Mechanical instability and titanium particles induce similar transcriptomic changes in a rat model for periprosthetic osteolysis and aseptic loosening

A translational murine model of aseptic loosening with osseointegration failure

An in vivo animal model of a weight-bearing intra-articular implant is crucial to the study of implant osseointegration and aseptic loosening caused by osseointegration failure. Osseointegration, defined as a direct structural and functional attachment between living bone tissue and the surface of a load-carrying implant, is essential for implant stability and considered a prerequisite for the long-term clinical success of implants in total joint arthroplasty. Compared to large animal models, murine models offer extensive genetic tools for tracing cell differentiation and proliferation. The 18- to 22-week-old C57BL/6J background mice underwent either press-fitted or loose implantation of a titanium implant, achieving osseointegration or fibrous integration. A protocol was developed for both versions of the procedure, including a description of the relevant anatomy. Samples were subjected to microcomputed tomography and underwent biomechanical testing to access osseointegration. Lastly, samples were fixed and embedded for histological evaluation. The absence of mineralized tissue and weakened maximum pull-out force in loose implantation samples indicated that these implants were less mechanically stable compared to the control at 4 weeks postoperation. Histological analysis demonstrated extensive fibrotic tissue in the peri-implant area of loose implantation samples and excellent implant osseointegration in press-fitted samples at 4 weeks. Both mechanically stable and unstable hemiarthroplasty models with either osseous ingrowth or a robust periprosthetic fibrosis were achieved in mice. We hope that this model can help address current limitations for in vivo study of aseptic loosening and lead to necessary translational benefits.

Roles of inflammatory cell infiltrate in periprosthetic osteolysis

Classically, particle-induced periprosthetic osteolysis at the implant-bone interface has explained the aseptic loosening of joint replacement. This response is preceded by triggering both the innate and acquired immune response with subsequent activation of osteoclasts, the bone-resorbing cells. Although particle-induced periprosthetic osteolysis has been considered a foreign body chronic inflammation mediated by myelomonocytic-derived cells, current reports describe wide heterogeneous inflammatory cells infiltrating the periprosthetic tissues. This review aims to discuss the role of those non-myelomonocytic cells in periprosthetic tissues exposed to wear particles by showing original data. Specifically, we discuss the role of T cells (CD3+, CD4+, and CD8+) and B cells (CD20+) coexisting with CD68+/TRAP- multinucleated giant cells associated with both polyethylene and metallic particles infiltrating retrieved periprosthetic membranes. This review contributes valuable insight to support the complex cell and molecular mechanisms behind the aseptic loosening theories of orthopedic implants.

Multifunctional natural polymer-based metallic implant surface modifications

High energy traumas could cause critical damage to bone, which will require permanent implants to recover while functionally integrating with the host bone. Critical sized bone defects necessitate the use of bioactive metallic implants. Because of bioinertness, various methods involving surface modifications such as surface treatments, the development of novel alloys, bioceramic/bioglass coatings, and biofunctional molecule grafting have been utilized to effectively integrate metallic implants with a living bone. However, the applications of these methods demonstrated a need for an interphase layer improving bone-making to overcome two major risk factors: aseptic loosening and peri-implantitis. To accomplish a biologically functional bridge with the host to prevent loosening, regenerative cues, osteoimmunomodulatory modifications, and electrochemically resistant layers against corrosion appeared as imperative reinforcements. In addition, interphases carrying antibacterial cargo were proven to be successful against peri-implantitis. In the literature, metallic implant coatings employing natural polymers as the main matrix were presented as bioactive interphases, enabling rapid, robust, and functional osseointegration with the host bone. However, a comprehensive review of natural polymer coatings, bridging and grafting on metallic implants, and their activities has not been reported. In this review, state-of-the-art studies on multifunctional natural polymer-based implant coatings effectively utilized as a bone tissue engineering (BTE) modality are depicted. Protein-based, polysaccharide-based coatings and their combinations to achieve better osseointegration via the formation of an extracellular matrix-like (ECM-like) interphase with gap filling and corrosion resistance abilities are discussed in detail. The hypotheses and results of these studies are examined and criticized, and the potential future prospects of multifunctional coatings are also proposed as final remarks.

