The foreign body reaction in total hip arthroplasties. A correlated light-microscopy, SEM, and TEM study

Microstructural effects on the wear behavior of a biomedical as-cast Co-27Cr-5Mo-0.25C alloy exposed to pulsed laser melting

In this work, the effect of pulsed laser melting on the exhibited microstructure and properties of a cast Co-27Cr-5Mo-0.25C alloy was investigated. In particular, properties such as surface hardness and wear behavior of the laser modified microstructure were determined as a function of the implemented laser melting parameters. It was found that laser melting promotes significant grain refinement while preventing the precipitation of coarse carbide phases. Apparently, a refined dendritic grain structure develops which is surrounded by a fine carbide distribution in the interdendritic regions. Moreover, the high-temperature face centered cubic (FCC) phase remains untransformed at room temperature. Hardness measurements and wear testing using a Pin-On-Disk tribological machine indicate that the modified laser surfaces exhibit both, high wear resistance and high microhardness when compared with the untreated as-cast Co-27Cr-5Mo-0.25C alloy. In particular, it was found that the laser modified surfaces exhibit improved wear and friction properties comparable to the ones found in Co-Cr-Mo alloys with a predominantly hexagonal closest packed (HCP) matrix. However, surface defects associated with the laser process can be detrimental for the improved wear performance and they should be considered in identifying the proper laser parameters in alloy melting.

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.

No difference in early cellular response of the pseudo-synovial membrane after total hip arthroplasty: comparison of 3 combinations of bearing materials

BACKGROUND

Wear-resistant bearing materials may hypothetically reduce chronic inflammation in the pseudosynovial membrane as compared to less wear-resistant bearing materials such as polyethylene. We assessed the foreign body response in the pseudosynovial membrane in vivo after total hip replacement.

METHODS

37 patients from a larger prospective randomized trial of 225 patients had biopsies taken arthroscopically from the artificial hip joint (i.e. the pseudosynovial membrane) 1 year after insertion of the implant. All patients had an identical hip prosthesis (Bimetric-RingLoc) except for the bearing materials, which consisted of polyethylene on zirconia, CoCr on CoCr, or alumina on alumina. Histological quantification was performed on 2-mum-thick semi-thin plastic sections or paraffin sections by point counting technique to compare the volume fraction of macrophages, granulomas and endothelial cells in biopsies of the pseudosynovial membrane.

RESULTS

The median macrophage volume fractions for polyethylene-on-zirconia bearing material (n = 15), CoCr-on-CoCr (n = 9), and alumina-on-alumina (n = 11) were 0.02, 0.04, and 0.004, respectively. The median granuloma volume fractions for polyethylene-on-zirconia (n = 13), CoCr-on-CoCr (n = 9), and alumina-on-alumina (n = 13) were 0.02, 0.04, and 0.02, respectively. The median endothelial cell volume fractions for polyethylene-on-zirconia (n = 15), CoCr-on-CoCr (n = 9), and alumina-on-alumina (n = 11) were 0.03, 0.02, and 0.05, respectively. Statistical analysis showed no significant differences between the three groups with the different bearings with respect to volume fraction of macrophages, granulomas and endothelial cells.

INTERPRETATION

Our study demonstrated that a granulomatous inflammation is a common finding in non-loose implants as early as 1 year after the operation not demonstrating a difference in macrophages and granuloma formation with the various bearing materials. Thus a high volume fraction of macrophages was found in the osteoarthritis control group compared to the operated group.

Metal debris from bony resection in knee arthroplasty--is it an issue?

BACKGROUND

Metal particles are generated during bone preparation in knee arthroplasty. These particles may produce third-body wear, or may have a role in osteolysis. Knowledge of their characteristics may help in the development of methods to reduce the amount of metal debris during bone cutting procedures.

MATERIAL AND METHODS

We performed bony resection of the distal femur and proximal tibia on 15 pig knees, simulating a total knee arthroplasty (TKA). Metal debris was collected from the saw blades, cutting blocks and bone surfaces and cleaned for microanalysis.

