Sensitivity to titanium. A cause of implant failure?

Prevalence of clinically significant improvement following total knee replacement

OBJECTIVE

Although total knee replacement (TKR) has a high reported success rate, the pain relief and functional improvement after surgery vary. The purpose of our retrospective cohort study was to determine the prevalence of patients showing no clinically important improvement 1 year after TKR, and patient factors that may predict this outcome.

METHODS

We reviewed primary TKR registry data that were collected from 2 academic hospitals: the Toronto Western Hospital and the Hamilton Health Sciences Henderson Hospital in Ontario, Canada. Relevant covariates including demographic data, body mass index, and comorbidity were recorded. Knee joint pain and functional status were assessed at baseline and at 1-year followup with the Western Ontario McMaster University Osteoarthritis Index (WOMAC) and Oxford Knee Score (OKS) to measure the change using the minimal clinically important difference (MCID). Logistic regression modeling was used to identify the predictors of interest.

RESULTS

Overall, 11.7% (373/3177) of patients reported no clinically important improvement 1 year after surgery. Logistic regression modeling showed that a greater patient age independently predicted no clinically important improvement on the WOMAC scale 1 year after surgery (p = 0.0003), while being male independently predicted no clinically important improvement on the OKS 1 year after surgery (p = 0.008).

CONCLUSION

Awareness of the prevalence of patients who may show no clinically important improvement and factors that predict this outcome will help patients and surgeons set realistic expectations of surgery.

Tribological properties of Ti-based alloys in a simulated bone-implant interface with Ringer's solution at fretting contacts

The wear properties of oxidized and non-oxidized gamma-TiAl (a potential biomaterial) as well as Ti-6Al-4V and CP-Ti disks were studied and characterized by means of standard wear tests using a custom made bone pin arrangement. The Ti-based disks were oxidized in air at 500 and 800 degrees C for one hour. The tribological properties of the oxides formed over the disks were studied using a linear reciprocating wear testing machine under both dry and simulated biological conditions using Ringer's solution. Loss of metal oxide and coefficient of friction values were determined from wear testing. From the results, abrasion and adhesion were the primary wear mechanisms in each of the three alloy-bone pairs. Specifically, the oxide formed on gamma-TiAl possessed the highest COF and wear resistance of the three materials which were studied. Also, as expected, bone wears down faster than the Ti-based metal oxide.

Titanium uptake, induction of RANK-L expression, and enhanced proliferation of human T-lymphocytes

There is increasing evidence that titanium ions are released from orthopedic implants by biocorrosion. The aim of this study was to investigate titanium uptake by human T-lymphocytes and its effects on phenotype and proliferation. Freshly isolated human nonadherent peripheral blood mononuclear cells (NA-PBMC), were exposed to TiCl4 [Ti(IV)]. Bioavailability and distribution of Ti(IV) in T-lymphocytes was determined by energy-filtered electron microscopy (EFTEM). The effects of Ti(IV) challenge on nonactivated and PHA-activated cells were assessed by flow cytometric analysis of surface markers, RANK-L production, and proliferation assays. EFTEM colocalized Ti(IV) with phosphorus in the nucleus, ribosomes, cytoplasmic membranes, and the surface membrane of T-lymphocytes. Ti(IV) increased significantly the expression of CD69, CCR4, and RANK-L in a concentration-dependent manner. Titanium enters T-lymphocytes through a currently unknown mechanism and binds to phosphorus-rich cell structures. Titanium influences phenotype and function of T-lymphocytes, resulting in activation of a CD69+ and CCR4+ T-lymphocyte population and secretion of RANK-L. These results strongly suggest the involvement of titanium ions challenged T-lymphocytes in the complex pathophysiological mechanisms of aseptic loosening of orthopedic implants.

In vitro reactivity to implant metals demonstrates a person-dependent association with both T-cell and B-cell activation

Hypersensitivity to metallic implants remains relatively unpredictable and poorly understood. We initially hypothesized that metal-induced lymphocyte proliferation responses to soluble metal challenge (ions) are mediated exclusively by early T-cell activation (not B-cells), typical of a delayed-type-hypersensitivity response. We tested this by comparing proliferation (6 days) of primary lymphocytes with early T-cell and B-cell activation (48 h) in three groups of subjects likely to demonstrate elevated metal reactivity: group 1 (n = 12) history of metal sensitivity with no implant; group 2a (n = 6) well performing metal-on-metal THRs, and group 2b (n = 20) subjects with poorly performing metal-on-polymer total joint arthroplasties (TJA). Group 1 showed 100% (12/12) metal reactivity (stimulation index > 2) to Ni. Groups 2a and 2b were 83% (5/6) and 75% (15/22) metal reactive (to Co, Cr, or Ni), respectively. Of the n = 32 metal-reactive subjects to Co, Cr, or Ni (SI > 2), n = 22/32 demonstrated >2-fold elevations in % of T-cell or B-cell activation (CD25+, CD69+) to metal challenge when compared with untreated control. 18/22 metal-activated subjects demonstrated an exclusively T-cell or B-cell activation response to metal challenge, where 6/18 demonstrated exclusively B-cell activation and 12/18 demonstrated a T-cell only response, as measured by surface activation markers CD25+ and CD69+. However, there was no direct correlation (R(2) < 0.1) between lymphocyte proliferation and % T-cell or B-cell activation (CD25+:CD69+). Proliferation assays (LTT) showed greater ability to detect metal reactivity than did subject-dependent results of flow-cytometry analysis of T-cell or B-cell activation. The high incidence of lymphocyte reactivity and activation indicate that more complex than initially hypothesized immune responses may contribute to the etiology of debris-induced osteolysis in metal-sensitive individuals.

