Preliminary observations on possible premalignant changes in bone marrow adjacent to worn total hip arthroplasty implants

An Update on Implant-Associated Malignancies and Their Biocompatibility

Implanted medical devices are widely used across various medical specialties for numerous applications, ranging from cardiovascular supports to orthopedic prostheses and cosmetic enhancements. However, recent observations have raised concerns about the potential of these implants to induce malignancies in the tissues surrounding them. There have been several case reports documenting the occurrence of cancers adjacent to these devices, prompting a closer examination of their safety. This review delves into the epidemiology, clinical presentations, pathological findings, and hypothesized mechanisms of carcinogenesis related to implanted devices. It also explores how the surgical domain and the intrinsic properties and biocompatibility of the implants might influence the development of these rare but serious malignancies. Understanding these associations is crucial for assessing the risks associated with the use of medical implants, and for developing strategies to mitigate potential adverse outcomes.

Elevated cobalt levels in metal-on-polyethylene knee megaprostheses: a prospective 1-year cohort study of 56 patients with hip and knee megaprostheses

BACKGROUND AND PURPOSE

Concerns have emerged regarding elevated levels of cobalt and chromium in patients with metal-on-metal megaprostheses. This prospective study aims to identify systemic cobalt and chromium levels in metal-on-polyethylene knee and hip megaprostheses and their associations with other factors.

METHODS

56 patients underwent knee or hip megaprosthesis surgery at 2 sarcoma centers. Serum cobalt and chromium levels were measured preoperatively and thrice within the first year using inductively coupled plasma mass spectrometry.

RESULTS

A statistically significant difference in serum cobalt levels (1.4 ppb; 95% confidence interval [CI] 0.0-3.3) was observed 1 year after knee megaprosthesis surgery compared with preoperative levels. In contrast no difference in chromium levels was observed after 1 year compared with preoperative levels (0.05 ppb; CI 0.0-0.8). An association between younger age, higher eGFR, and increased cobalt levels was observed. No significant correlations were found between ion levels and resection length or the number of modular connections.

CONCLUSION

We found elevated serum ion levels in metal-on-polyethylene knee megaprostheses in contrast to metal-on-polyethylene hip megaprostheses. Furthermore, a positive correlation between cobalt and chromium levels, and between cobalt and eGFR was identified, along with a negative correlation between cobalt and age. This study highlights the importance of monitoring systemic cobalt and chromium levels in patients with megaprostheses.

Exfoliated oral mucosa cells as bioindicators of short- and long-term systemic titanium contamination

BACKGROUND

Humans are exposed to exogenous sources of titanium-containing particles that can enter the body mainly by inhalation, ingestion, or dermal absorption. Given the widespread use of biomaterials in medicine, the surface of a titanium (Ti) biomedical device is a potential endogenous source of Ti ions and/or Ti-containing particles, such as TiO₂ micro-(MPs) and nano-particles (NPs), resulting from biotribocorrosion processes. Ti ions or Ti-containing particles may deposit in epithelial cells of the oral mucosa, and the latter may therefore serve as bioindicators of short and long-term systemic Ti contamination. The aim of the present study was to histologically and quantitatively evaluate the presence of Ti traces in cells exfoliated from the oral mucosa as possible bioindicators of systemic contamination with this metal at short and long-term experimental time points METHODS: Thirty Wistar rats were intraperitoneally injected with a suspension of titanium dioxide (TiO₂) (0.16 g/100 g body weight of TiO₂ in 5 ml of NaCl 0.9%) using 5 nm NPs (Group: TiO₂-NP5; n = 10), 45 µm MPs (Group: TiO₂-MP45; n = 10), or vehicle alone (Control group; n = 10). At one and six months post-injection, right-cheek mucosa cells were obtained by exfoliative cytology using a cytobrush; they were spray fixed and stained using Safranin or the Papanicolaou technique. The smears were cytologically evaluated (light microscopy) to determine the presence of particulate material, which was also analyzed microchemically (SEM-EDS). Left-cheek mucosa cells were similarly obtained and re-suspended in 5 ml of PBS (pH: 7.2-7.4); the samples corresponding to each group were pooled together and analyzed spectrometrically (ICP-MS) to determine Ti concentration in each of the studied groups. Blood samples were obtained for histological determination of the presence of particulate material on Safranin-stained blood smears and determination of plasma concentration of Ti by ICP-MS RESULTS: Different size and shape metal-like particles were observed inside and outside epithelial cells in TiO₂-NP5 and TiO₂-MP45 cytological smears at both one and six months post-injection. EDS analysis showed the presence of Ti in the particles. ICP-MS revealed higher Ti concentrations in both TiO₂ injected groups compared to the control group. In addition, Ti concentration did not vary with time or particle size. Monocytes containing particles were observed in blood smears of TiO₂-exposed animals one- and six-months post-injection. Plasma levels of Ti were significantly higher in TiO₂-NP5- and TiO₂-MP45- exposed animals than in controls (p < 0.05), and Ti concentration was significantly higher at one month than at six months in both TiO₂-exposed groups (p < 0.05).

CONCLUSIONS

Cells exfoliated from the oral mucosa could be used as bioindicators of short- and long-term systemic contamination with Ti. Exfoliative cytology could be used as a simple, non-invasive, and inexpensive diagnostic method for monitoring biotribocorrosion of Ti implants and patient clinical follow-up.

