics and traditional bacterial-killing agents, even silver nanoparticles, can induce bacterial resistance during long-term interaction with bacteria. Hence, rapid surface sterilization and prevention of bacterial infection in the long term are urgent for biomedical devices, especially for artificial implant materials. Herein, a hybridized chitosan (CS), silver nanoparticles (AgNPs), and MnO₂ nanosheets coating was designed on the surface of titanium plates, which can ensure the implants a rapid and highly effective antibacterial efficacy of 99.00% against Staphylococcus aureus ( S. aureus) and 99.25% against Escherichia coli ( E. coli) within 20 min of 808 nm near-infrared light (NIR) irradiation. The exogenous NIR irradiation can trigger the MnO₂ nanosheets to produce enough hyperthermia within 10 min, which can combine with a low concentration of prereleased Ag⁺ from the coating to achieve superior antimicrobial efficacy through synergistic effects. In contrast, either prereleased Ag ions or a photothermal effect alone can achieve much lower antibacterial efficiency under the same concentration, i.e., 24.00% and 30.01% for the former and 30.00% and 42.54% for the later toward S. aureus and E. coli, respectively. The possible cytotoxicity of coatings could be eliminated owing to the low concentration of AgNPs and chitosan encapsulation. Thus, the novel bifunctional coating Ag/CS@MnO₂ can exhibit great potential in deep site disinfection of Ti implants through the synergy of prereleased Ag ions and a photothermal effect within a short time.

In vitro and in vivo investigations of a-C/a-C:Ti nanomultilayer coated Ti6Al4V alloy as artificial femoral head

Hydrogen-free a-C/a-C:Ti nanomultilayer (a-C NM) films were deposited on medical Ti6Al4V by the magnetron sputtering technique under bias-graded voltage. Cell tests and implantations were performed for the a-C NM films coated Ti6Al4V with the uncoated Ti6Al4V as the control. The canine total hip arthroplasty (THA) surgeries were conducted for 12 dogs using the coated femoral heads, with the CoCr heads as the control. Results of cell tests showed that the coated Ti6Al4V had no cytotoxicity, and there was no statistical difference of the cell attachment rates between the coated and uncoated sample (P = 0.091). No significant difference of the tissue response around the coated and uncoated implants were observed after the intramuscular (P = 0.679) and intraosseous implantations (P = 0.122). After two years of successful canine THA, the polyethylene wear particles isolated from periprosthetic soft tissue showed similar sizes, shapes and counts in the two groups (all of the P values >0.05). The retrieved femoral heads showed slightly change of the surface roughness, but no statistical differences between groups (P = 0.696). However, the systemic metal ion analysis indicated that the content of Co and Cr ions released in the coated group (Co: 0.71 ± 0.06 μg/L, Cr: 0.52 ± 0.05 μg/L) were significant lower than that in the control (Co: 1.98 ± 0.16 μg/L, Cr: 1.17 ± 0.19 μg/L) (both P < 0.005). Histological analysis of the periprosthetic tissue in CoCr group showed a severer histiocyte response than that in the coated group (P = 0.029). The head-taper interfaces showed galvanic corrosion attack in the CoCr group, but not in the coated Ti6Al4V group. Therefore, the a-C NM films coated Ti6Al4V exhibited good biocompatibility as an implant material. Compared with the CoCr, the coated Ti6Al4V femoral head could provide comparable in vivo wear properties, release less harmful metal ions and reduce the inflammatory response in periprosthetic tissue, which may help to prolong the longevity of prostheses.

