Bone formation and bone resorption in failed total joint arthroplasties: histomorphometric analysis with histochemical and immunohistochemical technique

Puricelli biconvex arthroplasty as an alternative for temporomandibular joint reconstruction: description of the technique and long-term case report

Background

There are several indications for partial or total replacement of the temporomandibular joint (TMJ), including neoplasms and severe bone resorptions. In this regard, several techniques have been suggested to increase the functionality and longevity of these prosthetic devices. This case report describes the treatment of a TMJ ankylosis patient with the Puricelli biconvex arthroplasty (ABiP) technique, with a long-term follow-up.

Case presentation

In 1978, a 33-year-old male polytraumatised patient developed painful symptoms in the right preauricular region, associated with restricted movement of the ipsilateral TMJ. Due to subcondylar fracture, an elastic maxillomandibular immobilisation (EMMI) was applied. Subsequently, the patient was referred for treatment when limitations of the interincisal opening (10 mm) and the presence of spontaneous pain that increased on palpation were confirmed. Imaging exams confirmed the fracture, with anteromedial displacement and bony ankylosis of the joint. Exeresis of the compromised tissues and their replacement through ABiP was indicated. The method uses conservative access (i.e., preauricular incision), partial resection of the ankylosed mass, and tissue replacement using two poly(methyl methacrylate) components, with minimal and stable contact between the convex surfaces. At the end of the procedure, joint stability and dental occlusion were tested. The patient showed significant improvement at the postoperative 6-month follow-up, with no pain and increased mouth opening range (30 mm). At the 43-year follow-up, no joint noises, pain or movement restrictions were reported (mouth opening of 36 mm). Imaging exams did not indicate tissue degeneration and showed the integrity of prosthetic components.

Conclusions

The present case report indicates that ABiP enables joint movements of the TMJ, allowing the remission of signs and symptoms over more than 40 years of follow-up. These data suggest that this technique is a simple and effective alternative when there is an indication for TMJ reconstruction in adult patients with ankylosis.

Bioactive coatings with anti-osteoclast therapeutic agents for bone implants: Enhanced compliance and prolonged implant life

The use of therapeutic agents that inhibit bone resorption is crucial to prolong implant life, delay revision surgery, and reduce the burden on the healthcare system. These therapeutic agents include bisphosphonates, various nucleic acids, statins, proteins, and protein complexes. Their use in systemic treatment has several drawbacks, such as side effects and insufficient efficacy in terms of concentration, which can be eliminated by local treatment. This review focuses on the incorporation of osteoclast inhibitors (antiresorptive agents) into bioactive coatings for bone implants. The ability of bioactive coatings as systems for local delivery of antiresorptive agents to achieve optimal loading of the bioactive coating and its release is described in detail. Various parameters such as the suitable concentrations, release times, and the effects of the antiresorptive agents on nearby cells or bone tissue are discussed. However, further research is needed to support the optimization of the implant, as this will enable subsequent personalized design of the coating in terms of the design and selection of the coating material, the choice of an antiresorptive agent and its amount in the coating. In addition, therapeutic agents that have not yet been incorporated into bioactive coatings but appear promising are also mentioned. From this work, it can be concluded that therapeutic agents contribute to the biocompatibility of the bioactive coating by enhancing its beneficial properties.

Periprosthetic Osteolysis in Cervical Total Disc Arthroplasty: A Single Institutional Experience

BACKGROUND

Cervical disc arthroplasty (CDA) affords an excellent alternative to cervical fusion for the treatment of symptomatic patients with degenerative disc disease. As more surgeons perform CDAs, an understanding of the complications associated with this technique is crucial. Periprosthetic osteolysis (PO) is a rare potential complication associated with CDA.

OBJECTIVE

To highlight potential complications associated with CDA.

METHODS

A retrospective chart review of patients who underwent CDA at our institution was performed. Patient outcomes and relevant clinical and radiographical data were analyzed in addition to associated complications. Explanted devices were subjected to macroscopic and microscopic analyses.

RESULTS

A total of 88 patients were included: 68 patients underwent 1-level CDA and 20 patients had 2-level CDA. Implants used in this series included Mobi-C (Zimmer Biomet), Prestige LP (Medtronic), Secure C (Globus), Advent (Orthofix), and ProDisc C (DePuy). One patient demonstrated symptoms of myeloradiculopathy that correlated with radiographical periprosthetic osteolysis and required surgical intervention in the form of disc explantation, corpectomy, and cervical instrumented fusion. Device retrieval analysis demonstrated evidence of elevated oxidation levels and increased wear in the presence of high concentrations of metal ions and debris in the surrounding tissue. The tissue did not exhibit any immune response, infection, or acute inflammation.

CONCLUSION

PO is a potential complication of CDA that occurs irrespective of the type of implant used. We describe its occurrence and management and highlight the importance of being aware of this understated phenomenon.

Protective effects of sirtuin 3 on titanium particle-induced osteogenic inhibition by regulating the NLRP3 inflammasome via the GSK-3β/β-catenin signalling pathway

Periprosthetic osteolysis (PPO) remains the key factor in implant failure and subsequent revision surgery and is mainly triggered by wear particles. Previous studies have shown that inhibition of osteoblastic differentiation is the most widespread incident affecting the interface of trabecular and loosening prostheses. Additionally, the NLRP3 inflammasome is activated by prosthetic particles. Sirtuin3, an NAD⁺-dependent deacetylase of mitochondria, regulates the function of mitochondria in diverse activities. However, whether SIRT3 can mitigate wear debris-induced osteolysis by inhibiting the NLRP3 inflammasome and enhancing osteogenesis has not been previously reported. Therefore, we investigated the role of SIRT3 during the process of titanium (Ti) particle-induced osteolysis. We revealed that upregulated SIRT3 dramatically attenuated Ti particle-induced osteogenic inhibition through suppression of the NLRP3 inflammasome and improvement of osteogenesis in vivo and in vitro. Moreover, we found that SIRT3 interference in the process of Ti particle-induced osteolysis relied on the GSK-3β/β-catenin signalling pathway. Collectively, these findings indicated that SIRT3 may serve as a rational new treatment against debris-induced PPO by deacetylase-dependent inflammasome attenuation.

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Effect of SIRT3 on rescued wear particles-induced osteogenic inhibition.

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Effect of SIRT3 on inhibited the activation of pyroptosis-related NLRP3 inflammasome.

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Effect of SIRT3 on mitigated periprosthetic osteolysis via GSK-3β/β-catenin signaling.

Vitamin E-infused highly cross-linked polyethylene did not reduce the number of in vivo wear particles in total knee arthroplasty

AIMS

Vitamin E-infused highly cross-linked polyethylene (E1) has recently been introduced in total knee arthroplasty (TKA). An in vitro wear simulator study showed that E1 reduced polyethylene wear. However there is no published information regarding in vivo wear. Previous reports suggest that newly introduced materials which reduce in vitro polyethylene wear do not necessarily reduce in vivo polyethylene wear. To assist in the evaluation of the newly introduced material before widespread use, we established an in vivo polyethylene wear particle analysis for TKA. The aim of this study was to compare in vivo polyethylene wear particle generation between E1 and conventional polyethylene (ArCom) in TKA.

METHODS

A total of 34 knees undergoing TKA (17 each with ArCom or E1) were investigated. Except for the polyethylene insert material, the prostheses used for both groups were identical. Synovial fluid was obtained at a mean of 3.4 years (SD 1.3) postoperatively. The in vivo polyethylene wear particles were isolated from the synovial fluid using a previously validated method and examined by scanning electron microscopy.

RESULTS

The total number of polyethylene wear particles obtained from the knees with E1 (mean 6.9, SD 4.0 × 10⁷ counts/knee) was greater than that obtained from those with ArCom (mean 2.2, SD 2.6 × 10⁷ counts/knee) (p = 0.001). The particle size (equivalent circle of diameter) from the knees with E1 was smaller (mean 0.5 μm, SD 0.1) than that of knees with ArCom (mean 1.5, SD 0.3 μm) (p = 0.001). The aspect ratio of particles from the knees with E1 (mean 1.3, SD 0.1) was smaller than that with ArCom (mean 1.4, SD 0.1) (p < 0.001 ).

CONCLUSION

This is the first report of in vivo wear particle analysis of E1. E1 polyethylene did not reduce the number of in vivo polyethylene wear particles compared with ArCom in early clinical stage. Further careful follow-up of newly introduced E1 for TKA should be carried out. Cite this article: Bone Joint J 2020;102-B(11):1527-1534.

