Blood and plasma titanium levels associated with well-functioning hip implants

Surface adhered titanium particles on 3D printed off-the-shelf acetabular cups

3D printing is a rapidly growing manufacturing method of medical implants. In orthopedics, this method enables the construction of complex porous structures with the aim of improved bone fixation. A known by-product of the 3D printing process is surface adhered particles which are often challenging to remove from the strut surfaces of the porous region. This study investigates the presence of these particles in the porous region of unused 3D printed off-the-shelf acetabular cup from five manufacturers. Scanning Electron Microscopy (SEM) and image analysis software were used to determine the frequency and diameters of particles present on these implants. Surface adhered particles were found in the porous structures of all implants with some exhibiting more particles at the subsurface level than the surface level. Implants manufactured via Selective Laser Melting (SLM) exhibited a higher number of surface adhered particles per mm2 at both the surface and subsurface levels than those manufactured by Electron Beam Melting (EBM). Additionally, and consistent with previous literature, the particle diameter of the SLM cups was found to be smaller than those on the EBM cups, as well as having a visually lower level of adherence which could raise concern about the likelihood of breakage of these particles in-vivo.

Excellent Results of Large-Diameter Ceramic-On-Ceramic Bearings in Total Hip Arthroplasty at Minimum Ten-Year Follow-Up

BACKGROUND

This study reports the minimum 10 years results of total hip arthroplasty (THA) performed using a monoblock acetabular component with a large-diameter head ceramic-on-ceramic bearing.

METHODS

Of the 276 THAs included in this study, there were eleven deaths and 27 patients lost to follow up (11%) during the follow-up, leaving 237 (85%) hips available for review at a mean of 10.5 years (range, 10 to 12) postoperatively. Reoperations, implant revisions, adverse events, clinical outcomes, radiographic evaluation, and whole blood metal ion levels were assessed at the last follow-up.

RESULTS

After a minimum of 10 years, implant survivorship was 98.7%. There were 3 revisions (1.3%): one for insufficient acetabular cup primary fixation, one traumatic periprosthetic acetabular fracture, and one probable deep chronic infection. No dislocation or ceramic implant fracture was observed. The mean University of California at Los Angeles activity score, Western Ontario and McMaster Universities Osteoarthritis Index score, and Forgotten Joint Score were 5.6 (2 to 10), 90.1 (9 to 100), and 79.2 (4 to 100), respectively. All patients (100%) were satisfied or very satisfied. Since implantation, 43% of patients reported hearing a squeaking noise from the prosthesis. But all patients who reported squeaking were satisfied with the surgery. The mean titanium level was 2.2 μg/L (1.1 to 5.6). No progressive radiolucent lines, osteolysis, or implant loosening signs were observed at the last radiographic evaluation.

CONCLUSIONS

A large-diameter head ceramic-on-ceramic THA provides outstanding long-term (minimum 10 years) implant survivorship with unrestricted activity while avoiding implant impingement, liner fracture, and hip instability. Functional outcomes, satisfaction, and joint perception were excellent. Although the incidence of squeaking was high, it did not affect patient satisfaction or function. The systemic titanium levels were low, related to unavoidable passive corrosion of implant surfaces, and did not reveal any indirect signs of trunnionosis.

Concentrations of Cobalt, Chromium and Titanium and Immunological Changes after Primary Total Knee Arthroplasty-A Cohort Study with an 18-Year Follow-Up

