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

Early detachment of titanium particles from various different surfaces of endosseous dental implants

Titanium (Ti) endosseous dental screws with different surfaces (smooth titanium--STi, titanium plasma-sprayed-TPS, alumina oxide sandblasted and acid-etched--Al-SLA, zirconium oxide sandblasted and acid etched--Zr-SLA) were implanted in femura and tibiae of sheep to investigate the biological evolution of the peri-implant tissues and detachment of Ti debris from the implant surfaces in early healing. Implants were not loaded. Sections of the screws and the peri-implant tissues obtained by sawing and grinding were analysed by light microscopy immediately after implantation (time 0) and after 14 days. All samples showed new bone trabeculae and vascularised medullary spaces in those areas where gaps between the implants and host bone were visible. In contrast, no osteogenesis was induced in the areas where the implants were initially positioned in close contact with the host bone. Chips of the pre-existing bone inducing new peri-implant neo-osteogenesis were surrounded by new bone trabeculae. The threads of some screws appeared to be deformed where the host bone showed fractures. Ti granules of 3-60 microm were detectable only in the peri-implant tissues of TPS implants both immediately after surgery and after 14 days, thus suggesting that this phenomenon may be related to the friction of the TPS coating during surgical insertion.

Treatment of experimental visceral leishmaniasis with amphotericin B in stable albumin microspheres

Hydrophilic albumin microspheres are proposed as a new delivery system for amphotericin B (AMB; AMB microspheres). The acute toxicity of AMB microspheres was lower than that of the AMB-deoxycholate (AMB-Doc) reference formulation in hamsters. Lethal doses in healthy and infected animals were improved at least eight times. Intravenous bolus administration of doses of AMB microspheres up to 40 mg/kg of body weight did not produce acute symptoms of toxicity. The efficacy of this new formulation was tested against Leishmania infantum-infected hamsters at doses of 2, 10, 20, and 40 mg/kg. With the 2-mg/kg dose, the activity of AMB, as assessed through the parasite load reductions in the liver and spleen and the evolution of antibody levels, was also improved (P < 0.05) by use of the AMB microsphere system. At the higher doses of 10, 20, and 40 mg/kg, reductions in parasite levels of more than 99% were achieved in the liver and spleen after the administration of AMB microspheres. A pharmacokinetic study was performed to study the serum, liver, and spleen AMB concentrations after administration of AMB microspheres and the reference formulation. Interestingly, a significant accumulation of AMB in the spleen and liver was observed after AMB microsphere administration. Our results suggest that this new formulation is a promising alternative to the conventional AMB-Doc formulation for the treatment of visceral leishmaniasis.

Ultrastructural analysis of metallic debris and tissue reaction around spinal implants in patients with late operative site pain

STUDY DESIGN

Cross-sectional ultrastructural analysis of metallic debris as well as the tissue reaction surrounding spinal implants in patients with late operative site pain.

OBJECTIVE

To clarify the cause of late operative site pain by the ultrastructural analysis of the byproducts of metallic corrosion as well as the surrounding soft tissues.

SUMMARY OF THE BACKGROUND DATA

Late operative site pain has been identified as the most frequent cause of implant removal. Allergic reaction to metal as well as low-grade infection has been suggested as probable mechanisms.

METHODS

Fourteen spinal implants were removed because of late operative site pain. Tissues obtained from different zones surrounding these implants were analyzed by light microscopy, transmission electron microscopy, and scanning electron microscopy along with electron dispersion radiograph analysis.

RESULTS

No signs of infection were present. Either one of the 2 types of connective tissue (dense or loose) were found to surround the implants. Macrophage counts were most abundant in zone II (around pedicular screws) when compared to other zones (zone I: around the rods; zone III: around the transverse rod connectors). In contrast, particulate debris was more abundant and larger in size in specimens from zone III. Two types of metallic debris were identified. The rusty appearing particles contained mostly iron (Fe), whereas the black appearing particles were rich in chromium (Cr).

CONCLUSION

This study produced useful information regarding the production and distribution of particulate metallic debris around stainless steel spinal implants.

Increased viable osteoblast density in the presence of nanophase compared to conventional alumina and titania particles

In the present in vitro study, osteoblast (bone-forming cells) viability and cell density were investigated when cultured in the presence of nanophase compared to conventional (i.e. micron) alumina and titania particles at various concentrations (from 10,000 to 100 microg/ml of cell culture media) for up to 6h. Results confirmed previous studies of the detrimental influences of all ceramic particulates on osteoblast viability and cell densities. For the first time, however, results provided evidence of increased apoptotic cell death when cultured in the presence of conventional compared to nanophase alumina and titania particles. Moreover, since material characterization studies revealed that the only difference between respective ceramic particles was nanometer- and conventional-dimensions (specifically, phase and chemical properties were similar between respective nanophase and conventional alumina as well as titania particles), these results indicated that osteoblast viability and densities were influenced solely by particle size. Such nanometer particulate wear debris may result from friction between articulating components of orthopedic implants composed of novel nanophase ceramic materials. Results of a less detrimental effect of nanometer--as compared to conventional-dimensioned particles on the functions of osteoblasts provide additional evidence that nanophase ceramics may become the next generation of bone prosthetic materials with increased efficacy and, thus, deserve further testing.