Modulation of the Inflammatory Response and Bone Healing

The optimal treatment for complex fractures and large bone defects is an important unsolved issue in orthopedics and related specialties. Approximately 5-10% of fractures fail to heal and develop non-unions. Bone healing can be characterized by three partially overlapping phases: the inflammatory phase, the repair phase, and the remodeling phase. Eventual healing is highly dependent on the initial inflammatory phase, which is affected by both the local and systemic responses to the injurious stimulus. Furthermore, immune cells and mesenchymal stromal cells (MSCs) participate in critical inter-cellular communication or crosstalk to modulate bone healing. Deficiencies in this inter-cellular exchange, inhibition of the natural processes of acute inflammation, and its resolution, or chronic inflammation due to a persistent adverse stimulus can lead to impaired fracture healing. Thus, an initial and optimal transient stage of acute inflammation is one of the key factors for successful, robust bone healing. Recent studies demonstrated the therapeutic potential of immunomodulation for bone healing by the preconditioning of MSCs to empower their immunosuppressive properties. Preconditioned MSCs (also known as "primed/ licensed/ activated" MSCs) are cultured first with pro-inflammatory cytokines (e.g., TNFα and IL17A) or exposed to hypoxic conditions to mimic the inflammatory environment prior to their intended application. Another approach of immunomodulation for bone healing is the resolution of inflammation with anti-inflammatory cytokines such as IL4, IL10, and IL13. In this review, we summarize the principles of inflammation and bone healing and provide an update on cellular interactions and immunomodulation for optimal bone healing.

Inflammation and Bone Repair: From Particle Disease to Tissue Regeneration

When presented with an adverse stimulus, organisms evoke an immediate, pre-programmed, non-specific innate immune response. The purpose of this reaction is to maintain the organism's biological integrity and function, mitigate or eradicate the injurious source, and re-establish tissue homeostasis. The initial stage of this protective reaction is acute inflammation, which normally reduces or terminates the offending stimulus. As the inflammatory reaction recedes, the stage of tissue repair and regeneration follows. If the above sequence of events is perturbed, reconstitution of normal biological form and function will not be achieved. Dysregulation of these activities may result in incomplete healing, fibrosis, or chronic inflammation. Our laboratory has studied the reaction to wear particles from joint replacements as a paradigm for understanding the biological pathways of acute and chronic inflammation, and potential translational treatments to reconstitute lost bone. As inflammation is the cornerstone for healing in all anatomical locations, the concepts developed have relevance to tissue engineering and regenerative medicine in all organ systems. To accomplish our goal, we developed novel in vitro and in vivo models (including the murine femoral continuous intramedullary particle infusion model), translational strategies including modulation of macrophage chemotaxis and polarization, and methods to interfere with key transcription factors NFκB and MyD88. We purposefully modified MSCs to facilitate bone healing in inflammatory scenarios: by preconditioning the MSCs, and by genetically modifying MSCs to first sense NFκB activation and then overexpress the anti-inflammatory pro-regenerative cytokine IL-4. These advancements provide significant translational opportunities to enhance healing in bone and other organs.

Cytokine Profile in Patients with Aseptic Loosening of Total Hip Replacements and Its Relation to Metal Release and Metal Allergy

Metal release from total hip replacements (THRs) is associated with aseptic loosening (AL). It has been proposed that the underlying immunological response is caused by a delayed type IV hypersensitivity-like reaction to metals, i.e., metal allergy. The purpose of this study was to investigate the immunological response in patients with AL in relation to metal release and the prevalence of metal allergy. THR patients undergoing revision surgery due to AL or mechanical implant failures were included in the study along with a control group consisting of primary THR patients. Comprehensive cytokine analyses were performed on serum and periimplant tissue samples along with metal analysis using inductive coupled plasma mass spectrometry (ICP-MS). Patient patch testing was done with a series of metals related to orthopedic implant. A distinct cytokine profile was found in the periimplant tissue of patients with AL. Significantly increased levels of the proinflammatory cytokines IL-1β, IL-2, IL-8, IFN-γ and TNF-α, but also the anti-inflammatory IL-10 were detected. A general increase of metal concentrations in the periimplant tissue was observed in both revision groups, while Cr was significantly increased in patient serum with AL. No difference in the prevalence of metal sensitivity was established by patch testing. Increased levels of IL-1β, IL-8, and TNF-α point to an innate immune response. However, the presence of IL-2 and IFN-γ indicates additional involvement of T cell-mediated response in patients with AL, although this could not be detected by patch testing.

A study on the prevention and treatment of murine calvarial inflammatory osteolysis induced by ultra-high-molecular-weight polyethylene particles with neomangiferin

The present study aimed to examine the influence of neomangiferin on murine calvarial inflammatory osteolysis induced by ultra-high-molecular-weight polyethylene (UHMWPE) particles. Eight-week-old male C57BL/J6 mice served as an inflammatory osteolysis model, in which UHMWPE particles were implanted into the calvarial subperiosteal space. The mice were randomly distributed into four groups and treated with different interventions; namely, a sham group [phosphate-buffered saline (PBS) injection and no UHMWPE particles], model group (PBS injection and implantation of UHMWPE particles), low-dose neomangiferin group (UHMWPE particles +2.5 mg/kg neomangiferin), and high-dose neomangiferin group (UHMWPE particles +5 mg/kg neomangiferin). Following 3 weeks of feeding according to the above regimens, celiac artery blood samples were collected for an enzyme-linked immunosorbent assay (ELISA) to determine the expression of receptor activator of nuclear factor-κB ligand (RANKL), osteoclast-related receptor (OSCAR), cross-linked C-telopeptide of type I collagen (CTX-1); osteoprotegerin (OPG), tumor necrosis factor (TNF)-α, and interleukin (IL)-1β. Subsequently, the mice were sacrificed by cervical dislocation following ether-inhalation anesthesia, and the skull was separated for osteolysis analysis by micro-computed tomography (micro-CT). Following hematoxylin and eosin staining, tartrate-resistant acid phosphatase (TRAP) staining was performed to observe the dissolution and destruction of the skull. The micro-CT results suggested that neomangiferin significantly inhibited the murine calvarial osteolysis and bone resorption induced by UHMWPE particles. In addition, the ELISA results showed that neomangiferin decreased the expression levels of osteoclast markers RANKL, OSCAR, CTX-1, TNF-α and IL-1β. By contrast, the levels of OPG increased with the neomangiferin dose. Histopathological examination revealed that the TRAP-positive cell count was significantly reduced in the neomangiferin-treated animals compared with that in the positive control group, and the degree of bone resorption was also markedly reduced. Neomangiferin was found to have significant anti-inflammatory effects and to inhibit osteoclastogenesis. Therefore, it has the potential to prevent the aseptic loosening of a prosthesis following artificial joint replacement.

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.

Wear Characteristics of Conventional Ultrahigh-Molecular-Weight Polyethylene Versus Highly Cross-Linked Polyethylene in Total Ankle Arthroplasty

BACKGROUND

The aim of this study was to compare the polyethylene wear rate, particle size, and particle shape of primary semiconstrained, fixed-bearing, bone-sparing total ankle arthroplasty using conventional ultrahigh-molecular-weight polyethylene (CPE) versus highly cross-linked polyethylene (HXLPE) by applying a level walking input using a joint simulator.

METHODS

Two fixed-bearing total ankle replacement systems with different types of polyethylene liners were tested: (1) CPE sterilized in ethylene oxide, and (2) HXLPE sterilized with gas plasma after electron beam irradiation. Three implants for each design underwent wear testing using gravimetric analysis over 5 million simulated walking cycles. A fourth implant was used as a load soak control. Equivalent circle diameter (ECD) and equivalent shape ratio (ESR) were computed to determine particle size and particle shape, respectively.

RESULTS

The mean wear rate from 1.5 to 5 million cycles (MC) was 2.0 ± 0.3 mg/MC for HXLPE and 16.7 ± 1.3 mg/MC for CPE ( P < .001). The total number of particles per cycle generated for HXLPE and CPE were 0.17 × 10⁶ particles/cycle and 0.53 × 10⁶ particles/cycle, respectively ( P < .001). The mean ECD of HXLPE particles (0.22 ± 0.11 μm) was significantly smaller than the mean ECD of CPE particles (0.32 ± 0.14 μm) ( P < .001). HXLPE particles were significantly more round than CPE particles ( P < .001).

CONCLUSIONS

HXLPE liners had a significantly lower wear rate and produced significantly fewer and rounder particles than CPE liners. The results of this study suggest that HXLPE has more favorable wear characteristics for total ankle arthroplasty.

CLINICAL RELEVANCE

Polyethylene wear particles have been linked to osteolysis after total ankle arthroplasty. There is no consensus on the importance of highly cross-linked polyethylene in total ankle arthroplasty with regard to implant wear. This is the first nonindustry study to compare the polyethylene wear rate, particle size, and particle shape of fixed-bearing total ankle arthroplasty conventional polyethylene versus highly cross-linked polyethylene. The lower wear rate and different particle size/morphology of highly cross-linked polyethylene could be beneficial in vivo to decrease osteolysis.

