Orthopaedic metals and their potential toxicity in the arthroplasty patient

Early Failure of a Novel Modular Dual Mobility Liner After Metal Release: Clinical Presentation and Detailed Retrieval Analysis

Cobalt chrome alloy (CoCrMo) corrosion and subsequent metal release has been described as a potential complication of total hip arthroplasty. Here, we present the case of a patient with a well-seated dual mobility (DM) implant revised after 10 months. Prior to revision, the patient experienced pain and stiffness. Following a negative infection workup, we measured elevated metal concentrations, hypothesized to originate from the CoCrMo DM liner. While corrosion has been extensively reported in other constructs, the CoCrMo liner described here includes a post and tabs, features added to reduce the risk of corrosion. Retrieval analysis demonstrated a severe chemically based corrosion attack on the liner. Continued caution and ongoing close monitoring of outcomes associated with the use of modular DM constructs is likely warranted.

Metal-on-metal arthroplasty, cobalt toxicity, and development of cognitive impairment: a systematic review

BACKGROUND

Neurological dysfunction secondary to cobalt toxicity has been described as a potential complication of metal on metal (MoM) arthroplasty, however, to date the full extent of this association remains unclear. Currently, no national guideline on the management or follow-up of MoM arthroplasty patients recommends monitoring for potential insidious cognitive decline or long term consequences. The aim of this study was to summarise the available evidence regarding the relationship between MoM arthroplasty associated cobalt toxicity and cognitive impairment (CI).

METHODS

A systematic review of literature describing cobalt concentrations associated with neurocognitive symptoms in patients with MoM implants was undertaken. The study was registered with PROSPERO on the 18th July 2023 (CRD42023436880), in concordance with PRISMA guidelines. The Downs and Black Checklist assessed the risk of bias and evidence quality. Primary outcomes were reports of CI and blood cobalt concentration at presentation and following revision surgery.

RESULTS

Of 361 records identified, 15 relevant publications were included. Downs and Black Checklist assessment revealed that few high-quality studies currently exist. A clear association between MoM arthroplasty and CI, across varied follow up periods, was described by all 15 studies. Mean serum cobalt concentrations at presentation of CI were 9.75ug- 625ug, however no threshold cobalt concentration was identified. Over 85% of papers which recorded post-revision outcomes reported partial, if not complete, resolution of pre-operative CI following revision surgery.

CONCLUSIONS

This study provides the first robust systematic examination of the evidence surrounding metal on metal arthroplasty, cobalt toxicity, and potential CI. While further research is required to evaluate the exact nature of this relationship, our findings suggest that national and international guidelines should highlight the possible cognitive dysfunction secondary to MoM arthroplasty associated cobalt toxicity, including the need for routine assessment of cognitive function in those who received MoM implants.

Rethinking Biomedical Titanium Alloy Design: A Review of Challenges from Biological and Manufacturing Perspectives

Current biomedical titanium alloys have been repurposed from other industries, which has contributed to several biologically driven implant failure mechanisms. This review highlights the added value that may be gained by building an appreciation of implant biological responses at the onset of alloy design. Specifically, the fundamental mechanisms associated with immune response, angiogenesis, osseointegration and the potential threat of infection are discussed, including how elemental selection can modulate these pivotal systems. With a view to expedite inclusion of these interactions in alloy design criteria, methods to analyze these performance characteristics are also summarized. While machine learning techniques are being increasingly used to unearth complex relationships between alloying elements and material properties, much is still unknown about the correlation between composition and some bio-related properties. To bridge this gap, high-throughput methods are also reviewed to validate biological response along with cutting edge manufacturing approaches that may support rapid discovery. Taken together, this review encourages the alloy development community to rethink their approach to enable a new generation of biomedical implants intrinsically designed for a life in the body, including functionality to tackle biological challenges thereby offering improved patient outcomes.

Aggressive granulomatous pseudotumor following total hip prosthesis: Diagnostic and therapeutic strategies from a single institution experience

Introduction

Granuloma formation following total hip arthroplasty (THA) can occur regardless of the bearing surface. In very rare cases, extensive granulomas mimicking tumors may develop which are known as pseudotumors. The aim of this study is to report on these rare yet complex situations to stimulate reflection in diagnostic and therapeutic approaches.

Methods

A retrospective case series study of 5 patients (2 females, 3 males) of aggressive granulomatous lesions on primary prostheses and 4 revision prostheses for aseptic loosening, implanted at a mean age of 74.8 years (range 64-83). A clinical, functional, radiographic, and anatomopathological analysis were conducted.

Results

Four patients underwent revision surgery, while one died before intervention. Functional impairment was significant with a mean pre-reintervention Postel-Merle d'Aubigné (PMA) score of 8.2 (range 4-11). Femoral involvement was constant, associated with acetabular involvement in only one case. bony involvement was major, with a minimum of 5 Gruen zones affected, showing complete cortical lysis. Histopathological analysis consistently revealed multinucleated giant cells and macrophages, predominantly with metallic wear particles. In 2 cases, vascular involvement was suspected without a clearly delineated tumor. Two cases required femoral resection prostheses, one necessitated inter-ilio-abdominal amputation due to extensive soft tissue involvement, one underwent implant removal which failed to prevent progression, and one patient died before reoperation.

Conclusion

The volume of lesions in these 5 cases appears markedly larger than reported cases.Extensive pseudo-tumoral granulomatous lesions following THA are rare but carry poor functional prognosis. Evaluation to rule out infection and neoplastic pathology is imperative. Surgical management often resembling tumor treatment should be considered. Early diagnosis is crucial to allow intervention before reaching the stage of massive prosthetic replacement.

Level of evidence

IV retrospective study.

Possible Transformation of Pseudotumor to Synovial Sarcoma in a Failed Metal-on-Metal Total Hip Arthroplasty

Adverse local tissue reaction (ALTR) from the release of chromium and cobalt ions in metal-on-metal total hip arthroplasty (MoM THA) is a well-reported complication, but there is little evidence suggesting that this inflammatory reaction causes malignancy. We present a 69-year-old female with MoM THA who developed synovial sarcoma (SS). She underwent mass resection and revision THA. Postoperative pathologic analysis revealed the unanticipated diagnosis of SS. She subsequently underwent chemotherapy, sarcoma resection, and endoprosthetic reconstruction. We hypothesize that the SS developed from an ALTR in the setting of failed MoM THA. Given the paucity of data on possible malignant transformation of an ALTR to SS, we advise surgeons to consider potential malignancies when diagnosing ALTR in the setting of failed MoM THA bearings.

Long Noncoding RNA NR_030777 Alleviates Cobalt Nanoparticles-Induced Neurodegenerative Damage by Promoting Autophagosome-Lysosome Fusion

Potential exposure to cobalt nanoparticles (CoNPs) occurs in various fields, including hard alloy industrial production, the increasing use of new energy lithium-ion batteries, and millions of patients with metal-on-metal joint prostheses. Evidence from human, animal, and in vitro experiments suggests a close relationship between CoNPs and neurotoxicity. However, a systematic assessment of central nervous system (CNS) impairment due to CoNPs exposure and the underlying molecular mechanisms is lacking. In this study, we found that CoNPs induced neurodegenerative damage both in vivo and in vitro, including cognitive impairment, β-amyloid deposition and Tau hyperphosphorylation. CoNPs promoted the formation of autophagosomes and impeding autophagosomal-lysosomal fusion in vivo and in vitro, leading to toxic protein accumulation. Moreover, CoNPs exposure reduced the level of transcription factor EB (TFEB) and the abundance of lysosome, causing a blockage in autophagosomal-lysosomal fusion. Interestingly, overexpression of long noncoding RNA NR_030777 mitigated CoNPs-induced neurodegenerative damage in both in vivo and in vitro models. Fluorescence in situ hybridization assay revealed that NR_030777 directly binds and stabilizes TFEB mRNA, alleviating the blockage of autophagosomal-lysosomal fusion and ultimately restoring neurodegeneration induced by CoNPs in vivo and in vitro. In summary, our study demonstrates that autophagic dysfunction is the main toxic mechanism of neurodegeneration upon CoNPs exposure and NR_030777 plays a crucial role in CoNPs-induced autophagic dysfunction. Additionally, the proposed adverse outcome pathway contributes to a better understanding of CNS toxicity assessment of CoNPs.