Metal ion release from bearing wear and corrosion with 28 mm and large-diameter metal-on-metal bearing articulations: a follow-up study

We have updated our previous randomised controlled trial comparing release of chromium (Cr) and cobalt (Co) ions and included levels of titanium (Ti) ions. We have compared the findings from 28 mm metal-on-metal total hip replacement, performed using titanium CLS/Spotorno femoral components and titanium AlloFit acetabular components with Metasul bearings, with Durom hip resurfacing using a Metasul articulation or bearing and a titanium plasma-sprayed coating for fixation of the acetabular component. Although significantly higher blood ion levels of Cr and Co were observed at three months in the resurfaced group than in total hip replacement, no significant difference was found at two years post-operatively for Cr, 1.58 microg/L and 1.62 microg/L respectively (p = 0.819) and for Co, 0.67 microg/L and 0.94 microg/L respectively (p = 0.207). A steady state was reached at one year in the resurfaced group and after three months in the total hip replacement group. Interestingly, Ti, which is not part of the bearing surfaces with its release resulting from metal corrosion, had significantly elevated ion levels after implantation in both groups. The hip resurfacing group had significantly higher Ti levels than the total hip replacement group for all periods of follow-up. At two years the mean blood levels of Ti ions were 1.87 microg/L in hip resurfacing and and 1.30 microg/L in total hip replacement (p = 0.001). The study confirms even with different bearing diameters and clearances, hip replacement and 28 mm metal-on-metal total hip replacement produced similar Cr and Co metal ion levels in this randomised controlled trial study design, but apart from wear on bearing surfaces, passive corrosion of exposed metallic surfaces is a factor which influences ion concentrations. Ti plasma spray coating the acetabular components for hip resurfacing produces significantly higher release of Ti than Ti grit-blasted surfaces in total hip replacement.

A review of the biologic effects of spine implant debris: Fact from fiction

BACKGROUND

Biologic-reactivity to implant-debris is the primary determinant of long-term clinical performance. The following reviews: 1) the physical aspects of spinal-implant debris and 2) the local and systemic biologic responses to implant debris.

METHODS

Methods included are: 1) gravimetric wear analysis; 2) SEM and LALLS; 3) metal-ion analysis; 4) ELISA, toxicity testing, patch testing; and 5) metal-lymphocyte transformation testing (metal-LTT).

RESULTS

Wear and corrosion of spine-implants produce particles and ions. Particles (0.01-1000 μm) are generally submicron ( <1 µm). Wear rates of metal-on-polymer and metal-on-metal disc arthroplasties are approximately 2-20 and 1 mm(3)/yr, respectively. Metal-on-metal total disc replacement components have significant increases in circulating metal (less than 10-fold that of controls at 4 ppb-Co and 3 ppb-Cr or ng/mL). Debris reactivity is local and systemic. Local inflammation is caused primarily by ingestion of debris by local macrophages, which produce pro-inflammatory cytokines TNFα, IL-1β, IL-6, and PGE2. Systemic responses associated with implant-debris have been limited to hypersensitivity reactions. Elevated amounts of in the liver, spleen, etc of patients with failed TJA have not been associated with remote toxicological or carcinogenic pathology to date. Implant debris are differentially bioreactive. Greater numbers are pro-inflammatory; the smaller-sized debris are more bioreactive by virtue of their greater numbers (dose) for a given amount of implant mass loss (one 100-μm-diameter particle is equivalent in mass to 1 million 1-μm-diameter particles). Elongated particles are pro-inflammatory (ie, aspect ratio of greater than 3). Metal particles are more proinflammatory than polymers, ceteris paribus.

CONCLUSION

Spinal arthroplasty designs have been in use for more than 20 years internationally; therefore, concerns about neuropathology, toxicity, and carcinogenicity are mitigated. Debris-induced inflammation still depends on the individual and the type of debris. The consequence of debris-induced inflammation is continued; vigilance by physicians is recommended monitoring of spinal implants using physical exams and testing of metal content and bioreactivity, as is planning for the likelihood of revision in younger individuals.

In vitro reaction of human osteoblasts on alumina-toughened zirconia

OBJECTIVES

Alumina toughening enhances the mechanical properties of zirconia ceramics but the biocompatibility of this material has rarely been addressed. In this study, we examined the osteoblast response to alumina-toughened zirconia (ATZ) with different surface topographies.

MATERIAL AND METHODS

Human osteoblasts isolated from maxillary biopsies of four patients were cultured and seeded onto disks of the following substrates: ATZ with a machined surface, airborne-particle abraded ATZ, airborne-particle abraded and acid etched ATZ. Airborne-particle abraded and acid etched titanium (SLA) and polystyrene disks served as a reference control. The surface topography of the various substrates was characterized by profilometry (R(a), R(p-v)) and scanning electron microscopy (SEM). Cell proliferation, cell-covered surface area, alkaline phophatase (ALP) and osteocalcin production were determined. The cell morphology was analyzed on SEM images.

RESULTS

The surface roughness of ATZ was increased by airborne-particle abrasion, but with the R(a) and R(p-v) values showing significantly lower values compared with SLA titanium (Mann-Whitney U-test P<0.05). The proliferation assay revealed no statistically significant differences between the ATZ substrates, SLA titanium and polystyrene (Kruskal-Wallis test, P>0.05). All substrates were densely covered by osteoblasts. ALP and osteocalcin production was similar on the examined surfaces. Cell morphology analysis revealed flat-spread osteoblasts with cellular extensions on all substrates.

CONCLUSIONS

These results indicate that ATZ may be a viable substrate for the growth and differentiation of human osteoblasts. Surface modification of ATZ by airborne-particle abrasion alone or in combination with acid etching seems not to interfere with the growth and differentiation of the osteoblasts.

Hip fracture implants increase serum metal levels

OBJECTIVE

Hip fractures are disabling accidents in the elderly. The purpose of this prospective study was to investigate systemic exposure to metals from hip implants used for fracture fixation.

MATERIAL AND METHODS

Serum levels of Cr, Ni and Mo in patients with compression hip screws (n = 22) or cervical fracture screws (n = 23) were measured by inductively coupled plasma mass spectrometry. Blood samples were collected before surgery and at 3 and 12 months postoperatively.

RESULTS

At 3 months, patients with compression hip screws showed higher concentrations of Cr and Ni than did those with cervical screws. Both types of screws led to a 2-fold increase in serum Mo, which was not expected for the freestanding cervical screws. After 12 months, the levels had decreased, but the compression hip screw was still associated with higher values for Cr and Mo.

