For patients who took joint replacement, one of the complications, aseptic joint loosening, could cause a high risk of revision surgery. Studies have shown that MSCs have the ability of homing and differentiating, and also have highly effective immune regulation and anti-inflammatory effects. However, few studies had focused on the stem cells in preventing the occurrence and development of aseptic loosening. In this research, we aimed to clarify whether human umbilical cord mesenchymal stem cells could inhibited the aseptic joint loosening caused by wear particles. A Cranial osteolysis mice model was established on mice to examine the effect of hUC-MSCs on the Titanium particles injection area through micro-CT. The amount of stem cells injected was 2 × 10 5 cells. One week later, the mouse Cranial were obtained for micro-CT scan, and then stained with HE analysis immunohistochemical analysis of TNF-α, CD68, CCL3 and Il-1β. All mice were free of fever and other adverse reactions, and there was no death occurred. Titanium particles caused the osteolysis at the mice cranial, while local injection of hUC-MSCs did inhibit the cranial osteolysis, with a lower BV/TV and a higher porosity. Immunohistochemical results suggested that the expression of TNF-α, CD68, CCL3 and Il-1β in the cranial in Titanium particles mice increased significantly, but was significantly reduced in mice injected with hUC-MSCs. The inhibited CD68 expression indicated that the number of macrophage was lower, which might be a result of the inhibition of CCL3. According to the studies above, HUC-MSCs treatment of mouse cranial osteolysis model can significantly reduce osteolysis, inhibit macrophage recruitment, alleviate inflammatory response, without causing adverse reactions. It may become a promising treatment of aseptic joint loosening

As peri-prosthetic aseptic loosening is one of the main causes of implant failure, inhibiting wear particles induced macrophages inflammation is considered as a promising therapy for AL to expand the lifespan of implant. Here, we aim at exploring the role of p110δ, a member of class IA PI3K family, and Krüppel-like factor 4 (KLF4) in titanium particles (TiPs) induced macrophages-inflammation and osteolysis. Firstly, IC87114, the inhibitor of p110δ and siRNA targeting p110δ were applied and experiments including ELISA and immunofluorescence assay were conducted to explore the role of p110δ. Sequentially, KLF4 was predicted as the transcription factor of p110δ and the relation was confirmed by dual luciferase reporter assay. Next, assays including RT-PCR, western blotting and flow cytometry were performed to ensure the specific role of KLF4. Finally, TiPs-induced mice cranial osteolysis model was established, and micro-CT scanning and immunohistochemistry assay were performed to reveal the role of p110δ and KLF4 in vivo. Here, we found that p110δ was upregulated in TiPs-stimulated macrophages. The inhibition of p110δ or knockdown of p110δ could significantly dampen the TiPs-induced secretion of TNFα and IL-6. Further mechanistic studies confirmed that p110δ was responsible for TNFα and IL-6 trafficking out of Golgi complex without affecting their expression in TiPs-treated macrophages. Additionally, we explored the upstream regulators and confirmed that Krüppel-like factor 4 (KLF4) was the transcription repressor of p110δ. Apart from that, KLF4, targeted by miR-92a, could also attenuate TiPs-induced inflammation by mediating NF-κB pathway and M1/M2 polarization. By the establishment of TiPs-induced mice cranial osteolysis model, we found that KLF4 knockdown exacerbated TiPs-induced osteolysis which was strikingly ameliorated by knockdown of p110δ. In summary, our study suggests the key role of miR-92a/KLF4/p110δ signal in TiPs-induced macrophages inflammation and osteolysis

Failure of osseointegration and periprosthetic joint infection (PJI) are the two main reasons of implant failure after total joint replacement (TJR). Nanofiber (NF) implant surface coating represents an alternative local drug eluting device that improves osseointegration and decreases the risk of PJI. The purpose of this study was to investigate the therapeutic efficacies of erythromycin (EM)-loaded coaxial PLGA/PCL-PVA NF coating in a rat S. aureus-infected tibia model. NF coatings with 100mg and 1000mg EM were prepared. NF without EM was included as positive control. 56 Sprague Dawley rats were divided into 4 groups. A titanium pin (1.0-mm x 8 mm) was placed into the tibia through the intercondylar notch. S. aureus (SA) was introduced by both direct injection of 10 μl broth (1 × 10. 4. CFU) into the medullary cavity and single dip of Ti pins into a similar solution prior to insertion. Rats were sacrificed at 8 and 16 weeks after surgery. The outcome measurements include μCT based quantitative osteolysis evaluation and hard tissue histology. Results: EM-NF coating (EM100 and EM1000) reduced osteolysis at 8 and 16 weeks, compared to EM0 and negative control. The effective infection control by EM-NFs was further confirmed by hard tissue section analysis. The Bone implant contact (BIC) and bone area fraction Occupancy (BAFO) within 200 µm of the surface of the pins were used to evaluate the osseointegration and new bone formation around the implants. At 16 weeks, the bone implant contact (BIC) of EM 100 (35.08%) was higher than that of negative control (3.43%) and EM0 (0%). The bone area fraction occupancy within 200 µm (BAFO) of EM100 (0.63 mm2) was higher than that of negative control (0.390 mm2) and EM0 (0.0 mm. 2. ). The BAFO of EM100 was also higher than that of EM1000 (0.3mm. 2. ). There was much less osteolysis observed with EM100 and EM1000 NF coatings at 16 weeks, as compared to EM0 positive control, p=0.08 and p=0.1, respectively. Osseointegration and periprosthetic bone formation was enhanced by EM-NFs, especially EM100. Data from this pilot study is promising for improving implant surface fabrication strategies