Bilateral massive osteolysis of uncertain origin after total knee arthroplasty: A case report and review of literature

INTRODUCTION AND IMPORTANCE

Periprosthetic osteolysis (PPOL) is a common complication after total knee arthroplasty (TKA) and is most commonly caused by wear-induced particles.

CASE PRESENTATION

We report an unusual case of massive bilateral PPOL in the posterior flanges of the femur and patellae 4 years after bilateral uncemented TKA without patellar resurfacing in a 71-year old female. Bilateral staged revision surgery including polyethylene exchange and allograft morselized bone impaction was performed to treat the osteolytic lesions. There were no signs of implant malalignment, polyethylene wear or component loosening.

CLINICAL DISCUSSION

Several factors are associated with an increased risk on PPOL (e.g. polyethylene sterilization method, patient age, male gender). Surgical intervention in the context of massive PPOL should include replacement of a potential particle generator (most often polyethylene), correction of potential malalignment, treatment of bone defects and assessment of implant anchorage.

CONCLUSION

This report highlights the available evidence on clinical presentation, associated risk factors and preferred treatment strategy of massive osteolytic lesions after TKA according to available evidence.

Titanium Porous Coating Using 3D Direct Energy Deposition (DED) Printing for Cementless TKA Implants: Does It Induce Chronic Inflammation?

Because of the recent technological advances, the cementless total knee arthroplasty (TKA) implant showed satisfactory implant survival rate. Newly developed 3D printing direct energy deposition (DED) has superior resistance to abrasion as compared to traditional methods. However, there is still concern about the mechanical stability and the risk of osteolysis by the titanium (Ti) nanoparticles. Therefore, in this work, we investigated whether DED Ti-coated cobalt-chrome (CoCr) alloys induce chronic inflammation reactions through in vitro and in vivo models. We studied three types of implant surfaces (smooth, sand-blasted, and DED Ti-coated) to compare their inflammatory reaction. We conducted the in vitro effect of specimens using the cell counting kit-8 (CCK-8) assay and an inflammatory cytokine assay. Subsequently, in vivo analysis of the immune profiling, cytokine assay, and histomorphometric evaluation using C57BL/6 mice were performed. There were no significant differences in the CCK-8 assay, the cytokine assay, and the immune profiling assay. Moreover, there were no difference for semi-quantitative histomorphometry analysis at 4 and 8 weeks among the sham, smooth, and DED Ti-coated samples. These results suggest that DED Ti-coated printing technique do not induce chronic inflammation both in vitro and in vivo. It has biocompatibility for being used as a surface coating of TKA implant.

Periprosthetic Osteolysis: Mechanisms, Prevention and Treatment

Clinical studies, as well as in vitro and in vivo experiments have demonstrated that byproducts from joint replacements induce an inflammatory reaction that can result in periprosthetic osteolysis (PPOL) and aseptic loosening (AL). Particle-stimulated macrophages and other cells release cytokines, chemokines, and other pro-inflammatory substances that perpetuate chronic inflammation, induce osteoclastic bone resorption and suppress bone formation. Differentiation, maturation, activation, and survival of osteoclasts at the bone-implant interface are under the control of the receptor activator of nuclear factor kappa-Β ligand (RANKL)-dependent pathways, and the transcription factors like nuclear factor κB (NF-κB) and activator protein-1 (AP-1). Mechanical factors such as prosthetic micromotion and oscillations in fluid pressures also contribute to PPOL. The treatment for progressive PPOL is only surgical. In order to mitigate ongoing loss of host bone, a number of non-operative approaches have been proposed. However, except for the use of bisphosphonates in selected cases, none are evidence based. To date, the most successful and effective approach to preventing PPOL is usage of wear-resistant bearing couples in combination with advanced implant designs, reducing the load of metallic and polymer particles. These innovations have significantly decreased the revision rate due to AL and PPOL in the last decade.

