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

Breast milk metal ion levels in a young and active patient with a metal-on-metal hip prosthesis

Metal-on-metal resurfacing arthroplasty of the hip has been used increasingly over the last 10 years in younger active patients. The dissolution of the metal wear particles results in measurable increases in cobalt and chromium ions in the serum and urine of patients with a metal-on-metal bearing. We measured the cobalt, chromium, and molybdenum ion levels in urine; serum; and breast milk in a young and active patient with a metal-on-metal hip prosthesis after a pathologic fracture of the femoral neck. Metal-on-metal hip prosthesis leads to increasing levels of molybdenum in breast milk in the short-term follow-up. There are no increasing levels of chromium and cobalt ions in breast milk. Besides the already known elevated concentrations in serum of chromium and cobalt after implantation of a metal-on-metal hip prosthesis, we found no increasing levels of chromium and cobalt in urine.

Metal-on-metal vs conventional total hip arthroplasty: a systematic review and meta-analysis of randomized controlled trials

Metal-on-metal (MOM) hip articulations represent a potential alternative to conventional metal-on-polyethylene total hip arthroplasty (THA). We performed a systematic review of the peer-reviewed literature in search of studies comparing MOM with conventional primary THA with regard to functional outcomes, radiographic outcomes, and complication rates. Four Level I randomized controlled trials remained following our screening process. The data published in these studies were extracted and aggregated using a Mantel-Haenszel cumulative fixed effects meta-analysis. We found no significant difference between MOM and conventional THA with regard to functional outcomes as measured by Harris hip scores and radiographic outcomes as measured by radiolucent lines. Patients with MOM THA did however demonstrate a 3.37 times greater complication rate (1.57, 7.26). In light of the lack of superiority, the increased complication rate, the greater cost, and the potential for adverse medical consequences associated with MOM THA, these bearing surfaces should be used with caution.

Wear-corrosion synergism in a CoCrMo hip bearing alloy is influenced by proteins

BACKGROUND

Although numerous in vitro studies report on the tribological performance of and, separately, on the corrosion properties of cobalt-based alloys in metal-on-metal (MoM) bearings, the few studies that take into account the synergistic interaction of wear and corrosion (tribocorrosion) have used canonical tribo-test methods. We therefore developed synergistic study using a test method that more closely simulates hip bearing conditions.

QUESTIONS/PURPOSES

(1) Is the total material loss during tribocorrosion larger than the sum of its components generated during isolated mechanical wear and isolated corrosion? (2) How is the tribocorrosive process affected by the presence of protein?

METHODS

High carbon CoCrMo alloy discs (18) were subjected to corrosion and tribocorrosion tests under potentiostatic conditions in an apparatus simulating hip contact conditions. The input variables were the applied potential and the protein content of the electrolyte (NaCl solution versus bovine serum, 30 g/L protein). The output variables were mass loss resulting from wear in the absence of corrosion, mass loss resulting from corrosion in the absence of wear, and the total mass loss under tribocorrosion, from which the additional mass loss resulting from the combined action of wear and corrosion, or synergism, was determined in the presence and absence of protein.

RESULTS

The degradation mechanisms were sensitive to the interaction of wear and corrosion. The synergistic component (64 μg) in the presence of protein amounted to 34% of total material loss (187 μg). The presence of protein led to a 23% decrease in the total mass loss and to a considerable reduction in the mean current (4 μA to 0.05 μA) under tribocorrosion.

CONCLUSIONS

Synergistic effects during tribocorrosion may account for a considerable portion of MoM degradation and are affected by proteins.

CLINICAL RELEVANCE

The in vivo performance of some large-diameter MoM joints is unsatisfactory. The synergistic component resulting from tribocorrosion may have been missed in conventional preclinical wear tests.

Successful long-term fixation and progression of osteolysis associated with first-generation cementless acetabular components retrieved post mortem

BACKGROUND

Primary cementless acetabular reconstruction has shown durable long-term fixation. Late failures secondary to aseptic loosening are rare but may occur in patients with previously well-fixed components. In the present study, the histopathological characteristics of postmortem specimens were correlated with wear damage and radiographic data in an attempt to better understand the long-term events in the periacetabular tissue around well-functioning devices.

METHODS

Seventeen primary cementless Harris-Galante I acetabular components with adjacent tissues were harvested after a mean of eleven years (range, four to twenty-five years) from patients whose implants were well functioning at the time of death. Undecalcified and paraffin sections were used to quantify the extent of bone and soft tissues within the porous coating and at the interface between the coating and the surrounding bone. Wear particles were identified with use of polarized light microscopy and energy-dispersive x-ray analysis. Bearing-surface volumetric wear and backside wear damage of the polyethylene liner were assessed.

RESULTS

All of the components were fixed by bone ingrowth (mean extent, 33% ± 21%). Particle-induced granulomas were present in the porous coating and along the interface and progressed through screw holes, ballooning into the retroacetabular bone in the longer-term specimens. Particles of femoral and acetabular origin were identified in the granulomas. Bearing-surface volumetric wear (mean, 41.6 mm3/year) increased with duration and correlated with increasing extent of granuloma in the porous coating and the increasing size of pelvic granulomas. Radiolucencies on radiographs correlated with the extent of bone and fibrous tissue ingrowth. Of the six pelvic granulomas that were identified histologically, only one was apparent on routine radiographs.