Introduction and Objective. Total joint replacement is indicated for osteoarthritis where conservative treatment has failed, and in the UK the number of patients requiring hip and knee replacements is set to increase with an ageing population. Survival of total hip replacements is around 85% at 20 years with the most common reason for revision being aseptic loosening of the implant secondary to osteolysis, which is caused by immune-mediated reactions to implant debris. These debris can also cause pseudotumour formation. As revision surgery is associated with higher morbidity, mortality, infection rates, venous thromboembolism, resource demand and poorer subsequent function it is important to understand the mechanisms underlying the pro-inflammatory process to improve implant survival. Toll-like receptor 4 (TLR4), an innate immune receptor, has been demonstrated to mediate deleterious immune responses by the Tyson-Capper research group, including inflammatory cytokine interleukin-8 (IL-8) secretion. Statin use in epidemiological studies has been associated with reduced overall risk of revision surgery after hip replacement. In-vitro studies have demonstrated the potential for statins to reduce orthopaedic debris-induced immune responses which can lead to osteolysis and pseudotumour formation. As literature from cardiological investigations demonstrate that statins can reduce the expression and responsiveness of TLR4, this could be an exciting mechanism to exploit to reduce the host immune response to orthopaedic wear debris, thereby improving implant survival by reducing immune mediated osteolysis. This ongoing study investigates simvastatin's effect on cobalt ion-mediated changes in gene and protein expression of interleukin-8 and soluble-ICAM-1 (sICAM-1) which is an angiogenic factor implicated in pseudotumour formation. Materials and Methods. TLR4-expressing human monocyte/macrophage THP-1 cells were pre-incubated with 50μM simvastatin for 2-hours or a vehicle control, before being exposed to exposed to 0.75mM cobalt chloride, in addition to a further 24-hour co-incubation with 50μM simvastatin or vehicle control. IL-8 protein and sICAM-1 secretion was measured by enzyme-linked immunosorbent assay (ELISA). Gene expression changes were quantified by TaqMan-based real time polymerase chain reaction. Results. Pre-treatment with simvastatin significantly reduced cobalt-mediated IL-8 protein secretion (n=3) and sICAM-1 protein secretion (n=2) in THP-1 cells (p-value<0.0001). Work will be undertaken to determine changes in gene expression, the role of TLR4 in these responses and the effect of simvastatin on additional inflammatory markers. Conclusions. Simvastatin significantly reduces cobalt-ion mediated IL-8 and sICAM-1 protein secretion in THP-1 cells. This in-vitro finding demonstrates the potential for simvastatin to reduce recruitment of leukocytes which mediate the deleterious inflammatory processes driving aseptic loosening and pseudotumour formation

Wear debris from implant interfaces is the major factor leading to periprosthetic osteolysis. Fibroblast-like synoviocytes (FLSs) populate the intimal lining of the synovium and are in direct contact with wear debris. This study aimed to elucidate the effect of Ti particles as wear debris on human FLSs and the mechanism by which they might participate in the bone remodeling process during periprosthetic osteolysis. FLSs were isolated from synovial tissue from patients, and the condition medium (CM) was collected after treating FLSs with sterilized Ti particles. The effect of CM was analyzed for the induction of osteoclastogenesis or any effect on osteogenesis and signaling pathways. The results demonstrated that Ti particles could induce activation of the NFκB signaling pathway and induction of COX-2 and inflammatory cytokines in FLSs. The amount of RANL in the conditioned medium collected from Ti particle-stimulated FLSs (Ti CM) showed the ability to stimulate osteoclast formation. The Ti CM also suppressed the osteogenic initial and terminal differentiation markers for osteoprogenitors, such as alkaline phosphate activity, matrix mineralization, collagen synthesis, and expression levels of Osterix, Runx2, collagen 1α, and bone sialoprotein. Inhibition of the WNT and BMP signaling pathways was observed in osteoprogenitors after the treatment with the Ti CM. In the presence of the Ti CM, exogenous stimulation by WNT and BMP signaling pathways failed to stimulate osteogenic activity in osteoprogenitors. Induced expression of sclerostin (SOST: an antagonist of WNT and BMP signaling) in Ti particletreated FLSs and secretion of SOST in the Ti CM were detected. Neutralization of SOST in the Ti CM partially restored the suppressed WNT and BMP signaling activity as well as the osteogenic activity in osteoprogenitors. Our results reveal that wear debris-stimulated FLSs might affect bone loss by not only stimulating osteoclastogenesis but also suppressing the bone-forming ability of osteoprogenitors. In the clinical setting, targeting FLSs for the secretion of antagonists like SOST might be a novel therapeutic approach for preventing bone loss during inflammatory osteolysis