RESULTS

The average loss of metal from the saw blades was 1.13 mg. The average volume of a wear particle was 3.4 x 10(-16) m(3). From this, it was estimated that approximately 500,000 particles are released from the saw blade alone. Material analysis of the particles indicated that the majority originated from the metallic cutting guides, suggesting that many millions of wear particles would be generated during the surgical procedure. Two particle shapes predominated: platelet shape and ploughed shape.

INTERPRETATION

Wear particles are produced during resection for a TKA. These may enter the artificial articulation and cause accelerated wear and macrophage activation. Redesign of cutting blocks and saw blades may reduce the amount of debris produced during surgery.

The role of implant alignment on stability and particles on periprosthetic osteolysis?A rabbit model of implant failure

The study objective was to determine the tissue response to polyethylene and/or titanium particles and the role that these play in peri-prosthetic osteolysis in a rabbit model of implant failure. Twenty-two mature rabbits were used. Unilateral tibial arthroplasty was performed on all of them. The test animals received implants that were intentionally rotationally unstable with reference to the host tibia in order to create a model of failure. The test rabbits were divided into three groups. Group 1 consisted of seven rabbits in which only the carrier was implanted. Group 2 consisted of seven rabbits that received only polyethylene particles suspended in the carrier. Group 3 consisted of eight rabbits that received a mixture of polyethylene and titanium alloy particles suspended in the carrier. The rabbits were sacrificed at 6 months post surgery. The entire knee, together with the immediately surrounding soft tissue, was retrieved. The position of the implant in each rabbit was assessed with reference to its alignment to the tibia. The number of inflammatory, foreign-body reactive cells, the presence of neovascularization, edema, and necrosis in the periprosthetic zones were recorded and assessed in a qualitative and semiquantitative manner. Quantitative histomorphometry was used to determine the proportion of implant surface that interfaced with osseous or fibrous tissue. Also assessed was the thickness and maturity of the fibrous tissue and the endosteal remodeling activity in the peri-implant bone counting both osteoclastic and osteoblastic activity. The results showed that implanted particles and misalignment of the implants combined to produce peri-prosthetic bone resorption. Bone resorption was found to be proportional to the degree of misalignment. The animals that received combined polyethylene/titanium particles had a greater degree of foreign-body and inflammatory response with osteolysis than the other groups. The combination of bio-material particles (polyethylene and titanium alloy) produced a greater degree of bone resorption than the single biomaterial particles (polyethylene). The amount of bone resorption surrounding the implant was directly proportional to the degree of misalignment of the implant.

Observations at the articular surface of hip prostheses: an analytical electron microscopy study on wear and corrosion

We used scanning electron microscopy in combination with X-ray microanalysis to evaluate Co-, Cr-, and Mo-based human femoral hip prostheses. In total, 23 retrieved implants and four new implants were included in this study. Scanning electron microscopy of the polished surface of all arthroplasties showed, in addition to the polishing marks, small round and angular holes or pits. Other types of surface irregularities were interpreted as wear or corrosion of the metal compound. In all cases studied, corrosion propagated from holes at the surface of the polished prosthesis heads, in some cases also along phase boundaries. X-ray microanalysis of the intact prosthetic surface showed a relative composition of the elements Co, Cr, and Mo, which was in agreement with the manufacturer's information (63:33:4%). However, X-ray microanalysis spot analysis of the surface holes showed deviation in the relative composition of the elements Co, Cr, and Mo and also the presence of Si, Ti, and Al. Furthermore, Ti and Al could be traced back at an artificially made fracture plane of a new prosthesis. Therefore, Ti and Al have to be present during the manufacturing process. These impurities in the metal prosthesis alloy may create a galvanic element with the Co, Cr, Mo alloy of the implant. If this is the case, such a galvanic element in combination with the electrolyte environment formed by body fluids, can induce galvanic corrosion with release of metal particles.