Amorphous TiO2nano-coating on stainless steel to improve its biological response

This study delves into the potential of amorphous titanium oxide (aTiO2) nano-coating to enhance various critical aspects of non-Ti-based metallic orthopedic implants. These implants, such as medical-grade stainless steel (SS), are widely used for orthopedic devices that demand high strength and durability. The aTiO2nano-coating, deposited via magnetron sputtering, is a unique attempt to improve the osteogenesis, the inflammatory response, and to reduce bacterial colonization on SS substrates. The study characterized the nanocoated surfaces (SS-a TiO2) in topography, roughness, wettability, and chemical composition. Comparative samples included uncoated SS and sandblasted/acid-etched Ti substrates (Ti). The biological effects were assessed using human mesenchymal stem cells (MSCs) and primary murine macrophages. Bacterial tests were carried out with two aerobic pathogens (S. aureusandS. epidermidis) and an anaerobic bacterial consortium representing an oral dental biofilm. Results from this study provide strong evidence of the positive effects of the aTiO2nano-coating on SS surfaces. The coating enhanced MSC osteoblastic differentiation and exhibited a response similar to that observed on Ti surfaces. Macrophages cultured on aTiO2nano-coating and Ti surfaces showed comparable anti-inflammatory phenotypes. Most significantly, a reduction in bacterial colonization across tested species was observed compared to uncoated SS substrates, further supporting the potential of aTiO2nano-coating in biomedical applications. The findings underscore the potential of magnetron-sputtering deposition of aTiO2nano-coating on non-Ti metallic surfaces such as medical-grade SS as a viable strategy to enhance osteoinductive factors and decrease pathogenic bacterial adhesion. This could significantly improve the performance of metallic-based biomedical devices beyond titanium.

Cytotoxic effects and comparative analysis of Ni ion uptake by osteoarthritic and physiological osteoblasts

Nickel(Ni)-containing materials have been widely used in a wide range of medical applications, including orthopaedics. Despite their excellent properties, there is still a problem with the release of nickel ions into the patient's body, which can cause changes in the behaviour of surrounding cells and tissues. This study aims to evaluate the effects of Ni on bone cells with an emphasis on the determination of Ni localization in cellular compartments in time. For these purposes, one of the most suitable models for studying the effects induced by metal implants was used-the patient's osteoarthritic cells. Thanks to this it was possible to simulate the pathophysiological conditions in the patient's body, as well as to evaluate the response of the cells which come into direct contact with the material after the implantation of the joint replacement. The largest differences in cell viability, proliferation and cell cycle changes occurred between Ni 0.5 mM and 1 mM concentrations. Time-dependent localization of Ni in cells showed that there is a continuous transport of Ni ions between the nucleus and the cytoplasm, as well as between the cell and the environment. Moreover, osteoarthritic osteoblasts showed faster changes in concentration and ability to accumulate more Ni, especially in the nucleus, than physiological osteoblasts. The differences in Ni accumulation process explains the higher sensitivity of patient osteoblasts to Ni and may be crucial in further studies of implant-derived cytotoxic effects.

Interfaces between Cranial Bone and AISI 304 Steel after Long-Term Implantation: A Case Study of Cranial Screws

Interfaces between AISI 304 stainless steel screws and cranial bone were investigated after long-term implantation lasting for 42 years. Samples containing the interface regions were analyzed using state-of-the-art analytical techniques including secondary ion mass, Fourier-transform infrared, Raman, and X-ray photoelectron spectroscopies. Local samples for scanning transmission electron microscopy were cut from the interface regions using the focused ion beam technique. A chemical composition across the interface was recorded in length scales covering micrometric and nanometric resolutions and relevant differences were found between peri-implant and the distant cranial bone, indicating generally younger bone tissue in the peri-implant area. Furthermore, the energy dispersive spectroscopy revealed an 80 nm thick steel surface layer enriched by oxygen suggesting that the AISI 304 material undergoes a corrosion attack. The attack is associated with transport of metallic ions, namely, ferrous and ferric iron, into the bone layer adjacent to the implant. The results comply with an anticipated interplay between released iron ions and osteoclast proliferation. The interplay gives rise to an autocatalytic process in which the iron ions stimulate the osteoclast activity while a formation of fresh bone resorption sites boosts the corrosion process through interactions between acidic osteoclast extracellular compartments and the implant surface. The autocatalytic process thus may account for an accelerated turnover of the peri-implant bone.

Immunoglobulin A Nephropathy in a Patient With Bilateral Metal-on-Metal Hip Arthroplasty

Immunoglobulin A (IgA) nephropathy in the presence of a metal-on-metal (MoM) hip arthroplasty is a rare condition that requires close monitoring. A 61-year-old male with bilateral hip osteoarthritis underwent resurfacing hip arthroplasty with MoM articulating surfaces. Prior to his four-year postoperative visit, the patient was diagnosed with IgA nephropathy. During this visit, the patient reported clicking in the left resurfacing hip arthroplasty, and serum metal ions were significantly elevated. Consequently, the patient underwent conversion to bilateral ceramic-on-cross-linked polyethylene total hip arthroplasty, which resulted in the restoration of metal ion levels to normal. This case highlights that IgA nephropathy played a critical role in impeding the clearance of metal ions. Routine metal ion counts are warranted in patients with MoM articulating interfaces and a newly diagnosed nephropathy.

Enteral N-acetylcysteine to reduce serum cobalt concentrations secondary to prosthetic knee-associated metallosis: A case report

PURPOSE

Cobalt metallosis is a rare but dangerous complication of total joint arthroplasty resulting from deterioration of the joint leading to metal-on-metal friction and breakdown. Potential manifestations vary in severity and include dilated cardiomyopathy, thyroid dysfunction, cognitive disturbances, neuropathy, fatigue, and weakness. The therapeutic role of N-acetylcysteine in metallosis has been investigated due to its ability to chelate with heavy metal ions, such as cobalt and chromium.

SUMMARY

Here we report the case of a 71-year-old female who presented with suspected metallosis diagnosed in the outpatient setting due to symptoms of significant weight loss and failure to thrive. This metallosis was secondary to the hardware breakdown of a left knee revision roughly 6 years previously. The patient was not a surgical candidate due to her poor nutrition status and was started on nasojejunal tube feeds along with N-acetylcysteine 600 mg by mouth twice daily for 45 days. The patient's serum cobalt levels decreased from 61.7 µg/L on admission to 16.2 µg/L prior to her undergoing proper revision of the left knee roughly 2 months after admission to the hospital. The patient tolerated treatment well and was able to be discharged the day after surgery, with no further complaints or complications.

CONCLUSION

This case report contributes to the body of literature suggesting that administration of N-acetylcysteine can reduce serum cobalt concentrations, without notable adverse effects, in the context of prosthetic knee-associated metallosis.

Mettl3‑mediated m6A RNA methylation regulates osteolysis induced by titanium particles

Peri‑prosthetic osteolysis (PPO) induced by wear particles is considered the primary cause of titanium prosthesis failure and revision surgery. The specific molecular mechanisms involve titanium particles inducing multiple intracellular pathways, which impact disease prevention and the targeted therapy of PPO. Notably, N6‑methyladenosine (m6A) serves critical roles in epigenetic regulation, particularly in bone metabolism and inflammatory responses. Thus, the present study aimed to determine the role of RNA methylation in titanium particle‑induced osteolysis. Results of reverse transcription‑quantitative PCR (RT‑qPCR), western blotting, ELISA and RNA dot blot assays revealed that titanium particles induced osteogenic inhibition and proinflammatory responses, accompanied by the reduced expression of methyltransferase‑like (Mettl) 3, a key component of m6A methyltransferase. Specific lentiviruses vectors were employed for Mettl3 knockdown and overexpression experiments. RT‑qPCR, western blotting and ELISA revealed that the knockdown of Mettl3 induced osteogenic inhibition and proinflammatory responses comparable with that induced by titanium particle, while Mettl3 overexpression attenuated titanium particle‑induced cellular reactions. Methylated RNA immunoprecipitation‑qPCR results revealed that titanium particles mediated the methylation of two inhibitory molecules, namely Smad7 and SMAD specific E3 ubiquitin protein ligase 1, via Mettl3 in bone morphogenetic protein signaling, leading to osteogenic inhibition. Furthermore, titanium particles induced activation of the nucleotide binding oligomerization domain 1 signaling pathway through methylation regulation, and the subsequent activation of the MAPK and NF‑κB pathways. Collectively, the results of the present study indicated that titanium particles utilized Mettl3 as an upstream regulatory molecule to induce osteogenic inhibition and inflammatory responses. Thus, the present study may provide novel insights into potential therapeutic targets for aseptic loosening in titanium prostheses.

Metal levels and glomerular filtration rate after unilateral Birmingham Hip Resurfacing

Aims

The first aim of this study was to evaluate whether preoperative renal function is associated with postoperative changes in whole blood levels of metal ions in patients who have undergone a Birmingham Hip Resurfacing (BHR) arthroplasty with a metal-on-metal bearing. The second aim was to evaluate whether exposure to increased cobalt (Co) and chromium (Cr) levels for ten years adversely affected renal function.