CONCLUSIONS

Acetabular fixation by bone ingrowth can be successful into the third decade after implantation. Osteolysis and secondary replacement of bone with particle-induced granuloma are commonly seen in the presence of excellent clinical function. Strategies designed to minimize bearing-surface wear and backside damage are important to maintain long-term bone ingrowth fixation.

Differential distribution of cobalt, chromium, and nickel between whole blood, plasma and urine in patients after metal-on-metal (MoM) hip arthroplasty

Evidence shows that raised cobalt (Co), chromium (Cr), and nickel (Ni) whole blood concentrations correlate with poor device outcome in patients following metal-on-metal (MoM) hip arthroplasty. To understand the local and systemic pathological effects of these raised metal concentrations it is important to define their distribution between whole blood, plasma, and urine. The metals were measured by Inductively Coupled Plasma Mass Spectrometry (ICPMS). Two hundred and five plasma, 199 whole blood, and 24 sets of urine samples were analyzed from 202 patients with Co-Cr alloy MoM hip prostheses implanted between 8 months to 12 years (mean 6.0 years) prior to analysis. Plasma Co (median 39.1 nmol/L) showed significantly positive 1:1 correlation with whole blood Co (median 45.9 nmol/L; R(2)  = 0.98, p < 0.001, slope = 1.0). Plasma Cr (median 53.8 nmol/L) and whole blood Cr (median 40.3 nmol/L) were also correlated; however, concentrations were significantly higher in plasma indicating relatively little blood cell uptake (R(2)  = 0.96, p < 0.001, slope = 1.6). Urinary Co was up to threefold higher than Cr (median 334.0 vs. 97.3 nmol/L respectively). Nickel concentrations in whole blood, plasma, and urine were low relative to Co and Cr. The analysis shows fundamental differences in the physiological handling of these metals: Co is distributed approximately equally between blood cells and plasma, whereas Cr is mainly in plasma, despite which, Cr had far less renal excretion than Co.

Bone formation around zirconia implants combined with rhBMP-2 gel in the canine mandible

OBJECTIVE

The aim of this study was to estimate the effects of zirconia implants and recombinant human bone morphogenetic protein-2 (rhBMP-2) gel on the acceleration of local bone formation and osseointegration in the canine mandible.

MATERIALS AND METHODS

Four groups of 48 implants with identical geometry were installed in the mandibles of beagle dogs: alumina-blasted zirconia implants applied with rhBMP-2, alumina-blasted zirconia implants applied with demineralized bone matrix (DBM), alumina-blasted zirconia implants, and resorbable blast media-treated titanium (Ti) implants. For the first two groups, zirconia implants were inserted after the surgical sites were filled with rhBMP-2 or DBM gel. For the other two groups, zirconia or Ti implants were installed with no adjunctive treatment. Fluorescent bone markers were administered to monitor bone remodeling at weeks 2, 4, and 5 postimplantation. After healing periods of 3 weeks and 6 weeks, the animals were sacrificed, and fluorescent microscopy, histology, and histomorphometric analyses were performed.

RESULTS

Fluorescent microscopy showed that bone formation around the zirconia implants installed with rhBMP-2 gel was the most prominent at 2 weeks postimplantation, while the Ti implants acquired bone apposition mainly at week 5. No significant differences were found in bone area among the groups (P > 0.05). The zirconia implants showed similar bone-to-implant contact to the Ti implants. There were no significant differences in bone-to-implant contact between the zirconia implants with rhBMP-2 gel and those with DBM (P > 0.05).

CONCLUSIONS

The zirconia implants with alumina-blasted surfaces may achieve osseointegration in much the same manner as the well-established Ti implants. The area influenced by rhBMP-2 gel, including the alveolar crest, may cause active remodeling and early bone formation.

Reactive granular histiocytosis secondary to arthroplasty prosthesis: a novel reaction pattern

A reactive histiocytic infiltrate can be seen as an incidental finding in a lymph node biopsy from a patient with a history of joint arthroplasty. We report the case of a 74-year-old female who underwent surgical revision of a polyethylene-based right total knee prosthesis due to chronic wear. At the time of surgery, a soft tissue mass adjacent to the tibial prosthetic insert was noted and excised. Histopathologic examination revealed a sheet-like proliferation of large, histiocytoid cells within the subcutis and superficial fascia. The cells showed abundant eosinophilic, granular cytoplasm and small round bland nuclei. Immunohistochemical evaluation revealed the cells to be positive only for CD68. In addition, abundant PAS-positive cytoplasmic granules were found, and minute particles of polarizable material were noted intracellularly and scattered throughout the interstitium of the infiltrate. These findings were interpreted as consistent with a reactive, non-Langerhans cell histiocytosis secondary to the patient's polyethylene knee prosthesis. This finding appears to be a local correlate of the process previously described in regional lymph nodes as reactive granular histiocytosis. Dermatopathologists should be cognizant of this uncommon reaction pattern to avoid mistaking it for a neoplastic process.

Serum metal levels after minimally invasive repair of pectus excavatum

BACKGROUND

Metal implants may wear and corrode, resulting in systemic dissemination of metallic debris that is measurable in serum. Concern exists regarding adverse health effects related to implant-derived debris. Minimally invasive repair of pectus excavatum (MIRPE) is a popular technique in which a stainless steel substernal bar is implanted to achieve deformity correction. Serum metal levels have not previously been investigated after MIRPE.