Tuning the tribofilm nanostructures of polymer-on-metal joint replacements for simultaneously enhancing anti-wear performance and corrosion resistance

Total joint replacement is currently the most successful clinical treatment for improving the life quality of individuals afflicted with end-stage osteoarthritis of knee or hip joints. However, release of wear and corrosion products from the prostheses is a critical issue causing adverse physiological responses of local issues. β-SiC nanoparticles were dispersed into polyetheretherketone (PEEK) materials and their role in tribocorrosion performance of PEEK-steel joints exposed to simulated body fluid was investigated. It is demonstrated that β-SiC nanoparticles increase greatly the wear resistance of the PEEK materials, and meanwhile mitigate significantly corrosion of the steel counterpart. It is revealed that tribochemical reactions of β-SiC nanoparticles promoted formation of a robust tribofilm having complex structures providing protection and shielding effects. The present work proposes a strategy for developing high-performance polymer-on-metal joint replacement materials of enhanced lifespan and biocompatibility via tuning interface nanostructures. STATEMENT OF SIGNIFICANCE: Adverse tissue responses to metal wear and corrosion products from metal base implants remain a challenge to surgeons and patients. We demonstrated that leaching of metal ions and release of metallic debris are well decreased via tuning interface nanostructures of metal-polymer joint bearings by dispersing β-SiC nanoparticles into polyetheretherketone (PEEK). It is identified that the addition of β-SiC greatly improves the tribological performances of the PEEK materials and mitigated corrosion of the steel. Tribo-chemistry reactions of SiC induce the formation of complex structures which provide protection and shielding effects. Nanostructures of the tribofilm were also comprehensively investigated. These novel findings proposed a potential route for designing high performance metal-polymer joint replacement materials.

Diagnostic guidelines for the histological particle algorithm in the periprosthetic neo-synovial tissue

BACKGROUND

The identification of implant wear particles and non-implant related particles and the characterization of the inflammatory responses in the periprosthetic neo-synovial membrane, bone, and the synovial-like interface membrane (SLIM) play an important role for the evaluation of clinical outcome, correlation with radiological and implant retrieval studies, and understanding of the biological pathways contributing to implant failures in joint arthroplasty. The purpose of this study is to present a comprehensive histological particle algorithm (HPA) as a practical guide to particle identification at routine light microscopy examination.

METHODS

The cases used for particle analysis were selected retrospectively from the archives of two institutions and were representative of the implant wear and non-implant related particle spectrum. All particle categories were described according to their size, shape, colour and properties observed at light microscopy, under polarized light, and after histochemical stains when necessary. A unified range of particle size, defined as a measure of length only, is proposed for the wear particles with five classes for polyethylene (PE) particles and four classes for conventional and corrosion metallic particles and ceramic particles.

RESULTS

All implant wear and non-implant related particles were described and illustrated in detail by category. A particle scoring system for the periprosthetic tissue/SLIM is proposed as follows: 1) Wear particle identification at light microscopy with a two-step analysis at low (× 25, × 40, and × 100) and high magnification (× 200 and × 400); 2) Identification of the predominant wear particle type with size determination; 3) The presence of non-implant related endogenous and/or foreign particles. A guide for a comprehensive pathology report is also provided with sections for macroscopic and microscopic description, and diagnosis.

CONCLUSIONS

The HPA should be considered a standard for the histological analysis of periprosthetic neo-synovial membrane, bone, and SLIM. It provides a basic, standardized tool for the identification of implant wear and non-implant related particles at routine light microscopy examination and aims at reducing intra-observer and inter-observer variability to provide a common platform for multicentric implant retrieval/radiological/histological studies and valuable data for the risk assessment of implant performance for regional and national implant registries and government agencies.

Cobalt and Titanium nanoparticles influence on human osteoblast mitochondrial activity and biophysical properties of their cytoskeleton

We investigated the biophysical effects (cell elasticity and spring constant) caused on Saos-2 human osteoblast-like cells by nanosized metal (Co and Ti) wear debris, as well as the adhesive characteristics of cells after exposure to the metal nanoparticles. Cell mitochondrial activity was investigated using the MTT assays; along with LDH assay, metal uptake, cell apoptosis and mineralisation output (alizarin red assay) of the cells. Osteoblasts mitochondrial activity was not affected by Ti nanoparticles at concentrations up to 1 mg/ml and by Cobalt nanoparticles at concentrations < 0.5 mg/ml; however elasticity and spring constant were significantly modified by the exposure to nanoparticles of these metals in agreement with the alteration of cell conformation (shape), as result of the exposure to simulated wear debris, demonstrated by fluorescence images after actin staining.