Biological reactions to wear debris in total joint replacement

The vast majority of total hip prostheses currently implanted consist of a hard metal or ceramic femoral head articulating against an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup. Over the last 10 years, evidence has accumulated to show that these prostheses are prone to failure due to late aseptic loosening and few survive beyond 25 years. With an increasing need to implant hip prostheses in the younger, more active patient the need to understand the mechanisms of failure and to develop artificial hip joints using alternative materials have become major issues in the orthopaedic community. This review focuses initially on our current understanding of the biological reactions to UHMWPE prosthetic wear debris in vivo and in vitro since this is believed to be the main cause of late aseptic loosening. While the precise mechanisms of osteolysis induced by UHMWPE wear debris have not been elucidated, the major message to emerge is that it is not the wear volume that determines the biological response to the debris, but the concentration of the wear volume that is within the critical size range (0.2-0.8 micron) for macrophage activation. The review then considers whether the problem of wear-debris-induced osteolysis may be overcome with the use of new generation metal-on-metal or ceramic-on-ceramic prostheses. For metal-on-metal prostheses, the prospects for increasing the osteolysis free life of the implant are good but additional biological problems associated with the nanometre size and reactivity of the wear particles in vivo may emerge. For the ceramic-on-ceramic prostheses, although initial prospects are encouraging, more data are needed on the characteristics of the wear particles generated in vivo before predictions can be made. It is concluded that the pre-clinical testing of any new materials for joint replacement must include an analysis of the wear particle characteristics and their biological reactivity in addition to the usual assessment of wear.

Metal release from total hip articulations in vitro: substantial from CoCr/CoCr, negligible from CoCr/PE and alumina/PE

We used a hip joint simulator to compare the metal release from CoCr/CoCr, CoCr/PE, and alumina/PE total hip articulations. The metal release was quantified by analyzing the Co, Cr, and Ni contents of the bovine serum lubricant used with atomic absorption spectroscopy. CoCr/CoCr articulations released substantial amounts of metal, whereas CoCr/PE was equal to the control, alumina/PE, in that metal release was negligible. The metal release was in accordance with the known clinical wear rates of CoCr/CoCr articulations. The largest dimensional changes occurred in polyethylene cups, the penetrations of CoCr heads to the polyethylene cups being twice that of the alumina head, which is consistent with clinical experience. The research on the wear behavior of different materials, aiming to find a prosthesis with negligible wear, needs to be continued. Due to the substantial metal release, the CoCr/CoCr articulation is hardly the final solution of the wear problem in total hip arthroplasty.

The theory of early loosening of hip prostheses

The issue of prosthetic loosening is currently a matter of debate, particularly with regard to the timing and nature of the precipitating events. The theory presented here postulates that loosening begins at an early stage due to either insufficient initial fixation or early loss of fixation. The loosened prosthetic component is then affected by varying degrees of mechanical stress associated with normal daily activity, which differs according to patient characteristics (body weight and level of physical activity) and the components used (prosthetic design, positioning, friction, and wear). This theory of early loosening can explain without supplementary ad hoc assumptions the rapid early prosthetic migration detected by roentgen stereophotogrammetry, the development of focal osteolysis and wear granulomas, the phenomenon known as stress-shielding, and, to a great extent, the epidemiology of clinical failure.

Tissue response to particulate polymethylmethacrylate in mice with various immune deficiencies

We examined the tissue response to subcutaneous injections of particulate polymethylmethacrylate powder in fully immunocompetent C3Hf/Sed mice as well as three strains of mice with different levels of lymphocyte dysfunction. Five weeks after the injection, we found clearly demarcated granulomas. Histological and immunohistochemical studies showed that these granulomas were similar among all strains, with either paucity or absence of lymphoid cells. In situ hybridization with use of complementary RNA probes indicated that macrophages were synthesizing interleukin-1 beta messenger RNA (mRNA), a marker of macrophage activation, and a cytokine implicated in pathological bone resorption. We concluded that, in mice, there is a lymphocyte-independent pathway of macrophage activation in response to particulate polymethylmethacrylate. This suggests that the foreign-body response to particulate orthopaedic biomaterials is macrophage-initiated and maintained and that lymphocytes are not essential to this response, although they may modulate it.