METHODS

Serum chromium, molybdenum, and nickel levels were measured in this cross-sectional study of 11 children implanted with pectus bars after MIRPE. Samples were analyzed using high-resolution inductively coupled plasma mass spectrometry.

RESULTS

Median serum chromium and nickel values were elevated 3.3-fold (P = .0003) and 2.3-fold (P = .25), respectively, compared with age-matched controls. Serum chromium and nickel levels were abnormally elevated in 6 (55%) of 11 and 5 (45%) of 11, respectively. In patients whom postexplantation metal levels were measured, previously elevated levels were lowered. Serum chromium levels in children after MIRPE are comparable with adult cohorts with hip arthroplasty implants measured 1-year postoperatively. No acute metal toxicity was observed.

CONCLUSIONS

Abnormally elevated levels of serum metal levels are measurable in children implanted with pectus bars. These findings warrant further investigation to assess the biocompatibility of this surgical implant in children.

Transosseous fixation in insertional Achilles tendonitis

The surgical approach of severe insertional Achilles tendonitis involves debridement, repair, and reattachment. Previously described techniques for bone-tendon reattachment involved the use of suture anchors in the sparsely trabeculated calcaneus. The following technique tip is a reintroduction of bicortical transosseous fixation previously used in rotator cuff repairs. Bone tunnels are a viable option in the treatment of insertional Achilles tendonitis; however, additional research is necessary to validate its efficacy in this application.

Risk of cancer with metal-on-metal hip replacements: population based study

OBJECTIVE

To assess the risk of cancer associated with modern primary metal-on-metal hip replacements.

DESIGN

Population based study.

SETTING

Nationwide retrospective comparative register.

PARTICIPANTS

10,728 patients who underwent metal-on-metal total hip arthroplasty and 18,235 patients who underwent conventional metal-on-polyethylene, ceramic-on-polyethylene, and ceramic-on-ceramic total hip arthroplasty (the non-metal-on-metal cohort) in the Finnish Arthroplasty Register 2001-10. Data on cancer cases up to 2010 for these cohorts were extracted from the Finnish Cancer Registry.

MAIN OUTCOME MEASURES

The relative risk of cancer was expressed as the ratio of observed to expected number of cases from the Finnish population--that is, the standardised incidence ratio. The relative risk of cancer in the metal-on-metal cohort compared with the non-metal-on-metal cohort was estimated with analyses of these ratios and Poisson regression.

RESULTS

The overall risk of cancer in patients with metal-on-metal hip implants was similar to that in the Finnish population (378 observed v 400 expected, standardised incidence ratio 0.95, 95% confidence interval 0.85 to 1.04). The overall risk of cancer in patients with metal-on-metal hip implants was also no higher than in patients who had received non-metal-on-metal hip implants (relative risk 0.92, 0.81 to 1.05).

CONCLUSIONS

Metal-on-metal hip replacements are not associated with an increased overall risk of cancer during a mean follow-up of four years.

Simple isolation method for the bulk isolation of wear particles from metal on metal bearing surfaces generated in a hip simulator test

Isolation and characterization of metal-on-metal (MoM) wear particles from simulator lubricants is essential to understand wear behaviour, ion release and associated corrosive activity related to the wear particles. Substantial challenges remain to establish a simple, precise and repeatable protocol for the isolation and analysis of wear particles due to their extremely small size, their tendency to agglomerate and degrade. In this paper, we describe a simple and efficient method for the bulk isolation and characterisation of wear particles from MoM bearings. Freeze drying was used to remove the large volume of water from the serum lubricant, enzymes used to digest the proteins and ultracentrifugation to finally isolate and purify the particles. The present study involved a total of eight steps for the isolation process and a wear particle extraction efficiency of 45% was achieved.

Modularity of the femoral component in total hip arthroplasty

Modular femoral components have been developed to aid in recreating native femoral version, limb length, and offset in total hip arthroplasty. Use of modular implants results in cost savings, as well. Inventory can be reduced while allowing intraoperative flexibility and options. With modular implants, the femoral prosthesis can be built in situ, which is helpful in minimizing incision length and surgical dissection. However, additional modular junctions are associated with increased concern for component failure through taper fretting, fatigue fracture, and local corrosion, which may contribute to elevated serum metal ion levels. The recent trend toward using larger diameter femoral heads may impart higher loads and stress than were seen previously. Although modular components offer a plethora of intraoperative options in primary and revision total hip arthroplasty, the long-term effects of these additional junctions remains unknown.

Clinical usefulness of blood metal measurements to assess the failure of metal-on-metal hip implants

In April 2010, a Medicines and Healthcare Products Regulatory Agency safety alert concerning all metal-on-metal (MOM) hip replacements recommended measuring chromium and cobalt concentrations when managing patients with painful prostheses. The need for this review is illustrated by the recent surge in requests for these blood tests from orthopaedic surgeons following this alert. The aim is to provide guidance to laboratories in assessing these requests and advising clinicians on interpretation. First, we summarize the basic terminology regarding the types of hip replacements, with emphasis on the MOM type. Second, we describe the clinical concerns over implant-derived wear debris in the local tissues and distant sites. Analytical aspects of the measurement of the relevant metal ions and what factors affect the levels measured are discussed. The application of inductively coupled plasma mass spectrometry techniques to the measurement of these metals is considered in detail. The biological effects of metal wear products are summarized with local toxicity and systemic biological effects considered, including carcinogenicity, genotoxicity and systemic toxicity. Clinical cases are used to illustrate pertinent points.