A Biocompatible Ultrananocrystalline Diamond (UNCD) Coating for a New Generation of Dental Implants

Implant therapy using osseointegratable titanium (Ti) dental implants has revolutionized clinical dental practice and has shown a high rate of success. However, because a metallic implant is in contact with body tissues and fluids in vivo, ions/particles can be released into the biological milieu as a result of corrosion or biotribocorrosion. Ultrananocrystalline diamond (UNCD) coatings possess a synergistic combination of mechanical, tribological, and chemical properties, which makes UNCD highly biocompatible. In addition, because the UNCD coating is made of carbon (C), a component of human DNA, cells, and molecules, it is potentially a highly biocompatible coating for medical implant devices. The aim of the present research was to evaluate tissue response to UNCD-coated titanium micro-implants using a murine model designed to evaluate biocompatibility. Non-coated (n = 10) and UNCD-coated (n = 10) orthodontic Ti micro-implants were placed in the hematopoietic bone marrow of the tibia of male Wistar rats. The animals were euthanized 30 days post implantation. The tibiae were resected, and ground histologic sections were obtained and stained with toluidine blue. Histologically, both groups showed lamellar bone tissue in contact with the implants (osseointegration). No inflammatory or multinucleated giant cells were observed. Histomorphometric evaluation showed no statistically significant differences in the percentage of BIC between groups (C: 53.40 ± 13% vs. UNCD: 58.82 ± 9%, p > 0.05). UNCD showed good biocompatibility properties. Although the percentage of BIC (osseointegration) was similar in UNCD-coated and control Ti micro-implants, the documented tribological properties of UNCD make it a superior implant coating material. Given the current surge in the use of nano-coatings, nanofilms, and nanostructured surfaces to enhance the biocompatibility of biomedical implants, the results of the present study contribute valuable data for the manufacture of UNCD coatings as a new generation of superior dental implants.

An integrated benefit-risk assessment of cobalt-containing alloys used in medical devices: Implications for regulatory requirements in the European Union

In 2017, the European Union (EU) Committee for Risk Assessment (RAC) recommended the classification of metallic cobalt (Co) as Category 1B with respect to its carcinogenic and reproductive hazard potential and Category 2 for mutagenicity but did not evaluate the relevance of these classifications for patients exposed to Co-containing alloys (CoCA) used in medical devices. CoCA are inherently different materials from Co metal from a toxicological perspective and thus require a separate assessment. CoCA are biocompatible materials with a unique combination of properties including strength, durability, and a long history of safe use that make them uniquely suited for use in a wide-range of medical devices. Assessments were performed on relevant preclinical and clinical carcinogenicity and reproductive toxicity data for Co and CoCA to meet the requirements under the EU Medical Device Regulation triggered by the ECHA re-classification (adopted in October 2019 under the 14th Adaptation to Technical Progress to CLP) and to address their relevance to patient safety. The objective of this review is to present an integrated overview of these assessments, a benefit-risk assessment and an examination of potential alternative materials. The data support the conclusion that the exposure to CoCA in medical devices via clinically relevant routes does not represent a hazard for carcinogenicity or reproductive toxicity. Additionally, the risk for the adverse effects that are known to occur with elevated Co concentrations (e.g., cardiomyopathy) are very low for CoCA implant devices (infrequent reports often reflecting a unique catastrophic failure event out of millions of patients) and negligible for CoCA non-implant devices (not measurable/no case reports). In conclusion, the favorable benefit-risk profile also in relation to possible alternatives presented herein strongly support continued use of CoCA in medical devices.

Pseudotumors in Total Joint Arthroplasty

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The true incidence of pseudotumors in association with total joint arthroplasty is underestimated.

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Pseudotumors occur with metal-on-metal, metal-on-polyethylene, and metal-on-ceramic articulations.

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Metal ion levels should not be the only factor in decision-making regarding revision surgery.

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Revision surgery is only indicated in symptomatic patients with clinical and radiographic findings and elevated metal ion levels.

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Revision to a non-metal articulation is strongly suggested.

Titanium dental implant-related pathologies: A retrospective histopathological study

OBJECTIVES

To perform a retrospective, descriptive, histopathological study of peri-implant tissue pathologies associated with titanium dental implants (TDI), and to evaluate the presence of metallic particles in samples from a single diagnostic center.

METHODS

Sixty-eight cases of TDI-associated lesions were retrieved from the Surgical Pathology Laboratory archives, School of Dentistry, University of Buenos Aires (UBA) (1990-2018). The study included re-examining the histopathological features of the biopsy samples, analyzing the inflammatory infiltrate, and examining the samples to detect metallic particles whose chemical composition was determined spectrophotometrically (EDS). Available clinical and radiographic data were also reviewed.

RESULTS

The retrieved cases ranged from lesions of inflammatory origin to neoplastic lesions. Metallic particles were observed in 36 cases (52.9%), all of which showed inflammation. Particle length ranged from 2 to 85µm. EDS analysis of the particles/deposits observed in the tissues showed the presence of aluminum, titanium, iron, and nickel, among other elements.

CONCLUSIONS

A significant number of TDI-associated lesions, including cases not reported to date and diagnosed at a single diagnostic center, are shown here. Cases showing particles exhibited an inflammatory response, irrespective of the histopathological diagnosis. The role of metallic particles in the development of TDI-associated lesion is yet to be established.