Methods

As part of a multicentre, prospective post-approval study, whole blood samples were sent to a single specialized laboratory to determine Co and Cr levels, and the estimated glomerular filtration rate (eGFR). The study included patients with 117 unrevised unilateral BHRs. There were 36 females (31%). The mean age of the patients at the time of surgery of 51.3 years (SD 6.5), and they all had preoperative one-, four-, five-, and ten-year laboratory data. The mean follow-up was 10.1 years (SD 0.2).

Results

Median Co levels at one year postoperatively increased significantly compared with the preoperative values, by a factor of 9.7, from 0.13 to 1.26 ppb (p < 0.001), and the median Cr levels increased significantly by a factor of 2.5, from 0.60 to 1.50 ppb (p < 0.001). Lower preoperative eGFRs were associated with significantly larger increases in Co at one year compared with the preoperative levels (ρ = -0.26; p = 0.005), but there was no relationship between preoperative eGFRs and changes in Cr at one year (ρ = -0.13; p = 0.153). Metal levels remained relatively constant with the passage of time, with a median ten-year value of 1.12 ppb for Co and 1.29 ppb for Cr. There was no significant relationship between the Co and Cr levels at ten-year follow-up and the change in eGFR from the preoperative level to that at ten years (ρ = -0.02; p = 0.827 for Co; ρ = -0.008; p = 0.933 for Cr).

Conclusion

Although patients with lower preoperative eGFRs tended to have larger increases in Co levels at one year, increased metal levels for patients who underwent unilateral BHR did not adversely affect renal function during the first ten postoperative years.

Biphasic Bioceramic Obtained from Byproducts of Sugar Beet Processing for Use in Bioactive Coatings and Bone Fillings

This study focuses on developing hydroxyapatite synthesized from a CaCO3-rich byproduct of sugar beet processing called Carbocal® using a hydrothermal reactor. The purpose of this biomaterial is to enhance the osteoinductivity of implantable surfaces and serve as a bone filler, providing a sustainable and economically more affordable alternative. This research involved compositional analysis and micro- and macrostructural physicochemical characterization, complemented with bioactivity and live/dead assays. The biphasic nature of the Carbocal®-derived sample was significant within the context of the bioactivity concept previously proposed in the literature. The bioactivity of the biomaterial was demonstrated through a viability test, where the cell growth was nearly equivalent to that of the positive control. For comparison purposes, the same tests were conducted with two additional samples: hydroxyapatite obtained from CaCO3 and commercial hydroxyapatite. The resulting product of this process is biocompatible and possesses properties similar to natural hydroxyapatite. Consequently, this biomaterial shows potential as a scaffold in tissue engineering and as an adhesive filler to promote bone regeneration within the context of the circular bioeconomy in the geographical area proposed.

Metallosis in Total Hip Arthroplasty

» Metallosis is a rare but significant complication that can occur after total hip arthroplasty (THA) for a variety of reasons but most commonly in patients with metal-on-metal implants.» It is characterized by the visible staining, necrosis, and fibrosis of the periprosthetic soft tissues, along with the variable presence of aseptic cysts and solid soft tissue masses called pseudotumors secondary to the corrosion and deposition of metal debris.» Metallosis can present with a spectrum of complications ranging from pain and inflammation to more severe symptoms such as osteolysis, soft tissue damage, and pseudotumor formation.» Workup of metallosis includes a clinical evaluation of the patient's symptoms, imaging studies, serum metal-ion levels, and intraoperative visualization of the staining of tissues. Inflammatory markers such as erythrocyte sedimentation rate and C-reactive protein along with intraoperative frozen slice analysis may be useful in certain cases to rule out concurrent periprosthetic joint infection.» Management depends on the severity and extent of the condition; however, revision THA is often required to prevent rapid progression of bone loss and tissue necrosis.

Mitochondrial Redox Balance of Fibroblasts Exposed to Ti-6Al-4V Microplates Subjected to Different Types of Anodizing

Despite the high biocompatibility of titanium and its alloys, the need to remove titanium implants is increasingly being debated due to the potential for adverse effects associated with long-term retention. Therefore, new solutions are being sought to enhance the biocompatibility of titanium implants. One of them is to increase the thickness of the passive layer of the implant made of titanium dioxide. We were the first to evaluate the effect of hard-anodized (type II) Ti-6Al-4V alloy discs on the cytotoxicity, mitochondrial function, and redox balance of fibroblasts mitochondria compared to standard-anodized (type III) and non-anodized discs. The study used fibroblasts obtained from human gingival tissue. The test discs were applied to the bottom of 12-well plates. Cells were cultured for 24 h and 7, 14, and 21 days and mitochondria were isolated. We demonstrated the occurrence of oxidative stress in the mitochondria of fibroblasts of all tested groups, regardless of the presence and type of anodization. Type II anodization prevented changes in complex II activity (vs. control). The lowest degree of citrate synthase inhibition occurred in mitochondria exposed to titanium discs with type II anodization. In the last phase of culture, the presence of type II anodization reduced the degree of cytochrome c oxidase inhibition compared to the other tests groups and the control group, and prevented apoptosis. Throughout the experiment, the release of titanium, aluminium, and vanadium ions from titanium discs with a hard-anodized passive layer was higher than from the other titanium discs, but decreased with time. The obtained results proved the existence of dysfunction and redox imbalance in the mitochondria of fibroblasts exposed to hard-anodized titanium discs, suggesting the need to search for new materials perhaps biodegradable in tissues of the human body.

Advancement in biological and mechanical behavior of 3D printed poly lactic acid bone plates using polydopamine coating: Innovation for healthcare

The metallic biomaterials have been proclaimed to exhibit stress shielding with discharge of toxic ions, leading to polymeric implants attracting interest in 3D Printing domain. In this study, Poly Lactic Acid based 336 bone plates are fabricated using Fused Filament Fabrication with printing parameters being varied. Polydopamine, being biocompatible, is deposited on fabricated bone plates at varying submersion time, shaker speed and coating solutions concentration. The study involves witnessing the effect of printing and coating parameters on biological behavior of bone plates upon preservation in Simulated Body Fluid and Hank's Balanced Salt Solution. The findings propose the close relation of degradation with apatite growth. The highest degradation rate with significant reduction in mechanical characteristics are shown by uncoated bone plates. These bone plates have porous structure at 20% infill density, 0.5 mm layer height, 0.4 mm wall thickness and 100 mm/s print speed which could result in complete degradation with partial healing of bone fracture. The study suggests the preservation of bone plates coated at 120 h' submersion time and 120 RPM shaker speed in 3 mg/ml concentrated solution which showed lower apatite formation. Thus, the coating would slow down degradation of PLA bone plates, resulting in complete healing of bone fracture.

Metalloporphyrins as Tools for Deciphering the Role of Heme Oxygenase in Renal Immune Injury

Renal immune injury is a frequent cause of end-stage renal disease, and, despite the progress made in understanding underlying pathogenetic mechanisms, current treatments to preserve renal function continue to be based mainly on systemic immunosuppression. Small molecules, naturally occurring biologic agents, show considerable promise in acting as disease modifiers and may provide novel therapeutic leads. Certain naturally occurring or synthetic Metalloporphyrins (Mps) can act as disease modifiers by increasing heme oxygenase (HO) enzymatic activity and/or synthesis of the inducible HO isoform (HO-1). Depending on the metal moiety of the Mp employed, these effects may occur in tandem or can be discordant (increased HO-1 synthesis but inhibition of enzyme activity). This review discusses effects of Mps, with varying redox-active transitional metals and cyclic porphyrin cores, on mechanisms underlying pathogenesis and outcomes of renal immune injury.

Metal reactivity is present in dogs with tibial plateau leveling osteotomy and total hip replacement implants

OBJECTIVE

Determine whether dogs with well-functioning orthopedic metal implants can develop metal reactivity.

SAMPLE

Client-owned dogs that had tibial plateau leveling osteotomy (TPLO) or total hip replacement (THR) implants for 12 months or more and control dogs with no implants.

PROCEDURES

Lymphocyte transformation testing was performed by exposing peripheral blood lymphocytes to nickel (Ni), chromium (Cr), cobalt (Co), or a combination of these metals. Lymphocyte proliferation was assessed with flow cytometry. Lymphocyte stimulation indexes (SIs) were calculated. A SI > 2 was considered reactive. Median SIs of dogs in response to metal exposure were compared statistically.