Isolation and characterization of metallic wear debris from a dynamic intervertebral disc prosthesis

A dynamic intervertebral disc prosthesis (DIDP) has been developed. It consists of a CoCrMo body and uses Ti6Al4V springs to replicate the mechanical function of the lumbar joint. Wear studies have been performed previously on the DIDP using two specialized simulators to test the wear properties of the moving parts of the disc prosthesis. A pin-in-slot simulator generates wear that would occur in the hinge-pin assembly of the prosthesis. A spring-in-pocket simulator approximates the conditions under which the springs would wear against the body of the prosthesis. The spring-pocket interface is responsible for the production of approximately 90% of the total wear occurring in the prosthesis, and is therefore the main focus of this study. Bovine serum with a preservative has been used as a lubricant in both simulators. The spring-in-pocket simulator compares the effects of two different manufacturing techniques of CoCrMo (HIPing and forging) on their wear characteristics against Ti6Al4V springs. Debris from the spring-in-pocket simulator has been isolated from the serum lubricant and characterized using scanning electron microscopy techniques. The morphology of the Ti6Al4V fragments is rough and irregularly shaped. The size of these fragments ranges from < 1 microns to > 30 microns. The forged CoCrMo alloy debris has an irregular polyhedral shape, with sizes in the same range as the spring fragments. The morphology of the HIPed CoCrMo debris is spherical with a size range < 5 microns to > 30 microns. Length and width measurements of micron-size particles were made with the particle measurements feature of the scanning electron microscope. Micron-size particles were found in all stations. This article provides a unique way to isolate and analyze debris from serum lubricants used in simulators.

Theories of wear and loosening in hip prostheses. Wear-induced loosening vs loosening-induced wear--a review

The observation of perioprosthetic granulomas containing wear debris around apparently well-fixed as well as around loose-fitting prosthetic components has led to the development of the hypothesis of wear-induced loosening. However, the hypothesis of wear-induced loosening can neither explain the rapid early prosthetic migration detected by roentgen stereophotogrammetry nor the epidemiology of clinical failure without supplementary ad hoc-assumptions. By contrast, apart from explaining the rapid early prosthetic migration detected by roentgen stereophotogrammetry, the theory of early loosening can explain the development of wear granulomas as well as to a great extent the epidemiology of clinical failure.

Better histology and biochemistry for osteoblasts cultured on titanium-doped bioactive glass: bioglass 45S5 compared with iron-, titanium-, fluorine- and boron-containing bioactive glasses

In the present study we used an established cell culture model to compare Bioglass 45S5 with four other bioactive glasses. Small substitutions or additions of certain ions like iron, titanium, fluorine or boron modified the basic 45S5 glass network. We used several histological and biochemical parameters to interpret the results found in terms of the used model. Regarding 45S5 as a reference, we found that osteoblasts cultured on iron-doped bioactive glass showed a more flattened morphology, and both lower proliferation rate and osteoblast expression. Osteoblasts cultured on titanium-doped glasses also showed a flattened morphology, but higher proliferation and remarkably higher osteoblast expression. On fluorine- and boron-containing glasses the osteoblasts showed a rather compact morphology, a normal proliferation but only moderate osteoblast expression. With microprobe analysis it was shown that the formation of calcium and phosphorus on titanium-doped glass was relatively lower and the release of sodium slower when compared with 45S5. Osteoblasts cultured on titanium-doped bioactive glasses demonstrated superior histological and biochemical parameters when compared with the other glass types. Further research into the physico-chemical properties and the in vivo behaviour of doped bioactive glasses is recommended.

High cathepsin B activity in arthroplasty interface membranes. A histochemical study of 9 loose cemented total hip prostheses

We studied biopsies of interface membranes of 9 aseptically loosened total hip prostheses. The morphologic resemblance of the cement-facing surface of the membranes to synovial tissue of arthritic joints, as noticed by others, was confirmed by histochemical techniques. High cathepsin B activity was found in the bone-facing surface of the membranes. Since this enzyme also plays an important role in tissue destruction of arthritic joints, further similarities in the mechanisms of tissue breakdown in arthritis and aseptic loosening of cemented hip prostheses may be conjectured.

Histological patterns of bone and articular tissues after orthopaedic reconstructive surgery (artificial joint implants)

Revision surgery after failures of joint replacements leads to histological studies on joint and bone tissues close to the implanted material. Aspectic loosening is the main complication. The surgical pathologist has to identify wear debris (metal, polyethylene, polymethylmethacrylate, chiefly) which promotes a histiocytic granuloma. Some surgical procedures such as cup or resurfacing arthroplasties create a new articular surface and a bone remodeling or necrosis. Cemented joint prostheses show various membrane structures between bone and the cement mantle while there is an association of bone resorption and formation. Non-cemented, porous-coated joint prostheses induce little bone ingrowth, even in satisfactory clinical results. Mechanical factors are predominant in massive limb prostheses. For silicone elastomer implants or artificial ligaments, wear of material promotes many tissular reactions. Often used bone grafts show little creeping substitution process in case of homografts, even well-incorporated on X-rays. More retrieval specimen studies are necessary to delineate precise topographical histological lesions, including non-loosened joint implants.