Analysis of the Content of Chromium in Certain Parts of the Human Knee Joint

Chromium is an essential microelement in the human body. It exerts an effect on bones by modulating their biochemical parameters: alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP). With considerable accumulation of chromium in the skeleton, the activity of alkaline phosphatase was found to decrease, which affected bone formation rate. The study objective was to analyze chromium content in the knee tissues. Tissues for analysis were obtained during endoprosthesoplasty of the knee joint and included tibia, femur, and meniscus tissues. Samples were collected from 50 patients, including 36 women and 14 men. The analysis was performed using the inductively coupled plasma atomic emission spectroscopy (ICP-AES) method, by means of a Varian 710-ES apparatus. The results revealed no significant differences in the content of chromium in the knee joint tissues between women and men. The highest level of chromium was found in the femoral bone of the knee joint, then in the meniscus, and was lowest in the tibia, although the differences were statistically insignificant. Chromium content increased with age.

Journey into Bone Models: A Review

Bone is a complex tissue with a variety of functions, such as providing mechanical stability for locomotion, protection of the inner organs, mineral homeostasis and haematopoiesis. To fulfil these diverse roles in the human body, bone consists of a multitude of different cells and an extracellular matrix that is mechanically stable, yet flexible at the same time. Unlike most tissues, bone is under constant renewal facilitated by a coordinated interaction of bone-forming and bone-resorbing cells. It is thus challenging to recreate bone in its complexity in vitro and most current models rather focus on certain aspects of bone biology that are of relevance for the research question addressed. In addition, animal models are still regarded as the gold-standard in the context of bone biology and pathology, especially for the development of novel treatment strategies. However, species-specific differences impede the translation of findings from animal models to humans. The current review summarizes and discusses the latest developments in bone tissue engineering and organoid culture including suitable cell sources, extracellular matrices and microfluidic bioreactor systems. With available technology in mind, a best possible bone model will be hypothesized. Furthermore, the future need and application of such a complex model will be discussed.

Content of distinct metals in periprosthetic tissues and pseudosynovial joint fluid in patients with total joint arthroplasty

This prospective study examined the content of metals released from total joint arthroplasty into joint fluid, whole blood and periprosthetic tissues. We determined the levels of Ti, V, Nb, Co, Cr, and Mo, using inductively coupled plasma mass spectrometry, in samples from patients who underwent reoperation of total hip or knee arthroplasty. All of the patients (n = 117) included in the study had either metal on polyethylene or ceramic on polyethylene-bearing pairs. First, our results conclusively showed that the majority of released metals were deposited in periprosthetic tissues. In this context, the bloodstream turned out to be an ineffective biomarker of the effects occurring in local tissues. Second, there was a clear time-dependent nature of metallic accumulation. Based on our extensive dataset, we found significantly elevated levels of the released metals in joint fluid and periprosthetic tissues originating from loosened implants compared to stable ones, as well as recognizable differences between the groups with stable implants and aseptic loosening. Finally, it was proved that the concentrations of metals decreased dependent on the distance of the tissue from the implant. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 454-462, 2019.

Arthroprosthetic cobaltism associated with cardiomyopathy

Systemic cobaltism related to metal-on-metal total hip arthroplasty has been published in case reports and series with effects on the cardiac, neurologic, endocrine, and immunologic systems. This case report presents a 46-year-old male who underwent bilateral metal-on-metal total hip arthroplasty and subsequently developed cardiomyopathy requiring left ventricular assist device implantation. Intervention with bilateral revision to non-cobalt-containing implants resulted in improved cardiac function. This case report will alert clinicians to the presentation of this rare but devastating complication while also displaying improvement following revision total hip arthroplasty. It is our hope this case will aid in early recognition and intervention of this condition.

