Titanium particles suppress expression of osteoblastic phenotype in human mesenchymal stem cells.

Long-term stability of arthroplasty prosthesis depends on the integration between osseous tissue and the implant biomaterial. Integrity of the osseous tissue requires the contribution of mesenchymal stem cells and their continuous differentiation into an osteoblastic phenotype. This study aims to investigate the hypothesis that exposure to wear debris particles derived from orthopaedic biomaterials affects the osteoblastic differentiation of human mesenchymal stem cells (hMSC). Upon in vitro culture in the presence of osteogenic supplements (OS), we observe that cultures of hMSCs isolated from femoral head bone marrow are capable of osteogenic differentiation, expressing alkaline phosphatase, osteocalcin, and bone sialoprotein (BSP), in addition to producing collagen type I and BSP accompanied by extracellular matrix mineralization. Exposure of OS-treated hMSCs to submicron commercially pure titanium (cpTi) particles suppresses BSP gene expression, reduces collagen type I and BSP production, decreases cellular proliferation and viability, and inhibits matrix mineralization. In comparison, exposure to zirconium oxide (ZrO2) particles of similar size did not alter osteoblastic gene expression and resulted in only a moderate decrease in cellular proliferation and mineralization. Confocal imaging of cpTi-treated hMSC cultures revealed patchy groups of cells displaying disorganized cytoskeletal architecture and low levels of extracellular BSP. These in vitro findings suggest that chronic exposure of marrow cells to titanium wear debris in vivo may contribute to decreased bone formation at the bone/implant interface by reducing the population of viable hMSCs and compromising their differentiation into functional osteoblasts. Understanding the nature of hMSC bioreactivity to orthopaedic wear debris should provide additional insights into mechanisms underlying aseptic loosening.     

Direct and indirect induction of apoptosis in human mesenchymal stem cells in response to titanium particles.

The most frequent complication of total joint arthroplasty is periprosthetic osteolysis initiated by an inflammatory response to orthopaedic wear debris, which if left untreated, can result in implant instability and failure, eventually requiring revision surgery. We have previously reported that osteogenic differentiation of human marrow stroma-derived mesenchymal stem cells (hMSCs) is suppressed upon exposure to titanium particles, accompanied by reduced bone sialoprotein (BSP) gene expression, diminished production of collagen type I and BSP, decreased cellular viability and proliferation, and inhibition of extracellular matrix mineralization. In this study, we have further investigated hMSC cytotoxicity upon exposure to submicron particles of commercially pure titanium (cpTi) and zirconium oxide (ZrO(2)). Our results showed that direct exposure to cpTi and ZrO(2) particles compromises cell viability through the induction of apoptosis, eliciting increased levels of the tumor suppressor proteins p53 and p73, in a manner dependent on material composition, particle dosage, and time. Additionally, conditioned medium collected from hMSCs exposed to cpTi particles, but not to ZrO(2) particles, is cytotoxic to hMSCs, inducing apoptosis in the absence of particles. These findings demonstrate that exposure to orthopaedically derived wear particles can compromise hMSC viability through the direct and indirect induction of apoptosis. Thus, prolonged in vivo exposure of marrow-derived hMSCs to implant-derived wear debris is likely to reduce the population of viable osteoprogenitor cells, and may contribute to poor periprosthetic bone quality and implant loosening.     

Biological responses of human mesenchymal stem cells to titanium wear debris particles