The most common reason for revision surgery of total hip replacements is aseptic loosening of implants secondary to osteolysis, which is caused by immune-mediated reactions to implant debris. These debris can cause pseudotumour formation. As revision surgery is associated with higher mortality and infection, it is important to understand the pro-inflammatory process to improve implant survival. Toll-like receptor 4 (TLR4) has been shown to mediate immune responses to cobalt ions. Statin use in epidemiological studies has been associated with reduced risk of revision surgery. In-vitro studies have demonstrated the potential for statins to reduce orthopaedic debris-induced immune responses and there is evidence that statins can modulate TLR4 activity. This study investigates simvastatin's effect on orthopaedic biomaterial-mediated changes in protein expression of key inflammatory markers and soluble-ICAM-1 (sICAM-1), an angiogenic factor implicated in pseudotumour formation. Human macrophage THP-1 cells were pre-incubated with 50µM simvastatin for 2-hours or a vehicle control (VC), before being exposed to 0.75mM cobalt chloride, 50μm3 per cell zirconium oxide or LPS as a positive control, in addition to a further 24-hour co-incubation with 50µM simvastatin or VC. Interleukin −8 (IL-8), sICAM-1, chemokine ligand 2 (CCL2), CCL3 and CCL4 protein secretion was measured by enzyme-linked immunosorbent assay (ELISA). GraphPad Prism 10 was used for statistical analysis including a one-way ANOVA. Pre-treatment with simvastatin significantly reduced LPS and cobalt-mediated IL-8 secretion (n=3) and sICAM-1 protein secretion (n=2) in THP-1 cells. Pre-treatment with simvastatin significantly reduced LPS-mediated but not cobalt ion-mediated CCL2 (n=3) and CCL3 protein (n=3) secretion in THP-1 cells. Simvastatin significantly reduced zirconium oxide-mediated CCL4 secretion (n=3). Simvastatin significantly reduced cobalt-ion mediated IL-8 and sICAM-1 protein secretion in THP-1 cells. This in-vitro finding demonstrates the potential for simvastatin to reduce recruitment of leukocytes which mediate the deleterious inflammatory processes driving implant failure

Introduction and Objective. Total joint replacement (TJR) is indicated for patients with end-stage osteoarthritis (OA) where conservative treatment has failed. Approximately 1.3 million primary hip replacement surgeries have been recorded in the United Kingdom since 2003 and this number is set to rise due to an increase in obesity as well as an ageing population. Total hip replacement (THR) has a survival rate of 85% at 20 years; the most common reason for failure is aseptic loosening which often occurs secondary to osteolysis caused by immune-mediated inflammation responses to wear debris generated from the materials used in the THR implant. Therefore, by understanding the biological steps by which biomaterials cause immune-mediated reactions it should be possible to prevent them in the future thereby reducing the number of costly revision surgeries required. Materials and Methods. The human osteoblast-like cell line (MG-63) was seeded at a density of 100,000 cell per well of a 6-well plate and treated with and increasing doses (0.5, 5, and 50mm. 3. per cell) of cobalt-chromium (CoCr) particles generated on a six-station pin-on-plate wear generator or commercially available ceramic oxide nanopowders (Al. 2. O. 3. and ZrO. 2. ) for 24 hours. TNF-alpha was used as a positive control and untreated cells as a negative control. Cells were then analysed by transmission electron microscopy (TEM) to determine whether the osteoblasts were capable of phagocytosing these biomaterials. MG-63 cells were used in conjunction with trypan blue and the XTT Cell Proliferation II Kit to assess cytotoxicity of the biomaterials investigated. Cells supernatants were also collected and analysed by enzyme-linked immunosorbant assay (ELISA) to investigate changes in pro-inflammatory protein secretion. Protein extracted from lysed cells was used for western blotting analysis to investigate RANKL protein expression to determine changes to osteolytic activation. Lysed cells were also used for RNA extraction and subsequent cDNA synthesis for real-time quantitative polymerase chain reaction (RT-qPCR) in order to assess changes to pro-inflammatory gene expression. Results. There was no significant change to cellular viability or proliferation in the osteoblasts treated with CoCr, Al. 2. O. 3. or ZrO. 2. when compared to the untreated negative control. TEM images showed clear and distinct intracellular vesicles within the cell cytoplasm which contained CoCr, Al. 2. O. 3. and ZrO. 2. RANKL expression increased at 5 and 50mm. 3. per cell CoCr and 50mm. 3. per cell Al. 2. O. 3. and ZrO. 2. Pro-inflammatory protein secretion of CXCL10, IL-8, and IL-6 all significantly increased at 50mm. 3. per cell CoCr, Al. 2. O. 3. , and ZrO. 2. Similarly to the protein secretion, CXCL10, IL-8, and IL-6 gene expression was significantly upregulated at 50mm. 3. per cell CoCr, Al. 2. O. 3. , and ZrO. 2. Conclusions. Increased in vitro RANKL expression in response to CoCr, Al. 2. O. 3. , and ZrO. 2. may result in disruption of bone metabolism and lead to osteolysis which can contribute to aseptic loosening in vivo. Significant increases in IL-6 are particularly important because as well as being a pro-inflammatory cytokine, IL-6 is also secreted by osteoblasts in order to stimulate mature osteoclast formation to mediate bone breakdown. CXCL10 and IL-8 are chemotactic cytokines and increased secretion in response to implant biomaterials can contribute to ongoing pro-inflammatory responses through the recruitment of monocytes and neutrophils respectively. This is interesting as in vivo data demonstrates increased cellular infiltrate in patients experiencing responses to implant materials. Overall, these findings show clear immune activation as well as altered metabolism of MG-63 osteoblast cells in response to implant wear debris which is in agreement with in vivo clinical reports