Foreign body reactions in lymph nodes of oncology patients with joint prostheses—light-, electron microscopic and immunohistological investigations

Foreign body reactions in lymph nodes caused by wear particles from joint prostheses can mimic different lymphadenopathies, including metastatic cancer. The knowledge of these alterations is particularly important for pathologists performing frozen section diagnosis for oncology patients. As recent investigations of pseudocapsules have revealed that most of the wear particles are submicron-sized, transmission electron microscopic investigations were additionally performed. The histological investigation of the pelvic lymph nodes of 22 oncology patients with joint prostheses showed that the bone cement wear prevailed. At least small amounts of polyethylene wear particles were also found in all cases. Metallic wear particles were detected in 90% of the cases. The wear particles induce a macrophage-rich foreign body reaction that can cause an architectural effacement of the lymph nodes. The electron microscopic investigations showed that submicron-sized wear particles prevail. Some of them form conglomerates in size ranges detectable by light microscopy. The immunohistochemical studies showed that the foreign body reactions comprised mature CD163- and PGM1-positive macrophages and few lymphocytes, predominantly T-lymphocytes. The knowledge of the characteristic alterations of regional lymph nodes seems important in order to avoid misinterpretations. Therefore, in particular the detection of intracytoplasmatic wear particles is helpful in this respect.

Dosages sanguins de métaux chez 48 patients porteurs d’une prothèse totale de hanche en chrome-cobalt à couple métal-polyéthylène

PURPOSE OF THE STUDY

Component wear and dissemination of wear debris, particularly with metal-on-metal combinations, is the predominant long-term complication of total hip arthroplasty. The purpose of our work was to search for metal pArticles released when using the metal-on-polyethylene combination by analyzing serum levels of chromium (Cr), cobalt (Co), nickel (Ni), and molybdium (Mo) in patients with a metal-on-polyethylene chromium-cobalt total hip arthroplasty. We compared the observed levels with those observed in a control population and studied changes as a function of signs of loosening.

MATERIAL AND METHODS

During a thirty-Month period, 53 patients with degenerative hip disease underwent total hip arthroplasty. The same implant, PVL, being used for all hips. Forty-eight patients were available for analysis at a minimum follow-up of 32 Months. Results of the clinical and radiological examination of the operated hip were recorded. Serum metal levels were assayed by mass spectrometry on total blood samples. Patient activity was determined with the Devane classification and hip function with the Postel-Merle-d'Aubligné score; walking distance was recorded in kilometers. Signs of prosthetic loosening were identified on plain radiograms (AP and lateral views) searching for femoral and/or acetabular lucent lines, cement fracture, granuloma. The control group included 56 patients scheduled for total hip arthroplasty. Non-parametric statistical analysis was used to search for correlations between the clinical, radiological, and biological parameters.

RESULTS

At mean 44 Months follow-up, 17% of the patients had a fair or mediocre function score and 37% had radiological signs of femoral component loosening. Serum cobalt increased significantly in the implanted group (serum cobalt >or=0.60 microg/L in 50% of patients) compared with the control group (serum cobalt >or=0.60 microg/L in 9%) (P<0.001, Mann-Whittney test). Increased serum cobalt was highest in patients with radiographic signs of loosening. This significant difference was not found for other metals. Patient activity, hip function, and follow-up were not correlated with serum levels.

DISCUSSION

Serum cobalt appears to be a good biological marker of prosthetic function although intra- and inter-individual variations are influenced by assay technique, metal ion solubility, and metal dissemination in the organism. The metal-on-metal combination does not appear to be the only friction couple which increases the serum level of metal ions. Our results do not allow defining a time of latency between onset of radiographic signs and increased serum levels.

Contamination by metallic elements released from joint prostheses

When a metallic implant is in contact with human tissues, the organism reacts and a corrosion process starts. Consequently, we might observe liberation of metallic debris and wear. Our purpose is to measure the contamination and the migration of these metallic elements in the surrounding tissues of the implant. Two types of samples have been studied. First type is sample taken on post-mortem tissues around prostheses to study contamination gradients. Second type is sample taken on pathologic joints on periprosthetic capsular tissues in surgical conditions. These allow estimating contamination degree. The experiments were made on a Van de Graaff accelerator located at CERI (Centre d'Etude et de Recherche par Irradiation, Orléans, France). We measure elemental concentrations resulting from the contamination of the surface of each sample. Results are analysed in function of the pathology and the type of implants. According to the pathology and the location of the sampling, these measurements show a very heterogeneous contamination by metallic elements under particles and/or ionic species which can migrate through soft tissues by various mechanisms.