RESULTS

Samples from 10 dogs with TPLO, 12 dogs with THR, and 7 control dogs were analyzed. Six dogs out of 22 with metal implants had a reactive SI to 1 or more metals, while 2 of 7 control dogs had a SI > 2 when exposed to nickel only. When all metals were considered, no differences in metal reactivity were found between TPLO, THR, and control groups.

CLINICAL RELEVANCE

Metal reactivity is present in dogs and can be identified using lymphocyte transformation testing. Reactivity to Ni is present in dogs with and without metal implants. Reactivity to Co and Cr occurs in some dogs with metal implants.

Metals and Trace Elements in Calcified Valves in Patients with Acquired Severe Aortic Valve Stenosis: Is There a Connection with the Degeneration Process?

BACKGROUND

Acquired calcified aortic valve stenosis is the most common valve disease in adulthood. In the etiopathogenesis of this complex pathology, the importance of inflammation is mentioned, in which non-infectious influences represented by the biological effects of metal pollutants may participate. The main goal of the study was to determine the concentration of 21 metals and trace elements-aluminium (Al), barium (Ba), cadmium (Cd), calcium (Ca), chrome (Cr), cobalt (Co), copper (Cu), gold (Au), lead (Pb), magnesium (Mg), mercury (Hg), molybdenum (Mo), nickel (Ni), phosphorus (P), selenium (Se), strontium (Sr), sulfur (S), tin (Sn), titanium (Ti), vanadium (V) and zinc (Zn)-in the tissue of calcified aortic valves and to compare them with the concentrations of the same elements in the tissue of healthy aortic valves in the control group.

MATERIAL AND METHODS

The study group consisted of 49 patients (25 men, mean age: 74) with acquired, severe, calcified aortic valve stenosis with indicated heart surgery. The control group included 34 deceased (20 men, median age: 53) with no evidence of heart disease. Calcified valves were explanted during cardiac surgery and deep frozen. Similarly, the valves of the control group were removed. All valves were lyophilized and analyzed by inductively coupled plasma mass spectrometry. The concentrations of selected elements were compared by means of standard statistical methods.

RESULTS

Calcified aortic valves contained significantly higher (p < 0.05) concentrations of Ba, Ca, Co, Cr, Mg, P, Pb, Se, Sn, Sr and Zn and-in contrast-lower concentrations of Cd, Cu, Mo, S and V than valves of the control group. Significant positive correlations of concentrations between the pairs Ca-P, Cu-S and Se-S and strong negative correlations between the elements Mg-Se, P-S and Ca-S were found in the affected valves.

CONCLUSION

Aortic valve calcification is associated with increased tissue accumulation of the majority of the analyzed elements, including metal pollutants. Some exposure factors may increase their accumulation in the valve tissue. A relationship between exposure to environmental burden and the aortic valve calcification process cannot be ruled out. Advances in histochemical and imaging techniques allowing imaging of metal pollutants directly in valve tissue may represent an important future perspective.

Midterm results of the Birmingham hip resurfacing: a single-surgeon series

INTRODUCTION

Birmingham hip resurfacing (BHR) is readily used as alternative to total hip replacement in younger patients. The current study aims to compare outcomes in terms of adverse local tissue reactions (ALTR), elevated metal ion levels and survival rates between low-risk (femoral component size ≥ 48 mm) and high-risk (femoral component size < 48 mm) BHR patients at a minimum 5-year follow-up (FU).

MATERIALS AND METHODS

We report the minimum 5-year, single surgeon outcome results of 183 BHRs, performed between 2007 and 2012. 154 patients, 18 women (20 hips) and 136 men (163 hips) were included in the study. Patients were grouped in 149 low-risk cases (femoral component size ≥ 48 mm) and in 34 high-risk cases (18 female/12 male) patients with a femoral head size < 48 mm).

RESULTS

At a minimum of 5-years FU time, 91% of the patients were available for FU. The overall survival rate was 91.8%. There were five revisions (survival rate 96.6%) in the low-risk group and ten revisions (survival rate 70.6%) in the high-risk group. In the low-risk group, six patients (6.5%) showed elevated metal ion levels (> 7 μg/l), compared to five patients (20.8%) in the high risk-group (p = 0.03).

CONCLUSION

Including the surgeon's initial learning curve, the BHR shows very good mid-term survival rates in the low-risk group but should, as previously demonstrated, not be considered for patients with less than 48 mm femoral head size.

LEVEL OF EVIDENCE

Level III: retrospective cohort study.

No increased risk of cancer associated with metal-on-metal or ceramic-on-ceramic procedures compared to other bearing surfaces in patients with total hip arthroplasty: A nationwide linked registry cohort analysis of 167,837 patients

OBJECTIVES

Studies have identified increased cancer risk among patients undergoing total hip arthroplasty (THA) compared to the general population. However, evidence of all-cause and site-specific cancer risk associated with different bearing surfaces has varied, with previous studies having short latency periods with respect to use of modern Metal-on-Metal (MoM) bearings. Using the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) linked to Australasian Association of Cancer Registries data, our aim was to evaluate risk of all-cause and site-specific cancer according to bearing surfaces in patients undergoing THA for osteoarthritis and whether risk increased with MoM bearings.

METHODS

Standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) were calculated by comparing number of observed cancer cases to expected number based on incidence rate in the Australian population. All-cause and site-specific cancer rates were calculated for all conventional stemmed THA (csTHA) and resurfacing THA (rsTHA) procedures performed for osteoarthritis. Cox proportional hazards models were used to compare cancer rates for MoM, ceramic-on-ceramic (CoC) and resurfacing procedures with a comparison group comprising metal-on-polyethylene (MoP) or ceramic-on-polyethylene (CoP) procedures.

RESULTS

There were 156,516 patients with csTHA procedures and 11,321 with rsTHA procedures for osteoarthritis performed between 1999 and 2012. Incidence of all-cause cancer was significantly higher for csTHA (SIR 1.24, 95% CI 1.22-1.26) and rsTHA (SIR 1.74, 95% CI 1.39-2.04) compared to the Australian population. For csTHA, there was no significant difference in all-site cancer rates for MoM (Hazard Ratio (HR) 1.01, 95%CI 0.96-1.07) or CoC (HR 0.98, 95%CI 0.94-1.02) compared to MoP and CoP bearings. Significantly increased risk of melanoma, non-Hodgkins lymphoma, myeloma, leukaemia, prostate, colon, bladder and kidney cancer was found for csTHA and, prostate cancer, melanoma for rsTHA procedures when compared to the Australian population, although risk was not significantly different across bearing surfaces.

CONCLUSIONS

csTHA and rsTHA procedures were associated with increased cancer incidence compared to the Australian population. However, no excess risk was observed for MoM or CoC procedures compared to other bearing surfaces.

Hip Resurfacing: A Single Surgeon U.S. Series With Minimum Ten-Year Follow-up

BACKGROUND

Metal-on-metal hip resurfacing is an alternative to total hip arthroplasty (THA). The aim of this study was to determine implant survivorship, analyze patient-reported outcomes measures and to determine patient satisfaction for patients who underwent metal-on-metal hip resurfacing at a large US academic institution by a single surgeon with a minimum of 10-year follow-up.

METHODS

Patients who underwent hip resurfacing from September 2006 through November 2009 were included. Patient demographics and variables were collected from a prospectively maintained institutional database and patients completed an additional questionnaire with patient-reported outcomes measures.

RESULTS

A total of 350 patients (389 hips) out of 371 (433 hips) with a minimum 10-year follow-up were successfully contacted (94.3% follow-up). Mean age was 53 years, 258 were male (73%). 377 out of 389 hips (96.9%) did not require additional surgery. Gender was significantly related to implant survivorship (males 99.0%, females 90.9%; P < .001). 330 patients (369 hips, 94.8%) were satisfied with their surgery. Males had higher proportion of satisfaction scores (P = .02) and higher modified Harris Hip Score (odds ratio = 2.63 (1.39, 4.98), P = .003). Median modified Harris Hip Score score for non-revised hips was 84.0 [80.0; 86.0] versus those requiring revision, 81.5 [74.0; 83.0], (P = .009).

CONCLUSION

At a minimum 10-year follow-up, hip resurfacing, using an implant with a good track record, demonstrates 99.0% survivorship in male patients with an average age of 52 years. We believe that the continued use of metal-on-metal hip resurfacing arthroplasty in this population is justified by both positive patient reported outcomes and survivorship.