CONCLUSIONS

The difference between the screws is most likely due to the potential for fretting and crevice corrosion between components in the compression hip screws. The apparent short-term systemic elevation of stainless steel elements in patients with hip screws does not support routine removal of asymptomatic hip fracture implants.

[Metal sensitivity in patients with joint replacement arthroplasties before and after surgery]

The object of the present study was to determine the incidence of metal sensitivity in patients with joint replacement arthroplasties before and after surgery and whether this is of significance as regards the final outcome of the operative procedure. A questionnaire-based survey involved 1,335 patients with an average age of 61 years and joint replacement arthroplasties before and after surgery. A history of dermal sensitivity to metal was given in 99 (7%) patients with almost equal frequency in the pre- and postoperative groups (7.6 vs 7.2%). In only 27 of 99 cases was the metal sensitivity recorded in the patient chart. In 46 cases investigation was done after knee or hip replacement arthroplasty with an average implant time in situ of 68 months. In 32 of 46 patients a sensitivity to the implanted material was known and they did not show any complications related to the metal sensitivity.It is currently unclear whether metal sensitivity could be induced by joint replacement arthroplasties and it remains uncertain whether loosening or infection causes the sensitization as a consequence of increased release of metal ions or vice versa. To draw further conclusions considerably more detailed studies involving more patients are clearly indicated.

Present status of titanium removable dentures--a review of the literature

Although porcelain and zirconium oxide might be used for fixed partial dental prostheses instead of conventional dental metals in the near future, removable partial denture (RPD) frameworks will probably continue to be cast with biocompatible metals. Commercially pure (CP) titanium has appropriate mechanical properties, it is lightweight (low density) compared with conventional dental alloys, and has outstanding biocompatibility that prevents metal allergic reactions. This literature review describes the laboratory conditions needed for fabricating titanium frameworks and the present status of titanium removable prostheses. The use of titanium for the production of cast RPD frameworks has gradually increased. There are no reports about metallic allergy apparently caused by CP titanium dentures. The laboratory drawbacks still remain, such as the lengthy burn-out, inferior castability and machinability, reaction layer formed on the cast surface, difficulty of polishing, and high initial costs. However, the clinical problems, such as discoloration of the titanium surfaces, unpleasant metal taste, decrease of clasp retention, tendency for plaque to adhere to the surface, detachment of the denture base resin, and severe wear of titanium teeth, have gradually been resolved. Titanium RPD frameworks have never been reported to fail catastrophically. Thus, titanium is recommended as protection against metal allergy, particularly for large-sized prostheses such as RPDs or complete dentures.

Suspected association of an allergic reaction with titanium dental implants: a clinical report

Recent reports have questioned whether metal sensitivity may occur after exposure to titanium. This clinical report demonstrates the emergence of facial eczema in association with a titanium dental implant placed for a mandibular overdenture supported by 2 implants. Complete remission was achieved by the removal of the titanium material. This clinical report raises the possibility that in rare circumstances, for some patients, the use of titanium dental implants may induce an allergic reaction.

Effects of titanium(iv) ions on human monocyte-derived dendritic cells

Orthopaedic metal implants composed of titanium are routinely used in bone fracture repair and for joint replacement therapies. A considerable fraction of implant recipients are unable to benefit due to implant failure resulting from aseptic loosening, while others may experience cutaneous sensitivity to titanium after implantation. An adaptive immune reactivity towards titanium ions, originating from the biocorrosion of the implants, could play a role. As an initiator of the adaptive immune response, dendritic cells (DC) were studied for uptake and characteristics after titanium exposure. Energy filtered transmission electron microscopy showed uptake of titanium(iv) (Ti(iv)) ions by DCs in vitro and co-localisation with phosphorus-rich cell structures of the DC membranes (phospholipids), cytoplasm (ribosomes and phosphorylated proteins) and the nucleus (DNA). DC maturation and function were investigated by measuring cell surface marker expression by flow cytometry. After exposure, DCs showed a decrease in MHC class II (HLA-DR), co-stimulatory molecules (CD40, CD80 & CD86) and chemokine receptors (CCR) 6 and CCR7 but an increase in CCR4 after Ti(iv) treatment. However, Ti(iv) treated DCs had an increased stimulatory capacity towards allogenic lymphocytes. A Ti(iv) concentration dependant increase of IL-12p70 was observed amidst decrease of the other measured cytokines (TGF-β1 and TGF-β2). Hence, Ti(iv) alters DC properties, resulting in an enhanced T lymphocyte reactivity and deviation towards a Th1 type immune response. This effect may be responsible for the inflammatory side effects of titanium implants seen in patients.

Titanium allergy in dental implant patients: a clinical study on 1500 consecutive patients

BACKGROUND

In dentistry, allergic reactions to Ti implants have not been studied, nor considered by professionals. Placing permanent metal dental implants in allergic patients can provoke type IV or I reactions. Several symptoms have been described, from skin rashes and implant failure, to non-specific immune suppression.

OBJECTIVE

Our objective was to evaluate the presence of titanium allergy by the anamnesis and examination of patients, together with the selective use of cutaneous and epicutaneous testing, in patients treated with or intending to receive dental implants of such material.

MATERIAL AND METHODS

Thirty-five subjects out of 1500 implant patients treated and/or examined (2002-2004) were selected for Ti allergy analysis. Sixteen presented allergic symptoms after implant placement or unexplained implant failures [allergy compatible response group (ACRG)], while 19 had a history of other allergies, or were heavily Ti exposed during implant surgeries or had explained implant failures [predisposing factors group (PFG)]. Thirty-five controls were randomly selected (CG) in the Allergy Centre. Cutaneous and epicutaneous tests were carried out.

RESULTS

Nine out of the 1500 patients displayed positive (+) reactions to Ti allergy tests (0.6%): eight in the ACRG (50%), one in the PFG (5.3%)(P=0.009) and zero in the control group. Five positives were unexplained implant failures (five out of eight).