Analytical technique for quantification of selected resorbable calcium phosphate bone void fillers with the use of polarized-light microscopy

Synthetic calcium phosphate bone void fillers promote varying rates of bone formation and material resorption depending on chemistry, porosity, pore structure, and implant site. The objective of this study was to quantify the resorption of a novel ultraporous beta-tricalcium phosphate cancellous bone void filler with simultaneous quantification of bone formation in a canine humerus model. Potential measurement error involved in conventional histomorphometry using Von Kossa stains inspired the development of a new technique. This technique utilizes bright-field and polarized-light microscopy in conjunction with image analysis software, allowing more accurate histomorphometry. This technique was validated with two separate controlled experiments. Scanning electron microscopy further supported the results. The findings suggest that the use of polarized-light microscopy combined with image analysis software can be an effective tool in simultaneously quantifying calcium phosphate resorption and bone formation.

Dissemination of metals from a failed patellar component made of titanium-base alloy

Complications related to the patella are the most common problems in total knee arthroplasty and major reasons for revision surgery. Among patellofemoral problems, metal-to-metal contact between patellar and femoral components is the worst. We measured levels of titanium, aluminum, and vanadium in serum and urine samples and compared these measures from cases in which metal-to-metal contact of the patellar component occurred with those in cases in which only polyethylene wear occurred. Serum levels of the metals in cases with metal-to-metal contact were over 10 times higher than those in cases without metal-to-metal contact. This suggests that different ranges of serum metal ion levels could eventually be correlated with a variety of mechanisms of patellar failure. Therefore, cases with metal-to-metal contact should be distinguished from cases without metal-to-metal contact. These should not be considered as a single group in patellar component failure.

Histomorphometric and microhardness assessments of sheep cortical bone surrounding titanium implants with different surface treatments

Several factors influence the healing process and the long-term mechanical stability of cementless fixed implants, such as bone remodeling and mineralization processes. Histomorphometric and bone hardness measurements were taken in implants inserted in sheep femoral cortical bone at different times to compare the in vivo osseointegration of titanium screws (diam.; 3.5 x 7 mm length) with the following surface treatments: machined (Ti-MA); acid-etched (Ti-HF); HA vacuum plasma spray (Ti-HA); and Ca-P anodization followed by a hydrothermal treatment (Ti-AM/HA). Ti-MA and Ti-AM/HA implants presented the lowest (Ra = 0.20 +/- 0.01 microm) and highest (Ra = 1.97 +/- 0.64 microm) significant (p < 0.0005) roughness value, respectively. Bone-to-implant contact of Ti-HF was lower than that of the other surface treatments at both experimental times (8 weeks: -20%, ns; 12 weeks: -30%, p < 0.01). Significant differences in MAR (mineral apposition rate) were also found between the different experimental times for Ti-MA (115%, p < 0.01) and Ti-HF (57%, p < 0.01), demonstrating that bone growth had slowed inside the screw threads of Ti-HA and Ti-AM/HA after 12 weeks. No bone microhardness changes in preexisting host bone were found, while Ti-MA showed the lowest value for the inner thread area at 8 weeks (HV(200 microm)= 49.8 +/- 3.8 HV). These findings confirm that osseointegration may be accelerated by adequate surface roughness and bioactive ceramic coating such as Ca-P anodization followed by a hydrothermal treatment, which enhance bone interlocking and mineralization.

Molecular and antibiofilm approaches to prosthetic joint infection

The majority of patients with prosthetic joint replacement (arthroplasty) experience dramatic relief of pain and restoration of satisfactory joint function. In the United States, more than.5 million people have a primary arthroplasty each year. Less than 10% of prosthesis recipients have complications develop during their lifetime, commonly as a result of aseptic biomechanical failure, followed by prosthetic joint infection. The pathogenesis of prosthetic joint infection is related to bacteria in biofilms, in which they are protected from antimicrobial killing and host responses rendering these infections difficult to eradicate. Current microbiology laboratory methods for diagnosis of prosthetic joint infection depend on isolation of a pathogen by culture. However, these methods have neither ideal sensitivity nor ideal specificity. Therefore, culture-independent molecular methods have been used to improve the diagnosis of prosthetic joint infection. In the research setting, detection of 16S ribosomal deoxyribonucleic acid by polymerase chain reaction has been used in the molecular diagnosis of prosthetic joint infection. Various antibiofilm strategies directed at disruption of adherent bacteria are the focus of intense research to improve the detection of biofilm organisms and their eradication. In this article, molecular and antibiofilm approaches to prosthetic joint infection are reviewed.