The influence of Co-Cr and UHMWPE particles on infection persistence: an in vivo study in mice

Wear of metal-on-metal (cobalt-chromium, Co-Cr particles) and metal-on-polyethylene (ultra-high-molecular-weight polyethylene, UHMWPE particles) bearing surfaces in hip prostheses is a major problem in orthopedics. This study aimed to compare the influence of Co-Cr and UHMWPE particles on the persistence of infection. Bioluminescent Staphylococcus aureus Xen36 were injected in air pouches prepared in subcutaneous tissue of immuno-competent BALB/c mice (control), as a model for the joint space, in the absence or presence of Co-Cr or UHMWPE particles. Bioluminescence was monitored longitudinally up to 21 days, corrected for absorption and reflection by the particles and expressed relative to the bioluminescence found in the presence of staphylococci only. After termination, air pouch fluid and air pouch membrane were cultured and histologically analyzed. Bioluminescence was initially lower in mice exposed to UHMWPE particles with staphylococci than in mice injected with staphylococci only, possibly because UHMWPE particles initially stimulated a higher macrophage presence in murine air pouch membranes. For mice exposed to Co-Cr particles with staphylococci, bioluminescence was observed to be higher in two out of six animals compared to the presence of staphylococci alone. In the majority of mice, infection risk in the absence or presence of Co-Cr and UHMWPE particles appeared similar, assuming that the longevity of an elevated bioluminescence is indicative of a higher infection risk. However, the presence of Co-Cr particles yielded a higher bioluminescence in two out of six mice, possibly because the macrophage degradative function was hampered by the presence of Co-Cr particles.

Molecular and immune toxicity of CoCr nanoparticles in MoM hip arthroplasty

Theoretical, desirable features of second-generation metal-on-metal (MoM) hip prostheses have led to their widespread use. However, the bearing surfaces, consisting of complex cobalt-chromium alloys, are subject to wear and the release of cobalt and chromium (CoCr) nanoparticles. These nanoparticles can reduce cellular viability, induce DNA damage, lead to chromosomal aberrations, and possibly stimulate increased metal hypersensitivity. Clinically, the effects can be both local (soft-tissue reactions) and systemic (arthroprosthetic cobaltism). This review assesses the literature concerning the in vitro and in vivo cytotoxic, genotoxic, and immunotoxic effects of CoCr wear particles, which is increasingly important in view of the large number of MoM arthroplasties performed.

New method for determining in vitro structure stiffness of ceramic acetabular liners under different impact conditions

Increasing both patient mobility and prosthesis life span requires improvements in the range of motion and wear behavior of the liner. With the use of new composite alumina-zirconia ceramic materials, the same stability of the liner can be achieved at lower wall thickness than it is possible with alumina-only materials. The aim of this study was developing a method for determining the in vitro structure stiffness of ceramic acetabular liners against impact stresses. The first trials were performed with a common alumina acetabular liner type (Ceramtec; Biolox forte; diameter 28 mm; thickness 7 mm) and a new type of alumina-zirconia (Ceramtec Biolox delta; same dimensions) liner. The clinically established alumina liner was reproducibly damaged using worst case Separation/subluxation equivalent to one-fourth or half of the head diameter, and an impact load of 15 J. The liners containing the new alumina-zirconia material were not damaged in any of the trials up to an impact load of 20 J and half head diameter offset.

Titanium dioxide in our everyday life; is it safe?

BACKGROUND

Titanium dioxide (TiO(2)) is considered as an inert and safe material and has been used in many applications for decades. However, with the development of nanotechnologies TiO(2) nanoparticles, with numerous novel and useful properties, are increasingly manufactured and used. Therefore increased human and environmental exposure can be expected, which has put TiO(2) nanoparticles under toxicological scrutiny. Mechanistic toxicological studies show that TiO(2) nanoparticles predominantly cause adverse effects via induction of oxidative stress resulting in cell damage, genotoxicity, inflammation, immune response etc. The extent and type of damage strongly depends on physical and chemical characteristics of TiO(2) nanoparticles, which govern their bioavailability and reactivity. Based on the experimental evidence from animal inhalation studies TiO(2) nanoparticles are classified as "possible carcinogenic to humans" by the International Agency for Research on Cancer and as occupational carcinogen by the National Institute for Occupational Safety and Health. The studies on dermal exposure to TiO(2) nanoparticles, which is in humans substantial through the use of sunscreens, generally indicate negligible transdermal penetration; however data are needed on long-term exposure and potential adverse effects of photo-oxidation products. Although TiO(2) is permitted as an additive (E171) in food and pharmaceutical products we do not have reliable data on its absorption, distribution, excretion and toxicity on oral exposure. TiO(2) may also enter environment, and while it exerts low acute toxicity to aquatic organisms, upon long-term exposure it induces a range of sub-lethal effects.

CONCLUSIONS

Until relevant toxicological and human exposure data that would enable reliable risk assessment are obtained, TiO(2) nanoparticles should be used with great care.