Wear debris-induced osteolysis is a major cause of orthopedic implant aseptic loosening, and various cell types, including macrophages, monocytes, osteoblasts, and osteoclasts, are involved. We recently showed that mesenchymal stem/osteoprogenitor cells (MSCs) are another target, and that endocytosis of titanium (Ti) particles causes reduced MSC proliferation and osteogenic differentiation. Here we investigated the mechanistic aspects of the endocytosis-mediated responses of MSCs to Ti particulates. Dose-dependent effects were observed on cell viability, with doses >300 Ti particles/cell resulting in drastic cell death. To maintain cell viability and analyze particle-induced effects, doses <300 particles/cell were used. Increased production of interleukin-8 (IL-8), but not IL-6, was observed in treated MSCs, while levels of TGF-β, IL-1β, and TNF-α were undetectable in treated or control cells, suggesting MSCs as a likely major producer of IL-8 in the periprosthetic zone. Disruptions in cytoskeletal and adherens junction organization were also observed in Ti particles-treated MSCs. However, neither IL-8 and IL-6 treatment nor conditioned medium from Ti particle-treated MSCs failed to affect MSC osteogenic differentiation. Among other Ti particle-induced cytokines, only GM-CSF appeared to mimic the effects of reduced cell viability and osteogenesis. Taken together, these results strongly suggest that MSCs play both responder and initiator roles in mediating the osteolytic effects of the presence of wear debris particles in periprosthetic zones.     

The effectiveness of polyethylene versus titanium particles in inducing osteolysis in vivo.

Bearing surface wear and periprosthetic osteolysis due to wear particles are among the most common reasons for joint replacement failure. A murine calvarial model of wear particle-induced osteolysis has been used to identify different biologic factors associated with this problem and to test nonsurgical methods of modulating the host response to particulate debris. This model has utilized titanium particles, however, in clinical practice the most common source of particulate debris is polyethylene particles from bearing surface wear. We now report a calvarial model of wear particle-induced osteolysis based on commercially available polyethylene particles. We found that compared to sham surgery osteoclast recruitment and bone resorption can be induced by introduction of the titanium particles or polyethylene particles. However, bone resorption was significantly higher with polyethylene particles compared to titanium particles (p=0.02). We consider the polyethylene based murine calvarial model of wear particle-induced osteolysis a reliable and clinically relevant tool to understand the host factors and potential pharmacologic interventions that can influence wear debris generated osteolysis. This model might serve as an extension of the well-established titanium based bone resorption model.     

Aseptic loosening in total hip arthroplasty secondary to osteolysis induced by wear debris from titanium-alloy modular femoral heads

Since 1984, we have used components made of titanium alloy for total joint arthroplasty. Recently, two patients needed revision hip arthroplasty, approximately three years after the initial procedure, because of aseptic loosening secondary to severe osteolysis that had been induced by metallic debris. Although implants made of titanium alloy have many favorable qualities--most importantly, superb biocompatibility--the alloy is more susceptible to wear by particles of acrylic cement and tends to generate more polyethylene wear than do components made of stainless steel or chromium-cobalt. A new process of implanting ions has reportedly improved resistance to wear as well as fatigue properties and has enhanced the resistance to corrosion of the implants. Although, to our knowledge, only in vitro studies of this process have been reported to date, we recommend avoiding the use of components made of titanium alloy in which ions have not been implanted. We suggest considering the possibility of osteolysis secondary to appreciable metallic debris in patients who have aseptic loosening of titanium-alloy components that were not implanted with ions.     

Microscopic metallic wear and tissue response in failed titanium hallux metatarsophalangeal implants: two cases

The membranes present at the implant-bone interface were retrieved from two patients with titanium single stem hallux implants that had failed. Both patients had pain and valgus deformity of the hallux, and radiographs showed a radiolucent shadow around the implant stem, with thinning of the dorsal cortex of the proximal phalanx in one patient. After removal of the implants, arthrodesis of the first metatarsophalangeal (MP) joint was performed. Histologic analysis of the membrane tissue at the implant-bone interface showed a synovial-like appearance. There was a fibrous tissue stroma adjacent to the bone surface, with multiple regions of scalloping covered by mononuclear cells. Fine metallic debris was seen throughout the fibrous tissue. Multinucleated foreign body giant cells were sparsely observed associated with fine particulate metallic wear debris similar to observations from failed total hip arthroplasties. The histologic appearance is evidence that foreign-body granulomatous infiltration associated with metallic wear debris may be a causative factor of peri-implant osteolysis leading to aseptic loosening and failure of titanium single stem hallux implants.     