The contribution of coating microstructure to degradation and particle release in hydroxyapatite coated prostheses

Plasma-sprayed coatings of hydroxyapatite powder are widely used on hip replacements. Commercially, they are supplied by a large number of companies and thus offer different coating design philosophies. This study focuses on a retrieved prosthetic stem that exhibited coating loss on the femoral stem occurring concurrently with third-body wear. The purpose of the research was to establish possible links between the coating microstructure and the clinical findings. A coated stem and cup were sectioned and the cross section was prepared to reveal the coating microstructure. Characterization included X-ray diffraction, FTIR spectroscopy, and crystalline particle quantification within the coating. It was found that the coating has a high amorphous content that provides fast resorption. The amount of crystalline particles increased on the distal location of the stem, the threads of the acetabular shell, and was generally higher on the cup. Accelerated degradation illustrated how the coating may be a particle-generating source by preferential dissolution of the amorphous phase, possibly allowing liberation of crystalline areas and other particulates at the substrate-coating interface. Such particles mainly include the less soluble hydroxyapatide formed from unmelted particles in the plasma or recrystallisation in the coating, but may also include entrapped grit lodged in the substrate during the roughening process. This study accents the importance of coating microstructure in understanding coating resorption.

Interfacial kinetics of titanium- and cobalt-based implant alloys in human serum: metal release and biofilm formation

The biocompatibility of metallic implant surfaces is governed in large part by the interfacial kinetics associated with metal release and protein binding. The kinetics of metal release from, and protein binding to, cobalt- and titanium-based implant alloys in human serum were investigated by (1). measuring the temporal release of Cr and Ti into serum from Co-Cr-Mo (ASTM F-75) and Ti implant alloys (Ti-6Al-4V: ASTM F136, and commercially pure Ti, cpTi: ASTM F67), respectively; (2). examining the composition of human serum proteins adsorbed onto the surfaces of Co- and Ti-based implant alloys; and (3). identifying the serum proteins associated with the binding of soluble Cr and Ti degradation products. Analysis of metal dissolution kinetics found that Cr was released from Co-based implant alloy at an order of magnitude higher than Ti was released from Ti-based implant alloys. Serum became saturated with soluble CR and Ti at levels as high as 3250 ng/mL Ti from cpTi; 3750 ng/mL Ti from Ti-6Al-4V; and 35400 ng/mL Cr from Co-Cr-Mo degradation. The observation that human serum binds more released metal from Co-based alloy dissolution was consistent with the observed differences in biofilm composition between the two alloys, where additional serum protein(s) of approximately approximately 140 (kDa) molecular weight were detected on Co-based implant alloy surfaces. However, both Cr and Ti released from Co- and Ti-based alloys exhibited a bimodal binding pattern to both low molecular weight serum protein(s) (<32 kDa), and to higher molecular weight protein(s) in the 180-250 kDa range. Identification of metal alloy-dependent biofilm compositions and dissolution products provides the basis for understanding the bioavailability and bioreactivity of these implant alloys and their degradation products.

New aspects in the histological examination of polyethylene wear particles in failed total joint replacements

The most important long-term complication in total joint replacements is aseptic osteolysis. Wear particles such as polyethylene (PE) debris are considered to be one of the causes that play a central role. Several studies indicated that PE can be visualised in paraffin-embedded tissue sections not only by polarised light, but also after oil red staining. To determine whether oil red staining enables sensitive detection of PE, we examined staining of mechanically-produced PE particles by oil red. Furthermore, we studied oil red staining of paraffin-embedded tissue specimens of patients with failed uncemented and cemented total knee and hip prostheses. We applied double labelling of sections by immunohistochemistry using the macrophage marker anti-CD68 and oil red staining. We found that oil red stains both isolated PE particles and PE particles in paraffin-embedded tissue sections. Polymethylmethacrylate particles in failed cemented arthroplasties did not stain in paraffin sections. Double labelling showed strong colocalisation of CD68 and PE. We suggest that oil red staining is a sensitive method to detect PE particles. Oil red staining is particularly helpful in these cases which show a characteristic histological feature of aseptic prosthesis loosening without particles being detectable with routine microscopy and polarised light. We also established that immunohistochemical methods can be applied together with the oil red staining method.

Standardized analysis of UHMWPE wear particles from failed total joint arthroplasties

Periprosthetic tissue obtained at revision surgery from eight total hip replacement cases was hydrolyzed, and polyethylene debris particles were isolated from each case. Individual particles were analyzed by scanning electron microscopy (SEM) and computerized image analysis in accordance with ASTM F1877-98, a standard for quantitative description of wear debris. For comparison, periprosthetic tissues from eight total knee revision and four total shoulder revision cases were processed and analyzed with identical methods. A total of 2599 hip, 4345 knee, and 1200 shoulder particles were analyzed. The morphologies of the isolated polyethylene particles from the total hip specimens were distinctly different from the total knee and total shoulder particles. The mean equivalent circle diameter (ECD) for hip particles was 0.694 microm +/- 0.005; knee particles measured 1.190 microm +/-0.009; and shoulder particles 1.183 microm +/- 0.017. The ECD was significantly different between hip particles and those from the shoulder and knee. The mean aspect ratio (AR) for the hip particles was 1.626 +/- 0.015, compared to the knee particles at 1.935 +/- 0.015 and shoulder particles at 2.082 +/- 0.033. The AR was statistically different among all three groups. Other descriptors from the ASTM standard, elongation (E), form factor (FF), and roundness (R) were all significantly different among the three groups of joints. This study demonstrates the utility of ASTM F1877-98 in differentiating wear debris particles from different sources.