Mechanically Induced Periprosthetic Osteolysis: A Systematic Review

BACKGROUND

Peri-prosthetic bone loss can result from chemical, biological, and mechanical factors. Mechanical stimulation via fluid pressure and flow at the bone-implant interface may be a significant cause. Evidence supporting mechanically induced osteolysis continues to grow, but there is no synthesis of published clinical and basic science data.

QUESTIONS/PURPOSES

We sought to review the literature on two questions: (1) What published evidence supports the concept of mechanically induced osteolysis? (2) What is the proposed mechanism of mechanically induced osteolysis, and does it differ from that of particle-induced osteolysis?

METHODS

A systematic review was performed of the PubMed and Web of Science databases. Additional relevant articles were recommended by the senior authors based on their expert opinion. Abstracts were reviewed and the manuscripts pertaining to the study questions were read in full. Studies showing support of mechanically induced osteolysis were quantified and findings summarized.

RESULTS

We identified 49 articles of experimental design supporting the hypothesis that mechanical stimulation of peri-prosthetic bone from fluid pressure and flow can induce osteolysis. While the molecular mechanisms may overlap with those implicated in particle-induced osteolysis, mechanically induced osteolysis appears to be mediated by distinct and parallel pathways.

CONCLUSIONS

The role of mechanical stimuli is increasingly recognized in the pathogenesis of peri-prosthetic osteolysis. Current research aims to elucidate the molecular mechanisms to better target therapeutic interventions.

Zoledronate induces cell cycle arrest and differentiation by upregulating p21 in mouse MC3T3-E1 preosteoblasts

Background: Increasing research has recently been focused on the supplementary use of drugs such as bisphosphonates that are known to influence bone turnover to prevent and treat periprosthetic bone loss and subsequent implant loosening following total joint replacements. However, there are still concerns about the conflicting effects of bisphosphonate treatment on osteoblastic bone formation in the literature. Methods: In this study, we investigate the role of zoledronate (ZOL) in regulating cell cycle distribution and differentiation in mouse MC3T3-E1 preosteoblasts and also explore the mechanism underlying this effect of ZOL. We examined the expression levels of osteocalcin (OCN) by quantitative polymerase chain reaction (qPCR), the total amount of CDK6, p21 and p27 proteins by Western blot analysis, and the cell cycle distribution by flow cytometric analysis in mouse MC3T3-E1 preosteoblasts to evaluate the effect of ZOL. Small interfering RNAs (siRNAs) were used to assess the individual contributions of genes to specific osteoblast phenotypes. Results: In addition to increased OCN expression, we found that ZOL treatment induces the G₀/G₁ arrest and results in the increase of p21 and p27 expressions and decrease of CDK6 expression in mouse MC3T3-E1 preosteoblasts. Both p21 and p27 mediates ZOL-induced cell cycle exit; however, p21, but not p27, is responsible for the increase of ZOL-induced OCN expression in these cells. Conclusions: These results endorse that ZOL might have an anabolic effect on osteoblasts. The CDK inhibitor p21 plays a key role in regulating osteoblast differentiation by controlling proliferation-related events in mouse MC3T3-E1 preosteoblasts.

Label-Free Monitoring of Uptake and Toxicity of Endoprosthetic Wear Particles in Human Cell Cultures

The evaluation of the biological effects of endoprosthetic wear particles on cells in vitro relies on a variety of test assays. However, most of these methods are susceptible to particle-induced interferences; therefore, label-free testing approaches emerge as more reliable alternatives. In this study, impedance-based real-time monitoring of cellular viability and metabolic activity were performed following exposure to metallic and ceramic wear particles. Moreover, label-free imaging of particle-exposed cells was done by high-resolution darkfield microscopy (HR-ODM) and field emission scanning electron microscopy (FESEM). The isolated human fibroblasts were exposed to CoCr28Mo6 and alumina matrix composite (AMC) ceramic particles. HR-ODM and FESEM revealed ingested particles. For impedance measurements, cells were seeded on gold-plated microelectrodes. Cellular behavior was monitored over a period of 48 h. CoCr28Mo6 and AMC particle exposure affected cell viability in a concentration-dependent manner, i.e., 0.01 mg/mL particle solutions led to small changes in cell viability, while 0.05 mg/mL resulted in a significant reduction of viability. The effects were more pronounced after exposure to CoCr28Mo6 particles. The results were in line with light and darkfield microcopy observations indicating that the chosen methods are valuable tools to assess cytotoxicity and cellular behavior following exposure to endoprosthetic wear particles.