Current status and future potential of wear-resistant coatings and articulating surfaces for hip and knee implants

Hip and knee joint replacements are common and largely successful procedures that utilise implants to restore mobility and relieve pain for patients suffering from e.g. osteoarthritis. However, metallic ions and particles released from both the bearing surfaces and non-articulating interfaces, as in modular components, can cause hypersensitivity and local tissue necrosis, while particles originating from a polymer component have been associated with aseptic loosening and osteolysis. Implant coatings have the potential to improve properties compared to both bulk metal and ceramic alternatives. Ceramic coatings have the potential to increase scratch resistance, enhance wettability and reduce wear of the articulating surfaces compared to the metallic substrate, whilst maintaining overall toughness of the implant ensuring a lower risk of catastrophic failure of the device compared to use of a bulk ceramic. Coatings can also act as barriers to inhibit ion release from the underlying material caused by corrosion. This review aims to provide a comprehensive overview of wear-resistant coatings for joint replacements - both those that are in current clinical use as well as those under investigation for future use. While the majority of coatings belong predominantly in the latter group, a few coated implants have been successfully marketed and are available for clinical use in specific applications. Commercially available coatings for implants include titanium nitride (TiN), titanium niobium nitride (TiNbN), oxidized zirconium (OxZr) and zirconium nitride (ZrN) based coatings, whereas current research is focused not only on these, but also on diamond-like-carbon (DLC), silicon nitride (SiN), chromium nitride (CrN) and tantalum-based coatings (TaN and TaO). The coating materials referred to above that are still at the research stage have been shown to be non-cytotoxic and to reduce wear in a laboratory setting. However, the adhesion of implant coatings remains a main area of concern, as poor adhesion can cause delamination and excessive wear. In clinical applications zirconium implant surfaces treated to achieve a zirconium oxide film and TiNbN coated implants have however been proven comparable to traditional cobalt chromium implants with regards to revision numbers. In addition, the chromium ion levels measured in the plasma of patients were lower and allergy symptoms were relieved. Therefore, coated implants could be considered an alternative to uncoated metal implants, in particular for patients with metal hypersensitivity. There have also been unsuccessful introductions to the market, such as DLC coated implants, and therefore this review also attempts to summarize the lessons learnt.

Toward long-live ceramic on ceramic hip joints: In vitro investigation of squeaking of coated hip joint with layer-by-layer reinforced PVA coatings

This study attempts to find a promising solution for the squeaking of ceramic on ceramic (COC) bearing surfaces by introducing reinforced poly(vinylalcohol) (PVA) layer-by-layer coatings on the bearing surface of Stryker Trident femoral head. A customized hip simulator was established to provide a realistic simulation of the normal gait (flexion–extension) of the hip joint, and to examine squeaking for coated and uncoated femoral heads. Different characterization techniques were employed to study the coatings’ structure. The PVA macromolecules were successfully cross-linked via epichlorohydrin agent, and chemically bonded onto the surface, forming a superior reinforced PVA coating on the femoral head’s surface. These coatings play a dominant role in increasing the pre-squeaking age of the hip joint due to reduction in hard-on-hard contact and femoral head liner clearance with their good viscoelastic properties. Which cause, damping friction-induced vibrations. This improvement resembles novel-type, long-life, and stable hip joint biomaterials with distinguished and promising pre-squeaking age.

The risk of all-cause mortality, heart outcomes, cancer, and neurodegenerative disorders with cobalt-chrome-containing total hip arthroplasty implants : an analysis of the National Joint Registry

AIMS

A recent report from France suggested an association between the use of cobalt-chrome (CoCr) femoral heads in total hip arthroplasties (THAs) and an increased risk of dilated cardiomyopathy and heart failure. CoCr is a commonly used material in orthopaedic implants. If the reported association is causal, the consequences would be significant given the millions of joint arthroplasties and other orthopaedic procedures in which CoCr is used annually. We examined whether CoCr-containing THAs were associated with an increased risk of all-cause mortality, heart outcomes, cancer, and neurodegenerative disorders in a large national database.

METHODS

Data from the National Joint Registry was linked to NHS English hospital inpatient episodes for 374,359 primary THAs with up to 14.5 years' follow-up. We excluded any patients with bilateral THAs, knee arthroplasties, indications other than osteoarthritis, aged under 55 years, and diagnosis of one or more outcome of interest before THA. Implants were grouped as either containing CoCr or not containing CoCr. The association between implant construct and the risk of all-cause mortality and incident heart failure, cancer, and neurodegenerative disorders was examined.

RESULTS

There were 158,677 individuals (42.4%) with an implant containing CoCr. There were 47,963 deaths, 27,332 heart outcomes, 35,720 cancers, and 22,025 neurodegenerative disorders. There was no evidence of an association between patients with CoCr implants and higher rates of any of the outcomes.

CONCLUSION

CoCr-containing THAs did not have an increased risk of all-cause mortality, or clinically meaningful heart outcomes, cancer, or neurodegenerative disorders into the second decade post-implantation. Our findings will help reassure clinicians and the increasing number of patients receiving primary THA worldwide that the use of CoCr-containing implants is not associated with significant adverse systemic effects. Cite this article: Bone Joint J 2022;104-B(3):359-367.

Serum Indicators of Oxidative Damage from Embedded Metal Fragments in a Rat Model

Injuries suffered in armed conflicts often result in embedded metal fragments. Standard surgical guidance recommends leaving embedded fragments in place except under certain circumstances in an attempt to avoid the potential morbidity that extensive surgery often brings. However, technological advances in weapon systems and insurgent use of improvised explosive devices now mean that practically any metal can be found in these types of wounds. Unfortunately, in many cases, the long-term toxicological properties of embedded metals are not known, further complicating treatment decisions. Because of concerns over embedded metal fragment injuries, the U.S. Departments of Defense and Veterans' Affairs developed a list of “metals of concern” for these types of injuries. In this study, we selected eight of these metals including tungsten, nickel, cobalt, iron, copper, aluminum, lead, and depleted uranium to investigate the long-term health effects using a rodent model developed in our Institute to study embedded fragment injuries. In this report, we show that metals surgically implanted into the gastrocnemius muscle of laboratory rats to simulate a shrapnel wound induce a variety of cytokines including IFN-γ, IL-4, IL-5, IL-6, IL-10, and IL-13. TNF-α and KC/GRO were not affected, and IL-1β was below the limit of detection. Serum levels of C-reactive protein were also affected, increasing with some metals and decreasing with others. The TBARS assay, an assessment of lipid peroxidation, demonstrated that implanted aluminum and lead increased markers of lipid peroxidation in serum. Taken together, the results suggest that serum cytokine levels, as well as other indicators of oxidative damage, may prove useful in identifying potential adverse health effects of embedded metals.

The risk of all-cause mortality, heart outcomes, cancer, and neurodegenerative disorders with cobalt-chrome-containing total hip arthroplasty implants : an analysis of the National Joint Registry

AIMS

A recent report from France suggested an association between the use of cobalt-chrome femoral heads in total hip arthroplasties (THAs) and an increased risk of dilated cardiomyopathy and heart failure. Cobalt-chrome is a commonly used material in orthopaedic implants. If the reported association is causal, the consequences would be significant given the millions of joint replacements and other orthopaedic procedures in which cobalt-chrome is used annually. We examined whether cobalt-chrome-containing THAs were associated with an increased risk of all-cause mortality, heart outcomes, cancer, and neurodegenerative disorders in a large national database.

METHODS

Data from the National Joint Registry was linked to NHS English hospital inpatient episodes for 374,359 primary THAs with up to 14.5 years follow-up. We excluded any patients with bilateral THAs, knee replacements, indications other than osteoarthritis, aged under 55 years, and diagnosis of one or more outcome of interest before THA. Implants were grouped as either containing cobalt-chrome or not containing cobalt-chrome. The association between implant construct and the risk of all-cause mortality and incident heart failure, cancer, and neurodegenerative disorders was examined.

RESULTS

There were 158,677 individuals (42.4%) with an implant containing cobalt-chrome. There were 47,963 deaths, 27,332 heart outcomes, 35,720 cancers, and 22,025 neurodegenerative disorders. There was no evidence of an association that patients with cobalt-chrome implants had higher rates of any of the outcomes.

CONCLUSION

Cobalt-chrome-containing THAs did not have an increased risk of all-cause mortality, or clinically meaningful heart outcomes, cancer or neurodegenerative disorders into the second decade post-implantation. Our findings will help reassure clinicians and the increasing number of patients receiving primary THA worldwide that the use of cobalt-chrome containing implants is not associated with significant adverse systemic effects.