Cellular events in the mechanisms of prosthesis loosening

The functional restoration of a joint damaged by trauma or disease is obtained by prosthetic surgery. In particular the implantation of hip prostheses is regarded as routine in orthopedic surgery and thorough research has been developed in this field. The prosthetic replacement of the knee and even more so the ankle and elbow occurs less frequently in clinical practice and has been studied less intensively. The results of artifical hip replacement are generally good, both in terms of pain relief and the restoration of satisfactory joint function. Nevertheless, as time passes, a high rate of failures have been recorded due to prosthesis infections, fracture and wearing of the prosthetic components and prosthesis loosening by various causes. The use of ultra-filtered air and laminar flow in operating theatres and antibiotic prophylaxis have dramatically reduced the incidence of infections in total hip arthroplasty. Thanks to the setting up of new stem configurations and the use of superalloys that are highly resistant to fatigue failure, the fracture of the femoral component has been virtually eliminated as a complication of total hip arthroplasty replacements. Loosening is thus the most frequent complication in total hip replacement.

Fragmentation of methylmethacrylate: a cause of late failure of total hip replacement. A case report

Extensive localized bone lysis in the femur following implantation of a metal-on-metal total hip prosthesis was observed. Fragmentation of the cement occurred 10 years after implantation. Histologic and ultrastructural features of macrophages are consistent with the hypothesis that particles from the acrylic resin were the factors stimulating the macrophagic reaction. Both mechanical factors and changes of the physico-chemical properties of the cement may have an etiologic role.

Pathology of the bone-cement interface in loosening of total hip replacement

The histopathology of the bone-cement interface in nine retrieved hip prostheses is reported. Three cases presented features similar to those observed by Charnley in highly successful implants, and they were classified as stable prostheses, although signs of periprosthetic bone resorption were already present. In this group a macrophagic reaction was evident even in the presence of a stable bone-cement interface, supporting the view that the release of particles by the cement or by the prosthetic components can precede the mechanical instability and be the primary cause of loosening. In six prostheses the connective tissue layer between the cement and the bone was thick and no bone trabecula reached the cement surface. The polymorphous features of this connective membrane probably resulted from instability and movement at the bone-cement and stem-cement interfaces. On the basis of the pathological changes observed in the study, the process of loosening must be far advanced before it is detected on radiographs; it is suggested that scintigraphy is the best noninvasive technique to demonstrate macrophage activation and increased bone remodeling around the cement in the early phases of loosening.

The biochemical and histological effects of artificial ligament wear particles: in vitro and in vivo studies

Growing evidence suggests that biochemical mechanisms play a role in the pathogenesis of arthritis. Cartilaginous wear particles have been shown to induce destructive enzymes and cytokines. To assess the biocompatibility of artificial ACL replacements, the effects of wear particles from the following ligaments were analyzed biochemically and histologically: GORETEX, Stryker Dacron Ligament Prosthesis, Versigraft carbon, Kennedy LAD, Xenograft, Leeds-Keio, and human patellar tendon allograft. Ligaments were frozen and ground to produce wear particles similar to those seen clinically and were added to lapine synovial cell cultures. The resulting conditioned medium was analyzed for collagenase, gelatinase, and chondrocyte activating factor (CAF) production. All of the ligaments induced significantly elevated enzyme and CAF production by the synoviocytes, with Xenograft and carbon inducing significantly higher enzyme levels than those of the other five ligaments. Five milligrams of wear particles were injected into the knees of 4 kg to 5 kg rabbits that were analyzed histologically after 14 weeks. Wear particles accumulated in the periarticular synovial folds and induced modest to severe macrophage infiltration in the synovium. A hypothetical model explaining the role of artificial ligament wear particles in the pathogenesis of arthritis is presented.