Background: Total knee arthroplasty (TKA) generates elevated metal ion concentrations, but long-term changes in the concentrations of cobalt (Co), chromium (Cr) and titanium (Ti) after primary TKA and potential subsequent immune system activation-not limited to the joint but systemically-are not known. Patients and Methods: We conducted a cohort study on 26 patients with TKA (19 women; 16 with metal-backed and 10 with all-polyethylene tibial components) 18.3 years (min. 16.7, max. 20.5) after index TKA. A total of 69% of patients additionally underwent subsequent arthroplasty of the contralateral knee or either hip after the index surgery. Blood samples were analysed by inductively coupled plasma-mass spectrometry, and leukocytes were characterised by flow cytometry. Patients were clinically assessed using the Knee Society score and by plain radiography of the knee. Results: The median metal ion concentrations were 0.7 (0.1-13.0) µg/L for Co, 0.9 (0.4-5.0) µg/L for Cr, and 1.0 (0.2-13.0) µg/L for Ti. There was no relevant difference in systemic metal ion concentrations between patients exposed to single and multiple arthroplasties. The absolute count and proportion of CD3+CD4+CD8+ T cells was inversely correlated with both Co (rho -0.55, p = 0.003) and Cr concentrations (rho -0.59, p = 0.001). Conclusions: Between the first and second decades after primary TKA, in most patients, the concentrations of Co, Cr and Ti in blood samples were below the thresholds that are considered alarming. The negative correlation of Co and Cr concentrations with a subset of lymphocytes that commonly increases during immune activation is reassuring. This represents a worst-case scenario, underscoring that the investigated metal ions remain within reasonable ranges, even after additional hardware exposure.

Whole Blood Titanium Concentration after Limb Salvage Surgery with Three-Dimensional-Printed Ti6Al4V Implants

Background

Three-dimensional (3D)-printed customized implants can be fabricated and utilized for all bones with massive bone defects. The main safety issues with 3D-printed implants made of Ti6Al4V alloy are related to the release of metal debris and residual powder. In this study, we investigated the perioperative titanium concentrations in whole blood and peri-implant fluid samples of patients who underwent limb salvage surgery with a 3D-printed Ti6Al4V implant.

Methods

Nineteen patients who underwent limb salvage surgery with 3D-printed Ti6Al4V implants were divided into two groups: the serial samples group and the follow-up group. To observe metal distribution and clearance in the body, serial samples of blood and peri-implant fluid from the surgical drain were prospectively collected for five patients in the serial samples group. For the remaining 14 patients who were followed up for more than a year, blood samples were collected only once.

Results

In the serial samples group, the mean baseline titanium concentration was 0.78 µg/L (range, 0.1-2.2 µg/L): 3 patients showed peak concentration before the third postoperative month, while 2 patients still showed an increasing pattern at this point. Total titanium mass in the surgical drain showed a wash-out phenomenon in a week, with a significant uniform decrease (p = 0.04). In 14 patients in the follow-up group, the mean titanium concentration in the whole blood was 10.8 µg/L (range, 0.3-36.6 µg/L). For the 14 patients with a long-term follow-up, the aluminum and vanadium concentrations were all negligible.

Conclusions

Whole blood titanium concentrations were higher after surgery using 3D-printed implants than after that using conventional orthopedic implants, but markedly lower than in patients with implant failure. None of the patients developed serious clinical adverse effects during follow-up.

Blood titanium levels in patients with large and sliding titanium implants

Background

Titanium, which is known to be a highly biologically inert element, is one of the most commonly used metals in orthopaedic implants. While cobalt and chromium blood metal ion testing is routinely used in the clinical monitoring of patients with metal-on-metal hip implants, much less is known about the levels of titanium in patients with other implant types. The aim of this study was to better understand the normal ranges of blood titanium levels in patients implanted with large and sliding titanium constructs by comparison with reference levels from conventional titanium hips.

Methods

This study examined data collected from 136 patients. Over a period of 24 months, whole blood samples were collected from 41 patients implanted with large titanium implants: long (range 15 to 30 cm) spine rods with a sliding mechanism (“spine rods”, n = 18), long bone tumour implants (“tumour implants”, n = 13) and 3D-printed customised massive acetabular defect implants (“massive acetabular implants”, n = 10). This data was compared with standard, uncemented primary titanium hip implants (“standard hips”, 15 cm long) (n = 95). Clinical, imaging and blood titanium levels data were collected for all patients and compared statistically between the different groups.

Results

The median (range) of blood titanium levels of the standard hip, spine rods, femoral tumour implants and massive acetabular implants were 1.2 ppb (0.6–4.9), 9.7 ppb (4.0–25.4), 2.6 ppb (0.4–104.4) and 5.7 ppb (1.6–31.5) respectively. Spine rods and massive acetabular implants had significantly greater blood titanium levels compared to the standard hips group (p < 0.001).