Breast cancer is the most frequent malignancy in women with an estimation of 2.1 million new diagnoses in 2018. Even though primary tumours are usually efficiently removed by surgery, 20–40% of patients will develop metastases in distant organs. Bone is one of the most frequent site of metastases from advanced breast cancer, accounting from 55 to 58% of all metastases. Currently, none of the therapeutic strategies used to manage breast cancer bone metastasis are really curative. Tailoring a suitable model to study and evaluate the disease pathophysiology and novel advanced therapies is one of the major challenges that will predict more effectively and efficiently the clinical response. Preclinical traditional models have been largely used as they can provide standardization and simplicity, moreover, further advancements have been made with 3D cultures, by spheroids and artificial matrices, patient derived xenografts and microfluidics. Despite these models recapitulate numerous aspects of tumour complexity, they do not completely mimic the clinical native microenvironment. Thus, to fulfil this need, in our study we developed a new, advanced and alternative model of human breast cancer bone metastasis as potential biologic assay for cancer research. The study involved breast cancer bone metastasis samples obtained from three female patients undergoing wide spinal decompression and stabilization through a posterior approach. Samples were cultured in a TubeSpin Bioreactor on a rolling apparatus under hypoxic conditions at time 0 and for up to 40 days and evaluated for viability by the Alamar Blue test, gene expression profile, histology and immunohistochemistry. Results showed the maintenance and preservation, at time 0 and after 40 days of culture, of the tissue viability, biological activity, as well as molecular markers, i.e. several key genes involved in the complex interactions between the tumour cells and bone able to drive cancer progression, cancer aggressiveness and metastasis to bone. A good tis sue morphological and microarchitectural preservation with the presence of lacunar osteolysis, fragmented trabeculae locally surrounded by osteoclast cells and malignant cells and an intense infiltration by tumour cells in bone marrow compartment in all examined samples. Histomorphometrical data on the levels of bone resorption and bone apposition parameters remained constant between T0 and T40 for all analysed patients. Additionally, immunohistochemistry showed homogeneous expression and location of CDH1, CDH2, KRT8, KRT18, Ki67, CASP3, ESR1, CD8 and CD68 between T0 and T40, thus further confirming the invasive behaviour of breast cancer cells and indicating the maintaining of the metastatic microenvironment. The novel tissue culture, set-up in this study, has significant advantages in comparison to the pre-existent 3D models: the tumour environment is the same of the clinical scenario, including all cell types as well as the native extracellular matrix; it can be quickly set-up employing only small samples of breast cancer bone metastasis tissue in a simple, ethically correct and cost-effective manner; it bypasses and/or decreases the necessity to use more complex preclinical model, thus reducing the ethical burden following the guiding principles aimed at replacing/reducing/refining (3R) animal use and their suffering for scientific purposes; it can allow the study of the interactions within the breast cancer bone metastasis tissue over a relatively long period of up to 40 days, preserving the tumour morphology and architecture and allowing also the evaluation of different biological factors, parameters and activities. Therefore, the study provides for the first time the feasibility and rationale for the use of a human-derived advanced alternative model for cancer research and testing of drugs and innovative strategies, taking into account patient individual characteristics and specific tumour subtypes so predicting patient specific responses

Introduction. Durable bone fixation of uncemented porous-coated acetabular cups can be observed at a long-term, however, polyethylene (PE) wear and osteolysis may affect survivorship. Accurate wear measurements correlated with clinical data may offer unique research information of clinical interest about this highly debated issue. Objetive. We assessed the clinical and radiological outcome of a single uncemented total hip replacement (THR) system after twenty years analysing polyethylene wear and the appearance of osteolysis. Materials and Methods. 82 hips implanted between 1992 and 1995 were prospectively evaluated. The mean follow-up was 20.6 years (range, 18 to 23). A hemispherical porous-coated acetabular cup matched to a proximally hydroxyapatite-coated anatomic stem and a 28 mm standard PE liner, sterilised by gamma irradiation in air, was used in all hips. Radiological position and the possible appearance of loosening and osteolysis were recorded over time. Penetration of the prosthetic head into the liner was measured by the Roentgen Monographic Analysis (ROMAN) Tool at 6 weeks, 6 months, one year and yearly thereafter. Results. Six cups were revised due to wear and four due to late dislocation. All cups were radiographically well-fixed and all stems showed radiographic ingrowth. Six un-revised hips showed osteolysis on the acetabular side and two on the proximal femoral side. Creep at one year was 0.30 (±0.23) mm. Mean total femoral head penetration was 1.23 mm at 10 years, 1.52 mm at 15 years and 1.92 mm at 23 years. Overall mean wear was 0.12 (± 0.1) mm/year and 0.09 (±0.06) mm/year after the creep period. Mean wear was 0.08 (± 0.06) mm/year in hips without osteolysis and 0.14 (±0.03) mm/year in revised hips or with osteolysis (p<0.001). Conclusions. Although continued durable fixation can be observed with a porous-coated cups and a proximally hydroxyapatite-coated anatomic stem, true wear continues to increase at a constant rate over time. PE wear remains as the main reason for revision surgery and osteolysis in uncemented THR and does not stop after twenty years

Introduction and Objective. Difficult primary total knee arthroplasty (TKA) and revision TKA are high demanding procedures. Joint exposure is the first issue to face off, in order to achieve a good result. Aim of this study is to evaluate the clinical and radiological outcomes of a series of patients, who underwent TKA and revision TKA, where tibial tubercle osteotomy (TTO) was performed. Materials and Methods. We retrospectively reviewed a cohort of 79 consecutives TKAs where TTO was performed, from our Institution registry. Patients were assessed clinically and radiographically at their last follow-up (mean, 7.4 ± 3.7 years). Clinical evaluation included the Knee Society Score (KSS), the pain visual analogue scale (VAS), and range of motion. Radiological assessment included the evaluation of radiolucent lines, osteolysis, cortical bone hypertrophy, time of bone healing of the TTO fragment, and the hardware complication. Results. KSS raised from 40.7 ± 3.1 to 75 ± 4.3 (p < 0.0001). Knee flexion increased from 78.7 ± 9.9° to 95.0 ± 9.5° (p < 0.0001), and VAS improved from 7.9 ± 0.9 to 3.8 ± 1 (p < 0.0001). No signs of loosening or evolutive radiolucency lineswere found. Osteolytic areas around the stem were detected. No significant association was found between the implant design and the outcomes, while aseptic loosening showed significantly better results. Complications were: 4 painful hardware, 3 late periprosthetic infections, 1 extension lag of 5°, and 3 flexion lag. Conclusions. Our experience suggests the use of TTO to improve the surgical approach in difficult primary TKA or revision TKA. A strict surgical technique leads to good results with low risk of complications