Hyperoside decreases the apoptosis and autophagy rates of osteoblast MC3T3‑E1 cells by regulating TNF‑like weak inducer of apoptosis and the p38mitogen activated protein kinase pathway

Wear particles generated between the interface of joints and artificial joint replacements are one of the primary causes of aseptic loosening. The aim of the present study was to investigate the influence of titanium (Ti) particles on the apoptosis and autophagy of osteoblasts, and probe into the potential use of hyperoside (Hy) as a protector for osteoblasts in Ti particle-induced injury. MC3T3-E1 cells were divided into control, Ti, Hy-1+Ti and Hy-2+Ti groups. Cell viability was detected using a Cell Counting Kit-8 assay. Apoptosis and autophagy rates were determined using flow cytometry. Expression levels of apoptosis-associated genes, including caspase-3, apoptosis regulator BAX, apoptosis regulator Bcl-2 and cellular tumor antigen p53, in addition to autophagy-associated genes, including Beclin1 and microtubule-associated protein light chain 3 conversion LC3-II/I, were measured using reverse transcription-quantitative polymerase chain reaction and western blotting. Activation of the tumor necrosis factor ligand superfamily member 12 (TWEAK)-mitogen activated protein kinase 11 (p38) mitogen activated protein kinase (MAPK) pathway was observed by western blotting. The present study demonstrated that pretreatment with Hy was able to increase cell viability and proliferation, and decrease apoptosis and autophagy to protect MC3T3-E1 cells against Ti particle-induced damage. Activation of the TWEAK-p38 pathway contributed to the repair processes of treatment with Hy. The present results suggested that Hy protected osteoblasts against Ti particle-induced damage by regulating the TWEAK-p38 pathway, which suggested the potential of Hy as a protective agent for bones.

Endotoxin Contributes to Artificial Loosening of Prostheses Induced by Titanium Particles

Background

Aseptic loosening of orthopedic implants caused by wear particles is a major cause of joint replacement failure. However, the mechanism of aseptic loosening has not yet been defined. The present study explored whether endotoxin adherent on the titanium (Ti) particles contributes to aseptic loosening.

Material/Methods

Limulus amebocyte lysate detection was conducted to detect the levels of endotoxin adhered to the Ti particles. A mouse air pouches model was established and mice were divided into 4 groups and injected with phosphate-buffered saline (PBS) or Ti particles suspensions (0.1, 1, 10 mg/mL), following detection of the number of macrophages and the level of endotoxin. Scanning electron microscopy (SEM) was used to characterize the microstructures of Ti particles adhered with endotoxin.

Results

In vitro experiments showed that the level of endotoxin adhered to the Ti particles was significantly increased after adding LPS back to these “endotoxin-free” particles. In vivo experiments showed that Ti particles injection significantly increased the number of macrophages and the level of endotoxin.

Conclusions

In conclusion, these results suggest that adherent endotoxin may play an important role in aseptic loosening induced by Ti particles.

Total hip arthroplasty following failure of tantalum rod implantation for osteonecrosis of the femoral head with 5- to 10-year follow-up

BACKGROUND

Total hip arthroplasty (THA) with failure of tantalum rod implant for osteonecrosis of the femoral head (ONFH) will be the only choice for patients. However,it remains unknown whether tantalum rod implantation has an adverse effect on the survival time of implants following conversion to THA. The aim of this study was to retrospectively evaluate the clinical and radiographic outcomes of conversion to THA in patients who were previously treated with implantation of a tantalum rod.