Conclusion

This study showed that titanium orthopaedic implants that are large and/or have a sliding mechanism have higher blood titanium levels compared to well-functioning, conventionally sized titanium hips. Reassuringly, the increased levels did not appear to induce adverse metal reactions. This study provides useful baseline data for future studies aimed at assessing blood titanium levels as a biomarker for implant function.

Titanium wear from magnetically controlled growing rods (MCGRs) for the treatment of spinal deformities in children

Magnetically controlled growing rods (MCGRs) are an effective treatment method for early-onset scoliosis (EOS). In recent years, increasing titanium wear was observed in tissue adjacent to implants and in blood samples of these patients. This study aims to investigate the potential correlation between amount of metal loss and titanium levels in blood during MCGR treatment as well as influencing factors for metal wear. In total, 44 MCGRs (n = 23 patients) were retrieved after an average of 2.6 years of implantation and analyzed using a tactile measurement instrument and subsequent metal loss calculation. Titanium plasma levels (n = 23) were obtained using inductively coupled plasma-mass spectrometry (ICP-MS). The correlation of both parameters as well as influencing factors were analyzed. Titanium abrasion on MCGRs was observed in the majority of implants. There was no correlation of metal implant wear or titanium plasma values to the duration of MCGR implantation time, number of external lengthening procedures, patient’s ambulatory status, gender, weight or height. Material loss on the MCGRs showed a positive correlation to titanium blood plasma values. The present study is one of the first studies to analyze retrieved MCGRs using high-precision metrological techniques and compare these results with ICP-MS analyses determining blood titanium values.

Histomorphometry of Ossification in Functionalised Ceramics with Tripeptide Arg-Gly-Asp (RGD): An In Vivo Study

The present study investigated the osseointegration promoted by functionalised ceramics with peptide Arg-Gly-Asp (RGD) in a rabbit model in vivo. Histomorphometry of the RGD functionalised ceramic implants was conducted by a trained pathologist to quantify the amount of mature and immature ossification at the bone interface, and then compared to titanium alloy implants. The region of interest was the area surrounding the implant. The percentage of ROI covered by osteoid implant contact and mature bone implant contact were assessed. The presence of bone resorption, necrosis, and/or inflammation in the areas around the implant were quantitatively investigated. All 36 rabbits survived the experimental period of 6 and 12 weeks. All implants remained in situ. No necrosis, bone resorption, or inflammation were identified. At 12 weeks follow-up, the overall mean bone implant contact (p = 0.003) and immature osteoid contact (p = 0.03) were improved compared to the mean values evidenced at 6 weeks. At 6 weeks follow-up, the overall osteoid implant contact was greater in the RGD enhanced group compared to the titanium implant (p = 0.01). The other endpoints of interest were similar between the two implants at all follow-up points (p ≥ 0.05). Functionalised ceramics with peptide RGD promoted ossification in vivo. The overall osteoid and bone implant contact improved significantly from 6 to 12 weeks. Finally, RGD enhanced ceramic promoted faster osteoid implant contact in vivo than titanium implants. Overall, the amount of ossification at 12 weeks is comparable with the titanium implants. No necrosis, bone resorption, or inflammation were observed in any sample.

Benefits and Biosafety of Use of 3D-Printing Technology for Titanium Biomedical Implants: A Pilot Study in the Rabbit Model

BACKGROUND

Titanium has been used in osteosynthesis for decades and its compatibility and safety is unquestioned. Studies have shown that there is release and collection of titanium in the organ systems with little note of toxicity. The gold standard is considered to be titanium osteosynthesis plate produced by milling methods. The use of customized titanium plates produced with 3D printing, specifically direct metal laser sintering, have found increasing use in recent years. It is unknown how much titanium is released in these printed titanium implants, which is known to be potentially porous, depending on the heat settings of the printer. We hypothesize that the amount of titanium released in printed titanium implants may be potentially more or equal compared to the gold standard, which is the implant produced by milling.