Biological effects of metal degradation in hip arthroplasties

Metals and metal alloys are the most used materials in orthopedic implants. The focus is on total hip arthroplasty (THA) that, though well tolerated, may be associated with local and remote adverse effects in the medium-long term. This review aims to summarize data on the biological consequences of the metal implant degradation that have been attributed predominantly to metal-on-metal (MoM) THA. Local responses to metals consist of a broad clinical spectrum ranging from small asymptomatic tissue lesions to severe destruction of bone and soft tissues, which are designated as metallosis, adverse reactions to metal debris (ARMD), aseptic lymphocytic vasculitis associated lesion (ALVAL), and pseudotumors. In addition, the dissemination of metal particles and ions throughout the body has been associated with systemic adverse effects, including organ toxicity, cancerogenesis, teratogenicity, and immunotoxicity. As proved by the multitude of studies in this field, metal degradation may increase safety issues associated with THA, especially with MoM hip systems. Data collection regarding local, systemic and long-term effects plays an essential role to better define any safety risks and to generate scientifically based recommendations.

Multi-elemental nanoparticle exposure after tantalum component failure in hip arthroplasty: In-depth analysis of a single case

Porous tantalum components are widely used for complex acetabular reconstructions in revision hip arthroplasty. Multiple other metal alloys such as titanium-aluminum-vanadium or cobalt-chromium-molybdenum are principally used in artificial joint setups. We report a case of tantalum component failure being both cause and effect of a multiple metal exposure. Our aims were to assess and to characterize associated particle exposure and biological consequences. Metal level quantification revealed substantial in vivo exposure to particulate and dissociated tantalum, zirconium, chromium, cobalt, molybdenum, titanium, aluminum and vanadium in periprosthetic compartments. Aside from micron-sized particles, nanoparticles of a broad size range and elemental composition were obtained. Histological exams verified a spectrum of necrotic changes in the periprosthetic tissues. In the presented case tantalum release was accompanied by concomitance of particles originating from other utilized metals. We conclude that an overall in vivo exposure assessment is mandatory for realistic appraisal of metal toxicity and associated risks.

Immunological Responses to Total Hip Arthroplasty

The use of total hip arthroplasties (THA) has been continuously rising to meet the demands of the increasingly ageing population. To date, this procedure has been highly successful in relieving pain and restoring the functionality of patients’ joints, and has significantly improved their quality of life. However, these implants are expected to eventually fail after 15–25 years in situ due to slow progressive inflammatory responses at the bone-implant interface. Such inflammatory responses are primarily mediated by immune cells such as macrophages, triggered by implant wear particles. As a result, aseptic loosening is the main cause for revision surgery over the mid and long-term and is responsible for more than 70% of hip revisions. In some patients with a metal-on-metal (MoM) implant, metallic implant wear particles can give rise to metal sensitivity. Therefore, engineering biomaterials, which are immunologically inert or support the healing process, require an in-depth understanding of the host inflammatory and wound-healing response to implanted materials. This review discusses the immunological response initiated by biomaterials extensively used in THA, ultra-high-molecular-weight polyethylene (UHMWPE), cobalt chromium (CoCr), and alumina ceramics. The biological responses of these biomaterials in bulk and particulate forms are also discussed. In conclusion, the immunological responses to bulk and particulate biomaterials vary greatly depending on the implant material types, the size of particulate and its volume, and where the response to bulk forms of differing biomaterials are relatively acute and similar, while wear particles can initiate a variety of responses such as osteolysis, metal sensitivity, and so on.