Serum metal ion concentration: comparison between small and large head metal-on-metal total hip arthroplasty

The purpose of this study was to compare serum metal ion concentrations (chromium and cobalt) in 3 groups, 2 with metal-on-metal articulations and a control metal-on-polyethylene group. Forty-six patients with good to well-functioning hips were recruited for the study. Serum ion levels of all patients were drawn, and Harris Hip Score, University of California, Los Angeles activity score, and radiographs were performed. Serum chromium concentrations were significantly lower in the large head group compared with the small head group (P = .013). There was no difference in the cobalt concentrations between the 2 groups (P = .087). There was a significant difference between both metal-on-metal groups when compared with controls for both chromium and cobalt levels (P = .0005 and P = .0004, control vs small; P = .001 and P = .0001, control vs large, respectively).

Response of osteoblast-like cells cultured on zirconia to bone morphogenetic protein-2

Purpose

The aim of this study was to compare osteoblast behavior on zirconia and titanium under conditions cultured with bone morphogenetic protein-2.

Methods

MC3T3-E1 cells were cultured on sandblasted zirconia and sandblasted/etched titanium discs. At 24 hours after seeding MC3T3-E1, the demineralized bone matrix (DBM) gel alone and the DBM gel with bone morphogenetic protein-2 (BMP-2) were added to the culture medium. The surface topography was examined by confocal laser scanning microscopy. Cellular proliferation was measured at 1, 4, and 7 days after gel loading. Alkaline phosphatase activity was measured at 7 days after gel loading. The mRNA expression of ALPase, bone sialoprotein, type I collagen, runt-related transcription factor 2 (Runx-2), osteocalcin, and osterix were evaluated by real-time polymerase chain reaction at 4 days and 7 days.

Results

At 1, 4, and 7 days after loading the DBM gel alone and the DBM gel with BMP-2, cellular proliferation on the zirconia and titanium discs was similar and that of the groups cultured with the DBM gel alone and the DBM gel with BMP-2 was not significantly different, except for titanium with BMP-2 gel. ALPase activity was higher in the cells cultured with BMP-2 than in the other groups, but there was no difference between the zirconia and titanium. In ALPase, bone sialoprotein, osteocalcin, Runx-2 and osterix gene expression, that of cells on zirconia or titanium with BMP-2 gel was much more highly increased than titanium without gel at day 7. The gene expression level of cells cultured on zirconia with BMP-2 was higher than that on titanium with BMP-2 at day 7.

Conclusions

The data in this study demonstrate that the osteoblastic cell attachment and proliferation of zirconia were comparable to those of titanium. With the stimulation of BMP-2, zirconia has a more pronounced effect on the proliferation and differentiation of the osteoblastic cells compared with titanium.

Hypersensitivity reactions to metallic implants - diagnostic algorithm and suggested patch test series for clinical use

Cutaneous and systemic hypersensitivity reactions to implanted metals are challenging to evaluate and treat. Although they are uncommon, they do exist, and require appropriate and complete evaluation. This review summarizes the evidence regarding evaluation tools, especially patch and lymphocyte transformation tests, for hypersensitivity reactions to implanted metal devices. Patch test evaluation is the gold standard for metal hypersensitivity, although the results may be subjective. Regarding pre-implant testing, those patients with a reported history of metal dermatitis should be evaluated by patch testing. Those without a history of dermatitis should not be tested unless considerable concern exists. Regarding post-implant testing, a subset of patients with metal hypersensitivity may develop cutaneous or systemic reactions to implanted metals following implant. For symptomatic patients, a diagnostic algorithm to guide the selection of screening allergen series for patch testing is provided. At a minimum, an extended baseline screening series and metal screening is necessary. Static and dynamic orthopaedic implants, intravascular stent devices, implanted defibrillators and dental and gynaecological devices are considered. Basic management suggestions are provided. Our goal is to provide a comprehensive reference for use by those evaluating suspected cutaneous and systemic metal hypersensitivity reactions.

Mediators of the inflammatory response to joint replacement devices

Joint replacement surgery is one of the success stories of modern medicine, restoring mobility, diminishing pain and improving the overall quality of life for millions of people. Unfortunately, wear of these prostheses over time generates debris, which activates an innate immune response that can ultimately lead to periprosthetic resorption of bone (osteolysis) and failure of the implant. Over the past decade, the biological interactions between the particulate debris from various implant materials and the immune system have begun to be better understood. The wear debris induces a multifaceted immune response encompassing the generation of reactive oxygen species and damage-associated molecular patterns, Toll-like receptor signaling and NALP3 inflammasome activation. Acting alone or in concert, these events generate chronic inflammation, periprosthetic bone loss and decreased osteointegration that ultimately leads to implant failure.

Cobalt, chromium and molybdenum ions kinetics in the human body: data gained from a total hip replacement with massive third body wear of the head and neuropathy by cobalt intoxication

INTRODUCTION

A patient with a total hip replacement developed optic, acoustic and peripheral neuropathy from metal ions intoxication, due to the wear products released from the prosthesis. Subsequently the kinetics of the metal ions was studied.

MATERIALS AND METHODS

Massive wear and acute intoxication allowed a study of the metal ions kinetics and of EDTA treatment.