METHODS

We studied the biosafety of this technology and its products by measuring serum and organ titanium levels after implantation of 3D-printed versus traditionally fabrication titanium plates and screws in a pilot study using the rabbit model. A total of nine rabbits were used, with three each in the control, milled and printed titanium group. The animals were euthanized after six months. Serum and organs of the reticuloendothelial system were harvested, digested and assayed for titanium levels.

RESULTS

Organ and serum titanium levels were significantly higher in rabbit subjects implanted with titanium implants (milled and printed) compared to the control group. However, there was no significant difference in organ and serum titanium levels of subjects implanted with milled and traditionally fabricated titanium implants.

CONCLUSIONS

The biosafety of use of 3D-printed titanium implants and traditionally fabricated titanium implants are comparable. With this in mind, 3D-printed custom implants can not only replace, but will very possibly surpass traditionally fabricated titanium implants in the mode and extent of use.

Local and Systemic In Vivo Responses to Osseointegrative Titanium Nanotube Surfaces

Orthopedic implants requiring osseointegration are often surface modified; however, implants may shed these coatings and generate wear debris leading to complications. Titanium nanotubes (TiNT), a new surface treatment, may promote osseointegration. In this study, in vitro (rat marrow-derived bone marrow cell attachment and morphology) and in vivo (rat model of intramedullary fixation) experiments characterized local and systemic responses of two TiNT surface morphologies, aligned and trabecular, via animal and remote organ weight, metal ion, hematologic, and nondecalcified histologic analyses. In vitro experiments showed total adherent cells on trabecular and aligned TiNT surfaces were greater than control at 30 min and 4 h, and cells were smaller in diameter and more eccentric. Control animals gained more weight, on average; however, no animals met the institutional trigger for weight loss. No hematologic parameters (complete blood count with differential) were significantly different for TiNT groups vs. control. Inductively coupled plasma mass spectrometry (ICP-MS) showed greater aluminum levels in the lungs of the trabecular TiNT group than in those of the controls. Histologic analysis demonstrated no inflammatory infiltrate, cytotoxic, or necrotic conditions in proximity of K-wires. There were significantly fewer eosinophils/basophils and neutrophils in the distal region of trabecular TiNT-implanted femora; and, in the midshaft of aligned TiNT-implanted femora, there were significantly fewer foreign body giant/multinucleated cells and neutrophils, indicating a decreased immune response in aligned TiNT-implanted femora compared to controls.

No radiological and biological sign of trunnionosis with Large Diameter Head Ceramic Bearing Total Hip Arthroplasty after 5 years

BACKGROUND

Trunnionosis of large diameter (LDH) metal-on-metal total hip arthroplasty (THA) was linked to high systemic chromium (Cr) and cobalt (Co) ion levels and local adverse reactions to metal debris (ARMD). The safety of CoC LDH THA is not yet available at mid-term. Measuring whole blood Ti level of ceramic on ceramic (CoC) LDH THA with a titanium (Ti) stem is an indirect way to assess the performance of its head-neck taper modular junction. Therefore, we wanted to determine: (1) if the whole blood Ti ion levels in patients with LDH CoC THA after a minimum of 5 years of implantation is within the expected values for similar well performing Ti THA, (2) if Ti level scientifically increases over time, which would suggest the presence of a progressive modular head/neck junction wear process, (3) if clinical or radiographical manifestations of implant dysfunction are present?

HYPOTHESIS

Ti blood levels of LDH CoC THA will indirectly reflect the expected levels due to passive corrosion of the implants and will be stable over time.

PATIENTS AND METHODS

We report the whole blood Ti, Cr, and Co levels at 5years minimum for 57 patients with unilateral primary LDH CoC THA with head sizes ranging from 36 to 48mm using Ti stem and acetabular component. To compare Ti ion levels modification over time, in 25 patients were a previous measurement (1-3years) was available, we compared it to their last follow-up results (>5 years). Mean Ti level in well performing Ti THAs is recognized to be around 2.0 ug/L. Although, there are no universally accepted Ti levels associated with problematic implant, we used safety threshold of 10 ug/L. Clinical and radiological outcomes were recorded at last follow-up.