磨屑在人工关节无菌性松动中作用的实验研究

目的：观察磨屑在动物体内引起的组织学反应，比较了不同磨屑所致反应差别，比较磨屑在羟基磷灰石涂层钛合金棒－骨界面和光滑钛合金棒－骨界面间移动差别，探讨人工关节无菌性松动机制。方法：６４只家兔分为８组（ｎ＝８），分别将羟基磷灰石涂层钛合金棒和光滑钛合金棒经膝关节置入股骨远端，定期膝关节注入聚乙烯，钛合金及两者的混合磨屑。光镜、偏振光显微镜和电镜观察关节滑膜、两种钛合金棒－骨界面的组织学和超微结构。结果     

Polyethylene particles from a hip simulator cause (45)Ca release from cultured bone

Periprosthetic osteolysis is a dominant factor in the success or failure of total hip prostheses. Polyethylene wear debris has been implicated in the process of bone resorption and subsequent implant loosening. The present study is the first to examine the effect of ultra high molecular weight polyethylene (UHMWPE) wear debris produced by a hip simulator on calvarial bone resorption in vitro. (45)Ca release was measured in cultured mouse calvarial bone samples. Although short-term exposure to UHMWPE particles (2 h) decreased (45)Ca release, longer-term exposure for 1-2 days increased release in a dose-dependent manner. After one-day exposure to 7.5 x 10(6) particles per mL, 18% more (45)Ca was released from cultured calvarial bone than from control samples. It was concluded that UHMWPE wear particles either directly or indirectly stimulated osteoclasts to activate bone resorption. Polyethylene wear debris contributes to the osteolytic process at the bone-implant interface.     

New insight into the mechanism of hip prosthesis loosening: effect of titanium debris size on osteoblast function.

The incidence of rheumatoid arthritis and osteoarthritis is on the rise due to our expanding elderly population. Total joint arthroplasty is the most successful, prevalent treatment modality for these and other degenerative hip conditions. Despite the wide array of prosthetic devices commercially available, hip prostheses share a common problem with a gradual and then accelerating loss of bone tissue and bone-implant interface integrity, followed by implant instability and loosening. Implant failure is largely the result of inevitable wear of the device and generation of wear debris. To provide information for the development of improved prosthetic wear characteristics, we examined the effects of size-separated titanium particles on bone forming cell populations. We demonstrate unequivocally that particle size is a critical factor in the function, proliferation, and viability of bone-forming osteoblasts in vitro. In addition, we have elucidated the time-dependent distribution of the phagocytosed particles within the osteoblast, indicating an accumulation of particles in the perinuclear area of the affected cells. The report finds that particle size is a critical factor in changes in the bone formation-related functions of osteoblasts exposed to simulate wear debris, and that 1.5-4 microm titanium particles have the greatest effect on osteoblast proliferation and viability in vitro. The size of titanium particles generated through wear of a prosthetic device may be an important consideration in the development of superior implant technology.     

Osteolysis in third-generation alumina ceramic-on-ceramic hip bearings with severe impingement and titanium metallosis

The most common cause of long-term failure of total hip arthroplasty is osteolysis and aseptic loosening secondary to wear debris. Combinations of hard materials such as ceramic-on-ceramic generate smaller volumes of particulate wear debris than traditional combinations such as metal-on-polyethylene. We describe 2 cases where osteolysis arose in hips with third-generation alumina ceramic-on-ceramic couplings. Periarticular tissue in both cases contained titanium wear debris due to impingement of the neck of the titanium femoral component against the rim of the titanium shell and ceramic debris from edge loading wear (stripe wear) of the ceramic. It is not clear whether the titanium debris, the ceramic debris, or both caused the osteolysis. These cases illustrate that the risk of osteolysis persists, even with third-generation alumina ceramics.     