Metal distribution patterns in tissues from implanted Sprague-Dawley rats

Background: Injuries with fragments of embedded metal are a common occurrence in armed conflicts. Unfortunately, the list of metals encountered on the modern battlefield are practically endless while the short- and long-term health effects, especially when embedded as in a shrapnel wound, are not well understood. One of the major concerns with these types of injuries is the solubilization of the embedded metal and the translocation and deposition to various organs of the body. Methods: Using a rodent model system developed in our laboratory to assess the health effects of embedded metal fragments, we surgically implanted metal pellets into the gastrocnemius muscles of male Sprague-Dawley rats. Test metals were chosen from a list promulgated by the U.S. Department of Defense as “metals of concern” with respect to embedded fragment wounds and included tungsten, nickel, cobalt, iron, copper, aluminum, lead, and depleted uranium. Tantalum was used as a control metal. Cohorts of the metal-implanted rats were humanely euthanized at 1, 3, 6, and 12-months post-implantation and a variety of tissues collected and analyzed for metal content using inductively coupled plasma-mass spectrometry. Results: With few exceptions, the embedded metal fragments eventually released solubilized metal ions, with the metals deposited in numerous tissues in the rats. Not all of the embedded metals localized to all tissues at significant levels. Copper, iron, and aluminum were not found in statistically significant levels, versus control, in any of the tissues analyzed. The other metals tested all appeared in elevated levels in the kidney which is not surprising since previous research has shown that they are also excreted in the urine at appreciable amounts. Tungsten and nickel were found in only a small number of tissues, tungsten in spleen, and nickel in liver and testes. Cobalt, lead, and depleted uranium showed the widest distribution with significant levels in liver, spleen, testes, lung, tibia, fibula, and femur. Conclusion: In this study, we showed that embedded metal fragments, such as those suffered in a shrapnel wound, could solubilize and metals become deposited in tissues far from the original site of implantation. Tissue deposition was metal-specific and many of the metals were found to cross the blood-testes barrier and were also found in bone. Since standard surgical guidance recommends leaving embedded fragments in place except for certain circumstances, this report will expand the understanding of tissue deposition of the solubilized metals and will hopefully aid healthcare professionals in developing long-term treatment strategies for dealing with these types of wounds.

Biofunctional magnesium-coated Ti6Al4V scaffolds promote autophagy-dependent apoptosis in osteosarcoma by activating the AMPK/mTOR/ULK1 signaling pathway

The recurrence of osteosarcoma (OS) after reconstruction using Ti6Al4V prostheses remains a major problem in the surgical treatment of OS. Modification of the surfaces of Ti6Al4V prostheses with antitumor functions is an important strategy for improving therapeutic outcomes. Magnesium (Mg) coating has been shown to be multifunctional: it exhibits osteogenic and angiogenic properties and the potential to inhibit OS. In this study, we determined the proper concentration of released Mg²⁺ with respect to OS inhibition and biosafety and evaluated the anti-OS effects of Mg-coated Ti6Al4V scaffolds. We found that the release of Mg²⁺ during short-term and long-term degradation could significantly inhibit the proliferation and migration of HOS and 143B cells. Increased cell apoptosis and excessive autophagy were also observed, and further evidence of AMPK/mTOR/ULK1 signaling pathway activation was obtained both in vitro and in vivo, which suggested that the biofunctional scaffolds induce OS inhibition. Our study demonstrates the ability of an Mg coating to inhibit OS and may contribute to the further application of Mg-coated Ti6Al4V prostheses.

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Multifunctional Mg coating is considerable surface modification for Ti6Al4V prostheses.

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Mg²⁺ releasing by the scaffolds could significantly inhibit the proliferation and migration of OS cells.

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The biofunctional scaffolds could inhibit OS by activating autophagy-dependent apoptosis.

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The AMPK/mTOR/ULK-1 pathway was involved in autophagy-depended apoptosis induced by the scaffolds.

The Expression Levels of Toll-like Receptors after Metallic Particle and Ion Exposition in the Synovium of a Murine Model

To date, the exact role of specific Toll-like receptors (TLRs) in regulating immune reactivity to metallic byproducts of orthopedic implants has not been fully clarified. In light of the situation, our objective in this investigation was to assess the expression levels of surface TLRs after metallic particle and ion exposure in an established animal model. Ten female BALB/c mice in each group received intra-articular injections of phosphate buffer (PBS) (control), metallic particles (MP), and metallic ions (MI), respectively. Seven days later, immunohistochemical staining was undertaken in the synovial layer of the murine knee joints using anti-TLR 1, 2, 4, 5, and 6 polyclonal antibodies. In addition to increased cellular infiltrates and a hyperplastic synovial membrane, the MP group showed significantly elevated TLR expression compared to the control group and had higher TLR 1-, 4-, and 6-positive cells than the MI group (p < 0.0167). TLR 4- and TLR 6-positive cells were significantly augmented for the MI group compared to the control group (p < 0.0167). Additionally, greenish corrosion particles found in the necrotic tissue suggested that metallic particles might release a certain level of locally toxic metallic ions in vivo.

Systemic toxicity eliciting metal ion levels from metallic implants and orthopedic devices - A mini review

The metal/metal alloy-based implants and prostheses are in use for over a century, and the rejections, revisions, and metal particle-based toxicities were reported concurrently. Complications developed due to metal ions, metal debris, and organo-metallic particles in orthopedic patients have been a growing concern in recent years. It was reported that local and systemic toxicity caused by such released products from the implants is one of the major reasons for implant rejection and revision. Even though the description of environmental metal toxicants and safety limits for their exposure to humans were well established in the literature, an effort was not adequately performed in the case of implant-based metal toxicology. Since the metal ion concentration in serum acts as a possible indicator of the systemic toxicity, this review summarizes the reported human serum safe limits, toxic limits, and concentration range (μg/L, ppb, etc.) for mild to severe symptoms of six (cardiac, hepatic, neuro, nephron, dermal and endocrine) systemic toxicities for twelve most commonly used metallic implants. It also covers the widely used metal ion quantification techniques and systemic toxicity treatments reported.

Diamond in the Rough: Toward Improved Materials for the Bone-Implant Interface

The ability of an orthopedic implant to integrate successfully with the surrounding bone tissue is imperative for optimal patient outcomes. Here, the recent advances and future prospects for diamond-based coatings of conventional osteo-implant materials (primarily titanium) are explored. The ability of these diamond coatings to enhance integration into existing bone, improved implant mechanical properties, facilitate surface chemical functionalization, and provide anti-microbial properties are discussed in context of orthopedic implants. These diamond-based materials may have the additional benefit of providing an osteo-inductive effect, enabling better integration into existing bone via stem cell recruitment and bone regeneration. Current and timely research is highlighted to support the discussion and suggestions in further improving implant integration via an osseoinductive effect from the diamond composite materials.

Comparison of Biocompatible Coatings Produced by Plasma Electrolytic Oxidation on cp-Ti and Ti-Zr-Nb Superelastic Alloy

The paper compares the coatings produced by plasma electrolytic oxidation (PEO) on commercially pure titanium and a novel superelastic alloy Ti-18Zr-15Nb (at. %) for implant applications. The PEO coatings were produced on both alloys in the identical pulsed bipolar regime. The properties of the coatings were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). The PEO process kinetics was modeled based on the Avrami theorem and Cottrell equation using a relaxation method. The resultant coatings contain TiO2, for both alloys, and NbO2, Nb2O5, ZrO2 for Ti-18Zr-15Nb alloy. The coating on the Ti-18Zr-15Nb alloy has a higher thickness, porosity, and roughness compared to that on cp-Ti. The values of the kinetic coefficients of the PEO process—higher diffusion coefficient and lower time constant for the processing of Ti-18Zr-15Nb—explain this effect. According to the electrochemical studies, PEO coatings on Ti-18Zr-15Nb alloy provide better corrosion protection. Higher corrosion resistance, porosity, and roughness contribute to better biocompatibility of the PEO coating on Ti-18Zr-15Nb alloy compared to cp-Ti.

Post-Processing and Surface Characterization of Additively Manufactured Stainless Steel 316L Lattice: Implications for BioMedical Use

Additive manufacturing of stainless steel is becoming increasingly accessible, allowing for the customisation of structure and surface characteristics; there is little guidance for the post-processing of these metals. We carried out this study to ascertain the effects of various combinations of post-processing methods on the surface of an additively manufactured stainless steel 316L lattice. We also characterized the nature of residual surface particles found after these processes via energy-dispersive X-ray spectroscopy. Finally, we measured the surface roughness of the post-processing lattices via digital microscopy. The native lattices had a predictably high surface roughness from partially molten particles. Sandblasting effectively removed this but damaged the surface, introducing a peel-off layer, as well as leaving surface residue from the glass beads used. The addition of either abrasive polishing or electropolishing removed the peel-off layer but introduced other surface deficiencies making it more susceptible to corrosion. Finally, when electropolishing was performed after the above processes, there was a significant reduction in residual surface particles. The constitution of the particulate debris as well as the lattice surface roughness following each post-processing method varied, with potential implications for clinical use. The work provides a good base for future development of post-processing methods for additively manufactured stainless steel.