RESULTS

At 79 months mean follow-up, all mean Ti levels were 1.9μg/L (min 1.2, max 4.4) and all subject had values below the safety threshold of 10ug/L. In the subgroup of 25 cases with a previous measurement, there was a decrease in mean Ti levels between 20 months and 78 months follow-up (2.2μg/L (1.6-3.9) versus 2.0μg/L (1.4-2.8), p=0.007). No statistically significant relation was observed between Ti level at last FU and bearing diameter (rho=0.046, p=0.0734) or the presence or absence of a Ti adaptor sleeve (p=0.454): 1.94ug/L (min 1.20, max 2.80) versus 1.90ug/L (min 1.20, max 4.40). At last follow up, no patients presented osteolysis signs on radiographs, clinical signs of ARMD or were reoperated. Most patients had excellent clinical with 98% of them reporting minor (29%) or no functional limitation (69%) and 44% perceive their THA as a natural hip joint. However, 3/57patients (5%) temporarily experienced hip squeaking and 18/57 (31%) reported clicking sound.

CONCLUSION

With the tested LDH CoC THA, Ti levels were low and related the uneventful and unavoidable passive corrosion of implant surfaces. Mid-term measurement of Ti in subjects with LDH CoC did not reveal any indirect signs of trunnionosis, which should already be observable by this time.

LEVEL OF EVIDENCE

IV, retrospective study.

Metal Ion Release, Clinical and Radiological Outcomes in Large Diameter Metal-on-Metal Total Hip Arthroplasty at Long-Term Follow-Up

Total hip arthroplasty (THA) with metal-on-metal (MoM) bearings have shown problems of biocompatibility linked to metal ion release at the local level causing an adverse reaction to metal debris (ARMD) and at a systemic level. The aim of this study was to evaluate clinical and radiological outcomes, and metal ion concentrations in the blood and urine of patients who underwent THA with the LIMA Met-Met hip system. Patients with ceramic-on-ceramic (CoC) bearings were included as a control group. In this study, 68 patients were enrolled: 34 with MoM THAs and 34 with CoC THAs. Patients were evaluated clinically (Harris Hip Score, SF-36) and radiologically at a median of 7.4 years after surgery. Whole blood and urinary cobalt and chromium levels were also assessed. Both types of implants were comparable in terms of clinical and functional results. Ion levels were significantly higher in the MoM group compared with CoC group 7 years after surgery. No correlations were found between metal ion levels and patient demographics, functional and radiological outcomes, and prosthesis features. Patient monitoring is thus advised to establish if prosthesis revision is necessary, especially in the case of MoM THA.

Systemic Effects of Metals Released from Arthroplasty Implants – a Brief Summary

In recent years, increasing concern has been raised regarding potential systemic toxicity of metals released from arthroplasty implants. A lack of valid metal thresholds for human (organ) toxicity and the prospect of multi-decade survival of modern hip and knee replacements pose special challenges. Indeed, evidence of systemic effects of metals released from such implants is largely missing. Systemic cobalt exposure has repeatedly been associated with cardiotoxic and neurotoxic effects, and also with thyroid dysfunction. The toxic potential of chromium is considered less pronounced. Yet, in arthroplasty there is usually a co-exposure to chromium and cobalt which complicates evaluation of element-specific effects. Toxicity of titanium dioxide nanoparticles has been subject to debate among international regulatory authorities. Their wide use in a variety of products in everyday life, such as toothpaste, cosmetics and food colorants, hampers the assessment of an arthroplasty-induced systemic titanium exposure. To date there is no clear evidence for systemic complications due to titanium dioxide released from arthroplasty implants. Release of further metals such as tantalum, niobium, nickel, vanadium and zirconium from hip and knee replacement implants has been described occasionally, but systemic effects of respective long-term exposure scenarios are unknown. Generally, the characterization of all released metals regarding their chemical and physical specifications is critical for the evaluation of potential systemic risks. Systematic studies investigating the accumulation of metals relevant in arthroplasty in different organs/organ systems and the biological consequences of such accumulations are urgently needed.