The nature and dissemination of UHMWPE wear debris retrieved from periprosthetic tissue of THR

The role of wear debris in provoking joint replacement failure through bone resorption is now supported by much research. This study presents the analysis of 104 tissue samples using laser diffraction wear particle analysis in conjunction with standard histologic methods. The number and volume distributions were correlated to a range of joint and patient parameters. The median particle diameter by number was 0.69 microm. No particles smaller than 0.113 microm were resolved. No variation in terms of particle distribution was found among joint types. The ability of particles to migrate away from their point of origin was found to be inversely proportional to their size. The numbers of particles per gram of tissue found in various regions around the prosthesis varied little. Further, the numbers of particles in tissue samples shown to have a chronic foreign-body reaction was > 1 x 10(9) particles/gram.

Detachment of titanium and fluorohydroxyapatite particles in unloaded endosseous implants

The shape, surface composition and morphology of orthopaedic and endosseous dental titanium implants are key factors to achieve post-surgical and long-term mechanical stability and enhance implant osteointegration. In this study a comparison was made between 12 titanium screws, plasma-spray-coated with titanium powders (TPS), and 12 screws with an additional coating of fluorohydroxyapatite (FHA-Ti). Screws were implanted in the femoral and tibial diaphyses of two mongrel sheep and removed with peri-implant tissues 12 weeks after surgery. The vibrational spectroscopic, ultrastructural and morphological analyses showed good osteointegration for both types of implants in host cortical bone. The portion of the FHA-Ti implants in contact with the medullary canal showed a wider area of newly formed peri-implant bone than that of the TPS implants. Morphological and EDAX analyses demonstrated the presence of small titanium debris in the bone medullary spaces near the TPS surface, presumably due to the friction between the host bone and the implant during insertion. Few traces of titanium were detected around FHA-Ti implants, even if smaller FHA debris were present. The present findings suggest that the FHA coating may act as a barrier against the detachment of titanium debris stored in the medullary spaces near the implant surface.

Immuno-inflammatory tissue reaction to stainless-steel and titanium plates used for internal fixation of long bones

The immuno-inflammatory responses to stainless-steel (21 implants in 20 patients) and titanium plates (22 implants in 20 patients) used in the treatment of long bone fractures were studied immunohistochemically. All fractures healed without complications. In the soft tissue adjacent to the surface of the implants a dark discolouration of the tissue was visible in 18/21 stainless-steel and 20/22 titanium plates. Tissue specimens of all patients contained positive staining for macrophages (CD68-positive cells). Serial sections showed that the majority of cells were found to express the HLA-DR molecule indicating their activation. Many of the macrophages were surrounded by clusters of T-lymphocytes (CD3-positive cells). 17 out of 21 steel specimens and 15 out of 22 titanium specimens showed the infiltration of moderate amounts of cytotoxic T-lymphocytes (CD8-positive cells). Moderate amounts of B-lymphocytes (CD79alpha positive cells) were evident in four patients with steel and six patients with titanium implants. The results of the present study clearly demonstrate the presence of a marked inflammation and tissue reaction in the soft tissue covering stainless-steel and titanium plates used for internal fixation of fractures of long bones independently from the material used.

Comparative study of metallic biomaterials toxicity: a histochemical and immunohistochemical demonstration in mouse spleen

Metallic biomaterials available for orthopaedic purposes become essential to perform important physical activities, due to their low cost and excellent mechanical properties. In addition, they are frequently used in dentistry. However, corrosion phenomena of such devices are the main problems resulting in subsequent spreading of the elements through the whole body via lymph and blood. The spleen is the most important lymphoid organ and the only one included in the blood circulation. Thus, the aim of this study was to evaluate the short-term effects on spleen tissues of heavy metals released from stainless steel and Cr-Co-Mo alloys, as well as from titanium, at histochemical and immunohistochemical levels. For this purpose, metallic suspensions were obtained by electrochemical dissolution of the mentioned biomaterials: stainless steel (Fe 490 mg/L, Cr 224 mg/L, Ni 150 mg/L), Cr-Co-Mo (Cr 200 mg/L, Co 375 mg/L), and titanium (400 mg/L). Then 0.5 ml of each solution was subcutaneously administered to male Charles River mice each 72 hours during 30 days. Cryostat sections of the spleen from all groups were submitted to routine staining with haematoxylin/eosin, peroxidase detection by 3-3' diaminobenzidine (DAB), and alkaline phosphatase anti-alkaline phosphatase (APAAP) for lymphocyte detection. Several pronounced alterations were found in the spleen architecture, as manifested by irregular features within the capsule and medulla, namely depletion of T4 and B cells. Altogether these results suggest toxic alterations within the spleen induced by some of the metallic elements, indicating that the immune system may be hampered and so interfering in the body mechanisms of defence.