Systemic and local toxicity of metal debris released from hip prostheses: A review of experimental approaches

Despite the technological improvements in orthopedic joint replacement implants, wear and corrosion products associated with the metal components of these implants may result in adverse local tissue and perhaps systemic reactions and toxicities. The current review encompasses a literature review of the local and systemic toxicity studies concerning the effect of CoCrMo wear debris released from wear and corrosion of orthopedic implants and prostheses. Release of metallic debris is mainly in the form of micro- and nano-particles, ions of different valences, and oxides composed of Co and Cr. Though these substances alter human biology, their direct effects of these substances on specific tissue types remain poorly understood. This may partially be the consequence of the multivariate research methodologies employed, leading to inconsistent reports. This review proposes the importance of developing new and more appropriate in-vitro methodologies to study the cellular responses and toxicity mediated by joint replacement wear debris in-vivo.

Sequentially annealed highly cross-linked polyethylene reduced in vivo wear particle generation in total knee arthroplasty

INTRODUCTION

Sequentially annealed highly cross-linked polyethylene (HXLPE) was recently introduced to reduce the wear in total knee arthroplasty (TKA). However, an in vivo advantage of sequentially annealed HXLPE on wear particle generation is still controversial. The purpose of this study is to compare the characteristics of in vivo wear particles between sequentially annealed HXLPE and conventional polyethylene after TKA.

MATERIALS AND METHODS

Synovial fluid was obtained from the eight knees with sequentially annealed HXLPE and from eight knees with conventional polyethylene 12 months after the operation. Polyethylene particles were isolated and examined using a scanning electron microscope and image analyzer.

RESULTS

Total number of wear particles in each knee was 2.1 ± 1.0 × 10⁷ with sequentially annealed HXLPE (mean ± standard deviation) and 4.9 ± 3.6 × 10⁷ with conventional polyethylene ( p = 0.036). Particle size (equivalent circle diameter) was 1.01 ± 0.26 μm with sequentially annealed HXLPE and 1.02 ± 0.20 μm with conventional polyethylene ( p = 0.674). Aspect ratio was 1.33 ± 0.04 with sequentially annealed HXLPE and 1.39 ± 0.10 with conventional polyethylene ( p = 0.462).

CONCLUSIONS

The sequentially annealed HXLPE reduced the in vivo polyethylene wear particles by 58% compared with conventional polyethylene without the significant change of particle size and shape.

Osteoclasts in Periprosthetic Osteolysis: The Charnley Arthroplasty Revisited

BACKGROUND

Periprosthetic osteolysis by polyethylene wear debris-triggered osteoclasts is viewed as the main pathophysiological pathway in aseptic loosening in total hip arthroplasty. The present aim was to study osteoclast occurrence in osteolytic lesions in early and late revisions of the Charnley low-friction torque arthroplasty (CLFA).

METHODS

Biopsies of the soft interface membrane and the adjacent bone were taken from osteolytic lesions during revision of 16 loose CLFA, early (2-6 years) or late (>10 years) after primary surgery. By light microscopy (LM), cell-dense regions with signs of osteoclast-mediated bone resorption were selected for transmission electron microscopy. Three additional patients were studied in LM for osteoclast markers (tartrate-resistant acid phosphatase and Cathepsin K).

RESULTS

LM disclosed a low-grade chronic inflammation and birefringent particles in most sections. Multiple conglomerates of tartrate-resistant acid phosphatase positive and Cathepsin K positive mononuclear and multinucleated cells were found deep in the fibrous interface membrane. Transmission electron microscopy showed traces of polyethylene-like particles in 67%-100% of the cells. Osteoclast-like cells exhibiting resorptive activity were few (mean, 0.7%; standard deviation, 0.2%), and multinucleated cells, possibly osteoclast precursor cells, located immediately on the bone were also scarce (mean, 2.7%; standard deviation, 5.3%). Multinucleated (odds ratio, 3.0; 95% confidence interval, 1.7-5.5) and macrophage-like cells (odds ratio, 3.6; 95% confidence interval, 2.2-5.6) were typically located deeper in the inflammatory interface membrane with a pathologic appearance with distension and abundance of phagocytic vacuoles. There were no systematic differences in cell populations between early or late revisions.

CONCLUSION

Despite probable ongoing osteoclastogenesis in the osteolytic lesions, there were few sites of osteoclast-mediated bone resorption. These findings attach a contributing biological explanation to the longevity of the CLFA.

GSK-3β inhibition suppresses instability-induced osteolysis by a dual action on osteoblast and osteoclast differentiation

Currently, there are no medications available to treat aseptic loosening of orthopedic implants. Using osteoprotegerin fusion protein (OPG-Fc), we previously blocked instability-induced osteoclast differentiation and peri-prosthetic osteolysis. Wnt/β-catenin signaling, which regulates OPG secretion from osteoblasts, also modulates the bone tissue response to mechanical loading. We hypothesized that activating Wnt/β-catenin signaling by inhibiting glycogen synthase kinase-3β (GSK-3β) would reduce instability-induced bone loss through regulation of both osteoblast and osteoclast differentiation. We examined effects of GSK-3β inhibition on regulation of RANKL and OPG in a rat model of mechanical instability-induced peri-implant osteolysis. The rats were treated daily with a GSK-3β inhibitor, AR28 (20 mg/kg bw), for up to 5 days. Bone tissue and blood serum were assessed by qRT-PCR, immunohistochemistry, and ELISA on days 3 and 5, and by micro-CT on day 5. After 3 days of treatment with AR28, mRNA levels of β-catenin, Runx2, Osterix, Col1α1, and ALP were increased leading to higher osteoblast numbers compared to vehicle-treated animals. BMP-2 and Wnt16 mRNA levels were downregulated by mechanical instability and this was rescued by GSK-3β inhibition. Osteoclast numbers were decreased significantly after 3 days of GSK-3β inhibition, which correlated with enhanced OPG mRNA expression. This was accompanied by decreased serum levels of TRAP5b on days 3 and 5. Treatment with AR28 upregulated osteoblast differentiation, while osteoclastogenesis was blunted, leading to increased bone mass by day 5. These data suggest that GSK-3β inactivation suppresses osteolysis through regulating both osteoblast and osteoclast differentiation in a rat model of instability-induced osteolysis.

Comparison of in vivo polyethylene wear particles between mobile- and fixed-bearing TKA in the same patients

PURPOSE

Polyethylene wear particle generation is one of the most important factors that affects the mid- to long-term results of total knee arthroplasties (TKA). Mobile-bearing total knee prostheses were developed to reduce polyethylene wear generation. However, whether mobile-bearing prostheses actually generate fewer polyethylene wear particles than fixed-bearing prostheses remains controversial. The aim of this study was to compare, within individual patients, the in vivo polyethylene wear particles created by a newly introduced mobile-bearing prosthesis in one knee and a conventional fixed-bearing prosthesis in other knee.

METHODS

Eighteen patients receiving bilateral TKAs to treat osteoarthritis were included. The synovial fluid was obtained from 36 knees at an average of 3.5 years after the operation. The in vivo polyethylene wear particles were isolated from the synovial fluid using a previously validated method and examined using a scanning electron microscope and an image analyser.

RESULTS

The size and shape of the polyethylene wear particles from the mobile-bearing prostheses were similar to those from the conventional fixed-bearing prostheses. Although the number of wear particles from the mobile-bearing prosthesis (1.63 × 10⁷ counts/knee) appeared smaller than that from the fixed-bearing prosthesis (2.16 × 10⁷ counts/knee), the difference was not statistically significant.

CONCLUSIONS

The current in vivo study shows that no statistically significant differences were found between the polyethylene wear particles generated by a newly introduced mobile-bearing PS prosthesis and a conventional fixed-bearing PS prosthesis during the early clinical stage after implantation.

LEVEL OF EVIDENCE

Therapeutic study, Level III.