RESULTS

Plasma and other organic fluids were saturated by each of the metal ions released from the exposed surface according to the solubility of each ion; a larger fraction of Co ions was bound within red cells, while the plasmatic fraction appeared more movable. In a patient with a prosthesis subjected to wear, the ions released are from the prosthetic and from the debris surface (spread in the body). The latter is a function of the number and size of particles.

DISCUSSION

Revision of the prosthesis from the point of view of the metal ions kinetics corresponded to a reduction of the releasing surface because of debris washed out by irrigation and tissue excision; however, the metal particles spread by lymphatic circulation continued to release ions even though the source of wear had been removed. Early diagnosis of high metal wear can be ascertained with mass spectrometry and after revision high levels of metal ions can only be reduced with repeated chelating treatment. It is preferable not to revise fractured ceramic components with a polyethylene-metal articulation.

Do tissues from THA revision of highly crosslinked UHMWPE liners contain wear debris and associated inflammation?

BACKGROUND

Polyethylene wear debris is a major contributor to inflammation and the development of implant loosening, a leading cause of THA revisions. To reduce wear debris, highly crosslinked ultrahigh-molecular-weight polyethylene (UHMWPE) was introduced to improve wear properties of bearing surfaces. As highly crosslinked UHMWPE revision tissues are only now becoming available, it is possible to examine the presence and association of wear debris with inflammation in early implant loosening.

QUESTIONS/PURPOSES

We asked: (1) Does the presence of UHMWPE wear debris in THA revision tissues correlate with innate and/or adaptive immune cell numbers? (2) Does the immune cell response differ between conventional and highly crosslinked UHMWPE cohorts?

METHODS

We collected tissue samples from revision surgery of nine conventional and nine highly crosslinked UHMWPE liners. Polarized light microscopy was used to determine 0.5- to 2-μm UHMWPE particle number/mm2, and immunohistochemistry was performed to determine macrophage, T cell, and neutrophil number/mm2.

RESULTS

For the conventional cohort, correlations were observed between wear debris and the magnitude of individual patient macrophage (ρ=0.70) and T cell responses (ρ=0.71) and between numbers of macrophages and T cells (ρ=0.77) in periprosthetic tissues. In comparison, the highly crosslinked UHMWPE cohort showed a correlation between wear debris and the magnitude of macrophage responses (ρ=0.57) and between macrophage and T cell numbers (ρ=0.68). Although macrophages and T cells were present in both cohorts, the highly crosslinked UHMWPE cohort had lower numbers, which may be associated with shorter implantation times.

CONCLUSIONS

The presence of wear debris and inflammation in highly crosslinked UHMWPE revision tissues may contribute to early implant loosening.

Analysis of the cytotoxicity of differentially sized titanium dioxide nanoparticles in murine MC3T3-E1 preosteoblasts

There is an increased use of nanophase titanium dioxide (TiO(2)) in bone implants and scaffolds. However, nano-debris is generated at the bone-biomaterial interface. Therefore, TiO(2) nanoparticles (NPs) of many sizes were investigated for cytotoxic effects on murine MC3T3-E1 preosteoblasts. These TiO(2) NPs induced a time- and dose-dependent decrease in cell viability. There was a significant increase in lactate dehydrogenase (LDH) release, apoptosis and mitochondrial membrane permeability following short-term exposure of the cells to TiO(2) NPs. These NPs also increased granulocyte-macrophage colony stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) gene expression. Compared with the 32 nm TiO(2) NPs, 5 nm TiO(2) NPs were more toxic, induced more apoptosis, increased mitochondrial membrane permeability and stimulated more GM-CSF expression at a high concentration (≥100 μg/ml). The results implied that the differential toxicity was associated with variations in size, so more attention should be given to the toxicity of small NPs for the design of future materials for implantation.

Characterization of Wear Particles Generated from CoCrMo Alloy under Sliding Wear Conditions

Biological effects of wear products (particles and metal ions) generated by metal-on-metal (MoM) hip replacements made of CoCrMo alloy remain a major cause of concern. Periprosthetic osteolysis, potential hypersensitivity response and pseudotumour formation are possible reactions that can lead to early revisions. To accurately analyse the biological response to wear particles from MoM implants, the exact nature of these particles needs to be characterized. Most previous studies used energy-dispersive X-ray spectroscopy (EDS) analysis for characterization. The present study used energy filtered transmission electron microscopy (TEM) and electron diffraction pattern analysis to allow for a more precise determination of the chemical composition and to gain knowledge of the crystalline structure of the wear particles.Particles were retrieved from two different test rigs: a reciprocating sliding wear tribometer (CoCrMo cylinder vs. bar) and a hip simulator according to ISO 14242-1 (CoCrMo head vs. CoCrMo cup). All tests were conducted in bovine serum. Particles were retrieved from the test medium using a previously published enzymatic digestion protocol.Particles isolated from tribometer samples had a size of 100 - 500 nm. Diffraction pattern analysis clearly revealed the lattice structure of strain induced hcp ε-martensite. Hip simulator samples revealed numerous particles of 15 - 30 nm and 30 - 80 nm size. Most of the larger particles appeared to be only partially oxidized and exhibited cobalt locally. The smallest particles were Cr(2)O(3) with no trace of cobalt. It optically appeared that these Cr(2)O(3) particles were flaking off the surface of larger particles that depicted a very high intensity of oxygen, as well as chromium, and only background noise of cobalt. The particle size difference between the two test rigs is likely related to the conditions of the two tribosystems, in particular the difference in the sample geometry and in the type of sliding (reciprocating vs. multidirectional).Results suggest that there may be a critical particle size at which chromium oxidation and cobalt ionization is accelerated. Since earlier studies have shown that wear particles are covered by organic residue which may act as a passive layer inhibiting further oxidation, it would suggest that this organic layer may be removed during the particle isolation process, resulting in a change of the particle chemical composition due to their pyrophoric properties. However, prior to being isolated from the serum lubricant, particles remain within the contact area of head and cup as a third-body. It is therefore possible that during that time, particles may undergo significant transformation and changes in chemical composition in the contact area of the head and cup within the tribological interface due to mechanical interaction with surface asperities.