The causes of insert backside wear in total knee arthroplasty

Wear of the insert backside occurs ostensibly because of micromotion at the undersurface articulation that occurs with loading. When a cyclic axial load was applied to contemporary knee implants, all inserts tested moved 2 to 25 microm in the shear plane relative to the metal backing suggesting that undersurface motion may be inevitable. Variables that increase the forces between the insert and metal backing can worsen relative micromotion and backside wear. Forces at the undersurface articulation, created during physiologic loading, are influenced by insert type, articular design, and surgical technique. Increasing articular insert constraint can cause forces at the main articulation to be resisted and transferred to this and the other interfaces. Designs with a cam post mechanism that force rollback at a certain flexion angle create a significant force in this shear plane. Inserts with highly conforming articular geometries can have a similar affect if used to inhibit anteroposterior or mediolateral motion of the femur on the tibial insert. Component alignment and position, and ligament balance also may influence backside wear as suggested by the great variability of wear patterns seen on like insert retrievals and by kinematic differences observed in fluoroscopic studies of the same implant design. Only by understanding these potential causes of backside motion and subsequent wear, can backside wear be mitigated.

A study of tissue interface membranes from revision accord knee arthroplasty: the role of T lymphocytes

Despite four decades of advances in the design of orthopaedic devices aseptic loosening remains a major cause for the revision of total joint arthroplasty. This study used the techniques of immunohistochemistry and reverse transcription polymerase chain reaction to identify the inflammatory cell types, cytokines and chemokines within the interface tissue surrounding failed Accord Knee prostheses. Many T cells were identified within the tissue: however, the classical marker of activation, CD25 was expressed on very few cells. Molecular analysis failed to detect the synthesis of either Th1 or Th2 cytokines. These results suggest that the T cells are being actively recruited to the site of inflammation along the chemokine gradients but are not participating in a classical immune response.

Concentration- and composition-dependent effects of metal ions on human MG-63 osteoblasts

Metal debris from implants has been shown to alter the function of osteoblasts in cell cultures. Its remains unclear, however, if specific forms of released ionic metals are involved in the pathogenesis of periprosthetic osteolysis. We evaluated the relative effects of ionic forms of implant metals by treating human osteoblast-like MG-63 osteosarcoma cells with eight concentrations (0.001-10.0 mM) of Cr(+3), Mo(+5), Al(+3), Ta(+5), Co(+2), Ni(+2), Fe(+3), Cu(+2), Mn(+2), Mg(+2), Na(+2), and V(+3) chloride solutions. The results demonstrated that the metal ions differentially affected osteoblast proliferation, viability, type-I collagen gene expression, and cytokine release. The metal ions were ranked in order from least to most toxic (based on a 50% reduction in viability) as follows: Na < Cr < Mg < Mo < Al < Ta < Co < Ni < Fe < Cu < Mn < V. Metal-induced decreases in osteoblast proliferation were similar in ranking. Nontoxic concentrations of metals had no effect on procollagen alpha1[I] gene expression; only at toxic concentrations did metals produce a decrease in gene expression. The most toxic metals (V, Mn, Fe, and Ni) were also the only metals found to induce IL-6 secretion on a per cell basis (of the cytokines tested, interleukin 6 (IL-6), interleukin beta 1 (IL-1beta), transforming growth factor beta 1 (TGF-beta1), and tumor necrosis factor alpha (TNF-alpha), only IL-6 was detectable in the culture medium after 48 h for any metal at any concentration). Less toxic metals (e.g., Co and Cr) had little effect on IL-6 release, even at high concentrations. In general, metal ions reduced osteoblast function (i.e., proliferation and collagen gene expression) in proportion to the degree of toxicity. These results support the hypothesis that adverse local cellular responses (particularly necrotic responses) associated with metal debris from implanted metallic devices may be due in part to metal ions released from implants or from particulate debris.

Direct compression molded polyethylene for total hip and knee replacements

Direct compression molded polyethylene is a process of creating a net-shaped component with finished articular surfaces from ultrahigh molecular weight polyethylene by applying heat and pressure to the raw resin (usually Hi-fax 1900) with the use of fixed geometry metallic tools. The final product has no machining or finishing. Sterilization was by gamma radiation in air. Between 1974 and 1978, there were 378 cemented T-28 stems (321 patients) and 171 cemented TR-28 stems (158 patients) articulating with a cemented direct compression molded acetabular component. Radiographically, linear wear was 0.06 mm per year for the T-28 stem and 0.05 mm for the TR-28 stems. The revision rates for the acetabulum were 9.5% and 7.9%, respectively with only two acetabula having osteolysis. On the femoral side, the revision rates were 11.1% and 12.8%, with 11 cases and one case of osteolysis, respectively. Between 1983 and 1996, 4583 AGC cemented total knee replacements were done with direct compression molded nonmodular tibial components. There was no osteolysis seen in these nonmodular compression molded total knee replacements even with 0.1% failure of the femoral components and 0.4% failure of the tibial components. Failure of all of the hip and knee implants was because of poor cement technique, instability, or both. Wear and osteolysis were minimal. Direct compression molded polyethylene has stood the test of time and is a good choice among the currently available polyethylenes.