CONCLUSIONS

Ti allergy can be detected in dental implant patients, even though its estimated prevalence is low (0.6%). A significantly higher risk of positive allergic reaction was found in patients showing post-op allergy compatible response (ACRG), in which cases allergy tests could be recommended.

The combined role of wear particles, macrophages and lymphocytes in the loosening of total joint prostheses

This review considers the causes of loosening of prosthetic joint replacement paying attention to the biological mechanisms rather than other effects that are physical, such as component fracture and other failure related to mechanical problems. Infection accounts for approximately 1.5 per cent of joint loosening and when it occurs it is a cause of serious concern to the surgeon. The loosening of prosthetic joints in the absence of infection is by far the most common reason for revision surgery and is known as aseptic loosening. While this may be multifactorial in terms of causation, and non-biological factors may contribute significantly in a particular individual, a significant part is undoubtedly played by the generation of wear debris, mainly from the bearing surfaces of the joint, and the cellular reaction to this in the implant bed. Phagocytic cells (macrophages and multinucleated giant cells) are the ones that remove foreign material from the tissues, and the ways in which these cells function in the interface between implant and bone are described. Mediators produced locally include numerous cytokines, enzymes and integrins. There is evidence for interactions between macrophages and locally recruited lymphocytes, which may or may not give rise to an immunologically mediated process.Sensitization of individuals having metal implants in place has been shown by positive skin tests or blood lymphocyte transformation tests and in these cases has been accompanied by loosening and failure of the replacement joint. The question remains as to whether this process is also present in a proportion of individuals with aseptic loosening in the absence of clearly defined clinical evidence of sensitization.Numerous studies performed by the author's group and, latterly, by others suggest that the cellular reactions detected in the tissues in cases of aseptic loosening are indeed those of contact sensitization. There is good evidence to show that a type IV cell-mediated immune reaction is taking place, with TH1 cell involvement and active antigen presentation. The extent to which sensitization is present in individual cases of aseptic loosening remains a subject for further work and this needs all the sophisticated molecular methods now available to modern biology to be applied in appropriate prospective clinical studies coupled with experimental models in vitro and in vivo. Immunological processes may play a more important part in joint loosening than previously considered.

Immune responses in patients with metal-on-metal hip articulations: a long-term follow-up

Metal-on-metal (MoM) hip bearings are being inserted into ever-younger patients. The effects on the immune system of chronic exposure are unknown. We investigated the immune response of patients with MoM hip bearings. In patients with MoM implants, the expression of antigen-presenting cell (APC) surface molecules (CD86 and HLA-DR) was seen to be significantly higher (P < .05) than control group. High levels of APC surface molecules suggest an activated state and attempts to propagate an immune response. However, in the same group, the expression of T-cell markers (CD3 and CD28) was low, indicating a small T-cell population. This suggests, despite the activation of APCs, that T cells down-regulate immune responses in MoM articulations. Conversely, in metal-on-polyethylene articulations, expression of T-cell molecules was elevated and expression of APC molecules lowered.

Tissue compatibility of biomaterials: benefits and problems of skin biointegration

The integration of biomaterials with skin is necessary to enable infection-free access to vasculature and body cavities. Also, integrating plastics and metals with skin increases options for the reconstruction of surgical and traumatic defects and enables the permanent implantation of robotic and electronic devices. Until now, attempts to integrate biomaterials with skin permanently have failed because of epidermal marsupialization and infection. This article reviews the general properties required of biomaterials to optimize integration with body tissues, the modifications that increase biocompatibility, focusing particularly on surface functionalization and the specific requirements for biomaterial integration into skin. Critical pathophysiological processes relating to biocompatibility are discussed with particular emphasis on the skin-biomaterial interface. Future directions are speculated on, in particular, the specific utility of subatmospheric pressure dressings in facilitating tissue integration into biomaterials.

[Orthopedic surgical implants and allergies. Joint statement by the Implant Allergy Working Group (AK 20) of the DGOOC (German Association of Orthopedics and Orthopedic Surgery), DKG (German Contact Dermatitis Research Group) and DGAKI (German Society for Allergology and Clinical Immunology)]

Materials used in osteosynthesis or artificial joint replacement are usually well tolerated. Complaints after such operations are mostly related to infection or mechanical problems but may also be caused by allergic reactions. The latter encompass skin changes, e.g., eczema, delayed wound/bone healing, recurrent effusion, pain, or implant loosening. In contrast to the high incidence of cutaneous metal contact allergy, allergies associated with implants are a rare condition. However, epidemiological data on the incidence of implant-related allergic reactions are still missing. Typical elicitors are nickel, chromium, cobalt, and constituents of bone cement (acrylates und additives such as gentamicin or benzoyl peroxide). After exclusion of the most common differential diagnoses, allergy diagnostic procedures are primarily based on patch tests including a metal and bone cement component series. Additional analysis of periimplant tissue is recommended. However, further studies are necessary to show the significance of the histologic findings and the role of the lymphocyte transformation test (LTT). Which combinations of factors will induce allergic sensitization to implants or trigger periimplant allergic reactions in the case of preexisting cutaneous metal allergy is still unknown. Titanium-based osteosynthesis materials are recommended for metal allergic patients. In elective hip replacements, a ceramic/polyethylene (PE) articulation should be used, and in knee replacements "alternative materials". If a regular, potentially applicable CoCr/PE articulation is preferred, the patient must be well informed and must give his/her written consent.

Th1 type lymphocyte reactivity to metals in patients with total hip arthroplasty

BACKGROUND

All prostheses with metallic components release metal debris that can potentially activate the immune system. However, implant-related metal hyper-reactivity has not been well characterized. In this study, we hypothesized that adaptive immunity reaction(s), particularly T-helper type 1 (Th1) responses, will be dominant in any metal-reactivity responses of patients with total joint replacements (TJAs). We tested this hypothesis by evaluating lymphocyte reactivity to metal "ions" in subjects with and without total hip replacements, using proliferation assays and cytokine analysis.