Implant-derived CoCrMo alloy nanoparticle disrupts DNA replication dynamics in neuronal cells

The complexity of cobalt-chromium-molybdenum (CoCrMo) nanoparticles generated from the hip modular taper interfaces resulted in inconclusive outcomes on the level of toxicity in orthopedic patients. We used a hip simulator to generate physiologically relevant CoCrMo degradation products (DPs) to demonstrate the variation in the level of toxicity in neurons in comparison to processed degradation products (PDPs). The study outcomes indicate that DP induces a higher level of DNA damage in the form of double- and single-stranded DNA breaks and alkaline labile DNA adducts versus PDPs. The scientific advancements of this study are the following: (i) how DPs mimic more closely to the implant debris from hip implants in terms of bioactivity, (ii) how hip implant debris causes local and systemic issues, and (iii) methods to augment the biologic impact of implant debris. We discovered that DP is bioactive compared with PDP, and this should be considered in the toxicity evaluation related to implants. • The physicochemical characteristics of the CoCrMo is a major factor to consider for implant-related cytotoxicity or genotoxicity experimental design. • Elevated levels of intracellular ROS induced by the physiologically relevant wear particle are detrimental to the neuronal cells. • The DP can induce variation in DNA replication dynamics compared to PDP.

Genotoxic properties of materials used for endoprostheses: Experimental and human data

Approximately 2 million endoprostheses are implanted annually and metal ions as well as particles are released into the body from the materials which are used. This review describes the results of studies concerning genotoxic damage caused by artificial joints. DNA damage leads to various adverse long-term health effects in humans including cancer. Experiments with mammalian cells showed that metal ions and particles from orthopedic materials cause DNA damage. Induction of chromosomal aberrations (CA) was found in several in vitro experiments and in studies with rodents with metals from orthopedic materials. Human studies focused mainly on induction of CA (7 studies). Only few investigations (4) concerned sister chromatid exchanges, oxidative DNA damage (2) and micronucleus formation (1). CA are a reliable biomarker for increased cancer risks in humans) and were increased in all studies in patients with artificial joints. No firm conclusion can be drawn at present if the effects in humans are due to oxidative stress and if dissolved metal ions or release particles play a role. Our findings indicate that patients with artificial joints may have increased cancer risks due to damage of the genetic material. Future studies should be performed to identify safe materials and to study the molecular mechanisms in detail.

No generally increased risk of cancer after total hip arthroplasty performed due to osteoarthritis

Previous studies on the risk of cancer after total hip arthroplasty (THA) contradict each other, and many are hampered by small cohort sizes, residual confounding, short observation times or a mix of indications underlying the THA procedure. We evaluated the risk of cancer after total hip arthroplasty due to osteoarthritis in a nationwide cohort by comparing cancer incidences in individuals exposed to total hip arthroplasty due to osteoarthritis and in unexposed, sex-, age- and residence matched individuals. To address some previous studies' shortcomings, information on comorbidity and socioeconomic background were obtained and adjusted for. We included 126,276 patients exposed to a cemented THA between 1992 and 2012, and 555,757 unexposed individuals. Follow-up started on the day of surgery for exposed individuals and respective date for matched, unexposed individuals, and ended on the day of death, emigration, censuring or December 31st, 2012, whichever came first. The Swedish Hip Arthroplasty Registry (SHAR), the Swedish Cancer Registry, the Swedish National Patient Registry and Statistics Sweden were accessed to obtain information on procedural details of the THA, cancer diagnoses, comorbidities, and socioeconomic background. The primary outcome measure was the occurrence of any cancer after the index date. Exposed individuals had a slightly lower adjusted risk of developing any cancer than unexposed individuals (hazard ratio [HR] 0.97; CI 0.95-0.99). The only cancer with a statistically significant risk increase in exposed individuals was skin melanoma (HR 1.15; CI 1.05-1.24). We attained similar risk estimates in analyses stratified by sex, in individuals with minimum 5 years of follow-up, in an analysis including individuals with a history of previous cancer, and in patients with cementless THA. In this study on a large and well-defined population with long follow-up, we found no increased overall risk of cancer after THA. These reassuring findings could be included in the guidelines on preoperative information given to THA patients.

Midterm risk of cancer with metal-on-metal hip replacements not increased in a Finnish population

Background and purpose - Metal-on-metal (MoM) total hip arthroplasty (THA) and hip resurfacing arthroplasty (HRA) have been widely used during the early 21st century. We assessed the midterm risk of cancer of patients treated with modern MoM hip implants compared with patients with non-MoM hip implants and the general Finnish population with special interest in soft tissue sarcomas and basalioma due to the findings of our previous report. Patients and methods - All large-diameter head MoM THAs and hip resurfacings performed in Finland between 2001 and 2010 were extracted from the Finnish Arthroplasty Register (10,728 patients). Patients who underwent conventional THA formed the non-MoM reference cohort (18,235 patients). Data on cancer cases up to 2014 were extracted from the Finnish Cancer Registry. The relative risk of cancer in the general population was expressed as the ratio of observed to expected number of cases, i.e., standardized incidence ratio (SIR). Poisson regression analysis was used to compare the cancer risk between the cohorts. The mean follow-up was 7.4 years (1-14) in the MoM cohort and 8.4 years (1-14) in the non-MoM cohort. Results - The overall risk of cancer in the MoM cohort was comparable to the general Finnish population (SIR 0.9, 95% CI 0.9-1.0). Risk of basalioma in the MoM cohort was higher than in the general Finnish population (SIR 1.2, CI 1.1-1.4) and higher than in the non-MoM cohort in the stratified regression analysis (RR 1.2, CI 1.0-1.4, p = 0.02). The SIR of soft-tissue sarcoma in the MoM cohort was 1.4 (CI 0.6-2.8); the incidence was same as in the non-MoM cohort. Interpretation - Metal-on-metal hip implants are not associated with an increased overall risk of cancer during midterm follow-up.