微小假体磨损颗粒诱导置入物旁骨溶解的扫描电镜观察

为比较不同人工关节微小磨损颗粒对假体－骨界面处骨整合及骨整合及骨溶解的影响,探讨假体松动的机制。方法本实验采用扫描电镜技术对钛事金、钴－铬－钼与聚乙烯（ｕｌｔｒａｈｉｇｈｍｏｌｅｃｕｌａｒｗｅｉｇｈｔｐｏｌｙｅｔｈｙｌｅｎｅ,ＵＨＭＷＰＥ）三种微小颗粒诱导的假体周围骨组织改变进行超微结构观察。结果研究发现,直径２．５μｍ的Ｔｉ－６Ａｌ－４Ｖ颗粒诱导置入物旁骨吸收或骨溶解的程度明显低于相同直径的Ｃｏ     

The effect of spinal instrumentation particulate wear debris. an in vivo rabbit model and applied clinical study of retrieved instrumentation cases.

STUDY DESIGN: The current study was undertaken to determine if the presence of spinal instrumentation wear particulate debris deleteriously influences early osseointegration of posterolateral bone graft or disrupts an established posterolateral fusion mass.OBJECTIVES: Using an in vivo animal model, the first phase (basic science) of this study was to evaluate the effect(s) of titanium wear particulate on a posterolateral spinal arthrodesis based on serological, histological and immunocytochemical analyses. The second phase (clinical) was to perform the same analysis of soft tissue surrounding spinal instrumentation in 12 symptomatic clinical patients. SUMMARY OF BACKGROUND DATA: The effect of unintended wear particulate resulting from micromotion between the interconnection mechanisms in spinal instrumentation remains a clinical concern. METHODS: Thirty-four New Zealand White rabbits were randomized into two groups based on postoperative time periods of 2 months (Group 1, n=14) and 4 months (Group II, n=20). Group I underwent a posterolateral arthrodesis (PLF) at L5-L6 using tricortical iliac autograft or tricortical iliac autograft plus titanium particulate. Group 2 all received iliac autograft at the initial surgery and were reoperated on after 8 weeks and treated with PLF exposure alone or titanium particulate. Postoperative analysis included serological quantification of systemic cytokines. Postmortem microradiographic, immunocytochemical and histopathological assessment of the intertransverse fusion mass quantified the extent of osteolysis, local proinflammatory cytokines, osteoclasts and inflammatory infiltrates. Clinical aspect of study: Over the last 2 years, 12 patients more than 0.4 years after spinal instrumentation presented with painful paraspinal inflammation. At surgical exploration, the cultures were negative for infection and the surrounding soft tissue was examined for cytokine reactions. There was loosening of implants and osteolysis in the location of the wear debris in 8 of 12 patients. RESULTS: Basic science phase: serological analysis of systemic cytokines indicated no significant differences in cytokine levels (p>.05) between the titanium or autograft treatments. Immunocytochemistry indicated increased levels of local cytokines: TNF-alpha at the titanium-treated PLF sites at both time periods (p<.05). Osteoclast cell counts and regions of osteolytic resorption lacunae were higher in the titanium-treated versus autograft-alone groups (p<.05), and the extent of cellular apoptosis was markedly higher in the titanium-treated sites at both time intervals. Electron microscopy indicated definitive evidence of phagocytized titanium particles and foci of local, chronic inflammatory changes in the titanium-treated sites. Clinical aspect: Eleven of 12 clinical cases demonstrated elevated TNF-alpha levels and an increased osteoclastic response in the vicinity of wear debris caused by dry frictional wear particles of titanium or stainless steel. Osteolysis most commonly involved loose transverse connectors. Resection of the wear debris and surrounding fibroinflammatory glycocalyx resulted in resolution of clinical symptoms in all 12 cases. CONCLUSIONS: Titanium particulate debris introduced at the level of a spinal arthrodesis elicits a cytokine-mediated particulate-induced response favoring proinflammatory infiltrates, increased expression of intracellular TNF-alpha, increased osteoclastic activity and cellular apoptosis. This is the first basic scientific study and the first clinical study demonstrating associations of spinal instrumentation particulates wear debris and increased cytokines and increased osteoclastic activity. Osteolysis is the number one cause of failure of orthopedic implants in the appendicular skeleton. Spinal surgeons need to increase their awareness of this destructive process.     