Short-term results of the M2a-taper metal-on-metal articulation

A polyethylene-free, metal-on-metal acetabular system (M2a-taper [Biomet, Inc., Warsaw, IN]) was designed in an effort to improve total hip arthroplasty (THA) longevity. Minimum 2-year follow-up results involving 72 polyethylene liner THAs and 78 metal liner THAs from a multicenter, randomized, controlled, investigational device exemption study are reported. Mean Harris hip scores of 95.54 (polyethylene liner group) and 95.23 (metal liner group) were reported at mean follow-up intervals of 3.29 and 3.23 years. Radiographic evaluation revealed no evidence of early failure. No acetabular components have been revised or are pending revision. No statistically significant differences in the data were calculated between liner types except for the immediate postoperative (P=.0415) and minimum 2-year follow-up (P=.0341) angles of inclination. The M2a-taper metal-on-metal articulation may represent a viable alternative for THA in younger, higher demand patients.

The sphericity of the bearing surface in total hip arthroplasty

This study evaluated the sphericity of bearing surfaces in total hip arthroplasty. The out-of-roundness of metal femoral heads, the inner surface of polyethylene liners, and commercially available ball bearings was measured. The hip prostheses were obtained directly from the manufacturers. The sphericity of the bearing surfaces was significantly inferior to that of the ball bearings. The sphericity of the femoral head on the sagittal plane was inferior to that on the transverse plane. Several significant differences were found among different manufacturers. The sphericity of the femoral head on the sagittal plane and that of polyethylene significantly improved in 1999 and 2000 compared with those in 1995. Further improvement is desirable, however, because good sphericity is expected to prolong the functional performance of the prosthesis after total hip arthroplasty.

Liver and kidney foreign bodies granulomatosis in a patient with malocclusion, bruxism, and worn dental prostheses

Granulomatous reactions caused by foreign bodies have been described in drug abusers, in subjects exposed to occupational pollutants, and more rarely, in association with the use of prosthetic devices. We describe a 62-year-old patient with multiorgan parenchymal granulomatosis caused by inorganic debris of unknown origin. The patient presented with fever, hepatosplenomegaly, progressive cholestasis, and acute renal failure. Liver and kidney biopsies showed the presence of noncaseating epithelioid giant-cell granulomas containing scattered polarizable particles. Similar particles were also present in stools. Studies by innovative scanning electron microscopy and energy-dispersive microanalytical techniques showed that the particles isolated in liver, kidney, and stools were made by feldspars, the main component of porcelain. No occupational or environmental exposure to these materials could be identified in this patient and the only reliable source of the porcelain debris turned out to be constituted by 2 dental bridges evidently worn because of a possible inappropriate construction, malocclusion, and bruxism. The porcelain of the dental prostheses had the same elemental spectrum of the particles isolated from stool specimens and liver-kidney granuloma. After identification of the dental prostheses as the most likely source of ceramic debris, and after their removal, the particles from stool specimens disappeared. The patient was then treated with steroids leading to a remission of the clinical symptoms and a decrease in granulomatous inflammatory reaction in both liver and kidney. This is the first report suggesting that a foreign body systemic granulomatosis can be associated with worn dental prostheses.

The corrosion resistance of pure titanium in organic acids

The purpose of this study was to assess the corrosive properties of titanium at various pH values. Cast pure titanium specimens were immersed in 128 mmol/l of lactic and formic acids at pH 1.0-8.5 for 3 weeks at 37 degrees C. The solubility, color, weight and chemical binding state of specimens were observed. Titanium dissolved in all lactic acid. The amount of dissolved titanium tended to decrease with a higher pH. In formic acid, the amount of dissolved titanium at pH 1.0 was larger than that in lactic acid at the same pH, but less than the detectable limit at pH 4.0 or higher. Significant discoloration was macroscopically observed only in formic acid at pH 2.5 and 4.0. The weight of the titanium samples immersed in lactic acid all decreased, but it was not affected by pH. In formic acid, the weight decreased at pH 1.0 and increased at pH 2.5-5.5. Thickening of the TiO2 corresponding to that showing discoloration was observed in the superficial oxide film of the titanium samples. Our results show that the corrosive properties of titanium are markedly dependent on pH in formic acid, and relatively less dependent on pH in lactic acid in which titanium is dissolvable at pH 1.0-8.5.