Long-term Formation of Aggressive Bony Lesions in Dogs with Mid-Diaphyseal Fractures Stabilized with Metallic Plates: Incidence in a Tertiary Referral Hospital Population

The incidence of complications secondary to fracture stabilization, particularly osteolytic lesions and bony tumor formation, has long been difficult to evaluate. The objective of this study was to describe the long-term incidence of aggressive bony changes developing in dogs with long bone diaphyseal fractures stabilized by metallic bone plates compared to a breed-, sex-, and age-matched control group. The medical records of a tertiary referral center were retrospectively reviewed for dogs that matched each respective criterion. Signalment, history, cause of death (if applicable), and aggressive bony changes at previous fracture sites were recorded. Ninety dogs met the criteria for inclusion in the fracture group and were matched with appropriate control dogs. Four of the dogs in the fracture group developed aggressive bony changes at the site of previous fracture repairs most consistent with osseous neoplasia. One lesion was confirmed with cytology as neoplastic. The population of dogs was mixed with regard to breed and body weight, but all dogs with aggressive bony lesions were male. Incidence of aggressive bony lesion formation in the fracture group was 4 (4.4%) and was 0 (0%) in the control group; three (75%) of the affected dogs in the fracture group included cerclage as a component of their primary fracture stabilizations. Incidence of aggressive bony lesions in the fracture group compared to the control group was determined to be statistically significant (p = 0.0455), as was the incidence of cerclage among dogs affected by aggressive bony lesions compared to the rest of the fracture group (p = 0.0499). Development of aggressive bony lesions is an uncommon complication of fracture fixation. Additional research is needed to further identify and elucidate the long-term effects of metallic implants in dogs.

Implant-associated neoplasia in dogs: 16 cases (1983-2013)

OBJECTIVE

To characterize clinical and pathological features of implant-associated neoplasms in dogs.

DESIGN

Retrospective case-control study.

ANIMALS

16 dogs with implant-associated neoplasia and 32 control dogs with osteosarcoma without implants. Procedures: Medical records of dogs with tumors associated with metallic implants (cases) treated between 1983 and 2013 were reviewed. Two dogs with naturally occurring osteosarcoma (controls) were matched to each case on the basis of tumor location, age, and sex.

RESULTS

Median time from implant placement to diagnosis of neoplasia was 5.5 years (range, 9 months to 10 years). Pelvic limbs were most frequently affected, including the tibia (8/16) and femur (5/16), with 1 neoplasm involving both the femur and pelvis. Implant: associated tumors most commonly affected the diaphysis (15/16), with osteosarcomas significantly more likely to involve the long bone diaphysis in case dogs than in control dogs with naturally occurring osteosarcomas. Osteosarcoma was the most common tumor, accounting for 13 of 16 implant-associated tumors. For 7 of these osteosarcoma cases, review of histopathology results enabled subclassification into osteoblastic nonproductive (n = 3), chondroblastic (2), osteoblastic productive (1), and fibroblastic (1) groups. Three case dogs had a diagnosis of histiocytic sarcoma, fibrosarcoma, and spindle cell sarcoma.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of this study highlighted important anatomic differences between spontaneous and implant-associated neoplasia in dogs.

Lessons learnt from metal-on-metal hip arthroplasties will lead to safer innovation for all medical devices

Metal-on-metal bearings were re-popularised in the late 1990s with the introduction of modern hip resurfacing. Large diameter (LD) metal-on-metal (MoM) hips became more prevalent and have been the least successful group of hip implants ever used. They were rapidly adopted from 2004 until the British Hip Society stopped their use in 2012. Well functioning MoM hip results (including the BHR and Metasul) are hidden in the mire of poor results from the group of all MoM bearings.We have reviewed what happened and we make 3 observations. Firstly, collaboration between surgeons and then between surgeons and other disciplines, first identified and then solved the clinical management problems. Secondly, the problems with MoM hips occurred because hip simulation was inadequate at predicting performance in patients. They gave no indications of the biological effects of wear in the human environment. Lastly, retrieval of failed implants was essential to understanding why failure occurred.These lessons must never be forgotten and must form the basis by which new or altered implants are introduced and how they should be monitored. This will enable safer innovation for patients, surgeons and manufacturers. The problems with MoM hips will not have been in vain.

Metal-on-polyethylene versus metal-on-metal bearing surfaces in total hip arthroplasty

The long term biological effects of wear products following total hip arthroplasty (THA) are unclear. However, the indications for THA are expanding, with increasingly younger patients undergoing the procedure.

This prospective, randomised study compared two groups of patients undergoing THA after being randomised to receive one of two different bearing surfaces: metal-on-polyethylene (MoP) n = 22 and metal-on-metal (MoM) n = 23. We investigated the relationship between three variables: bearing surface (MoP vs MoM), whole blood levels of chromium (Cr) and cobalt (Co) and chromosomal aberrations in peripheral lymphocyte pre-operatively and at one, two and five years post-surgery.