METHODS

Lymphocytes from young healthy individuals without an implant or a history of metal allergy (Group 1: n = 8) were used to assess lymphocyte responses to metal challenge agents. In addition, individuals (Group 2: n = 15) with well functioning total hip arthroplasties (average Harris Hip Score = 91, average time in-situ 158 months) were studied. Age matched controls with no implants were also used for comparison (Group 3, n = 8, 4 male, 4 female average age 70, range 49-80). Group 1 subjects' lymphocyte proliferation response to Aluminum+3, Cobalt+2, Chromium+3, Copper+2, Iron+3, Molybdenum+5, Manganeese+2, Nickel+2, Vanadium+3 and Sodium+2 chloride solutions at a variety of concentrations (0.0, 0.05, 0.1, 0.5, 1.0 and 10.0 mM) was studied to establish toxicity thresholds. Mononuclear cells from Group 2 and 3 subjects were challenged with 0.1 mM CrCl3, 0.1 mM NiCl2, 0.1 mM CoCl2 and approx. 0.001 mM titanium and the reactions measured with proliferation assays and cytokine analysis to determine T-cell subtype prominence.

RESULTS

Primary lymphocytes from patients with well functioning total hip replacements demonstrated a higher incidence and greater magnitude of reactivity to chromium than young healthy controls (p < 0.03). Of the 15 metal ion-challenged subjects with well functioning total hip arthroplasties, 7 demonstrated a proliferative response to Chromium, Nickel, Cobalt and/or Titanium (as defined by a statistically significant >2 fold stimulation index response, p < 0.05) and were designated as metal-reactive. Metals such as Cobalt, Copper, Manganese, and Vanadium were toxic at concentrations as low as 0.5 mM while other metals, such as Aluminum, Chromium, Iron, Molybdenum, and Nickel, became toxic at much higher concentrations (>10 mM). The differential secretion of signature T-cell subsets' cytokines (Th1 and Th2 lymphocytes releasing IFN-gamma and IL-4, respectively) between those total hip arthroplasty subjects which demonstrated metal-reactivity and those that did not, indicated a Th1 type (IFN-gamma) pro-inflammatory response.

CONCLUSION

Elevated proliferation and production of IFN-gamma to metals in hip arthroplasty subjects' lymphocytes indicates that a Th1 (vs. Th2) type response is likely associated with any metal induced reactivity. The involvement of an elevated and specific lymphocyte response suggests an adaptive (macrophage recruiting) immunity response to metallic implant debris rather than an innate (nonspecific) immune response.

Formation of potential titanium antigens based on protein binding to titanium dioxide nanoparticles

Degradation products of titanium implants include free ions, organo-metallic complexes, and particles, ranging from nano to macro sizes. The biological effects, especially of nanoparticles, is yet unknown. The main objective of this study was to develop Ti-protein antigens in physiological solutions that can be used in testing of cellular responses. For this purpose, 0.1% TiO2 nanoparticles less than 100 nm were mixed with human serum albumin (HSA), 0.1% and 1%, in cell culture medium (DMEM, pH 7.2). The Ti concentrations in the resulting solutions were analyzed by inductively coupled plasma mass spectrometry. The stability of the nanoparticles in suspension was analyzed by UV-vis spectrophotometer and Dynamic Light Scattering. The concentration of Ti in suspension was dependent on the presence and concentration of HSA. Albumin prevented high aggregation rate of TiO2 nanoparticles in cell culture medium. It is shown that nano TiO2-protein stable aggregates can be produced under physiological conditions at high concentrations, and are candidates for use in cellular tests.

Preliminary experience with biodegradable implants for fracture fixation

BACKGROUND

Biodegradable implants were designed to overcome the disadvantages of metal-based internal fixation devices. Although they have been in use for four decades internationally, many surgeons in India continue to be skeptical about the mechanical strength of biodegradable implants, hence this study.

MATERIALS AND METHODS

A prospective study was done to assess the feasibility and surgeon confidence level with biodegradable implants over a 12-month period in an Indian hospital. Fifteen fractures (intra-articular, metaphyseal or small bone fractures) were fixed with biodegradable implants. The surgeries were randomly scheduled so that different surgeons with different levels of experience could use the implants for fixation.

RESULTS

Three fractures (one humeral condyle, two capitulum), were supplemented by additional K-wires fixation. Trans-articular fixator was applied in two distal radius and two pilon fractures where bio-pins alone were used. All fractures united, but in two cases the fracture displaced partially during the healing phase; one fibula due to early walking, and one radius was deemed unstable even after bio-pin and external fixator.

CONCLUSIONS

Biodegradable -implants are excellent for carefully selected cases of intra-articular fractures and some small bone fractures. However, limitations for use in long bone fractures persist and no great advantage is gained if a "hybrid" composite is employed. The mechanical properties of biopins and screws in isolation are perceived to be inferior to those of conventional metal implants, leading to low confidence levels regarding the stability of reduced fractures; these implants should be used predominantly in fracture patterns in which internal fixation is subjected to minimal stress.

Wear particles, periprosthetic osteolysis and the immune system

The immune system modulates many key biological processes in humans. However, the exact role of the immune system in particle-associated periprosthetic osteolysis is controversial. Human tissue retrieval studies, in vivo and in vitro experiments suggest that the immune response to polymer particles is non-specific and macrophage-mediated. Lymphocytes may modulate this response. However direct lymphocyte activation by polymer particle-protein complexes seems unlikely. However, metallic byproducts may complex with serum proteins and lead to a Type IV, lymphocyte-mediated immune reaction. In predisposed individuals, this reaction may rarely lead to persistent painful joint effusions, necessitating debridement and excision of the bearing surfaces of the prosthesis. In these patients, retrieved periprosthetic tissues exhibit histological evidence of perivascular lymphocytic cuffing. These findings are worrisome, given the fact that increasing numbers of metal-on-metal joint implants are being implanted in younger more active individuals worldwide.

Hypersensitivity to benzoyl peroxide in a cemented total knee arthroplasty: cement allergy

A small but significant proportion of cemented total knee arthroplasties develop aseptic loosening. Polyethylene debris is unlikely to be the cause in the small subgroup that experiences early loosening. Allergy to polymethylmethacrylate bone cement or its constituents has been reported in several different industries and in dentistry, dermatology, and joint arthroplasty. Although allergy to polymethylmethacrylate bone cement or its constituents is unusual, the possibility of a systemic inflammatory response and consequent pain and loosening must be considered. We report a case history of a patient who developed a systemic reaction and intractable pain after a total knee arthroplasty who was subsequently shown to be hypersensitive to the benzoyl peroxide component of bone cement.