Human adipose stem cells induced to osteogenic differentiation by an innovative collagen/hydroxylapatite hybrid scaffold

Novel biomaterials are of paramount importance for bone regrowth. In this study, we investigated human adipose stem cells (hASCs) for osteogenic, osteoconductivity, and osteoinductivity effects of an innovative collagen/hydroxylapatite hybrid scaffold. In hASCs that were grown on this scaffold, osteogenic genes were analyzed for their expression profiles, together with adhesion and extracellular matrix genes. In hASC integrins, basement membrane constituents and collagens were up-regulated, together with cell proliferation. In addition, expression of osteopontin and activated focal adhesion kinase was studied at the protein level. Our in vitro data indicate that hASCs, together with hybrid biomaterial, is an important model of study to investigate in vitro bone induction.-Mazzoni, E., D'Agostino, A., Manfrini, M., Maniero, S., Puozzo, A., Bassi, E., Marsico, S., Fortini, C., Trevisiol, L., Patergnani, S., Tognon, M. Human adipose stem cells induced to osteogenic differentiation by an innovative collagen/hydroxylapatite hybrid scaffold.

Evaluation of the Size-Dependent Cytotoxicity of DLC (Diamondlike Carbon) Wear Debris in Arthroplasty Applications

Patients with DLC (diamond like carbon)-coated artificial joints may be exposed to a wide size range of DLC wear debris (DW). In this study, the cytotoxicity of DW of different size ranges (0-0.22, 0.22-0.65, 0.65-1.0, and 1.0-5.0 μm) was evaluated. The microstructure and physical characteristics of DW were investigated by Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscope (SEM), and dynamic light scattering (DLS). Macrophages, osteoblasts, and fibroblasts were incubated with DW of different size ranges respectively followed by cytotoxicity evaluations of inflammatory cytokines, alkaline phosphatase (ALP) assays, and related signal protein expression analysis. The results showed that, except for the size range of 0-0.22 μm, DW cytotoxicity showed a size-dependent (0.22-5.0 μm) decrease with increasing size. Within the range of 0.22-5.0 μm, DW of larger size resulted in lessened inflammatory response and enhanced osteoblastogenesis and fibrogenesis, with increased viability of cells (macrophages, osteoblasts, and fibroblasts), better morphology, less release of pro-inflammatory factors and more release of anti-inflammatory factors. The results demonstrated that DW sizes below 0.22 μm had less negative effects on cell adhesion and growth because of the BSA (bovine serum albumin) encapsulation effect. These findings provide valuable knowledge about the comprehensive mechanism of promotion of inflammatory response and inhibition of osteoblastogenesis and fibrogenesis induced by DW. In conclusion, an effective system of biocompatibility evaluation for different sizes of DW was derived.

Mesenchymal stem cells in the aseptic loosening of total joint replacements

Peri-prosthetic osteolysis remains as the main long-term complication of total joint replacement surgery. Research over four decades has established implant wear as the main culprit for chronic inflammation in the peri-implant tissues and macrophages as the key cells mediating the host reaction to implant-derived wear particles. Wear debris activated macrophages secrete inflammatory mediators that stimulate bone resorbing osteoclasts; thus bone loss in the peri-implant tissues is increased. However, the balance of bone turnover is not only dictated by osteoclast-mediated bone resorption but also by the formation of new bone by osteoblasts; under physiological conditions these two processes are tightly coupled. Increasing interest has been placed on the effects of wear debris on the cells of the bone-forming lineage. These cells are derived primarily from multipotent mesenchymal stem cells (MSCs) residing in bone marrow and the walls of the microvasculature. Accumulating evidence indicates that wear debris significantly impairs MSC-to-osteoblast differentiation and subsequent bone formation. In this review, we summarize the current understanding of the effects of biomaterial implant wear debris on MSCs. Emerging treatment options to improve initial implant integration and treat developing osteolytic lesions by utilizing or targeting MSCs are also discussed. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1195-1207, 2017.