Our results demonstrated significantly higher mean cobalt and chromium (Co and Cr) blood levels in the MoM group at all follow-up points following surgery (p < 0.01), but there were no significant differences in the chromosomal aberration indices between MoM and MoP at two or five years (two years: p = 0.56, p = 0.08, p = 0.91, p = 0.51 and five years: p = 0.086, p = 0.73, p = 0.06, p = 0.34) for translocations, breaks, loss and gain of chromosomes respectively. Regression analysis showed a strong linear relationship between Cr levels and the total chromosomal aberration indices in the MoM group (R2 = 0.90016), but this was not as strong for Co (R2 = 0.68991). In the MoP group, the analysis revealed a poor relationship between Cr levels and the total chromosomal aberration indices (R2 = 0.23908) but a slightly stronger relationship for Co (R2 = 0.64292). Across both groups, Spearman’s correlation detected no overall association between Co and Cr levels and each of the studied chromosomal aberrations. There remains no clear indication which THA bearing couple is the most biocompatible, especially in young active patients. While THA continues to be very successful at alleviating pain and restoring function, the long-term biological implications of the procedure still require further scrutiny.

Cite this article: Bone Joint J 2015;97-B:1183–91.

Primary Lymphoma of Bone Complicating Total Knee Arthroplasty: An Unexpected Mode of Prosthesis Failure: A Case Report

CASE

Primary lymphoma of bone is a rare musculoskeletal malignancy that typically arises in long bones. Few cases of bone lymphoma occurring alongside orthopaedic implants have been reported in the literature. We describe the complex case of a seventy-eight-year-old woman who developed diffuse large B-cell lymphoma of the proximal part of the tibia five years after a successful total knee arthroplasty.

CONCLUSION

Several studies have suggested a link between orthopaedic implants and genomic instability, although true carcinogenesis remains questionable. Lymphoma complicating joint arthroplasty poses a unique problem for orthopaedic physicians due to diagnostic challenges and the unique implications of disease and treatment-related complications.

Cancer incidence and cause-specific mortality in patients with metal-on-metal hip replacements in Finland

BACKGROUND AND PURPOSE

Metal-on-metal hip implants have been widely used, especially in the USA, Australia, England and Wales, and Finland. We assessed risk of death and updated data on the risk of cancer related to metal-on-metal hip replacements.

PATIENTS AND METHODS

A cohort of 10,728 metal-on-metal hip replacement patients and a reference cohort of 18,235 conventional total hip replacement patients were extracted from the Finnish Arthroplasty Register for the years 2001-2010. Data on incident cancer cases and causes of death until 2011 were obtained from the Finnish Cancer Registry and Statistics Finland. The relative risk of cancer and death were expressed as standardized incidence ratio (SIR) and standardized mortality ratio (SMR). SIR/SIR ratios and SMR/SMR ratios, and Poisson regression were used to compare the cancer risk and the risk of death between cohorts.

RESULTS

The overall risk of cancer in the metal-on-metal cohort was not higher than that in the non-metal-on-metal cohort (RR = 0.91, 95% CI: 0.82-1.02). The risk of soft-tissue sarcoma and basalioma in the metal-on-metal cohort was higher than in the non-metal-on-metal cohort (SIR/SIR ratio = 2.6, CI: 1.02-6.4 for soft-tissue sarcoma; SIR/SIR ratio = 1.3, CI: 1.1-1.5 for basalioma). The overall risk of death in the metal-on-metal cohort was less than that in the non-metal-on-metal cohort (RR = 0.78, CI: 0.69-0.88).

INTERPRETATION

The overall risk of cancer or risk of death because of cancer is not increased after metal-on-metal hip replacement. The well-patient effect and selection bias contribute substantially to the findings concerning mortality. Arthrocobaltism does not increase mortality in patients with metal-on-metal hip implants in the short term. However, metal-on-metal hip implants should not be considered safe until data with longer follow-up time are available.

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

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

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

OBJECTIVE

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

DESIGN

Population based study.

SETTING

Nationwide retrospective comparative register.

PARTICIPANTS

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

MAIN OUTCOME MEASURES

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

RESULTS

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

CONCLUSIONS

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

New insights into wear and biological effects of metal-on-metal bearings

BACKGROUND

Despite the renewed interest in metal-on-metal implants in the past two decades, the underlying wear mechanisms and biological effects are still not fully understood.

METHODS

This paper first reviews the tribology of metal-on-metal bearings, bringing new insights into the interaction of wear and corrosion, and putting the characteristics and the potential origin of wear particles in perspective with the proposed wear mechanisms. It then summarizes the current knowledge on the biological effects of particles and metal ions in relation to these wear mechanisms.

RESULTS

Tribochemical reactions play an important role in the wear of metal-on-metal joints. The generated tribomaterial, which progressively forms by mechanical mixing of the uppermost nanocrystalline zone of the metal surface with proteins from the synovial fluid, governs the wear rate and influences the corrosive behavior of the bearing. Nanometer-sized wear particles may initially originate from the passivation layer covering the implant surface and then detach from this tribolayer. The inflammatory response observed surrounding metal-on-metal implants appears to be lower than that around metal-on-polyethylene implants. However, metallic byproducts, which can complex with proteins, may lead to a T lymphocyte-mediated hypersensitivity response.

CONCLUSIONS

The tribolayer appears to have beneficial effects on the wear rate. Much information has been gained on wear particle characteristics, but the exact mechanisms of particle detachment remain to be further elucidated. Excessive wear along with a hypersensitivity response may be at the origin of the early adverse tissue reactions that have been recently reported in some patients with metal-on-metal implants.

Histological and Ultrastructural Reaction to Different Materials for Orthopaedic Application

Prosthetic joints loosening in absence of infection is the most common reason for revision surgery and is known as aseptic loosening. A significant role in the pathogenesis of implant failure undoubtedly played by the generation of wear debris, mainly from the load bearing joint surfaces, and the cellular reaction through the formation of tissue membrane around implants. This article analyzes histologic, immunohistochemical ad ultrastructural aspects of periprosthetic tissue membrane collected at time of surgical revision, paying attention on cell host response to different materials: metals, polyethylene and ceramics. Dimension of particles seems to be crucial in the activation of different cell population to wear debris.