Differential lymphocyte reactivity to serum-derived metal-protein complexes produced from cobalt-based and titanium-based implant alloy degradation

The lymphocyte response to serum protein complexed with metal from implant alloy degradation was investigated in this in vitro study using primary human lymphocytes from healthy volunteers (n = 10). Cobalt chromium molybdenum alloy (Co-Cr-Mo, ASTM F-75) and titanium alloy (Ti-6Al-4V, ASTM F-136) beads (70 microm) were incubated in agitated human serum at 37 degrees C to simulate naturally occurring metal implant alloy degradation processes. Particulate free serum samples that had been incubated with metal were then separated into molecular weight based fractions. The amounts of soluble Cr and Ti within each serum fraction were measured and correlated with lymphocyte proliferation response to the individual serum fractions. Lymphocytes from each subject were cultured with 11 autologous molecular weight based serum fractions either with or without added metal. Two molecular weight ranges of human serum proteins were associated with the binding of Cr and Ti from Co-Cr-Mo and Ti implant alloy degradation (at <30 and 180-250 kDa). High molecular weight serum proteins ( approximately 180 kDa) demonstrated greater lymphocyte reactivity when complexed with Cr alloy and Ti alloy than low (5-30 kDa) and midrange (30-77 kDa) serum proteins. When the amount of lymphocyte stimulation was normalized to both the moles of metal and the moles of protein within each fraction (metal-protein complex reactivity index), Cr from Co-Cr-Mo alloy degradation demonstrated approximately 10-fold greater reactivity than Ti in the higher molecular weight serum proteins ( approximately 180 kDa). This in vitro study demonstrated a lymphocyte proliferative response to both Co-Cr-Mo and Ti alloy metalloprotein degradation products. This response was greatest when the metals were complexed with high molecular weight proteins, and with metal-protein complexes formed from Co-Cr-Mo alloy degradation.

Total knee arthroplasty with 4.4 mm of tibial polyethylene: 10-year followup

A consecutive series of 387, one-piece, 8-mm tibial components were implanted in 313 patients. All tibial prostheses were manufactured with 4.4 mm of polyethylene directly molded to a 3.6 mm cobalt chrome metal baseplate. The average age of the patients at surgery was 70.6 years. From this group, a subset of 116 patients underwent bilateral total knee arthroplasties with an 8-mm tibial component on one side and at least a 10-mm thick tibial component (at least 6.4 mm of polyethylene) on the other side. The followup averaged 10.7 years. Postoperative knee and pain scores average 81.4 points and 47.2 points, respectively. No radiographic polyethylene wear or osteolytic lesions were identified. Tibial radiolucencies were observed in four knees. There were nine failures (2.3%). Three knees were revised for infection. Five knees were revised for metallosis secondary to failure of metal-backed patellas. No loose tibial components were identified. Defining failure as revision for any reason or loosening of any component, Kaplan-Meier survival rates at 5, 10, and 15 years were 98.7%, 95.4%, and 94.3%, respectively. There was no significant difference in clinical scores or survival rates between the knee components with thicker (at least 6.4 mm) or thinner (4.4 mm) polyethylene.

Sarcoma arising adjacent to a total hip arthroplasty

We present the case of a 79-year-old woman who developed a high grade spindle cell sarcoma adjacent to total hip arthroplasty 13 years after the index operation. MRI scan appeared to show a direct communication between the tumour and intra medullary canal through a breach in the femoral cortex.

Serum titanium level for diagnosis of a failed, metal-backed patellar component

A case is presented in which an elevated serum titanium level was used to make the diagnosis of a failed metal-backed patellar component. The preoperative serum titanium level was 536.8 ppb, which was 98 times higher than the patient's previous level (taken 1 year earlier, when he was asymptomatic) and 2 orders of magnitude higher than the expected level with a well-functioning implant of this type. Revision surgery confirmed that the polyethylene portion of the patellar component had worn through, leaving the titanium portion of the patellar implant to articulate with the femoral component. Wear-through was not evident on preoperative radiographs or clinical examination. As knowledge about the expected ranges for serum metal ion levels after total joint arthroplasty continues to increase, the diagnostic utility of serum metal ion testing in the evaluation of joint arthroplasty function will continue to improve.

Alternate bearing surfaces in total joint arthroplasty: biologic considerations

The problem of periprosthetic osteolysis is currently the major limiting factor in joint arthroplasty longevity. Because this process has been shown to be primarily a biologic response to wear particles, corrosion products, or both, efforts to reduce particle generation are being undertaken. These efforts include the development of modified polyethylene and alternative articulating surfaces. These alternate bearing surfaces currently include ceramic-on-polyethylene, ceramic-on-ceramic, and metal-on-metal. Although these alternate bearings diminish or eliminate the generation of polyethylene particles, ceramic and metal particles are produced. The purpose of the current review is to discuss the literature that addresses the biologic response to these particles, locally and systemically.