Failure of a metal-on-metal total hip arthroplasty from progressive osteolysis.

Ultra-high-molecular weight polyethylene (UHMWPE) wear, debris-induced osteolysis is a frequent cause of failure of total hip arthroplasty. Metal-on-metal total hip arthroplasty eliminates the generation of UHMWPE particulate debris. Although the volumetric wear of a metal-on-metal articulation may be lower than a metal-UHMWPE articulation, the number of particles may be higher. Osteolysis can develop in response to metallic and UHMWPE debris. The following case of massive osteolysis associated with large amounts of cobalt-chrome wear debris shows adhesive and abrasive wear mechanisms, as well as wear caused by third-body cobalt-chrome debris and impingement of the femoral component against the rim of the acetabular cup, which led to failure of a metal-on-metal total hip arthroplasty.     

Dissemination of wear particles to the liver, spleen, and abdominal lymph nodes of patients with hip or knee replacement

BACKGROUNDS: The importance of particles generated by wear and corrosion of joint replacement prostheses has been understood primarily in the context of the local effects of particle-induced periprosthetic osteolysis and aseptic loosening. We studied dissemination of wear particles in patients with total hip and knee replacement to determine the prevalence of and the histopathological response to prosthetic wear debris in the liver, spleen, and abdominal para-aortic lymph nodes. METHODS: Postmortem specimens from twenty-nine patients and biopsy specimens from two living patients with a failed replacement were analyzed. Specimens of tissue obtained from the cadavera of fifteen patients who had not had a joint replacement served as controls. The concentration of particles and the associated tissue response were characterized with the use of light microscopy of stained histological sections. Metallic particles were identified by electron microprobe analysis. Polyethylene particles were studied with the use of oil-red-O stain and polarized light microscopy. The composition of polyethylene particles was confirmed in selected cases by Fourier transform infrared spectroscopy and hot-stage thermal analysis. Twenty-one of the patients studied post mortem had had a primary total joint replacement. Eleven of them had had a hip prosthesis for a mean of sixty-nine months (range, forty-three to 171 months), and ten had had a knee replacement for a mean of eighty-four months (range, thirty-one to 179 months). The other eight patients studied post mortem had had a hip replacement in which one or more components had loosened and had been revised. The mean time between the initial arthroplasty and the time of death was 174 months (range, forty-seven to 292 months), and the mean time between the last revision procedure and the time of death was seventy-one months (range, one to 130 months). RESULTS: Metallic wear particles in the liver or spleen were more prevalent in patients who had had a failed hip arthroplasty (seven of eight) than in patients who had had a primary hip (two of eleven) or knee replacement (two of ten). The principal source of wear particles in the majority of these patients involved secondary nonbearing surfaces rather than wear between the two primary bearing surfaces as intended. In one living patient, dissemination of titanium alloy particles from a hip prosthesis with mechanical failure was associated with a visceral granulomatous reaction and hepatosplenomegaly, which required operative and medical treatment. Metallic wear particles were detected in the paraaortic lymph nodes in 68 percent (nineteen) of the twenty-eight patients with an implant from whom lymph nodes were available for study. In 38 percent (eleven) of all twenty-nine patients with an implant who were studied post mortem, metallic particles had been further disseminated to the liver or spleen, where they were usually found within small aggregates of macrophages occurring as infiltrates without apparent pathological importance. Polyethylene particles elicited a similar response. They were identified in the paraaortic lymph nodes of 68 percent (nineteen) of the twenty-eight patients and the liver or spleen of 14 percent (four) of the twenty-nine patients. The majority of the disseminated wear particles were less than one micrometer in size. Currently available methods lack the sensitivity and specificity necessary to detect very low concentrations of submicrometer polyethylene particles and probably underestimated the prevalence of polyethylene wear debris in the liver and spleen. CONCLUSIONS: In this study, systemic distribution of metallic and polyethylene wear particles was a common finding, both in patients with a previously failed implant and in those with a primary total joint prosthesis. The prevalence of particles in the liver or spleen was greater after reconstructions with mechanical failure. (ABSTRACT TRUNCATED)     