Brain region- and metal-specific effects of embedded metals in a shrapnel wound model in the rat

The health effects of prolonged exposure to embedded metal fragments, such as those found in shrapnel wounds sustained by an increasing number of military personnel, are not well known. As part of a large collaborative effort to expand this knowledge, we use an animal model of shrapnel wounds originally developed to investigate effects of embedded depleted uranium to investigate effects of military-relevant metals tungsten, nickel, cobalt, iron, copper, aluminum, lead, and depleted uranium compared to an inert control, tantalum. Rats are surgically implanted with pellets of one of the metals of interest in the gastrocnemius (leg) muscle and tracked until 1 month, 3 months, 6 months, or 12 months from the time of implant, at which point they are euthanized and multiple organs and tissue samples are collected for inspection. Here we focus on four regions of the brain: frontal cortex, hippocampus, amygdala, and cerebellum. We examined changes in accumulated metal concentration in each region as well as changes in expression of proteins related to blood brain barrier tight junction formation, occludin and ZO-1, and synapse function, PSD95, spinophilin, and synaptotagmin. We report few changes in metal accumulation or blood brain barrier protein expression, but a large number of synapse proteins have reduced expression levels, particularly within the first 6 months of exposure, but there are regional and metal-specific differences in effects.

In vivo performance of Al2O3-Ti bone implants in the rat femur

Background

Alumina-titanium (Al₂O₃-Ti) biocomposites have been recently developed with improved mechanical properties for use in heavily loaded orthopedic sites. Their biological performance, however, has not been investigated yet.

Methods

The aim of the present study was to evaluate the in vivo biological interaction of Al₂O₃-Ti. Spark plasma sintering (SPS) was used to fabricate Al₂O₃-Ti composites with 25 vol.%, 50 vol.%, and 75 vol.% Ti content. Pure alumina and titanium were also fabricated by the same procedure for comparison. The fabricated composite disks were cut into small bars and implanted into medullary canals of rat femurs. The histological analysis and scanning electron microscopy (SEM) observation were carried out to determine the bone formation ability of these materials and to evaluate the bone-implant interfaces.

Results

The histological observation showed the formation of osteoblast, osteocytes with lacuna, bone with lamellar structures, and blood vessels indicating that the healing and remodeling of the bone, and vasculature reconstruction occurred after 4 and 8 weeks of implantation. However, superior bone formation and maturation were obtained after 8 weeks. SEM images also showed stronger interfaces at week 8. There were differences between the composites in percentages of bone area (TB%) and the number of osteocytes. The 50Ti composite showed higher TB% at week 4, while 25Ti and 75Ti represented higher TB% at week 8. All the composites showed a higher number of osteocytes compared to 100Ti, particularly 75Ti.

Conclusions

The fabricated composites have the potential to be used in load-bearing orthopedic applications.

Ceramic-on-metal bearing in short stem total hip arthroplasty: ions, functional and radiographic evaluation at mid-term follow-up

INTRODUCTION

The aim of this study is to evaluate clinical, radiographic and laboratory results of ceramic-on-metal (CoM) (hybrid hard bearing) in total hip arthroplasty (THA), associated with a short stem implant.

METHODS

From a cohort of 37 patients suffering from primary or secondary hip osteoarthritis who underwent THA using CoM bearing, 19 were suitable for this study. All procedures were performed by the same surgeon using a posterior-lateral approach. All patients were compared clinically using the Harris Hip Score (HHS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), visual analogue scale (VAS), 12-item Short Form Health Survey (SF12F/M), and radiographically (offset, CD angle, limb length discrepancy, cup inclination and anteversion, subsidence, osseointegration, heterotopic ossification). Blood samples were collected in order to evaluate chromium (Cr) and cobalt (Co) ions level. Radiographic evaluations were carried out by 3 different blinded surgeons. A statistical analysis was performed.

RESULTS

At a mean follow-up of 97 (73-125) months all implanted stems were well-positioned and osseointegrated. Clear improvements were observed for clinical scores comparing preoperative and postoperative values. Radiographic evaluation showed a good ability to restore proper articular geometry. Cr ion analysis revealed values below the safety threshold except for 1 case. Serum levels of Co were below the threshold in all patients. There was a statistically significant correlation only between Cr metal ions and length of follow-up.

CONCLUSIONS

CoM bearing has proven to be reliable and safe at a mean 8-year follow-up for patients in whom the components were correctly implanted. The rise of blood metal ions was minimal and involved neither systemic or local toxicity nor influenced clinical results.

15-year follow-up of MoM 36-mm THA: clinical, laboratory, and radiological (CT and MRI) prospective assessment

INTRODUCTION

There is limited knowledge of the long-term results of metal-on-metal total hip arthroplasty (MoM THA), particularly concerning adverse local tissue reaction (ALTR), Co/Cr ions level and revision rate. Even if MoM bearing surfaces are no longer used, long-term data could help in defining the course and best management for these patients. The purpose of this study is to investigate the clinical outcomes, describe radiological findings including CT metal artefact reduction algorithm for orthopaedic implants (O-MAR) and MRI multi acquisition variable resonance image combination (MAVRIC) in 36-mm MoM THA.

METHODS

In this long-term prospective study, 46 consecutive patients with primary MoM THA (mono- or bilateral) were enrolled between 2004 and 2005. Pinnacle acetabular cup, Summit cementless stem with 36-mm metal head and Ultamet CoCr alloy liner (Depuy Inc.) were implanted, in the same centre by the same senior surgeon. Patients were reviewed at 5-, 10- and 15-years, including Co/Cr levels and standard radiographs at every follow-up, whilst the 15-year follow-up included hip sonography, MRI MAVRIC and CT O-MAR.

RESULTS

At 15 years, the overall survival rate of the implants (both stems and cups) was 83% (30/36). Revisions were performed in 9% (4/46) because of ALTR, 2% (1/46) septic loosening and 2% periprosthetic fracture. Both Cr and Co concentration increased over time, even though remaining at low level risk at 15 years: Co from 0.11 (+/- 0.18) to 4.29 (+/- 3.26) and Cr from 0.38 (+/- 0.32) to 1.37 (+/- 1.15). Functional scores in non-revised patients showed good to excellent results in more than 90%. Engh-score correlated with time from surgery (p = 0.017) and with sonographic, CT and RM findings (p < 0.05). Concordance has been found between CT and MRI findings (sign-rank test, p = 0.241; Intraclass Correlation Coefficients 0.987); however, no specific MRI or CT lesion patterns could be recognised among symptomatic and non-symptomatic patients.

DISCUSSION

The long-term rate of ALTR after 36-mm MoM THA was comparable with previous studies; a regular follow-up for those implants is mandatory. During follow-up Co-Cr levels increased over time and radiography was a suitable screening technique; the Engh score in particular, proved to be a reliable assessment tool. CT O-MAR and MRI with MAVRIC protocols may add valuable data in clinical practice, although MRI is significantly more efficient than CT in the identification of ALTR lesions, peri-articular effusion and in the evaluation of soft tissues.

Luteolin supplementation ameliorates cobalt-induced oxidative stress and inflammation by suppressing NF-кB/Kim-1 signaling in the heart and kidney of rats

Cobalt-induced cardiomyopathy and renal toxicity have been reported in workers in processing plants, hard metal industries, diamond polishing and manufacture of ceramics. This study was designed to investigate the influence of Luteolin supplementation on cobalt-induced cardiac and renal toxicity in rats. Exposure of rats to cobalt chloride (CoCl₂) alone caused significant (p < 0.05) increases in cardiac and renal H₂O₂, malondialdehyde (MDA) and nitric oxide (NO), along with increased serum myeloperoxidase (MPO) activity. In addition, there were significant (p < 0.05) reductions in cardiac and renal glutathione peroxidase (GPx), glutathione S-transferase (GST) and reduced glutathione (GSH). CoCl₂ induced higher immuno-staining of nuclear factor kappa beta (NF-κB) in the heart and kidneys, and the kidney injury molecule (Kim-1) in the kidneys. Treatment with Luteolin or Gallic acid produced significant reversal of the oxidative stress parameters with reductions in NF-κB and Kim-1 expressions, leading to suppression of histopathological lesions observed in the tissues.

Do Children With Spinal Deformity Who Have Metal Implants and Frequent Exposure to X-Rays Increase Their Risk of Cancer?