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

Wear debris particles released from prosthetic bearing surfaces and mechanical instability of implants are two main causes of periprosthetic osteolysis. While particle-induced loosening has been studied extensively, mechanisms through which mechanical factors lead to implant loosening have been less investigated. This study compares the transcriptional profiles associated with osteolysis in a rat model for aseptic loosening, induced by either mechanical instability or titanium particles. Rats were exposed to mechanical instability or titanium particles. After 15 min, 3, 48 or 120 h from start of the stimulation, gene expression changes in periprosthetic bone tissue was determined by microarray analysis. Microarray data were analyzed by PANTHER Gene List Analysis tool and Ingenuity Pathway Analysis (IPA). Both types of osteolytic stimulation led to gene regulation in comparison to unstimulated controls after 3, 48 or 120 h. However, when mechanical instability was compared to titanium particles, no gene showed a statistically significant difference (fold change ≥ ± 1.5 and adjusted p-value ≤ 0.05) at any time point. There was a remarkable similarity in numbers and functional classification of regulated genes. Pathway analysis showed several inflammatory pathways activated by both stimuli, including Acute Phase Response signaling, IL-6 signaling and Oncostatin M signaling. Quantitative PCR confirmed the changes in expression of key genes involved in osteolysis observed by global transcriptomics. Inflammatory mediators including interleukin (IL)-6, IL-1β, chemokine (C-C motif) ligand (CCL)2, prostaglandin-endoperoxide synthase (Ptgs)2 and leukemia inhibitory factor (LIF) showed strong upregulation, as assessed by both microarray and qPCR. By investigating genome-wide expression changes we show that, despite the different nature of mechanical implant instability and titanium particles, osteolysis seems to be induced through similar biological and signaling pathways in this rat model for aseptic loosening. Pathways associated to the innate inflammatory response appear to be a major driver for osteolysis. Our findings implicate early restriction of inflammation to be critical to prevent or mitigate osteolysis and aseptic loosening of orthopedic implants.

Predicting rates of in vivo degradation of recombinant spider silk proteins

Developing fundamental tools and insight into biomaterial designs for predictive functional outcomes remains critical for the field. Silk is a promising candidate as a biomaterial for tissue engineering scaffolds, particularly where high mechanical loads or slow rates of degradation are desirable. Although bioinspired synthetic spider silks are feasible biomaterials for this purpose, insight into how well the degradation rate can be programmed by fine tuning the sequence remains to be determined. Here we integrated experimental approaches and computational modelling to investigate the degradation of two bioengineered spider silk block copolymers, H(AB)₂ and H(AB)₁₂ , which were designed based on the consensus domains of Nephila clavipes dragline silk. The effect of protein chain length and secondary structure on degradation was analysed in vivo. The degradation rate of H(AB)₁₂ , the silk with longer chain length/higher molecular weight, and higher crystallinity, was slower when compared to H(AB)₂ . Using full atomistic modelling, it was determined that the faster degradation of H(AB)₂ was due to the lower folded molecular structure of the silk and the greater accessibility to solvent. Comparison of the specific surface areas of proteins via modelling showed that higher exposure of random coil and lower exposure of ordered domains in H(AB)₂ led to the more reactive silk with a higher degradation rate when compared with H(AB)₁₂ , as validated by the experimental results. The study, based on two simple silk designs demonstrated that the control of sequence can lead to programmable degradation rates for these biomaterials, providing a suitable model system with which to study variables in protein polymer design to predict degradation rates in vivo. This approach should reduce the use of animal screening, while also accelerating translation of such biomaterials for repair and regenerative systems. Copyright © 2016 John Wiley & Sons, Ltd.

Histological Analysis of Early Osteolysis in Total Ankle Arthroplasty

BACKGROUND

The purpose of this study was to perform a histological comparative analysis of tibiotalar joint samples taken from areas of osteolysis adjacent to total ankle arthroplasties vs control synovial specimens to determine the reaction to and presence of polyethylene (PE) particles.

METHODS

A total of 57 pathology samples were identified in the osteolysis group, while 11 were identified in the control group. For each sample, hematoxylin and eosin, Oil Red O (ORO), and macrophage marker CD163-stained slides were created. Polarized light and ORO stain were used to identify PE particles. The presence of metal particles and giant cell reaction to PE particles were also scored.

RESULTS

Macrophages, PE particles, metallosis, and foreign body giant cell reaction scores were significantly higher in the osteolysis group compared with the control group. In the osteolysis group, ORO staining was positive in 93% (53/57), birefringent material was present in 96.5% (55/57), and macrophage infiltrates were present in 96.5% (55/57). Foreign body giant cell reaction with giant cells surrounding PE particles was present in 49.1% (28/57) of osteolytic specimens. The presence of foreign body giant cell reaction was associated with significantly higher macrophage, ORO, and polarizable material scores. The average time to surgery for osteolysis from the index ankle replacement was 6.0 (range, 0-15) years for the 57 patients in the osteolysis group.

CONCLUSION

This study is the largest ankle arthroplasty histological analysis to show that areas of osteolysis consist of abundant polyethylene wear particles, present both intracellularly and extracellularly. Furthermore, these areas were associated with a CD163⁺ macrophage infiltrate and frequently a foreign body reaction with giant cells engulfing PE particles. It is likely that implant wear particles play a significant role in osteolysis based on the histopathology.

LEVEL OF EVIDENCE

Level III, retrospective comparative series.

Melatonin attenuates titanium particle-induced osteolysis via activation of Wnt/β-catenin signaling pathway

Wear debris-induced inhibition of bone regeneration and extensive bone resorption were common features in peri-prosthetic osteolysis (PPO). Here, we investigated the effect of melatonin on titanium particle-stimulated osteolysis in a murine calvariae model and mouse-mesenchymal-stem cells (mMSCs) culture system. Melatonin inhibited titanium particle-induced osteolysis and increased bone formation at osteolytic sites, confirmed by radiological and histomorphometric data. Furthermore, osteoclast numbers decreased dramatically in the low- and high-melatonin administration mice, as respectively, compared with the untreated animals. Melatonin alleviated titanium particle-induced depression of osteoblastic differentiation and mineralization in mMSCs. Mechanistically, melatonin was found to reduce the degradation of β-catenin, levels of which were decreased in presence of titanium particles both in vivo and in vitro. To further ensure whether the protective effect of melatonin was mediated by the Wnt/β-catenin signaling pathway, ICG-001, a selective β-catenin inhibitor, was added to the melatonin-treated groups and was found to attenuate the effect of melatonin on mMSC mineralization. We also demonstrated that melatonin modulated the balance between receptor activator of nuclear factor kappa-B ligand and osteoprotegerin via activation of Wnt/β-catenin signaling pathway. These findings strongly suggest that melatonin represents a promising candidate in the treatment of PPO.

STATEMENT OF SIGNIFICANCE

Peri-prosthetic osteolysis, initiated by wear debris-induced inhibition of bone regeneration and extensive bone resorption, is the leading cause for implant failure and reason for revision surgery. In the current study, we demonstrated for the first time that melatonin can induce bone regeneration and reduce bone resorption at osteolytic sites caused by titanium-particle stimulation. These effects might be mediated by activating Wnt/β-catenin signaling pathway and enhancing osteogenic differentiation. Meanwhile, the ability of melatonin to modulate the balance between receptor activator of nuclear factor kappa-B ligand and osteoprotegerin mediated by Wnt/β-catenin signaling pathway, thereby suppressing osteoclastogenesis, may be implicated in the protective effects of melatonin on titanium-particle-induced bone resorption. These results suggested that melatonin can be considered as a promising therapeutic agent for the prevention and treatment of peri-prosthetic osteolysis.

Factors regulating bone remodeling processes in aseptic implant loosening

This study was undertaken to screen periprosthetic tissues (PPTs) under specified conditions for a series of molecular components and describe them in bone remodeling processes within aseptic loosening. PPT samples were obtained from patients undergoing revision surgery of endoprostheses (n = 24) and synovial tissues from patients with OA (control) (n = 18), patients with any form of inflammatory arthritides were excluded. Tissue samples were examined via microbiology, histology (H&E, TRAP), immunohistochemistry (CD68/anti-S100a4), quantitative real-time PCR (ALP, COL1A1, cathepsin K, M-CSF, MMP13, OPG, RANK, RANKL, TNF-α, and TRAP) and an endotoxin-assay. PPT samples contained a variety of cellular components and stained positive for TRAP (56%), CD68 (100%), and S100a4 (100%). Wear debris were found in cells staining positive for CD68 and S100a4. In PPTs significantly higher ALP, COL1A1, MMP-13, RANK, RANKL, and TRAP expression were found along with a significantly higher RANKL/OPG ratio and a significantly lower OPG expression. No significant difference was observed for M-CSF, TNF-α, cathepsin K, and endotoxin levels. In conclusion we found osteogenic proteins (ALP, COL1A1), a proteolytic enzyme (MMP-13), markers for osteoclast differentiation (RANK, RANKL), and osteoclast activity (TRAP) to be increased in PPT, whereas OPG expression decreased significantly in comparison to control. We present data about a large series of molecular components in PPT and describe novel and key findings about their expression levels in regards to aseptic implant loosening. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:248-257, 2017.