Wear Debris in Total Joint Replacements

In vivo degradation of prosthetic implant materials is increasingly recognized as a major factor limiting the durability of total joint arthroplasty. In vivo degradation occurs primarily by means of wear processes that can generate large quantities of particulate debris. This debris can stimulate an adverse local host response leading to periprosthetic bone loss, which can compromise implant fixation and bone stock. The authors review the basic mechanisms of implant degradation and the host response to particulate degradation products, particularly in the context of the pathogenesis of osteolysis. Submicron polyethylene particles (mean size, 0.5 um) are the dominant type of wear particle present in periprosthetic tissues associated with uncemented hip replacements. Polyethylene wear can be minimized by improving the quality of the polyethylene, avoiding use of large-diameter (greater than 28 mm) femoral heads in total hip arthroplasty, and improving the design and fabrication of modular connections, which can be important sources of three-body wear particles. Advances in the understanding of the basic mechanisms of osteolysis are critical to the development of preventive measures that will minimize the clinical impact of this phenomenon.     

Rare complications of osteolysis and periprosthetic tissue reactions after hybrid and non-hybrid total disc replacement

Purpose

Few complications have been reported for lumbar total disc replacement (TDR) and hybrid TDR fixations. This study evaluated retrieved implants and periprosthetic tissue reactions for two cases of osteolysis following disc arthroplasty with ProDisc-L prostheses.

Methods

Implants were examined for wear and surface damage, and tissues for inflammation, polyethylene wear debris (polarized light microscopy) and metal debris (energy-dispersive X-ray spectroscopy).

Results

Despite initial good surgical outcomes, osteolytic cysts were noted in both patients at vertebrae adjacent to the implants. For the hybrid TDR case, heterotopic ossification and tissue necrosis due to wear-induced inflammation were observed. In contrast, the non-hybrid implant showed signs of abrasion and impingement, and inflammation was observed in tissue regions with metal and polyethylene wear debris.

Conclusions

In both cases, wear debris and inflammation may have contributed to osteolysis. Surgeons using ProDisc prostheses should be aware of these rare complications.

     

Orthopedic wear debris mediated inflammatory osteolysis is mediated in part by NALP3 inflammasome activation

Activation of myeloid cells by orthopedic particulate debris is a key event in the pathogenesis of periprosthetic osteolysis and implant loosening after total joint replacement (TJR). Several lines of evidence implicate NACHT, LRR, and PYD domains‐containing protein 3 (NALP3) inflammasome‐mediated production of interleukin 1 beta (IL‐1β) in the pathogenesis of clinical disorders ascribable to foreign particulate materials, including asbestos, silica, and urate crystals. Recent reports indicate that orthopedic polymer products and metallic particulates and ions may activate the same pathway. Here, we investigated the contribution of the NALP3 inflammasome to the pathogenesis of peri‐implant osteolysis. Pharmaceutical and genetic perturbations of caspase‐1 and inflammasome components were used to assess the role of the NALP3 inflammasome in IL‐1β production and osteoclast formation by human monocytes and mouse macrophages in response to polymethylmethacrylate (PMMA) particle phagocytosis. The role of caspase‐1 in a mouse calvarial model of particle‐mediated osteolysis was assessed using µCT. Phagocytosis of PMMA particles induces caspase‐1 dependent release of IL‐1β from human monocytes and mouse macrophages. Importantly, using macrophages from mice deficient in components of the NALP3 inflammasome, we show PMMA‐induced IL‐1β production is strictly dependent on these components. Mice lacking caspase‐1, the sole effector of the NALP3 inflammasome, show reduced orthopedic wear particle‐induced calvarial osteolysis compared to wild‐type controls. Absence of NALP3 inflammasome components fails to alter osteoclast formation in vitro. Our findings identify the NALP3 inflammasome as a critical mediator of orthopedic wear‐induced osteolysis and as a viable therapeutic target for the treatment of periprosthetic osteolysis. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:73–80, 2012