Titanium allergy: could it affect dental implant integration?

PURPOSE

Degradation products of metallic biomaterials including titanium may result in metal hypersensitivity reaction. Hypersensitivity to biomaterials is often described in terms of vague pain, skin rashes, fatigue and malaise and in some cases implant loss. Recently, titanium hypersensitivity has been suggested as one of the factors responsible for implant failure. Although titanium hypersensitivity is a growing concern, epidemiological data on incidence of titanium-related allergic reactions are still lacking.

MATERIALS AND METHODS

A computer search of electronic databases primarily MEDLINE and PUBMED was performed with the following key words: 'titanium hypersensitivity', 'titanium allergy', 'titanium release' without any language restriction. Manual searches of the bibliographies of all the retrieved articles were also performed. In addition, a complementary hand search was also conducted to identify recent articles and case reports.

RESULTS

Most of the literature comprised case reports and prospective in vivo/in vitro trials. One hundred and twenty-seven publications were selected for full text reading. The bulk of the literature originated from the orthopaedic discipline, reporting wear debris following knee/hip arthroplasties. The rest comprised osteosynthesis (plates/screws), oral implant/dental materials, dermatology/cardiac-pacemaker, pathology/cancer, biomaterials and general reports.

CONCLUSION

This review of the literature indicates that titanium can induce hypersensitivity in susceptible patients and could play a critical role in implant failure. Furthermore, this review supports the need for long-term clinical and radiographic follow-up of all implant patients who are sensitive to metals. At present, we know little about titanium hypersensitivity, but it cannot be excluded as a reason for implant failure.

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.

Distinct immunohistomorphologic changes in periprosthetic hip tissues from historical and highly crosslinked UHMWPE implant retrievals

Assessment of immune response to implant wear debris in periprosthetic tissue following total hip arthroplasty suggests that multiple factors are involved in the loss implant function. The current study investigated wear debris and the associated immunohistomorphologic changes in tissues from nine patients with historical (gamma air-sterilized) and nine highly crosslinked UHMWPE implant components. Paraffin embedded tissue sections were evaluated for the presence of histiocytes, giant cells, fibrocartilage/bone, and necrosis. To determine the incidence, degree and co-localization of immunohistomorphologic changes and wear, overlapping full-field tissue arrays were collected in brightfield and polarized light. The historical cohort tissues predominantly showed histiocytes associated with significant accumulations of small wear (0.5-2 microm), and giant cells associated with large wear (> or =2 microm). Frequently, focal regions of necrosis were observed in association with wear debris. For the highly crosslinked cohort, inflammation and associated wear debris were limited, but in tissues from patients revised after implantation times of >2 years a response was observed. Whereas significant amounts of fibrocartilage/bone were observed in patients at earlier implantation times. In both cohorts, tissue responses were more extensive in the retroacetabular or proximal femoral regions. The current findings suggest that wear debris-induced inflammation may be a major contributor to the loss of implant function for both the historical and highly crosslinked cohorts, but it is not the primary cause of early implant loosening. This study highlights the importance of using a more quantitative and standardized assessment of immunohistomorphologic responses in periprosthetic tissues, and emphasizes differences in specific anatomical regions of individual patient tissues.

Magnetic resonance imaging studies on gadonanotube-reinforced biodegradable polymer nanocomposites

We report about the in vitro cytotoxicity and MRI studies of Gd(3+)ions-doped ultra-short single-walled carbon nanotube (gadonanotubes), gadonanotubes- reinforced poly(lactic-co-glycolic acid) (PLGA) polymer nanocomposites and in vivo small animal MRI studies using the gadonanotubes. These studies were performed to explore the suitability of gadonanotubes-reinforced PLGA polymer nanocomposite as a model scaffold for noninvasive magnetic resonance imaging (MRI) to evaluate nanotube release during the degradation process of the scaffold and their biodistribution upon release from the polymer matrix in vivo. The gadonanotubes at 1-100 ppm and the gadonanotubes/PLGA nanocomposites (2 wt % gadonanotubes) did not show any cytotoxicity in vitro as demonstrated using the LIVE/DEAD viability assay. For the first time, r(2) relaxivity measurements were obtained for the superparamagnetic gadonanotubes. In vitro 7T MRI of the superparamagnetic gadonanotubes ([Gd] = 0.15 mM) suspended in a biocompatible 1% Pluronic F127 solution, gave a r(2) value of 578 mM(-1) s(-1). Upon subcutaneous injection of the gadonanotubes suspension into the dorsal region of rats, the high r(2) value translated into excellent and prolonged negative contrast enhancement of in vivo T(2)weighted proton MRI images. The in vitro characterization of the nanocomposite discs and their degradation process by MRI, showed strong influence of the gadonanotube on water proton relaxations. These results indicate that the gadonanotubes/PLGA nanocomposites are suitable for further in vivo studies to track by MRI the biodegradation release and biodistribution of gadonanotubes.