The biological response to orthopedic implants for joint replacement. II: Polyethylene, ceramics, PMMA, and the foreign body reaction

Novel evidence-based prosthetic designs and biomaterials facilitate the performance of highly successful joint replacement (JR) procedures. To achieve this goal, constructs must be durable, biomechanically sound, and avoid adverse local tissue reactions. Different biomaterials such as metals and their alloys, polymers, ceramics, and composites are currently used for JR implants. This review focuses on (1) the biological response to the different biomaterials used for TJR and (2) the chronic inflammatory and foreign-body response induced by byproducts of these biomaterials. A homeostatic state of bone and surrounding soft tissue with current biomaterials for JR can be achieved with mechanically stable, infection free and intact (as opposed to the release of particulate or ionic byproducts) implants. Adverse local tissue reactions (an acute/chronic inflammatory reaction, periprosthetic osteolysis, loosening and subsequent mechanical failure) may evolve when the latter conditions are not met. This article (Part 2 of 2) summarizes the biological response to the non-metallic materials commonly used for joint replacement including polyethylene, ceramics, and polymethylmethacrylate (PMMA), as well as the foreign body reaction to byproducts of these materials. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1685-1691, 2017.

Biological reaction to polyethylene particles in a murine calvarial model is highly influenced by age

Particle-induced osteolysis is driven by multiple factors including bone metabolism, inflammation, and age. The objective of this study was to determine the influence of age on polyethylene (PE) particle-induced osteolysis in a murine calvarial model comparing 2-month-old (young) versus 24-month-old (old) mice. After PE particle implantation, calvaria were assessed at days (D) 3, D7, D14, and D21 via chemoluminescent imaging for inflammation (L-012 probe). In addition micro-computed tomography (micro-CT) and histomorphometry end points addressed the bone reaction. Inflammation peaked at D7 in young mice and D14 in old mice. Using micro-CT, a nadir of mature bone was recorded at D7 for young mice, versus D21 for old mice. Besides, regenerating bone peaked at distinct timepoints: D7 for young mice versus D21 for old mice. In the young mice group, the histomorphometric findings correlated with micro-CT regenerating bone findings at D7, associated with ample osteoïd deposition. No osteoïd could be histologically quantified in the old mice group at D7. This study demonstrated that the biological reaction to polyethylene particles is highly influenced by age.

Cobalt, titanium and PMMA bone cement debris influence on mouse osteoblast cell elasticity, spring constant and calcium production activity

Periprosthetic osteolysis and implant loosening are the outcomes of wear debris generation in total joint replacements. Wear debris formed from the implanted materials consisting of metals, polymers, ceramic and bone cement initiate the immune system response. Often osteoblasts, the principal cell type in bone tissue adjacent to the prostheses, are directly impacted. In this study, the influence of cobalt, titanium and PMMA bone cement particles of different sizes, charges and compositions on mouse osteoblast adhesion, nanomechanics (elasticity and spring constant) and metabolic activity were investigated. These studies were accompanied by osteoblast mineralisation experiments and cell uptake after exposure to particles at defined time points. Our results demonstrate that alteration of the nanomechanical properties are mainly dependent on the metal type rather than nanoparticles size and concentration. Moreover, despite uptake increasing over exposure time, the cell characteristics exhibit changes predominately after the first 24 hours, highlighting that the cell responses to nanoparticle exposure are not cumulative. Understanding these processes is critical to expanding our knowledge of implant loosening and elucidating the nature of prosthetic joint failure.

A novel locking screw hip stem to achieve immediate stability in total hip arthroplasty: A biomechanical study

INTRODUCTION

As total hip arthroplasty is now applicable for younger, healthier, and more active patients, bone preservation becomes even more essential, and proximal fixation, resulting in less stress shielding, draws special attention with focus on new strategies and implant designs. Recently, a new type of non-cemented fixation of the femoral component, featured with the locking screw hip (LSH) stem, was developed by Scyon Orthopaedics AG (Au-Waedenswil, Switzerland). The idea to rigidly fix the femoral component of a prosthesis for total hip replacement in this fashion evolved from the very good results achieved with the internal point-contact fixator PC-Fix. The purpose of this study was to investigate the unique characteristics of the LSH-stem and to assess its biomechanical performance in comparison to a conventional cemented prosthesis (Mueller straight stem).

MATERIAL AND METHODS

Six paired human cadaveric femora were preserved with the method of Thiel, split in two study groups, implanted with either cemented Mueller straight stem or LSH-stem prostheses and biomechanically tested under progressively increasing axial loading until catastrophic failure. Bone mineral density (BMD) of all femora was evaluated in the femoral head prior to implantation. Axial construct stiffness, failure load and cycles to failure were calculated from the machine data and statistically evaluated at a level of significance p = 0.05.

RESULTS

No statistically significant difference between the LSH-stem and the Mueller straight stem was found in terms of axial construct stiffness (2031.5 N/mm ± 483.1 N/mm and 2403.6 N/mm ± 705.2 N/mm, p = 0.115), failure load (4958.8 N ± 1094.1 N and 5907.2 N ± 1562.8 N, p = 0.138) and cycles to failure (7917.7 ± 2188.1 and 9814.3 ± 3125.6, p = 0.138). BMD showed no significant difference between the two study groups, p = 0.616.

CONCLUSION

The LSH-stem seems to be stable enough to carry loads experienced during the rehabilitation period of a patient after THR. Its stability, which is similar to that of the Mueller straight stem, may justify the clinical application of the LSH-stem under thorough investigation.

Wear particles derived from metal hip implants induce the generation of multinucleated giant cells in a 3-dimensional peripheral tissue-equivalent model

Multinucleate giant cells (MGCs) are formed by the fusion of 5 to 15 monocytes or macrophages. MGCs can be generated by hip implants at the site where the metal surface of the device is in close contact with tissue. MGCs play a critical role in the inflammatory processes associated with adverse events such as aseptic loosening of the prosthetic joints and bone degeneration process called osteolysis. Upon interaction with metal wear particles, endothelial cells upregulate pro-inflammatory cytokines and other factors that enhance a localized immune response. However, the role of endothelial cells in the generation of MGCs has not been completely investigated. We developed a three-dimensional peripheral tissue-equivalent model (PTE) consisting of collagen gel, supporting a monolayer of endothelial cells and human peripheral blood mononuclear cells (PBMCs) on top, which mimics peripheral tissue under normal physiological conditions. The cultures were incubated for 14 days with Cobalt chromium alloy (CoCr ASTM F75, 1–5 micron) wear particles. PBMC were allowed to transit the endothelium and harvested cells were analyzed for MGC generation via flow cytometry. An increase in forward scatter (cell size) and in the propidium iodide (PI) uptake (DNA intercalating dye) was used to identify MGCs. Our results show that endothelial cells induce the generation of MGCs to a level 4 fold higher in 3-dimentional PTE system as compared to traditional 2-dimensional culture plates. Further characterization of MGCs showed upregulated expression of tartrate resistant alkaline phosphatase (TRAP) and dendritic cell specific transmembrane protein, (DC-STAMP), which are markers of bone degrading cells called osteoclasts. In sum, we have established a robust and relevant model to examine MGC and osteoclast formation in a tissue like environment using flow cytometry and RT-PCR. With endothelial cells help, we observed a consistent generation of metal wear particle- induced MGCs, which heralds metal on metal hip failures.

Biological response to prosthetic debris

Joint arthroplasty had revolutionized the outcome of orthopaedic surgery. Extensive and collaborative work of many innovator surgeons had led to the development of durable bearing surfaces, yet no single material is considered absolutely perfect. Generation of wear debris from any part of the prosthesis is unavoidable. Implant loosening secondary to osteolysis is the most common mode of failure of arthroplasty. Osteolysis is the resultant of complex contribution of the generated wear debris and the mechanical instability of the prosthetic components. Roughly speaking, all orthopedic biomaterials may induce a universal biologic host response to generated wear débris with little specific characteristics for each material; but some debris has been shown to be more cytotoxic than others. Prosthetic wear debris induces an extensive biological cascade of adverse cellular responses, where macrophages are the main cellular type involved in this hostile inflammatory process. Macrophages cause osteolysis indirectly by releasing numerous chemotactic inflammatory mediators, and directly by resorbing bone with their membrane microstructures. The bio-reactivity of wear particles depends on two major elements: particle characteristics (size, concentration and composition) and host characteristics. While any particle type may enhance hostile cellular reaction, cytological examination demonstrated that more than 70% of the debris burden is constituted of polyethylene particles. Comprehensive understanding of the intricate process of osteolysis is of utmost importance for future development of therapeutic modalities that may delay or prevent the disease progression.

In vivo wear particles of remelted highly crosslinked polyethylene after total hip arthroplasty: report of four cases

This is the first report of in vivo wear particles from four total hip arthroplasties using remelted highly crosslinked polyethylene. The number of particles was (1.51 ± 0.45) × 10(7) g(-1) (mean ± standard error); particle size (equivalent circle diameter), 0.72 ± 0.15 µm; and roundness, 1.45 ± 0.05. Remelted highly crosslinked polyethylene generates fewer, rounder, equivalently sized particles compared with corresponding reported values for particles generated from conventional polyethylene.

Do genetic susceptibility, Toll-like receptors, and pathogen-associated molecular patterns modulate the effects of wear?