Diffuse large B cell lymphoma complicating total knee arthroplasty: case report and literature review of the association of diffuse large B cell lymphoma with joint replacement

Primary lymphoma of bone is extremely rare. There are increasing reports of lymphoma arising in bone adjacent to metallic prostheses. Herein, we describe the case of a 76-year-old man who developed diffuse large B cell lymphoma in the tibia 3 years after total knee arthroplasty for osteoarthritis. A review of the literature has identified 11 other cases of lymphoma arising in the context of orthopaedic metallic implants. To our knowledge this is the first reported case of a primary lymphoma arising in bone adjacent to a knee prosthesis. Possible pathogenetic mechanisms may include chronic antigenic stimulation of lymphocytes, proliferation of EBV-infected B lymphocytes, and direct mutagenic effects of metallic ions. Further research is required to investigate this intriguing link between metallic orthopaedic prostheses and localized lymphoma.

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

BACKGROUND AND PURPOSE

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

METHOD

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

RESULTS

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

INTERPRETATION

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

A retrospective comparative study of mortality and causes of death among patients with metal-on-metal and metal-on-polyethylene total hip prostheses in primary osteoarthritis after a long-term follow-up

Background

All patients with total hip arthroplasty (THA), especially those with metal-on-metal (MM) THA, are exposed to metallic particles and ions, which may cause total or site-specific mortality. We analyzed the causes of total and site-specific mortality among a cohort of patients with MM and with metal-on-polyethylene (MP) THA after a long follow-up time.

Methods

Standardized mortality ratios (SMR) of total and site-specific causes of death were calculated for 579 patients with MM (McKee-Farrar) and 1585 patients with MP (Brunswik, Lubinus) THA for primary osteoarthritis.

Results

Mean follow-up time was 17.9 years for patients with MM and 16.7 years for patients with MP. Overall SMR was 0.95 for the MM cohort and 0.90 for the MP cohort, as compared to the normal population. Both cohorts showed significantly decreased mortality for the first decade postoperatively, equal mortality over the next 10 years, and significantly increased mortality after 20 years. Patients with MM THA had higher cancer mortality (SMR 1.01) than those with MP THA (SMR 0.66) during the first 20 years postoperatively, but not thereafter.

Conclusion

Both MM and MP prostheses are safe based on total and site-specific mortality of recipients during the first 20 postoperative years in comparison with the general population.

Cancer risk is not increased after conventional hip arthroplasty

BACKGROUND AND PURPOSE

Wear debris from conventional total hip arthroplasty (THA) induces chromosomal aberrations and DNA damage, which may promote cancerogenesis. A long latent period is required for solid tumors. We therefore re-analyzed a large THA cohort for cancer.

PATIENTS AND METHODS

We updated a cohort of 24,636 patients with primary osteoarthritis and metal-on-polyethylene THA who had been entered in the Finnish Arthroplasty Register between 1980 and 1995, and linked it to the Finnish Cancer Registry for cancer risk assessment up to 2005. The mean follow-up time was 13 years. The numbers of cancer cases observed were compared with expected rates based on incidence in the general population.

RESULTS

The standardized incidence ratio (SIR) for the whole follow-up period was 0.95 (95% confidence interval (CI): 0.92-0.97). After 10 years of follow-up, the SIR was equal to that in the normal population (SIR = 0.98, 95% CI: 0.94-1.03). Incidence of lung cancer was low throughout the follow-up time and that of prostate cancer was slightly elevated. The incidence rates for all other forms of cancer did not deviate significantly from those in the normal population.

INTERPRETATION

We found no increased cancer risk in patients with conventional THA after an average of 13 years and up to 25 years of follow-up.

Elevated serum concentrations of cobalt, chromium, nickel, and manganese after metal-on-metal alloarthroplasty of the hip: a prospective randomized study

In this prospective randomized study, we investigate metal ion concentrations and clinical outcome 2 years after metal-on-metal (28 patients) or metal-on-polyethylene (26 patients) hip arthroplasty with 28-mm modular heads. Metal ion concentrations in patient serum were analyzed by high-resolution plasma mass spectrometry. The clinical outcome was almost identical in both groups with respect to the Harris hip score and the Medical Outcome Study Short Form-36; and on plain radiography, no signs of loosening occurred in any group. In the metal-on-metal group, concentrations of all investigated ions increased significantly when compared with preoperative values: cobalt, 15.3-fold (95% confidence interval [CI], 9.4-21.2); chromium, 5.2-fold (CI, 3.5-7.0); nickel, 2.1-fold (CI, 1.2-3.0); and manganese, 1.6-fold (CI, 1.3-2.0). In the metal-on-polyethylene group, a smaller but significant increase in the concentrations of cobalt and nickel occurred, whereas concentrations of the other ions did not change significantly.

Metal-on-metal hip resurfacing arthroplasty: a review of periprosthetic biological reactions

Metal-on-metal hip resurfacing arthroplasty has undergone a recent resurgence as an alternative treatment option for young and active patients with significant osteoarthritis. The claimed advantages of metal-on-metal hip resurfacing arthroplasty include lower wear rate, preservation of bone stock for subsequent revision procedures, restoration of anatomic hip mechanics, and enhanced stability due to the larger diameter of articulation. A disadvantage, however, is that the metal-on-metal resurfacing releases large amounts of very small wear particles and metal ions. The long-term biological consequences of the exposure to these Co-Cr particles and ions remain largely unknown. The purpose of this review is to provide an overview of the current literature on the adverse periprosthetic biological reactions associated with metal-on-metal hip resurfacing arthroplasty.