Drug rash with eosinophilia and systemic symptoms (DRESS) syndrome: suspected association with titanium bioprosthesis

Drug rash with eosinophilia and systemic symptoms (DRESS), also known as hypersensitivity syndrome, is an idiosyncratic drug reaction presenting with fever, diffuse lymphadenopathy, exfoliative dermatitis, and visceral involvement, which may include hepatitis, pneumonitis, pericarditis, myocarditis, nephritis, and colitis. This report describes a 19-year-old, previously healthy man with manifestations of hypersensitivity (DRESS) syndrome after acquiring a titanium bioprosthesis for a spinal fracture. To our knowledge, there have been no prior reports of DRESS syndrome in association with titanium bioprosthetic implants.

Corrosion of pure titanium sternal wire

Titanium and its alloys are considered reliable materials commonly used in heart surgeries. A patient had severe inflammation at the median sternotomy wound develop after open heart surgery. Sternal wires were removed and were found to be seriously corroded on most of the surface. Energy dispersive spectroscopy identified titanium as the only elemental component of the explanted wire with grade 2 purity, and the polarization curve showed satisfactory corrosion resistance similar to commercial pure titanium. Prolonged inflammation might have caused extensive corrosion of titanium in the present case.

Behavior of CAL72 osteoblast-like cells cultured on zirconia ceramics with different surface topographies

OBJECTIVES

Because of its inherent strength, biocompatibility, and tooth-like color, zirconia ceramics have the potential to become an alternative to titanium as dental implant material. This study aimed at investigating the osteoblastic response to yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) with different surface topographies.

METHODS

CAL72 osteoblast-like cells were cultured on machined (TZP-m), airborne particle abraded (TZP-s), and airborne particle abraded and acid-etched Y-TZP (TZP-sa) surfaces. Polystyrene and airborne particle abraded with large grit and acid-etched (SLA) titanium served as a reference control. The surface topography was examined by scanning electron microscopy (SEM) and profilometry. At culture days 3, 6, and 12, cell proliferation, at day 12 cell morphology, and cell-covered surface area were determined.

RESULTS

The surface roughness of Y-TZP was increased by airborne particle abrasion and additionally by acid etching. No statistically significant differences were found between average roughness (R(a)) and maximum peak-to-valley height (R(p-v)) values of airborne particle abraded and acid-etched Y-TZP and SLA titanium. Whereas the cell proliferation assay revealed statistically significant greater values at day 3 for surface-treated Y-TZP and polystyrene cultures as compared with machined Y-TZP, no differences between the Y-TZP groups, SLA titanium, and polystyrene were observed at culture days 6 and 12.

CONCLUSIONS

Cell morphology and cell-covered surface area were not affected by the type of substrate. The results suggest that roughened Y-TZP is an appropriate substrate for the proliferation and spreading of osteoblastic cells.

Cytocompatibility and electrochemical properties of Ti–Au alloys for biomedical applications

The purpose of this study was to develop Ti-Au alloys with a higher resistant to corrosion, better biocompatibility, and better mechanical properties than the commercially pure titanium and its alloys. Ti-Au alloys were designed with a gold content that ranged from 0 to 5.0 at % in steps of 1.0 at %. Properties of the alloys including chemical composition, microstructure, phase, hardness, electrochemical properties, and the cytotoxicity were investigated. Only the alpha phase existed in the Ti-Au alloys. The addition of gold to the titanium decreased the alpha to beta transformation temperature. The acicular alpha phase became thinner and the hardness value increased with increasing gold content. In the electrochemical tests, Ti-Au alloys had a higher resistant to corrosion than had pure titanium and did not exhibit pitting corrosion in artificial saliva. The cytotoxicities of the Ti-Au alloys were similar to that of pure titanium. Therefore, Ti-Au alloys could be used as biomaterials in the medical and dental fields.

Surgical treatment of comminuted, displaced fractures of the greater tuberosity of the proximal humerus: a new technique of double-row suture-anchor fixation and long-term results

Conventional techniques of internal fixation of displaced fractures of the greater tuberosity may be insufficient in presence of comminution. A new surgical technique of internal fixation using a double-row of suture-anchors is described. Long-term results of this technique are evaluated in 21 patients with an isolated, displaced and comminuted greater tuberosity fracture at an average of 3.5 years (range 1-5 years) after surgery. The average age of the patients in the study was 51 years (range 17-93 years). Twenty fractures healed without post-operative displacement. The result was rated as excellent in 8, good in 10, satisfactory in 2 and unsatisfactory in 1 patient. Post-operative bicipital impingement in two patients and reaction to fixation material in one patient resulted in persistent, severe pain in the rehabilitation period, necessitating additional surgery.

Sensitivity to implant materials in patients undergoing total hip replacement

Sensitivity to implant materials is an unpredictable event, which may contribute to the process leading to the failure of the total hip replacement (THR). The aim of the current study was to investigate the informative power of skin testing in detecting the sensitization to the implant components in patients undergoing THR. A consecutive series of 223 patients was enrolled in the study, including 66 candidates to THR, 53 with stable implant, and 104 with THR loosening. The patch testing was performed by using the most relevant components of cobalt-based alloys (CoCrMo), Ti-based alloys (TiAlV), and bone cements. The frequency of positive patch testing in preimplant patients did not differ from that observed after THR. Patients with CoCrMo-failed implant showed a significant low frequency of nickel-positive skin reaction, while patients with TiAlV-THR had a high incidence of vanadium-positive patch testing. The panel of haptens showed a good performance in the identification of patients known to have a contact dermatitis. With regard to the THR outcome, patch testing was not able to discriminate between stable and failed implant. Sensitivity to at least one hapten, namely bone cement, as well as the positive medical history of hypersensitivity, influenced negatively the THR survival. Our results show the reliability of patch testing for investigating the sensitivity to implant components. The cause-effect relationship between sensitization and negative outcome cannot be established, but the shorter lifespan of THR in patients who have a positive patch testing supports the significant role of this event in contributing to the implant failure.