METHODS

This study included 31 patients (39 hips), who underwent conversion to THA due to failure of core decompression with an implanted tantalum rod. Among these 31 patients, 26 patients were male and five patients were female. The mean age of these patients was 49.3 years old (range: 36-64 years old). The control group included 33 patients (40 hips), who underwent total hip replacement without tantalum rod implantation. The hip Harris score, implant wear, osteolysis, radiolucencies and surgical complications were recorded during the follow-up. The distribution of tantalum debris in the proximal, middle and distal periprosthetic femoral regions, radiolucent lines and osteolysis were analyzed on post-operative radiographs.

RESULTS

There were no significant differences in Harris score, liner wear and complications between the two groups (P > 0.05). Osteolysis and radiolucent lines more likely occurred in patients with tantalum debris distributed in three regions than in one or two regions (P < 0.05).

CONCLUSIONS

The mid-term clinical outcome of patients who underwent THA with tantalum rod implantation was not different from those without a tantalum rod, suggesting that tantalum debris did not increase the liner wear rate. However, the distribution of periprosthetic tantalum debris in the proximal, middle and distal femoral regions may increase the risk of femoral osteolysis and radiolucent lines.

Prednisolone treatment reduces the osteogenic effects of loading in mice

Glucocorticoid treatment, a major cause of drug-induced osteoporosis and fractures, is widely used to treat inflammatory conditions and diseases. By contrast, mechanical loading increases bone mass and decreases fracture risk. With these relationships in mind, we investigated whether mechanical loading interacts with GC treatment in bone. Three-month-old female C57BL/6 mice were treated with high-dose prednisolone (15 mg/60 day pellets/mouse) or vehicle for two weeks. During the treatment, right tibiae were subjected to short periods of cyclic compressive loading three times weekly, while left tibiae were used as physiologically loaded controls. The bones were analyzed using peripheral quantitative computed tomography, histomorphometry, real-time PCR, three-point bending and Fourier transform infrared micro-spectroscopy. Loading alone increased trabecular volumetric bone mineral density (vBMD), cortical thickness, cortical area, osteoblast-associated gene expression, osteocyte- and osteoclast number, and bone strength. Prednisolone alone decreased cortical area and thickness and osteoblast-associated gene expression. Importantly, prednisolone treatment decreased the load-induced increase in trabecular vBMD by 57% (p < 0.001) and expression of osteoblast-associated genes, while completely abolishing the load-induced increase in cortical area, cortical thickness, number of osteocytes and osteoclasts, and bone strength. When combined, loading and prednisolone decreased the collagen content. In conclusion, high-dose prednisolone treatment strongly inhibits the loading-induced increase in trabecular BMD, and abolishes the loading-induced increase in cortical bone mass. This phenomenon could be due to prednisolone inhibition of osteoblast differentiation and function.

Topical zoledronic acid decreases micromotion induced bone resorption in a sheep arthroplasty model

Background

Initial micromotion of a total hip replacement is associated with aseptic loosening. The use of bisphosphonates could be one way to reduce peri-implant bone resorption induced by micromotion. Bisphosphonates compounds are inhibitors of bone resorption. The aim of this study was to investigate whether local treatment with bisphosphonate would reduce bone resorption and fibrous tissue around an experimental implant subjected to micromotion.

Methods

One micromotion implant were inserted into each medial femoral condyle in ten sheep. During each gait cycle the implant axially piston 0.5 mm. During surgery one of the femoral condyles were locally treated with 0.8 mg zoledronate. The other condyle served as control. Observation period was 12 weeks.

Results

Histological evaluation showed a fibrous capsule around both the control and bisphosphonate implants. Histomorphometrical analysis showed that 97% of the surface on both control and bisphosphonate implants were covered by fibrous tissue. However, the bisphosphonate was able to preserve bone in a 1 mm zone around the implants.

Conclusion

This study indicates that local treatment with bisphosphonate cannot prevent the formation of a fibrous capsule around an implant subjected to micromotion, but bisphosphonate is able to reduce resorption of peri-prosthetic bone.