Macrophages detoxify the genotoxic and cytotoxic effects of surgical cobalt chrome alloy particles but not quartz particles on human cells in vitro

Particles of surgical cobalt chrome alloy are cytotoxic and genotoxic to human fibroblasts in vitro. In vivo orthopaedic patients are exposed to cobalt chrome particles as a result of wear of a joint replacement. Many of the wear debris particles that are produced are phagocytosed by macrophages that accumulate at the site of the worn implant and are disseminated to local and distant lymph nodes the liver and the spleen. In this study we have tested whether this process of phagocytosis could have altered the cytotoxic and genotoxic properties of the cobalt chrome particles. Quartz particles have been investigated as a control. Micron-sized particles of cobalt chrome alloy were internalised by either white cells of peripheral blood or by THP-1 monocytes for 1 week and 1 day, respectively. The particles were then extracted and presented at different doses to fibroblasts for 1 day. There was a reduction of the cytotoxicity and genotoxicity of the cobalt chrome particles after phagocytosis by white cells or THP-1 cells. Cobalt chrome particles that were internalised by fibroblasts also showed a reduction of their cytotoxicity but not their genotoxicity. In contrast the cytotoxicity and genotoxicity of quartz particles was increased after internalisation by THP-1 cells. The surface morphology of the cobalt chrome particles but not the quartz particles was changed after phagocytosis by THP-1 cells. This study suggests that the genotoxic and cytotoxic properties of particles that fall within the size range for phagocytosis may be highly complex in vivo and depend on the combination of material type and previous phagocytosis. These results may have relevance for particle exposure from orthopaedic implants and from environmental or industrial pollution.

Release of chromium from orthopaedic arthroplasties

Many orthopaedic implants are composed of alloys containing chromium. Of particular relevance is the increasing number of Cobalt Chromium bearing arthroplasies being inserted into young patients with osteoarthritis. Such implants will release chromium ions. These patients will be exposed to the released chromium for over 50 years in some cases. The subsequent chromium ion metabolism and redistribution in fluid and tissue compartments is complex. In addition, the potential biological effects of chromium are also controversial, including DNA and chromosomal damage, reduction in CD8 lymphocyte levels and possible hypersensitivity reactions (ALVAL). The establishment of these issues and the measurement of chromium in biological fluids is the subject of this review.

Malignant fibrous histiocytoma associated with coxofemoral arthrodesis

The discovery of biomaterials led to their use in the manufacture of implants for biomedical applications. In vivo, no metal or alloy is completely inert. The potential toxicity of some of the metals most frequently employed in the manufacture of orthopedic implants has been reported. Their carcinogenic potential has been evaluated in experimental animal models. However, few reports have discussed the potential development of malignant tumors associated with prosthetic structures in humans. The present study documents a case of intraosseous sarcoma that developed in the vicinity of a metallic prosthesis 43 months after a coxofemoral arthrodesis with metallic pins and screws. With this report the authors seek to contribute to the understanding of the potential toxicity and risks of using metallic implants. Since metallic implants employed in the rehabilitation of osteo-muscular-articular disorders usually remain in the organism for long periods of time, the need to monitor the metallic structures and the adjacent tissues is extremely relevant.

Can cobalt levels estimate in-vivo wear of metal-on-metal bearings used in hip arthroplasty?

High levels of cobalt and chromium ions are detected in the blood and urine of patients with metal-on-metal (MoM) hip replacement. These elements are released as a result of wear at the bearing surfaces. Wear rates depend on a multitude of factors, which include the bearing geometry, carbon content, manufacturing processes, lubrication, speed and direction of sliding of the surfaces, pattern of loading, and orientation of the components. In-vivo wear of MoM bearings cannot be reliably measured on X-rays because no distinction can be made between the bearing surfaces. Hip simulator studies have shown that wear rates are higher during the initial bedding-in phase and subsequently drop to very low levels. Accordingly, metal ion levels would be expected to decrease with the use of the bearing, measured as implantation time following surgery. However, several clinical studies have found that metal ion levels either gradually rise or fluctuate instead of decreasing to lower levels. Moreover, hip simulator studies predict that large-diameter bearings have lower wear rates than small-diameter bearings. In clinical studies, however, metal levels in patients with large-diameter bearings are unexpectedly higher than those in patients with small-diameter bearings.

As a consequence, high cobalt ion levels in patients do not necessarily imply that their MoM bearings produce much wear debris at the time that their levels were measured; it may simply be due to accumulation of wear debris from the preceding time. Exercise-related cobalt rise may overcome this limitation and give a better assessment of the current wear status of a MoM bearing surface than a measure of cobalt levels only.

The effect of nano- and micron-sized particles of cobalt–chromium alloy on human fibroblasts in vitro

Wear debris from metal on polyethylene joint replacements causes asceptic loosening as a result of an inflammatory reaction of macrophages to micron-sized particles. Metal on metal implants, which generate nanoparticles, have been reintroduced into surgical practise in order to avoid this problem. There is a current concern about possible long-term effects of exposure to metal particles. In this study, the cytotoxic and genotoxic effects of nanoparticles and micron-sized particles of cobalt chrome alloy have been compared using human fibroblasts in tissue culture. Nanoparticles, which caused more free radicals in an acellular environment, induced more DNA damage than micron-sized particles using the alkaline comet assay. They induced more aneuploidy and more cytotoxicity at equivalent volumetric dose. Nanoparticles appeared to disintegrate within the cells faster than microparticles with the creation of electron dense deposits in the cell, which were enriched in cobalt. The mechanism of cell damage appears to be different after exposure to nanoparticles and microparticles. The concept of nanotoxicology is, therefore, an important consideration in the design of future surgical devices.