Host Response to Titanium Dental Implant Placement Evaluated in a Human Oral Model

BACKGROUND

Recent reports have questioned if metal sensitivity may arise from exposure to titanium. The objective of this study was to histologically evaluate non-perforated mucosa covering submerged maxillary titanium implants with regard to induced tissue reactions.

METHODS

Thirteen patients, 21 to 69 years of age, without previous implants were included. After initial examination, the bone crest areas destined for dental implant placement were exposed, and threaded external hex dental implants were inserted. Prior to wound closure, a full mucosal tissue slice was biopsied from the edge of the mucoperiosteal flap (baseline). The patients were monitored monthly for 6 months. At the abutment connection, biopsies were taken by a 6-mm punch, altogether yielding 26 specimens. Tissue reactions were analyzed by coded histometric analysis at four defined areas at increasing distance from the oral epithelium, including ratios of inflammatory cells (IC)/epithelial cells, IC/fibroblasts, and number of dense particles.

RESULTS

The stained sections portrayed gingival tissue with intact oral epithelium and connective tissue with variable accumulation of IC. Experimental biopsies demonstrated mineralized areas and dense particles of different sizes. Analysis of variance revealed a higher IC/fibroblast ratio for level 3 at baseline compared to level 3 at 6 months (P<0.01). Furthermore, a significant decrease in IC/fibroblast ratio was observed between levels 2 and 3 and 2 and 4 at 6 months (P<0.001). The connective tissue level facing the cover screw contained the highest number of dense particles (P<0.01).

CONCLUSIONS

Tissue sensitivity reactions to titanium implants were not disclosed. All 6-month biopsies contained dense particles that were most likely metals.

Development and problems of metal-on-metal hip arthroplasty

For over 40 years, the metal-on-polyethylene bearing has dominated the field of total hip replacement. Problems of wear, osteolysis (dissolution of bone), and ultimately failure of prostheses have led to the development of alternative bearing surfaces. Metal-on-metal hip resurfacing has taken current orthopaedic surgery almost by storm. However, metal ion release following metal-on-metal hip resurfacing remains a major cause for concern. This article looks into the development and examines problems and issues surrounding metal-on-metal resurfacing arthroplasty.

Implant-related inflammatory arthritis

BACKGROUND

A 54-year-old woman presented with myalgia and arthralgia predominantly in the knees and small joints of the hands and feet with morning stiffness lasting for at least 2 h. The patient had received a wrought titanium 6-aluminium 4-vanadium alloy C cage implant 1.5 years previously, following a severe disc prolapse. No signs of rheumatic disease were evident before the C cage was implanted.

INVESTIGATIONS

Physical examination, radiography, skin and muscle biopsies, serology tests, white blood cell count, HLA genotyping, tumor necrosis factor release assay, skin patch test, lymphocyte transformation test.

DIAGNOSIS

Implant-related inflammatory arthritis.

MANAGEMENT

Combination therapy with corticosteroids, disease-modifying antirheumatic drugs and nonsteroidal anti-inflammatory drugs, and replacement of the titanium cage with a polyetherketone cage.

Peri-implant osteogenesis in health and osteoporosis

Long-term clinical success of endosseous dental implants is critically related to a wide bone-to-implant direct contact. This condition is called osseointegration and is achieved ensuring a mechanical primary stability to the implant immediately after implantation. Both primary stability and osseointegration are favoured by micro-rough implant surfaces which are obtained by different techniques from titanium implants or coating the titanium with different materials. Host bone drilled cavity is comparable to a common bone wound. In the early bone response to the implant, the first tissue which comes into contact with the implant surface is the blood clot, with particular attention to platelets and fibrin. Peri-implant tissue healing starts with an inflammatory response as the implant is inserted in the bone cavity, but an early afibrillar calcified layer comparable to the lamina limitans or incremental lines in bone is just observable at the implant surface both in vitro than in vivo conditions. Just within the first day from implantation, mesenchymal cells, pre-osteoblasts and osteoblasts adhere to the implant surface covered by the afibrillar calcified layer to produce collagen fibrils of osteoid tissue. Within few days from implantation a woven bone and then a reparative trabecular bone with bone trabeculae delimiting large marrow spaces rich in blood vessels and mesenchymal cells are present at the gap between the implant and the host bone. The peri-implant osteogenesis can proceed from the host bone to the implant surface (distant osteogenesis) and from the implant surface to the host bone (contact osteogenesis) in the so called de novo bone formation. This early bone response to the implant gradually develops into a biological fixation of the device and consists in an early deposition of a newly formed reparative bone just in direct contact with the implant surface. Nowadays, senile and post-menopausal osteoporosis are extremely diffuse in the population and have important consequences on the clinical success of endosseous dental implants. In particular the systemic methabolic and site morphological conditions are not favorable to primary stability, biological fixation and final osseointegration. An early good biological fixation may allow the shortening of time before loading the implant, favouring the clinical procedure of early or immediate implant loading. Trabecular bone in implant biological fixation is gradually substituted by a mature lamellar bone which characterizes the implant ossoeintegration. As a final consideration, the mature lamellar bone observed in osseointegrated implants is not always the same as a biological turnover occurs in the peri-implant bone up to 1mm from the implant surface, with both osteogenesis and bone reabsorption processes.

Chemical nature of implant-derived titanium(IV) ions in synovial fluid

Previous investigations have indicated a deleterious leakage of Ti(III) and/or Ti(IV) species from Ti-Al-V alloy joint prostheses into adjacent tissue, synovium or synovial fluid (SF) in vivo. In view of the importance of the particular chemical nature of such complexes in determining their biological activity, we have employed high field proton (1H) NMR spectroscopy to "speciate" Ti(IV) in inflammatory SF. Treatment of osteoarthritic SF samples with increasing concentrations of Ti(IV) (0.10-1.03 mM [TiO(C2O4)2]2-) gave rise to a specific broadening of the citrate proton resonances, indicating that this bioavailable oxygen-donor ligand plays an important role in complexing implant-derived Ti(IV). 1H NMR analysis of Ti(IV)-loaded SF samples subsequently treated with a large excess of ascorbate (0.05 M) showed that this added Ti(IV) chelator was only poorly effective in removing this metal ion from Ti(IV)-citrate/Ti(IV)-oxycitrate complexes. The results obtained here provide evidence for complexation of the low-molecular-mass (non-protein-bound) fraction of implant-derived Ti(IV) by citrate in vivo.