Overwhelming evidence supports the concept that wear particles are the primary initiator of aseptic loosening of orthopaedic implants. It is likely, however, that other factors modulate the biologic response to wear particles. This review focuses on three potential other factors: genetic susceptibility, Toll-like receptors (TLRs), and bacterial pathogen-associated molecular patterns (PAMPs). WHERE ARE WE NOW?: Considerable evidence is emerging that both genetic susceptibility and TLR activation are important factors that modulate the biologic response to wear particles, but it remains controversial whether bacterial PAMPs also do so. WHERE DO WE NEED TO GO?: Detailed understanding of the roles of these other factors may lead to identification of novel therapeutic targets for patients with aseptic loosening. HOW DO WE GET THERE?: Highest priority should be given to polymorphism replication studies with large numbers of patients and studies to replicate the reported correlation between bacterial biofilms and the severity of aseptic loosening.

Interaction of Materials and Biology in Total Joint Replacement - Successes, Challenges and Future Directions

Total joint replacement (TJR) has revolutionized the treatment of end-stage arthritic disorders. This success is due, in large part, to a clear understanding of the important interaction between the artificial implant and the biology of the host. All surgical procedures in which implants are placed in the body evoke an initial inflammatory reaction, which generally subsides over several weeks. Thereafter, a series of homeostatic events occur leading to progressive integration of the implant within bone and the surrounding musculoskeletal tissues. The eventual outcome of the operation is dependent on the characteristics of the implant, the precision of the surgical technique and operative environment, and the biological milieu of the host. If these factors and events are not optimal, adverse events can occur such as the development of chronic inflammation, progressive bone loss due to increased production of degradation products from the implant (periprosthetic osteolysis), implant loosening or infection. These complications can lead to chronic pain and poor function of the joint reconstruction, and may necessitate revision surgery or removal of the prosthesis entirely. Recent advances in engineering, materials science, and the immunological aspects associated with orthopaedic implants have fostered intense research with the hope that joint replacements will last a lifetime, and facilitate pain-free, normal function.

Osteoclasts and their precursors are present in the induced-membrane during bone reconstruction using the Masquelet technique

In 2000, Masquelet reported a long bone reconstruction technique using an induced membrane formed around a polymethylmethacrylate (PMMA) spacer placed in the defect with appropriate stabilization followed by secondary bone graft after PMMA removal. This reconstruction procedure allows rapid and safe bone reformation for septic, traumatic, neoplastic or congenital bone defects. A rat model of the Masquelet technique was developed to further characterize the biological activities of this induced membrane. Our model allows healing of a critical-sized femoral defect (8 mm) by means of this procedure over a period of 18 weeks. Comparison of induced membranes obtained 3, 4, 5 and 6 weeks after PMMA insertion indicated that this tissue changes over time. Several mineralization spots and bone cells were observed in contact with the PMMA, when assessed by Alizarin Red, Von Kossa, Alkaline phosphatase and Tartrate-resistant acid phosphatase staining of the membranes. CTR (calcitonin receptor)- and RANK (Receptor Activator of Nuclear factor Kappa B)- positive mononuclear cells were detected in the induced membrane, confirming the presence of osteoclasts in this tissue. These cells were observed in a thin, highly cellular layer in the induced membrane in contact with the PMMA. Together, these findings suggest that the membrane is able to promote osteointegration of autologous corticocancellous bone grafts during the Masquelet technique by creating local conditions that may be favourable to graft bone remodelling and osteointegration. Copyright © 2014 John Wiley & Sons, Ltd.

Mitigative effect of erythromycin on PMMA challenged preosteoblastic MC3T3-E1 cells

Background. Aseptic loosening (AL) is a major complication of total joint replacement. Recent approaches to limiting AL have focused on inhibiting periprosthetic inflammation and osteoclastogenesis. Questions/Purposes. The purpose of this study was to determine the effects of erythromycin (EM) on polymethylmethacrylate (PMMA) particle-challenged MC3T3 osteoblast precursor cells. Methods. MC3T3 cells were pretreated with EM (0–10 μg/mL) and then stimulated with PMMA (1 mg/mL). Cell viability was evaluated by both a lactate dehydrogenase (LDH) release assay and cell counts. Cell differentiation was determined by activity of alkaline phosphatase (ALP). Gene expression was measured via real-time quantitative RT-PCR. Results. We found that exposure to PMMA particles reduced cellular viability and osteogenetic potential in MC3T3 cell line. EM treatment mitigated the effects of PMMA particles on the proliferation, viability and differentiation of MC3T3 cells. PMMA decreased the gene expression of Runx2, osterix and osteocalcin, which can be partially restored by EM treatment. Furthermore, EM suppressed PMMA- induced increase of NF-κB gene expression. Conclusions. These data demonstrate that EM mitigates the effects of PMMA on MC3T3 cell viability and differentiation, in part through downregulation of NF-κB pathway. EM appeared to represent an anabolic agent on MC3T3 cells challenged with PMMA particles.

No difference in in vivo polyethylene wear particles between oxidized zirconium and cobalt-chromium femoral component in total knee arthroplasty

PURPOSE

Polyethylene wear particle generation is one of the most important factors affecting mid- to long-term results of total knee arthroplasties. Oxidized zirconium was introduced as a material for femoral components to reduce polyethylene wear generation. However, an in vivo advantage of oxidized zirconium on polyethylene wear particle generation is still controversial. The purpose of this study was to compare in vivo polyethylene wear particles between oxidized zirconium total knee prosthesis and conventional cobalt-chromium (Co-Cr) total knee prosthesis.

METHODS

Synovial fluid was obtained from the knees of 6 patients with oxidized zirconium total knee prosthesis and from 6 patients with conventional cobalt-chromium (Co-Cr) total knee prosthesis 12 months after the operation. Polyethylene particles were isolated and examined using a scanning electron microscope and image analyser.

RESULTS

Total number of particles in each knee was 3.3 ± 1.3 × 10(7) in the case of oxidized zirconium (mean ± SD) and 3.4 ± 1.2 × 10(7) in that of Co-Cr (n.s.). The particle size (equivalent circle diameter) was 0.8 ± 0.3 μm in the case of oxidized zirconium and 0.6 ± 0.1 μm in that of Co-Cr (n.s.). The particle shape (aspect ratio) was 1.4 ± 0.0 in the case of oxidized zirconium and 1.4 ± 0.0 in that of metal Co-Cr (n.s).

CONCLUSIONS

Although newly introduced oxidized zirconium femoral component did not reduce the in vivo polyethylene wear particles in early clinical stage, there was no adverse effect of newly introduced material. At this moment, there is no need to abandon oxidized zirconium femoral component. However, further follow-up of polyethylene wear particle generation should be performed to confirm the advantage of the oxidized zirconium femoral component.

LEVEL OF EVIDENCE

Therapeutic study, Level III.

Novel biological strategies for treatment of wear particle-induced periprosthetic osteolysis of orthopaedic implants for joint replacement

Wear particles and by-products from joint replacements and other orthopaedic implants may result in a local chronic inflammatory and foreign body reaction. This may lead to persistent synovitis resulting in joint pain and swelling, periprosthetic osteolysis, implant loosening and pathologic fracture. Strategies to modulate the adverse effects of wear debris may improve the function and longevity of joint replacements and other orthopaedic implants, potentially delaying or avoiding complex revision surgical procedures. Three novel biological strategies to mitigate the chronic inflammatory reaction to orthopaedic wear particles are reported. These include (i) interference with systemic macrophage trafficking to the local implant site, (ii) modulation of macrophages from an M1 (pro-inflammatory) to an M2 (anti-inflammatory, pro-tissue healing) phenotype in the periprosthetic tissues, and (iii) local inhibition of the transcription factor nuclear factor kappa B (NF-κB) by delivery of an NF-κB decoy oligodeoxynucleotide, thereby interfering with the production of pro-inflammatory mediators. These three approaches have been shown to be viable strategies for mitigating the undesirable effects of wear particles in preclinical studies. Targeted local delivery of specific biologics may potentially extend the lifetime of orthopaedic implants.

Extracellular matrix degradation and tissue remodeling in periprosthetic loosening and osteolysis: focus on matrix metalloproteinases, their endogenous tissue inhibitors, and the proteasome

The leading complication of total joint replacement is periprosthetic osteolysis, which often results in aseptic loosening of the implant, leading to revision surgery. Extracellular matrix degradation and connective tissue remodeling around implants have been considered as major biological events in the periprosthetic loosening. Critical mediators of wear particle-induced inflammatory osteolysis released by periprosthetic synovial cells (mainly macrophages) are inflammatory cytokines, chemokines, and proteolytic enzymes, mainly matrix metalloproteinases (MMPs). Numerous studies reveal a strong interdependence of MMP expression and activity with the molecular mechanisms that control the composition and turnover of periprosthetic matrices. MMPs can either actively modulate or be modulated by the molecular mechanisms that determine the debris-induced remodeling of the periprosthetic microenvironment. In the present study, the molecular mechanisms that control the composition, turnover, and activity of matrix macromolecules within the periprosthetic microenvironment exposed to wear debris are summarized and presented. Special emphasis is given to MMPs and their endogenous tissue inhibitors (TIMPs), as well as to the proteasome pathway, which appears to be an elegant molecular regulator of specific matrix macromolecules (including specific MMPs and TIMPs). Furthermore, strong rationale for potential clinical applications of the described molecular mechanisms to the treatment of periprosthetic loosening and osteolysis is provided.