Abstract. Background/Objectives. The incidence of reverse total shoulder replacement (rTSR) implantation is increasing globally, but apprehension exists regarding complications and associated challenges. We retrospectively analysed the senior author's series of rTSR from a tertiary centre using the VAIOS shoulder system, a modular 4th generation implant. We hypothesised that the revision rTSR cohort would have less favourable outcomes and more complications. Methods. 114 patients underwent rTSR with the VAIOS system, over 7 years. The primary outcome was implant survival. Secondary outcomes were Oxford shoulder scores (OSS), radiographic analysis (scapular notching, tuberosity osteolysis, and periprosthetic radiolucent lines) and complications. Results. There were 55 Primary rTSR, 31 Revision rTSR and 28 Trauma rTSR. Implant survival: Primary rTSR- 0 revisions, average 3.35-year follow-up. Revision rTSR-1 revision (4.17%), average 3.52-year follow-up. Trauma rTSR- 1 revision (3.57%), average 4.56-year follow-up OSS: Average OSS improved from 15.39 to 33.8 (Primary rTSR) and from 15.11 to 29.1 (Revision rTSR). Average post-operative OSS for the Trauma rTSR was 31.4 Radiological analysis and complications: Low incidence of scapular notching One hairline fracture below the tip of stem, noted incidentally, which required no treatment. One periprosthetic fracture after alcohol related fall. Treated non-surgically One joint infection requiring two-stage revision to rTSR. One dislocation noted at 2 year follow up. This patient had undergone nerve grafting within 6 months of rTSR for axillary nerve injury sustained during the original fracture dislocation. One acromial fracture with tibial and distal humeral fracture after a fall. Conclusions. The 4th generation modular VAIOS implant is a reliable option for various indications. The revision rTSR cohort had favourable outcomes with low complication rates. In this series, early-to-medium term results suggest lower revision rates and good functional outcomes when compared to published reports. We plan to monitor long-term implant survivorship and patient reported outcomes. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Abstract. Objective. The aim of our systematic review was to report the latest evidence on the effects of CoCr particles on local soft tissue with a focus on its clinical relevance. Methods. PubMed, Embase, and Cochrane Library databases were screened to perform an extensive review. Inclusion criteria were studies of any level of evidence published in peer-reviewed journals reporting clinical and preclinical results written in English. Relative data were extracted and critically analyzed. PRISMA guidelines were applied, and the risk of bias was assessed, as was the methodological quality of the included studies. Results. 30 studies were included after applying the inclusion and exclusion criteria. Of these, 24 were preclinical studies (18 in vitro human studies, 6 animal modal studies, including 3 in vitro and 3 in vivo), 5 were clinical studies and 1 was previous review on similar topic. The presence of metal ions causes cell damage by reducing cell viability, inducing DNA damage, and triggering the secretion of cytokines. Mechanisms of apoptosis, autophagy and necrosis are responsible for the inflammatory reaction observed in ALTR. Conclusion. The available literature on the effects of CoCr particles released from MoM implants shows that metal debris can cause damage to skeletal muscle, the capsule, and provoke osteolysis and inflammation. Therefore, the cytotoxic and genotoxic damages, as well as the interaction with the immune system, affect the success of the arthroplasty and lead to a higher rate of revision surgeries. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Total Hip Arthroplasty (THA) is a well-established, cost-effective treatment for improving function and alleviating pain in patients who have disabling hip disease with excellent long-term results. Based on the excellent results, there is an ongoing trend for THA to be performed in younger and more active patients, having higher physical demands on their new total joints. Polyethylene (PE) wear and its biological consequences are one of the main causes of implant failure in THA. Macrophages phagocytise PE wear particles and this will result in osteolysis and loss of periprosthetic bone. The risk of these complications can be estimated in relation to the amount of volumetric wear based on two assumptions: that the number of PE particles dispersed in the peri-prosthetic tissues is controlled by the amount of PE wear; and that the development of osteolysis and the resulting aseptic loosening is triggered by these PE particles. Based on these assumptions, a model was developed to estimate the osteolysis-free life of a THA, depending on the Linear Wear Rate (LWR) and femoral head size of the PE bearing. A review of the literature was conducted to provide an estimate of the radiologic osteolysis threshold based on the volumetric wear of the PE bearing. This review demonstrates that this radiologic osteolysis threshold is approximated 670 mm3 for conventional PE. The osteolysis-free life of the THA was estimated by simply dividing this threshold volume by the annual Volumetric Wear Rate (VWR) of the bearing. The annual VWR is basically controlled by two parameters: (1) annual LWR and (2) head size, and was calculated by using published formulae. For 28 mm heads, following osteolysis-free life was determined in function of the annual LWR. LWR: 10 µm/y => 116.6 years / LWR: 25 µm/y => 46.6 years / LWR: 50 µm/y => 23.3 years / LWR: 100 µm/y => 11.6 years. For 40 mm heads, following osteolysis-free life was determined in function of the annual LWR. LWR: 10 µm/y => 57.1 years / LWR: 25 µm/y => 22.9 years / LWR: 50 µm/y => 11.4 years / LWR: 100 µm/y => 5.7 years. The osteolysis-free life determined by this model is in good agreement with the clinical results of PE bearings having a 28 mm head size and demonstrates that extreme low LWRs are mandatory to assure a descent osteolysis-free life for THA (PE bearings) using large heads, such as 40 mm. For such head sizes, small variations of the LWR may have large impacts on the osteolysis-free life of the THA