ICP-MS multielemental determination of metals potentially released from dental implants and articular prostheses in human biological fluids

A sector field high-resolution (HR)-ICP-MS and an octapole reaction system (ORS)-ICP-MS have been compared for the simultaneous determination of traces of metals (Ti, V, Cr, Co, Ni, and Mo) released from dental implants and articular prostheses in human biological fluids. Optimum sample treatments were evaluated to minimize matrix effects in urine and whole blood. Urine samples were diluted tenfold with ultrapure water, whereas whole blood samples were digested with high-purity nitric acid and hydrogen peroxide and finally diluted tenfold with ultrapure water. In both matrices, internal standardization (Ga and Y) was employed to avoid potential matrix interferences and ICP-MS signal drift. Spectral interferences arising from the plasma gases or the major components of urine and whole blood were identified by (HR)-ICP-MS at 3,000 resolving power. The capabilities of (HR)-ICP-MS and (ORS)-ICP-MS for the removal of such spectral interferences were evaluated and compared. Results indicate that polyatomic interferences, which hamper the determination of such metallic elements in these biological samples, could be overcome by using a resolving power of 3,000. Using (ORS)-ICP-MS, all those elements could be quantified except Ti and V (due to the polyatomic ions 31P16O and 35Cl16O, respectively). The accuracy of the proposed methodologies by (HR)- and (ORS)-ICP-MS was checked against two reference materials. Good agreement between the given values and the concentrations obtained for all the analytes under scrutiny was found except for Ti and V when analyzed by (ORS)-ICP-MS.

Das Allergiepotenzial von Implantatwerkstoffen auf Titanbasis

AIM

The aim of this investigation is to evaluate the allergic potential of titanium and titanium alloys for surgical implant applications.

MATERIALS AND METHODS

Discs cut from rods supplied by five different titanium suppliers in several diameters were investigated. The samples were cp-Titanium as well as Ti6Al4 V and Ti6Al7Nb, 6 mm thick with a diameter of between 6 and 60 mm. The material was checked by optical spectral analysis.

RESULTS

In all samples except iodidtitanium, a Nickel content of 0.012-0,034 wt% could be detected.

CONCLUSION

The low nickel content in the implant material results from the production process. The nickel atoms are in solid solution in the titanium lattice. Nickel allergic patients may develop hypersensitivity reactions even due to this low nickel content. Hence, this reaction may be falsely attributed to the titanium material itself. Measurements of ion concentration in the body are helpful for quantifying the maximum content of nickel in titanium materials for surgical implant applications. In addition, technical questions related to the production of nickel free titanium materials for allergic patients have to be solved.

Lymphocyte responses in patients with total hip arthroplasty

How lymphocyte-mediated metal sensitivity affects orthopaedic implant performance remains poorly understood. Do patients with implants exhibit elevated lymphocyte reactivity to metals and is this reactivity more generalized or more implant-alloy specific? We investigated these questions by measuring lymphocyte responses to implant metals (Cr(+3), Co(+2), Ni(+2) at 0.1mM, and Ti(+4) at 0.001 mM) in six subject groups: Group 1a=young controls, Group 1b=age matched controls, Group 2a=subjects with osteoarthritis (OA) and no history of metal sensitivity, Group 2b=OA subjects with history of metal sensitivity, Group 3a=total hip arthroplasty (THA) subjects with no to mild radiographic osteolysis, and Group 3b=THA subjects with moderate osteolysis. Lymphocyte proliferation, using Lymphocyte Transformation Testing (LTT), and cytokine release provided quantitative reactivity measurement, where a stimulation index of >2 indicated metal sensitivity. OA subjects with a history of metal sensitivity (Group 2b) were more metal reactive to Ni than any other group, as expected (66% incidence and Stimulation Index >20). However, THA subjects (Groups 3a and b) were >3 fold more reactive to Cr (p<0.04), than were controls (Groups 1a & b) or OA subjects (Groups 2a & b). THA subjects with moderate vs mild osteolysis (Group 3b vs 3a) were more reactive to Co (43% vs 0% incidence). Only osteolytic THA subjects demonstrated increased cytokine responses with >two-fold (p<0.05) increases in soluble interferon-gamma (IFN-gamma) and interleukin-2 (IL-2) levels in response to Cr challenge. This elevated incidence and averaged level of lymphocyte reactivity supports a metal-specific adaptive immune response and suggests involvement in the pathogenesis of poor implant performance, e.g. aseptic osteolysis.

Immune responses correlate with serum-metal in metal-on-metal hip arthroplasty

Cell-mediated hypersensitivity associated with metal components may be related to levels of implant debris. We tested this hypothesis by comparing lymphocyte reactivity to soluble Co, Cr, Ni, and Ti of patients with metal-on-polyethylene and metal-on-metal arthroplasties with healthy controls, and patients with osteoarthritis. The metal-on-metal group (n=9) demonstrated significantly elevated serum Co and Cr concentrations (13- and 58-fold, P<.05, respectively) and significantly elevated lymphocyte reactivity to Co (SI>5, P<.004) and Ni (SI>2.5, P<.01) when compared to controls (n=12) and subjects with metal-on-poly implants (n=7). These elevated in vivo metal levels demonstrated positive linear correlation with lymphocyte reactivity supporting our hypothesis that lymphocyte metal-induced reactivity increases with increased metal exposure. These results represent the first direct link between in vivo metal exposure and lymphocyte reactivity. Whether this lymphocyte reactivity to metal debris is etiologically linked to poor implant performance remains uncertain.