A Case of Titanium Pseudotumor and Systemic Toxicity After Total Hip Arthroplasty Polyethylene Failure

We describe the case of a 57-year-old female who underwent bilateral ceramic-on-polyethylene total hip arthroplasties performed in 2015. She presented to us in 2018 with headaches, fatigue, and right hip pain 5 months after an atraumatic right polyethylene liner failure for which she did not seek treatment. She was found to have imaging consistent with an adverse local tissue reaction and massive pseudotumor formation. During revision surgery, fracture of the acetabular liner was noted, with ceramic head wear through the titanium cup. In the months after her debridement and prosthesis revision, the patient continued to complain of systemic symptoms including weakness, fatigue, headaches, and vision problems. Serum titanium levels were found to be 100 times higher than normal. This case serves as a rarely reported example of titanium toxicity and titanium pseudotumor formation in the setting of polyethylene failure.

Management of patients with magnetically controlled growth rods amidst the global COVID-19 pandemic

Introduction

At the time of writing, we are all coping with the global COVID-19 pandemic. Amongst other things, this has had a significant impact on postponing virtually all routine clinic visits and elective surgeries. Concurrently, the Magnetic Expansion Control (MAGEC) rod has been issued with a number of field safety notices and UK regulator medical device alerts.

Methods

This document serves to provide an overview of the current situation regarding the use of MAGEC rods, primarily in the UK, and the impact that the pandemic has had on the management of patients with these rods.

Results and Conclusion

The care of each patient must of course be determined on an individual basis; however, the experience of the authors is that a short delay in scheduled distractions and clinic visits will not adversely impact patient treatment. The authors caution against a gap in distractions of longer than 6 months and emphasise the importance of continued remote patient monitoring to identify those who may need to be seen more urgently.

Whole blood titanium metal ion measurement reproducibility of two laboratories

Background

Metal ion blood concentrations evaluation can be useful in monitoring wear and corrosion of orthopedic implants. Elevated metal ion level may help detecting defective hip arthroplasty implants and serve as an indicator for revision surgery. Our objective was to evaluate the reproducibility of titanium metal ion level measurements by two different laboratories.

Methods

Seventy-one whole blood samples were collected from 64 patients with unilateral ceramic-on-ceramic hip arthroplasty. For each patient, two whole blood samples were collected and analyzed in two different laboratories.

Results

For each case, laboratory 1 had significantly higher values than laboratory 2. There was a clinically significant absolute difference between the two laboratories, above the predetermined threshold, for 90% of samples. A mean variation ratio of 410% between the two laboratories was found.

Conclusion

Not all laboratories use the same techniques and calibrations to perform these measurements. Therefore, their results should be interpreted with caution and clinical decision should rely on metal ion trends provided by the same laboratory.

Biological Monitoring of Metal Ions Released from Hip Prostheses

The aim of this study was to evaluate the levels of As, Be, Bi, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Se, Tl, V, and Zn, by inductively coupled plasma-mass spectrometry (ICP-MS) in the urine of two groups of patients with two different types of metal-on-metal (MoM) total hip prostheses (ASR DePuy^®, group A, 25 patients; total Met-Met System Lima^®, group B, 28 patients). The determination of metals reflected a steady-state release (group A: 9 years after surgery and group B: 6 years after surgery). The results obtained confirmed the increase of Co and Cr urinary levels in both group when compared with the reference values for the general population adopted by the Italian Society of Reference Values (SIVR). In particular, Co and Cr levels exceeded the threshold values in urine, respectively, of 30 μg and 21 µg, adjusted to creatinine based on the threshold in whole blood of 7 μg/L proposed by the Medicines and Healthcare Products Regulatory Agency (MHRA). Regarding the other investigated metals, significantly higher values were found in Group A than in Group B. These differences could be due to the type of hip prosthesis implanted, the longer period of time since the implantation, as well as many other factors such as diet, age, drug consumption, physical activity, or presence of dental fillings. The continuous monitoring over the years of metal concentrations in patients carrying a prosthesis could be useful to better identify the sources of these metals.