This longitudinal microCT study revealed the osteolytic response to a Staphylococcus epidermidis-infected implant in vivoand also demonstrates how antibiotics and/or a low bone mass state influence the morphological changes in bone and the course of the infection. Colonisation of orthopaedic implants with Staphylococcus aureusor S. epidermidisis a major clinical concern, since infection-induced osteolysis can drastically impair implant fixation or integration within bone. High fracture incidence in post-menopausal osteoporosis patients means that this patient group are at risk of implant infection. The low bone mass in these patients may exacerbate infection-induced osteolysis, or alter antibiotic efficacy. Therefore, the aims of this study were to examine the bone changes resulting from a S. epidermidisimplant infection in vivousing microCT imaging, and to determine if a low bone mass stateinfluences the course of the infection and the efficacy of antibiotic therapy. An in vivomodel system using microCT scanning [1], involving the implantation of either a sterile or a S. epidermidis-colonised PEEK screw into the proximal tibia of 24 week-old female Wistar rats, was used to investigate the morphological changes in bone following infection over a 28 day period. In addition, the efficacy of a combination antibiotic therapy (rifampin and cefazolin: administered twice daily from days 7–21 post-screw implantation) for affecting osteolysis was also assessed. A subgroup of animals was subjected to ovariectomy (OVX) at 12 weeks of age, allowing for a 12 week period for bone loss prior to screw implantation at 24 weeks. Bone resorption and formation rates, bone-implant contact and peri-implant bone volume in the proximity of the screw were assessed by microCT scanning at days 0, 3, 6, 9, 14, 20 and 28 days post-surgery. Following euthanasia at day 28, the implanted screw, bone and soft tissues were subjected to quantitative bacteriology as a measure of the efficacy of the antibiotic regimen. In non-OVX animals S. epidermidisinfection induced marked osteolysis, which peaked between 9 and 14 days post-screw implantation. Peak bone resorption was detected at day 6, before recovering to baseline levels at day 14. Infection also resulted in extensive deposition of mineralised tissue, initially within the periosteal region (day 9–14), then subsequently in the osteolytic region at day 20–28. Quantitative bacteriology indicated all non-OVX animals remained infected. Rifampin and cefazolin successfully cleared the infection in 5/6 non-OVX animals group although there was no difference observed in CT-derived bone parameters. OVX resulted in extensive loss of trabecular bone but this did not alter the temporal pattern of infection-induced osteolysis, or mineralised tissue deposition, which was similar to that observed in the non-OVX animals. Similarly, there was no difference in bacterial counts between non-OVX and OVX animals (39,005 colony-forming units (CFU) [range: 3,675–156,800] vs 37,665 CFU [range 3,250–84,000], respectively). Interestingly, antibiotic treatment was less effective in the OVX animals (3/5 remained infected), suggesting that antibiotics have reduced efficacy in OVX animals. This study demonstrates S. epidermidis-induced osteolysis displays a similar temporal pattern in both normal and low bone mass states, with comparable bacterial loads present within the localised infection site