Cobalt ions induce chemokine secretion in a variety of systemic cell lines

BACKGROUND AND PURPOSE

Metal ion toxicity both locally and systemically following MoM hip replacements remains a concern. Cobalt ions have been shown to induce secretion of proinflammatory chemokines locally; however, little is known about their effect systemically. We investigated the in vitro effect of cobalt ions on a variety of cell lines by measuring production of the proinflammatory chemokines IL-8 and MCP-1.

METHOD

Renal, gastrointestinal, and respiratory epithelium and also neutrophils and monocytes were exposed to cobalt ions at 4, 12, 24, and 48 hours.

RESULTS

We found that cobalt ions enhanced the secretion of IL-8 and MCP-1 in renal epithelial cells, gastric and colon epithelium, monocytes and neutrophils, and small airway epithelial cells but not in alveolar cells. Secretion of IL-8 and MCP-1 was markedly elevated in renal epithelium, where a 16-fold and 7-fold increase occurred compared to controls. There was a 6-fold and 4-fold increase in IL-8 and MCP-1 secretion in colon epithelium and a 4-fold and 3-fold increase in gastric epithelium. Small airway epithelial cells showed a maximum increase in secretion of 8-fold (IL-8) and of 4-fold (MCP-1). The increase in chemokine secretion observed in alveolar cells was moderate and did not reach statistical significance. Monocytes and neutrophils showed a 2.5-fold and 2-fold increase in IL-8 secretion and a 6-fold and 4-fold increase in MCP-1 secretion at 48 and 24 hours, respectively.

INTERPRETATION

These data demonstrate the potent bioactivity of cobalt ions in a variety of cell types and the potential to induce a proinflammatory response.

The role of albumin in human toxicology of cobalt: contribution from a clinical case

The distribution and adverse effects, especially to optic and acoustic nerves, of cobalt released from a hip arthroplasty and its association with albumin were studied. The analysis of cobalt was performed in plasma, whole blood, urine, and cerebrospinal fluid by inductively coupled plasma mass spectrometry (ICP-MS). The fraction of albumin binding the metal was determined by colorimetric assay using dithiothreitol (DTT). In all the biological matrices very high levels of cobalt were measured, but contrary to expected, a higher concentration in whole blood than in plasma was observed. The determination of altered albumin confirmed this hypothesis. This evidence might indicate an alteration in the binding of cobalt to albumin and a consequent increase in the concentration of the diffusible (free) fraction of the metal. This appears an interesting starting point for further investigations for identifying and better understanding cobalt neurotoxicity, apparently not so frequent in occupational medicine and clinical practice.

Effect of chromium and cobalt ions on phase I and phase II enzymatic activities in vitro in freshly isolated rat hepatocytes

The effect of in vitro exposure to the metal ions (chromium (VI) and cobalt (II)) on phase I and phase II enzymatic activities in freshly isolated rat hepatocytes is reported. Concentrations of metal ions used reflect those reported in the livers of cadavers that had worn metal-on-metal hip implants. To assess the effect of exposure to metal ions on enzymatic activities of phase I metabolic reactions the hydroxylations of testosterone were measured, and the phase II reactions measured were glucuronidation and sulfation. No effect was observed in the formation of the testosterone metabolites measured in the presence of either ion, Cr (VI) inhibited both glucuronidation and sulfation of 7-hydroxycoumarin (7-HC) and 1-naphthol, while Co inhibited only the glucuronidation of 7-HC and 1-naphthol. ATP levels were reduced in freshly isolated rat hepatocytes treated with Cr (VI) compared with control hepatocytes with no metal treatment. Cr (VI) probably inhibits the formation of 3'-phosphoadenosine 5'-phosphosulfate (PAPS), the high energy co-factor of sulfation, by reducing the availability of ATP and also by acting as a substrate analog and competing with sulfate for ATP-sulfurylase. High concentrations of these metal ions in the livers of patients with loose or worn metal implants may act synergistically, and have consequences for the metabolism of xenobiotics.

Effects of metal-on-metal wear on the host immune system and infection in hip arthroplasty

BACKGROUND AND PURPOSE

Joint replacement with metal-on-metal (MOM) bearings have gained popularity in the last decades in young and active patients. However, the possible effects of MOM wear debris and its corrosion products are still the subject of debate. Alongside the potential disadvantages such as toxicity, the influences of metal particles and metal ions on infection risk are unclear.

METHODS

We reviewed the available literature on the influence of degradation products of MOM bearings in total hip arthroplasties on infection risk.

RESULTS

Wear products were found to influence the risk of infection by hampering the immune system, by inhibiting or accelerating bacterial growth, and by a possible antibiotic resistance and heavy metal co-selection mechanism.

INTERPRETATION

Whether or not the combined effects of MOM wear products make MOM bearings less or more prone to infection requires investigation in the near future.