Evidence for active antigen presentation by monocyte/macrophages in response to stimulation with particles: the expression of NFκB transcription factors and costimulatory molecules

BACKGROUND

The macrophage and lymphocyte response to wear debris contributes to the failure of some joint replacements. Costimulatory molecule expression by particle-containing macrophages is an evidence for antigen presentation. The NFκB transcription factors are regulators of costimulatory molecules and are present in tissue near failed joint prostheses. The tissue localisation of NFκB and the expression of these factors and costimulatory molecules by U937 cells stimulated with nano- and microparticles are reported, together with the effects of an NFκB inhibitor (sc514).

MATERIALS AND METHODS

The tissue localisation of RelA, RelB, c-rel, p50, p52 and NF-IL6 was examined by immunohistochemistry in samples from 15 patients with failure of metal against polyethylene total hip replacements. The expression of these NFκB factors by U937 cells stimulated with microparticles (CoCr, diamond) and nanoparticles (diamond) was examined by quantified RT-PCR. Lipopolysaccharide provided positive controls while negative controls had no additions to culture. Inhibition of NFκB activity by sc-514 was studied. The expression of costimulatory molecules (CD80, CD86 and HLA-DR) was evaluated in parallel cell culture studies by tricolour flow cytometry.

RESULTS AND DISCUSSION

Immunohistochemistry of tissue showed the highest expression for NF-IL6 (32.56 ± 11.61 per cent), RelA (33.66 ± 9.98 per cent) and p52 (32.07 ± 12.90 per cent), then RelB (22.63 ± 7.49 per cent), c-rel (14.07 ± 6.72 per cent) and p50 (13.07 ± 5.99 per cent). NF-IL6 was localised to macrophages, RelB to RFD1+ dendritic cells. U937 cells showed an increased expression of all NFκB factors (p < 0.01) in response to CoCr and diamond microparticles. Only RelA and c-rel (p < 0.01) were increased by one diamond nanoparticle and p52 and c-rel (p < 0.01) by another nanoparticulate diamond. Inhibition by sc-514 of RelA, c-rel and p50 expression occurred with all four particles, p52 was decreased for all diamond particles (but not CoCr) and RelB was not inhibited with any of the particles. CD86 and HLA-DR expression were upregulated by microparticles (CoCr, diamond) (p ≪ 0.01) with lower levels (significant) of these molecules found with diamond nanoparticles. CD80 expression was much less than CD86 and HLA-DR. Costimulatory molecule expression in the bone-implant interface indicates antigen presentation by macrophages. Functional studies with U937 monocytes show the same molecules expressed on exposure to micro- and nanoparticles. Highest values occur with CoCr while the smallest diamond nanoparticles are the least stimulatory. NFκB expression gives an insight into the immunogenic potential of the different particles.

Exogenous MC3T3 preosteoblasts migrate systemically and mitigate the adverse effects of wear particles

Understanding how relevant cell types respond to wear particles will reveal new avenues for treating osteolysis following joint replacements. In this study, we investigate the effects of ultrahigh molecular weight polyethylene (UHMWPE) particles on preosteoblast migration and function. We infused UHMWPE particles or saline into the left femur of mice and injected luciferase-expressing preosteoblasts (MC3T3 cells) into each left ventricle. Bioluminescence imaging (BLI) confirmed systemic administration of MC3T3 cells. BLI throughout the 28-day experiment showed greater MC3T3 migration to the site of particle infusion than to the site of saline infusion, with significant differences on days 0, 4, and 6 (p≤0.055). Immunostaining revealed a greater number of osteoblasts and osteoclasts in the particle-infused femora, indicating greater bone turnover. The bone mineralization of the particle-infused femora increased significantly when compared to saline-infused femora (an increase of 146.4±27.9 vs. 12.8±8.7 mg/mL, p=0.008). These results show that infused preosteoblasts can migrate to the site of wear particles. Additionally, as the migrated cells were associated with increased bone mineralization in spite of the presence of particles, increasing osteoblast recruitment is a potential strategy for combating bone loss due to increased osteoclast/macrophage number and decreased osteoblast function.

Selective inhibition of the MCP-1-CCR2 ligand-receptor axis decreases systemic trafficking of macrophages in the presence of UHMWPE particles

The biological mechanisms leading to periprosthetic osteolysis involve both chemokines and the monocyte/macrophage cell lineage. Whether MCP-1 plays a major role in macrophage recruitment in the presence of wear particles is unknown. We tested two hypotheses: (1) that exogenous local delivery of MCP-1 induces systematic macrophage recruitment and (2) that blockade of the MCP-1 ligand-receptor axis decreases macrophage recruitment and osteolysis in the presence of ultra high molecular weight polyethylene (UHMWPE) particles. Six groups of nude mice were used. We used non-invasive imaging to assay macrophage recruitment and osteolysis. A murine macrophage cell line and primary wild type and CCR2 knockout murine macrophages were used as the reporter cells. Particles were infused into the femoral canal. Bioluminescence and immunohistochemical staining were used to confirm the migration of reporter cells. Locally infused MCP-1 induced systemic macrophage trafficking to bone. Injection of MCP-1 receptor antagonist significantly decreased reporter cell recruitment to bone infused with UHMWPE particles and decreased osteolysis. Systemic migration of reporter cells to infused particles was decreased when the reporter cells were deficient in the CCR2 receptor. Interruption of the MCP-1 ligand-receptor axis appears to be a viable strategy to mitigate trafficking of macrophages and osteolysis due to UHMWPE particles.

Electrospun polyvinyl alcohol-collagen-hydroxyapatite nanofibers: a biomimetic extracellular matrix for osteoblastic cells

The failure of prosthesis after total joint replacement is due to the lack of early implant osseointegration. In this study polyvinyl alcohol-collagen-hydroxyapatite (PVA-Col-HA) electrospun nanofibrous meshes were fabricated as a biomimetic bone-like extracellular matrix for the modification of orthopedic prosthetic surfaces. In order to reinforce the PVA nanofibers, HA nanorods and Type I collagen were incorporated into the nanofibers. We investigated the morphology, biodegradability, mechanical properties and biocompatibility of the prepared nanofibers. Our results showed these inorganic-organic blended nanofibers to be degradable in vitro. The encapsulated nano-HA and collagen interacted with the PVA content, reinforcing the hydrolytic resistance and mechanical properties of nanofibers that provided longer lasting stability. The encapsulated nano-HA and collagen also enhanced the adhesion and proliferation of murine bone cells (MC3T3) in vitro. We propose the PVA-Col-HA nanofibers might be promising modifying materials on implant surfaces for orthopedic applications.

Histological and Ultrastructural Reaction to Different Materials for Orthopaedic Application

Prosthetic joints loosening in absence of infection is the most common reason for revision surgery and is known as aseptic loosening. A significant role in the pathogenesis of implant failure undoubtedly played by the generation of wear debris, mainly from the load bearing joint surfaces, and the cellular reaction through the formation of tissue membrane around implants. This article analyzes histologic, immunohistochemical ad ultrastructural aspects of periprosthetic tissue membrane collected at time of surgical revision, paying attention on cell host response to different materials: metals, polyethylene and ceramics. Dimension of particles seems to be crucial in the activation of different cell population to wear debris.

Continuous infusion of UHMWPE particles induces increased bone macrophages and osteolysis

BACKGROUND

Aseptic loosening and periprosthetic osteolysis resulting from wear debris are major complications of total joint arthroplasty. Monocyte/macrophages are the key cells related to osteolysis at the bone-implant interface of joint arthroplasties. Whether the monocyte/macrophages found at the implant interface in the presence of polyethylene particles are locally or systemically derived is unknown.

QUESTIONS/PURPOSES

We therefore asked (1) whether macrophages associated with polyethylene particle-induced chronic inflammation are recruited locally or systemically and (2) whether the recruited macrophages are associated with enhanced osteolysis locally.

METHODS

Noninvasive in vivo imaging techniques (bioluminescence and microCT) were used to investigate initial macrophage migration systemically from a remote injection site to polyethylene wear particles continuously infused into the femoral canal. We used histologic and immunohistologic staining to confirm localization of migrated macrophages to the polyethylene particle-treated femoral canals and monitor cellular markers of bone remodeling.