Abstract. Objective. In this phase 2 clinical trial (EudraCT 2011-000541-20) we examined the effect of denosumab versus placebo on osteolytic lesion activity in patients undergoing revision surgery after THA. Methods. Men and women ≥ 30 years old scheduled for revision surgery for symptomatic, radiologically-confirmed osteolysis were randomised (1:1) to receive either denosumab 60mg or placebo subcutaneously eight weeks prior to operation. At surgery, biopsies from the osteolytic membrane-bone interface were taken for histomorphometric analysis of osteoclast number, the primary outcome measure. Secondary outcome measures included other static histomorphometric indices and systemic bone turnover markers. Adverse events and patient-reported clinical outcome scores were recorded as safety endpoints. Results. Of the 24 subjects enrolled, 22 completed the study (10 denosumab) and comprise the per-protocol analysis. There were no differences in baseline characteristics and bone turnover markers between groups (p>0.05). The denosumab group had 78% fewer osteoclasts at osteolytic lesion sites (95% CI −61 to −95, P=0.011), 81% lower osteoclast surface (−70 to −95, P=0.009), and 73% lower eroded surface (−54 to −92, P=0.020) compared to the placebo group. Number of osteoblasts and osteoblast surface were also reduced by 81% (−62 to −100, p=0.021) and 82% (−64 to −101, p=0.017), respectively. Immunocytochemistry for cell proliferation (Ki67) and apoptosis (Caspase 3) identified no differences between the groups (p>0.05). At surgery, serum CTX-I in the denosumab group was 80% lower (−65 to −95, p<0.001), TRAP5b −65% (−40 to −90, p<0.001), PINP −53% (−41 to −65, p<0.001). Patient-reported outcome measures and the rate of adverse events (denosumab 6, placebo 7) were similar between groups (P>0.05). Conclusion. A single dose of denosumab reduced osteoclast activity within osteolytic lesions and was safe to administer. These data provide a biological basis for a phase 3 trial using clinical outcomes of pain, function and prosthesis survival as the study endpoints. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Abstract. Objectives. Implant loosening remains a common cause of total ankle replacement (TAR) revision, and has been associated with wear-mediated osteolysis. Limited pre-clinical studies for TARs have been reported and the variety of experiment settings make it difficult to compare wear rates. Factors such as simulator control mechanism; whether pneumatic or electromechanical, may influence the integrity of the simulator outputs with respect to input profiles. This study compares the wear of a TAR, tested in electromechanical and pneumatic experimental simulators under identical input conditions. Methods. Twelve medium BOX® (MatOrtho Ltd) TARs (n=6 for each simulator) were tested in an electromechanical and pneumatic knee simulator (Simulation Solutions, UK) for 3 million cycles (Mc). Standard ‘Leeds’ displacement-controlled inputs were used. Kinematic performance was investigated by comparing the output profiles against the maximum demanded input values. The lubricant used was 25% new-born calf serum and wear was determined gravimetrically. Results. There was no significant difference (P=0.66) in wear rate between simulators (electromechanical = 15.96 ± 6.37mm. 3. /Mc; pneumatic = 14.51 ± 5.27mm. 3. /Mc). The electromechanical simulator (3157.06 ± 1.52N) achieved the maximum load (3150N), but the pneumatic simulator was unable to attain the demand (2542.34 ± 86.52N). Maximum AP displacement from the electromechanical simulator was 3.27 ± 0.07mm (3.1mm input), compared to 3.62 ± 0.95mm from the pneumatic simulator. Internal/external rotation angle was 7.97° ± 0.00 (8° input) and 7.24° ± 0.12 from the electromechanical and pneumatic simulators respectively. Both simulators achieved the demanded flexion angle (±15°). Conclusions. The outputs from the electromechanical simulator followed the input profiles more closely than the pneumatic simulator. Despite these differences, there was no significant influence on wear rate. The variation in kinematics between simulators was not sufficient to significantly change the tribological conditions of the TAR. The authors recommend the use of electromechanical simulators for future studies where more demanding and adverse conditions may be applied. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Summary Statement. Vitamin E-UHMWPE particles have a reduced osteolysis potential in vivo when compared to virgin, highly cross-linked UHMWPE in a murine calvarial bone model. Introduction. Ultra high-molecular weight polyethylene (UHMWPE) particle-induced osteolysis is one of the major causes of arthroplasty revisions. The lack of particle clearance from the joint inevitably leads to the upregulation of the inflammatory cascade, resulting in bone resorption and implant loosening. Recent in vitro findings (Bladed CL et al. ORS 2011 and J Biomed Mater Res B Appl Biomater, 2012) have suggested that UHMWPE wear particles containing vitamin-E (VE) may have reduced functional biologic activity and decreased potential to cause osteolysis. This is of significant importance since VE-stabilised cross-linked UHMWPEs were recently introduced for clinical use, and there is no in vivo data determining the effects of wear debris from this new generation of implants. In this study we hypothesised that particles from VE-stabilised, radiation cross-linked UHMWPE (VE-UHMWPE) would cause reduced levels of osteolysis in a murine calvarial bone model when compared to virgin gamma irradiated cross-linked UHMWPE. Methods. Study groups were the following: 1) Radiation cross-linked VE-UHMWPE, approximately 0.8% by weight, diffused after 100 kGy; 2). Radiation cross-linked virgin UHMWPE (virgin UHMWPE); 3). Shams. Particle generation and implantation: UHMWPE was sent to Bioengineering Solutions (Oak Park, IL) for particle generation. After IACUC approval, C57BL/6 mice (n=12 for each group) received equal amount of particulate debris (3mg) overlying the calvarium and were euthanised after 10 days. Micro-CT scans: High resolution micro-CT scans were performed using an X-Tek HMX ST 225 with a set voltage of 70 kV and current of 70 µA. Topographical Grading Scale: Each calvarial bone (interparietal, right and left parietal, right and left frontal) was blindly scored using the following scale: 0=No osteolysis, defined as intact bone; 1=Minimal osteolysis, affecting 1/3 or less of the bone area; 2=Moderate osteolysis, affecting at least 2/3 of the bone area; 3=Severe osteolysis, defined as completely osteolytic bone. Histological Analysis: H&E and TRAP staining was performed on tissue to confirm the micro-CT findings and to quantify osteoclasts. Statistical Analysis: Inter-rater analysis was performed using Cohen's kappa analysis. An inter-rater coefficient >0.65 was considered as high inter-rater agreement. Comparison between groups was made using one-way ANOVA with post hoc Bonferroni correction for multiple comparisons. Correlations are reported as Spearman's rho. A p-value<0.05 was considered statistically significant. Results. More than 83% of the VE-UHMWPE and more than 85% of the virgin UHMWPE particles measured less than 1 µm in mean particle size. The mean particle size for VE-UHMWPE was 1.12 µm (range 0.28 to 79.08 µm), while virgin UHMWPE particles measured 1.22 µm (range 0.28 to 82.04 µm). There was a statistically significant greater level of osteolysis visualized on the topographical grading scale in calvaria implanted with virgin UHMWPE wear particles. The micro-CT findings were confirmed histologically. A greater amount of inflammatory tissue overlaying the calvaria was observed in the virgin UHMWPE group when compared to both shams and VE-UHMWPE groups. Post hoc analysis revealed significant difference between VE-UHMWPE and virgin UHMWPE for the topographical osteolysis grading score (p = 0.002) but no difference in osteoclast count (p = 0.293). Discussion/Conclusion. This is the first in vivo study reporting the effects of clinically-relevant UHMWPE particles generated from a VE-UHMWPE implant that is in current clinical use. These results suggest that VE-UHMWPE particles have reduced osteolysis potential in vivo when compared to virgin, highly cross-linked UHMWPE in a murine calvarial bone model. Arthroplasty procedures using VE-UHMWPE might be less susceptible to peri-prosthetic loosening caused by wear debris