Characterisation of wear particles produced by metal on metal and ceramic on metal hip prostheses under standard and microseparation simulation

The failure of metal on polyethylene total hip replacements due to wear particle induced osteolysis and late aseptic loosening has focused interest upon alternative bearings, such as metal on metal implants. A recent advance in this field has been the development of a novel ceramic on metal implant. The characteristics of the wear particles generated in this low-wearing bearing have not been previously determined. The aims of this study were to characterise metal wear particles from metal on metal and ceramic on metal hips under standard and adverse (microseparation) wear conditions. Accurate characterisation of cobalt-chrome wear particles is difficult since the reactive nature of the particles prevents them from being isolated using acids and bases. A method was developed to isolate the metal wear particles using enzymes to digest serum containing lubricants from metal on metal and ceramic on metal hip simulations. High resolution scanning electron microscopy was then used to characterise the wear particles generated by both metal on metal and ceramic on metal implants under standard and microseparation wear conditions. The wear particles isolated from all simulations had a mean size of less than 50 nm with a rounded and irregular morphology. No significant difference was found between the size of wear particles generated under any conditions.

Genotoxic effects of particles of surgical cobalt chrome alloy on human cells of different age in vitro

Humans are exposed to metals from industry, the environment and from wear debris from worn orthopaedic joint replacements. Patients exposed to worn cobalt chrome hip replacements show an increase of chromosome aberrations in the bone marrow adjacent to the implant and an increase of chromosome translocations and aneuploidy in the peripheral blood. This study has tested whether particles of surgical cobalt chrome alloy are able to induce similar DNA damage and chromosome aberrations in human cells in vitro. Because increasingly young patients are receiving hip replacements it has also tested whether the response is altered at different cellular age in vitro. Primary human fibroblasts, were tested at different pre senescent population doublings (PD10 (young) and PD35 (older)) to particles of cobalt chrome alloy for up to 15 days. As in patients there was an increase of aneuploidy, chromosome translocations and DNA damage after exposure to the cobalt chrome particles in vitro. The overall level of DNA damage and numerical and structural aberrations was approximately the same in young and older cells. However, the cellular reaction to the DNA damage was different. Older cells showed a greater loss of viability and induction of senescence and a lesser rate of mitosis and cell growth than young cells. They showed less change in transcription, particularly of p38 and caspase 10 mRNA levels, than young cells. They showed more complex aneuploidy in association with unseparated or prematurely separated chromatids. This study suggests that at least part of the chromosome changes in patients with worn implants may be due to direct effects of the metal wear particles from the implant. It would be of interest to test whether the altered reaction of the human cells at different in vitro age might correspond with a different incidence of chromosome aberrations in patients at different ages.

Beyond foreign-body-induced carcinogenesis: Impact of reactive oxygen species derived from inflammatory cells in tumorigenic conversion and tumor progression

Foreign-body-induced carcinogenesis is a traditional, maybe old, way of understanding cancer development. A number of novel approaches are available today to elucidate cancer development. However, there are things we learn from the old, and thus I bring out some examples of various clinical cases and experimental models of foreign-body-induced tumorigenesis. What is notable is that the foreign bodies themselves are unrelated to each other, whereas commonly underlying in them is to induce inflammatory reaction, especially stromal proliferation, where those exogenous materials are incorporated and undigested. Such foreign-body-induced carcinogenesis is also recognized in the step of tumor progression, the final step of carcinogenesis that tumor cells acquire malignant phenotypes including metastatic properties. And the phenomenon is universally observed in several cell lines of different origins. In this review I would like to show the evidence that tumor development and progression are accelerated inevitably by inflammation caused from foreign bodies, and that reactive oxygen species derived from inflammatory cells are one of the most important genotoxic mediators to accelerate the process.

Biological effects of clinically relevant wear particles from metal-on-metal hip prostheses

The problems of osteolysis and late aseptic loosening associated with ultra-high molecular weight polyethylene (UHMWPE) particles has lead to a renewed interest in metal-on-metal prostheses. Wear particles generated by modern Co-Cr-on-Co-Cr prostheses are nanometre in size (range: 10-120 nm; mean: about 40 nm), an order of magnitude smaller than the size of UHMWPE known to be critical for activation of osteolytic cytokines by macrophages. Co-Cr wear particles will induce osteolytic cytokine production by human macrophages, but only at high volumetric concentrations. Unlike UHMWPE, Co-Cr particles are not inert. Co-Cr particles have the potential to release metal ions; they may be toxic to cells, induce deoxyribonucleic acid damage or cause host hypersensitivity. The nanometre size range of Co-Cr wear particles means that they may be disseminated widely in the body. The potential for metal-on-metal bearings to induce adverse effects clinically will be dependent upon the rate of wear. What constitutes a safe wear rate for modern metal-on-metal bearings is unknown. However, the wear of metal-on-metal prostheses is critically dependent upon the design and, in particular, the carbon content of the alloy, the radial clearance, and the head diameter. Thus, the potential for adverse biological reactions associated with metal-on-metal bearings can be reduced by selection of appropriately designed implants.