STUDY DESIGN

Spinal surgery cohort.

OBJECTIVE

The authors assess the risk of cancer in children who have undergone frequent radiographs and have metal implants for the treatment of spinal deformity.

SUMMARY OF BACKGROUND DATA

Concerns have been raised regarding the cancer risk to children exposed to repeated radiological examinations as part of routine surveillance to monitor progression of spinal deformity. Additionally, there are reports of increased cancer risk in adults having joint replacement with metal implants causing raised metal ion levels in the blood.

METHODS

A large number of consecutive children undergoing instrumented spinal surgery since 1979 were examined for their development of malignancy. High quality data on all invasive cancers from the South Australian Cancer Registry and deaths were linked to the spinal surgery cohort with the calculation of standardized incidence ratios (SIRs) using the Quinquinquennium method.

RESULTS

The study cohort was formed by 865 children. The average follow-up time from date of surgery to either death or censoring date was 18 years with a maximum of 36 years. A total of 15,921 person years were examined. There was no increased rate of cancer in these patients. For the total cohort, the SIR was 1.00 (95% confidence interval [CI] 0.50-1.79). For females the SIR was 0.83 (95% CI 0.33-1.70) and for males the SIR was 1.33 (95% CI 0.36-3.40). The male SIR reflected an expected cancer incidence of three cases, when four cases were observed, and was not statistically significant.

CONCLUSION

This study has found that radiation exposure and possible exposure to circulating metal ions as a result of routine instrumented spine surgery in children since 1979 is not associated with an increased risk of cancer in up to 36 years of follow up.

LEVEL OF EVIDENCE

2.

Metals and Metalloids Release from Orthodontic Elastomeric and Stainless Steel Ligatures: In Vitro Risk Assessment of Human Exposure

Elastomeric ligatures are increasingly used as a part of esthetic orthodontic treatment, particularly in children. The aim of the present study was to experimentally test whether these appliances may contribute to exposure to toxic elements. In the present study, elastomeric ligatures (ELs) were incubated in artificial human saliva for 1 month (a typical period of their use) and the release of 21 metals (Ba, Cd, Co, Cr, Cu, Fe, Li, Mn, Mg, Mo, Ni, Pb, Rb, Tl, Ti, Sb, Sr, Sn, Zn, U, V) and 2 metalloids (As and Ge) was studied using inductively coupled plasma-mass spectrometry. For comparison, stainless steel ligatures (SLs) were incubated for 1, 3, and 6 months (since sometimes their use is prolonged) under similar conditions. The determined metal levels were compared to the corresponding safety limits for human exposure. During 1 month, the ELs released Cd, Co, Cr, Mn, Ni, and Sn at total mean ± SD level of 0.31 ± 0.09, 0.98 ± 0.30, 3.96 ± 1.31, 14.7 ± 8.5, 13.8 ± 4.8, and 49.5 ± 27.7 μg, respectively. Other elements were always below the detection limits. In case of SL, the release of Co, Cr, Fe, Ni, Mn, and Sn was observed, and the determined values increased over the studied period. After 6 months, their total mean ± SD levels amounted to 28.6 ± 0.2, 21.7 ± 0.2, 623.5 ± 3.0, 1152.7 ± 1.8, 5.5 ± 0.3, and 22.6 ± 0.2 μg, respectively. The released metal levels from both ligature types were always below safety limits. The release of Ni from SL during 6 months would constitute 5.0 and 11.5% of tolerable intake in adults and children, respectively. The results of this in vitro study highlight that the use of ligatures in orthodontic treatment can be considered safe in terms of metal exposure although elastic ligatures replaced on a monthly basis appear to be advantageous in comparison to the prolonged use of stainless steel appliances.

In vitro evaluation of a novel nanostructured Ti-36Nb-6Ta alloy for orthopedic applications

Aim: To evaluate the impact of a nanostructured surface created on β-titanium alloy, Ti-36Nb-6Ta, on the growth and differentiation of human mesenchymal stem cells. Materials & methods: The nanotubes, with average diameters 18, 36 and 46 nm, were prepared by anodic oxidation. Morphology, hydrophilicity and mechanical properties of the nanotube layers were characterized. The biocompatibility and osteogenic potential of the nanostructured surfaces were established using various in vitro assays, scanning electron microscopy and confocal microscopy. Results: The nanotubes lowered elastic modulus close to that of bone, positively influenced cell adhesion, improved ALP activity, synthesis of type I collagen and osteocalcin expression, but diminished early cell proliferation. Conclusion: Nanostructured Ti-36Nb-6Ta with nanotube diameters 36 nm was the most promising material for bone implantation.

The management of embedded metal fragment patients and the role of chelation Therapy: A workshop of the Department of Veterans Affairs-Walter Reed National Medical Center

Exposure to retained metal fragments from war-related injuries can result in increased systemic metal concentrations, thereby posing potential health risks to target organs far from the site of injury. Given the large number of veterans who have retained fragments and the lack of clear guidance on how to medically manage these individuals, the Department of Veterans Affairs (VA) convened a meeting of chelation experts and clinicians who care for embedded fragment patients to discuss current practices and provide medical management guidance. Based on this group's clinical expertise and review of published literature, the evidence presented suggests that, at least in the case of lead fragments, short-term chelation therapy may be beneficial for embedded fragment patients experiencing acute symptoms associated with metal toxicity; however, in the absence of clinical symptoms or significantly elevated blood lead concentrations (greater than 80 µg/dL), chelation therapy may offer little to no benefit for individuals with retained fragments and pose greater risks due to remobilization of metals stored in bone and other soft tissues. The combination of periodic biomonitoring to assess metal body burden, longitudinal fragment imaging, and selective fragment removal when metal concentrations approach critical injury thresholds offers a more conservative management approach to caring for patients with embedded fragments.

Mesenchymal stem cell interaction with Ti6Al4V alloy pre-exposed to simulated body fluid

Titanium and its alloys are widely used for substitution of hard tissues, especially in orthopaedic and dental surgery. Despite the benefit of the use of titanium for such applications, there are still questions which must be sorted out. Surface properties are crucial for cell adhesion, proliferation and differentiation. Mainly, micro/nanostructured surfaces positively influence osteogenic differentiation of human mesenchymal stem cells. Ti6Al4V is a biocompatible α + β alloy which is widely used in orthopaedics. The aim of this study was to investigate the interaction of the nanostructured and ground Ti6Al4V titanium alloys with simulated body fluid complemented by the defined precipitation of hydroxyapatite-like coating and to study the cytotoxicity and differentiation capacity of cells with such a modified titanium alloy. Nanostructures were fabricated using electrochemical oxidation. Human mesenchymal stem cells (hMSC) were used to evaluate cell adhesion, metabolic activity and proliferation on the specimens. The differentiation potential of the samples was investigated using PCR and specific staining of osteogenic markers collagen type I and osteocalcin. Our results demonstrate that both pure Ti6Al4V, nanostructured samples, and hydroxyapatite-like coating supported hMSC growth and metabolic activity. Nanostructured samples improved collagen type I synthesis after 14 days, while both nanostructured and hydroxyapatite-like coated samples enhanced collagen synthesis on day 21. Osteocalcin synthesis was the most enhanced by hydroxyapatite-like coating on the nanostructured surfaces. Our results indicate that hydroxyapatite-like coating is a useful tool guiding hMSC osteogenic differentiation.

Inorganic Biomaterials for Regenerative Medicine

Regenerative medicine leverages the innate potential of the human body to efficiently repair and regenerate damaged tissues using engineered biomaterials. By designing responsive biomaterials with the appropriate biophysical and biochemical characteristics, cellular response can be modulated to direct tissue healing. Recently, inorganic biomaterials have been shown to regulate cellular responses including cell-cell and cell-matrix interactions. Moreover, ions released from these mineral-based biomaterials play a vital role in defining cell identity, as well as driving tissue-specific functions. The intrinsic properties of inorganic biomaterials, such as the release of bioactive ions (e.g., Ca, Mg, Sr, Si, B, Fe, Cu, Zn, Cr, Co, Mo, Mn, Au, Ag, V, Eu, and La), can be leveraged to induce phenotypic changes in cells or modulate the immune microenvironment to direct tissue healing and regeneration. Biophysical characteristics of biomaterials, such as topography, charge, size, electrostatic interactions, and stiffness can be modulated by addition of inorganic micro- and nanoparticles to polymeric networks have also been shown to play an important role in their biological response. In this Review, we discuss the recent emergence of inorganic biomaterials to harness the innate regenerative potential of the body. Specifically, we will discuss various biophysical or biochemical effects of inorganic-based materials in directing cellular response for regenerative medicine applications.