RESULTS

The values for bioluminescence were increased for animals receiving UHMWPE particles compared with the group in which the carrier saline was infused. At Day 8, the ratio of bioluminescence (operated femur divided by nonoperated contralateral femur of each animal) for the UHMWPE group was 13.95 ± 5.65, whereas the ratio for the saline group was 2.60 ± 1.14. Immunohistologic analysis demonstrated the presence of reporter macrophages in the UHMWPE particle-implanted femora only. MicroCT scans showed the bone mineral density for the group with both UHMWPE particles and macrophage was lower than the control groups.

CONCLUSIONS

Infusion of clinically relevant polyethylene particles, similar to the human scenario, stimulated systemic migration of remotely injected macrophages and local net bone resorption.

New animal models of wear-particle osteolysis

Particle debris resulting from in vivo degradation of total joint replacement components are recognised as the major factor limiting the longevity of joint reconstruction and the overall success of the procedure. Better understanding the complex cellular and tissue mechanisms and interactions resulting in wear-particle osteolysis requires a number of experimental approaches, including radiological monitoring and analysis of retrieved tissues from clinical cases, in vitro experiments, and also animal-model investigations. In consideration of both their advantages and drawbacks, this paper provides an historical overview of numerous animal models that have been developed over the last three decades to investigate the pathogenesis of wear-particle osteolysis and to facilitate the preclinical testing of new treatment options. The authors also focus on recent studies in order to provide a better understanding of the current state of the art on this subject and propose some perspectives regarding technical and fundamental questions.

Weight of polyethylene wear particles is similar in TKAs with oxidized zirconium and cobalt-chrome prostheses

BACKGROUND

The greater lubricity and resistance to scratching of oxidized zirconium femoral components are expected to result in less polyethylene wear than cobalt-chrome femoral components.

QUESTIONS/PURPOSES

We examined polyethylene wear particles in synovial fluid and compared the weight, size (equivalent circle diameter), and shape (aspect ratio) of polyethylene wear particles in knees with an oxidized zirconium femoral component with those in knees with a cobalt-chrome femoral component.

PATIENTS AND METHODS

One hundred patients received an oxidized zirconium femoral component in one knee and a cobalt-chrome femoral component in the other. There were 73 women and 27 men with a mean age of 55.6 years (range, 44-60 years). The minimum followup was 5 years (mean, 5.5 years; range, 5-6 years). Polyethylene wear particles were analyzed using thermogravimetric methods and scanning electron microscopy.

RESULTS

The weight of polyethylene wear particles produced at the bearing surface was 0.0223 +/- 0.0054 g in 1 g synovial fluid in patients with an oxidized zirconium femoral component and 0.0228 +/- 0.0062 g in patients with a cobalt-chrome femoral component. Size and shape of polyethylene wear particles were 0.59 +/- 0.05 microm and 1.21 +/- 0.24, respectively, in the patients with an oxidized zirconium femoral component and 0.52 +/- 0.03 microm and 1.27 +/- 0.31, respectively, in the patients with a cobalt-chrome femoral component. Knee Society knee and function scores, radiographic results, and complication rate were similar between the knees with an oxidized zirconium and cobalt-chrome femoral component.

CONCLUSIONS

The weight, size, and shape of polyethylene wear particles were similar in the knees with an oxidized zirconium and a cobalt-chrome femoral component. We found the theoretical advantages of this surface did not provide the actual advantage.

LEVEL OF EVIDENCE

Level I, therapeutic study. See the guidelines for Authors for a complete description of levels of evidence.

Cellular chemotaxis induced by wear particles from joint replacements

The destruction of bone around joint replacements (periprosthetic osteolysis) is an adverse biological response associated with the generation of excessive wear particles. Wear debris from the materials used for joint replacements stimulate a chronic inflammatory and foreign body reaction that leads to increased osteoclast differentiation and maturation, and decreased bone formation. Wear debris induces both local and systemic trafficking of inflammatory cells to the site of particle generation. Recent studies have shown that this effect is mediated primarily by chemotactic cytokines (chemokines) including macrophage chemotactic protein-1 (MCP-1, also known as CCL2), macrophage inhibitory protein-1 (MIP-1), Interleukin-8 (IL-8 or CXCL8) and others. These ligands migrate along a concentration gradient to interact with G-protein-linked transmembrane receptors on the cell surface. Chemokines are involved in the innate and adaptive immune responses, angiogenesis, wound healing and tissue repair. In vitro, in vivo and tissue retrieval studies have shown that chemokine-directed systemic trafficking of polymorphonuclear leukocytes and cells of the monocyte/macrophage lineage to wear particles result in the release of pro-inflammatory factors and subsequent bone loss. Modulation of the chemokine ligand-receptor axis is a potential strategy to mitigate the adverse effects of wear particles from joint replacements.

In vivo comparison of wear particles between highly crosslinked polyethylene and conventional polyethylene in the same design of total knee arthroplasties

Reduction of wear with highly crosslinked polyethylene (HXLPE) has been reported in in vitro and in vivo studies of total hip prostheses. However, use of HXLPE in total knee prostheses is still controversial. The aim of this study was to compare in vivo polyethylene wear particle generation of HXLPE with that of conventional polyethylene in total knee prostheses of the same design. Synovial fluid was obtained from four knees with HXLPE inserts and three knees with conventional polyethylene inserts at 1 year after operation. Polyethylene particles were isolated and examined using a scanning electron microscope and image analyzer. The total number of particles in each knee was 0.28 +/- 0.12 x 10(6) in HXPLE group (mean +/- standard error) and 6.87 +/- 2.85 x 10(6) in conventional polyethylene group (p = 0.040). Particle size (equivalent circle diameter) was 0.64 +/- 0.07 microm in HXPLE group and 1.21 +/- 0.21 microm in conventional polyethylene group (p = 0.030). Particle shape (aspect ratio) was 1.33 +/- 0.10 in HXLPE and 1.88 +/- 0.19 in conventional polyethylene (p = 0.035). Thepercentage of particles of submicron size was greater than 90% in HXLPE group and 55% in conventional polyethylene group. Except for the material of the polyethylene insert, the design and material of prostheses were completely the same in both groups. The HXLPE insert generated fewer, smaller, and rounder polyethylene wear particles than the conventional polyethylene insert in the early stage after surgery.

Comparison between highly cross-linked and conventional polyethylene in total knee arthroplasty

The use of highly cross-linked polyethylene in total knee prostheses is still controversial. The aim of the present study was to compare radiographic and clinical results of using conventional and highly cross-linked polyethylene in cruciate retaining total knee prostheses of completely the same design. Two hundred and two consecutive total knee arthroplasties (NexGen CR, Zimmer) were performed using the same procedure. The first consecutive 113 knees had conventional polyethylene insert and following consecutive 89 knees had highly cross-linked polyethylene insert (Prolong, Zimmer). Differences in the age, gender, and diagnosis between two groups were not statistically significant. Preoperative range of motion (ROM) of the knee, and Knee Society Score (KSS) was better in highly cross-linked polyethylene group. Clinical and radiographic results were evaluated at two years after operation. The difference of ROM and KSS between groups was not statistically significant. There was no revision surgery. No knee exhibited osteolysis, aseptic loosening, or polyethylene failure. There was no early catastrophic clinical failure due to use of the new material.

Ultrastructural Cytochemical and Ultrastructural Morphological Differences Between Human Multinucleated Giant Cells Elicited by Wear Particles from Hip Prostheses and Artificial Ligaments at the Knee

The authors investigated the ultrastructural cytochemical features of multinucleated and mononuclear cells in periprosthetic tissues associated with bone resorption (osteolysis) and those in tissues adjoining failed artificial ligaments having no relation to bone resorption. Clinical specimens of granulation tissue of each type, respectively numbering 4 and 3, were stained for tartrate-resistant acid phosphatase (TRAP) reactions and examined by light and electron microscopy. Both periprosthetic granulation tissues and those adjoining artificial ligaments contained TRAP-positive multinucleated and mononuclear cells. Near joint prostheses, multinucleated cells, including some giant cells, showed TRAP activity and cytoplasmic features resembling osteoclasts, while others had features consistent with foreign-body giant cells, and still others showed degenerative changes. Near artificial ligaments, TRAP-positive multinucleated cells lacked osteoclastic features. At both sites, TRAP-positive multinucleated cells had phagocytised wear particles. TRAP-positive mononuclear cells at both sites also showed phagocytic cytoplasmic features, but not osteoclastic cytoplasmic features. Human mononuclear phagocytes and multinucleated giant cells induced by wear particles possess TRAP activity. Those multinucleated giant cells at sites of osteolysis developed osteoclastic cytoplasmic features and have a phagocytic function.