INTRODUCTION. Staphylococci species account for ∼80 % of osteomyelitis cases. While the most severe infections are caused by Staphylococcus aureus (S. aureus), the clinical significance of coagulase negative Staphylococcus epidermidis (S. epidermidis) infections remain controversial. In general, S. epidermidis was known to be a protective commensal bacterium. However, recent studies have shown that intra-operative low-grade S. epidermidis contamination prevents bone healing. Thus, the purpose of this study is to compare the pathogenic features of S. aureus and S. epidermidis in an established murine model of implant-associated osteomyelitis. METHODS. All animal experiments were performed on IACUC approved protocols. USA300LAC (MRSA) and RP62A(S. epidermidis) were used as prototypic bacterial strains. After sterilization, stainless steel pins were implanted into the tibiae of BALB/c mice (n=5 each) with or without Staphylococci. Mice were euthanized on day 14, and the implants were removed for scanning electron microscopy (SEM). Tibiae were fixed for mCT prior to decalcification for histology. RESULTS. The histology of S. aureus infected tibiae demonstrated massive osteolysis and abscesses formation. In contrast, the histology from S. epidermidis infected tibiae was indistinguishable from uninfected controls. Gross mCT analyses revealed massive bone defects around the infected implant with reactive bone formation only in the S. aureus group. The osteolysis findings were confirmed by quantitative analysis, as the medial hole area of S. aureus infected tibiae (1.67 ± 0.37 mm2) was larger than uninfected (0.15 ± 0.10 mm2) (p < 0.001) and S. epidermidis (0.19 ± 0.14 mm2) (p < 0.001) groups. Consistently, the %biofilm area on the implants of the S. aureus group (39.0 ± 13.7 %) was significantly larger than uninfected (6.3 ± 2.3 %) (p < 0.001) and S. epidermidis (12.9 ± 7.4 %) (p < 0.001). Although the amount of biofilm of S. epidermidis was much smaller than S. aureus, the presence of bacteria on the implant were confirmed by SEM. In addition, the empty lacunae, which is a feature of mature biofilm and evidence of bacterial emigration, were also present on both S. epidermidis and S. aureus infected implants. DISCUSSION. In this study, we confirmed the aggressive pathologic features S. aureus on host bone, soft tissues and biofilm formation. In contrast, we show that S. epidermidis is incapable of inducing osteolysis, reactive bone formation or soft tissue abscesses, even though it colonizes the implant in small biofilms. Collectively, the results support a potential role for S. epidermidis in implant loosening and fracture non-unions, as the bacteria can form small biofilms that could interfere with osseous integration and bone healing. However, future studies are warranted to assess the effects of S. epidermidis biofilm on implant loosening

Aseptic loosening is a major cause of revision surgeries and occurs when osteolysis is stimulated around the implant by pro-inflammatory cytokines including IL-1β. Production of active IL-1β in response to orthopedic wear particles depends on processing by the NLRP3 inflammasome which requires priming followed by activation. We found that pathogen associated molecular patterns (PAMPs) adherent to wear particles are necessary to prime the NLRP3 inflammasome. In contrast, in pre-primed macrophages, particles themselves are sufficient to activate the NLRP3 inflammasome and induce secretion of active IL-1β. Particles themselves also induce cell death, kinetically preceding the release of active IL-1β. Phagocytosis of particles is required to initiate both responses as the phagocytosis inhibitor cytochalasin blocks cell death and IL-1β release. Lysosome membrane destabilization is also critical as inhibition of lysosomal function with bafilomycin or chloroquine significantly abrogated the release of active IL-1β and cell death in response to wear particles. The pan-cathepsin inhibitors Ca-074-Me or K777 also inhibit cell death and IL-1β release indicating that cathepsin release from lysosomes is also a necessary step in the particle-induced response. Our results open the possibility of clinical intervention with lysosomal or cathepsin inhibitors to treat aseptic loosening as these drugs have better specificity and less in vivo toxicity than the phagocytosis inhibitors. Testing of these inhibitors in vivo in models of particle induced osteolysis is a key future direction

Summary. Osteoporosis reduces particle-induced osteolysis in rat model. Introduction. Wear particle induced osteolysis is considered to be a vital factor that reduces the life span of joint prosthesis. Osteoporosis is not rare in patients with indication for arthroplasty. However, the influence of osteoporosis on wear particles induced osteolysis is not clear. This study is aimed to explore on this issue by using animal model. Methods. 42 female Sprague-Dawley (SD) rats aged 6 months were randomly divided into 3 groups: A, B and C group. Group A and B contained 18 rats each, and group C contained 6 rats. The rats in group A underwent bilateral ovariectomy. Group B was normal control, and group C was sham control. After 3 months, 6 rats in group A, 6 rats in group B and all the rats of group C were sacrificed. Bone mineral density (BMD), μCT and bone histomorphometry were conducted. The rest of rats in group A were randomly divided into 2 groups: group A1 and group A2, and so were the rats in group B. 5mg titanium particles were implanted onto the calvaria of groups A1 and B1, and isometric PBS solution were injected to group A2 and B2. Calvaria were harvested after 14 days. Calvaria were analyzed by μCT and histomorphometry to measure the osteolysis area of calvarial sagittal suture. Results. Compared with B and C group, BMD and bone histomorphometry index of group A was significantly reduced (P<0.05), and tibial trabeculae of group A was slimmer. Area of calvarial sagittal suture osteolysis were 0.262±0.009mm. 2. , 0.130±0.013mm. 2. , 0.307±0.013mm. 2. and 0.178±0.011mm. 2. in A1, A2, B1and B2 groups, respectively. There was significant difference among the groups. Conclusions. Osteoporosis may reduce particle-induced osteolysis in rat model