Study: Metal Hips Cause Higher Metal Ion Levels than Resurfacing

Title: Higher Blood Cobalt and Chromium Levels in Patients with unilateral metal-on-metal total hip arthroplasties compared to hip resurfacing

Abstract

High cobalt and chromium levels in the blood are known to cause negative side-effects in patients with metal on metal hip replacements. This study discusses the risk factors and the overall likelihood that that people with MoM implants are more likely to experience high cobalt and chromium levels.

This study looks at the blood cobalt and chromium levels of 1,748 patients. 692 of these had hip resurfacings and 1,056 of them had total hip replacements, also known as total hip arthroplasties (THA). In this study, “high” levels of metal ions means greater than 7 ppb.

This study found that patients with THA were more likely to have high metal ion levels than patients with hip resurfacings.

This study also found that these risk factors make hip resurfacing patients more likely to experience high metal ion levels:

  • Small femoral head
  • A high acetabular inclination angle
  • Young age.

These risk factors make MoM THA patients more likely to experience high metal ion levels:

  • Being female
  • Longer time between surgery
  • Ion measurement
  • Large femoral head size

The authors conclude that all large diameter MoM THA implants should definitely be supervised closely.

Introduction

MoM hip replacements have very high revision rates, largely because they cause a set of complications known as adverse reactions to metal debris (ARMD). The amount of cobalt and chromium metal ions in patients’ blood samples are often used to determine whether a metal on metal implant is wearing down because they shed tiny metal particles into patients’ bodies over time.

Because of these problems, guidelines have been put in place to monitor the health of patients with MoM implants. However, some experts believe the existing guidelines don’t do enough to predict whether an implant is failing.

Past studies have shown that large-diameter THA devices are more likely to fail, and some MoM brands are considered more dangerous because they fail way too often.

The authors believe there is only one other study that has compared the metal ion levels associated with different MoM brands.

Additionally, although blood metal ion levels are definitely related to implant failure, there is some debate about what amount of metal should be considered dangerous or “too high.”

The authors of this study tried to answer two questions: First, how common is it for MoM patients to experience blood metal ion levels greater than 7 parts per billion (ppb)? Second, what risk factors make patients with MoM hip implants more likely to experience high metal ion levels?

Patients and Methods

This study analyzed the blood metal ion levels of 1,928 patients with unilateral MoM hip implants (meaning only one of their hips had an implant). Of those patients, 751 of them had hip resurfacings, and 1,177 of them had large-diameter head total hip replacements (THR). Additionally, most of the resurfacing patients were relatively young (89% of them were 65 or younger).

Results

In the hip resurfacing group, 48 of the implants were Biomet ReCap devices. In the THA group, 67 of the implants were Biomet M2a devices.

Patients with THA implants were much more likely to have high metal ions than patients with resurfacing implants. Out of the 7 THA brands analyzed, 5 of them caused high metal ion levels in over 20% of their patients, including Biomet. Meanwhile, less than 10% of all resurfacing patients had high metal ion levels.

In the resurfacing group, there was a lower risk of high metal ions for patients that had BHR and Durom devices than patients with ASR implants. Other factors that increased risk in the resurfacing group were female gender, young age, high acetabular inclination angle, and small femoral head size.

In the THA group, patients with ASR devices had the highest risk for high metal ions. Other risk factors in the THA group were female gender, large femoral head size, and length of time since implantation.

In the resurfacing group, 4.7% patients with Biomet ReCap devices had high metal ion levels. In the THA group, 21.6% patients with Biomet M2a devices had high metal ion levels.

Discussion

This study, which is the largest of its kind, confirms that MoM THAs are more likely to cause increased metal ions than MoM resurfacings. This study also contributes important information about how metal ion levels vary across the different implant brands.

The authors recognize that their study had some limitations. For instance, some brands were more represented in this study than others, which could cause some error in the risk reporting. Second, not all blood samples were taken at the same time. This is important because metal ion levels increase over time, especially for THAs. Third, the medical community still isn’t sure what exact amount of metal in the blood indicates implant failure — different medical institutions have different standards. This study used 7 ppb as its cutoff value for “too much” metal, which is actually the highest standard cutoff value in the medical community. Therefore, this study somewhat understates the link between MoM implants and high metal ion levels.

Two other studies have found that MoM THAs produce higher blood metal ion levels than MoM resurfacings. Experts believe the main reason for higher metal ions in THAs is that the taper wears down. Importantly, this study found that Biomet MoM THAs with titanium sleeves produce lower cobalt levels in the blood. However, the authors believe more research is needed to determine the amount of wear caused by the contact between the titanium sleeve and the femoral head in Biomet implants. Additionally, because titanium sleeves often make revision surgery difficult, the authors cannot say whether a titanium sleeve is actually beneficial in the long run. Finally, although this study found relatively low blood levels of cobalt and chromium in patients with Biomet ReCap devices, other studies have actually found that ReCap implants cause high metal ion levels in a large percentage of patients.

Conclusion

This study presents important data based on the results of a large group of patients. Clearly, some brands of MoM implants pose a higher risk than others. Because high metal ion levels are very common among MoM patients, more studies are needed to determine the effects of high cobalt and chromium levels, especially because many patients with high metal ion levels don’t present any symptoms but could still be at risk of health problems.

Reference

Lainaiala, O. Moilanen, T., Hart, A., Huhtala, H., Sabah, S., Eskelinen, A. “Higher Blood Cobalt and Chromium Levels in Patients With Unilateral Metal-on-Metal Total Hip Arthroplasties Compared to Hip Resurfacings.” The Journal of Arthroplasty 31 (2016) 1261e1266.

Want to Discuss Your Metal on Metal Hip Case?

Maglio Christopher and Toale, P.A. is a national leader in metal on metal hip lawsuits. We have contacts within the orthopedic community and extensive medical and technical knowledge about these defective orthopedic hip replacements.

Our attorneys have sued almost all of the manufacturers in the orthopedic industry. In fact, our firm filed the FIRST metal-on-metal hip lawsuit in the United States.

Contact us at 888-952-5242 or fill out the online form below. Our Firm will review your information to determine if we can represent you.  We might even be able to review some of your medical information over the phone.

Continue Reading Study: Metal Hips Cause Higher Metal Ion Levels than Resurfacing

~9% Chance of Pseudotumors 5 Years After Biomet Magnum M2a Hip

Title: A 5-year survival analysis of 160 Biomet Magnum M2a metal-on-metal total hip prostheses

Abstract

Large-head metal-on-metal (MoM) total hip arthroplasties (THA), or hip implants, have high failure rates. This study looks at the conditions of 160 hip devices 5 years after implantation in order to determine their failure rate; all 160 devices were Biomet Magnum M2 large-head MoM total hip articulations.

Overall, a total of 13 implants – or 8.1% – failed and had to be revised. Additionally, this study found that 14 – or 8.75% – of the implants caused pseudotumors in their patients. Pseudotumors are enlarged masses of tissue that resemble tumors, and they’re a known side-effect of MoM implants. Pseudotumors were the leading reason for revision in this study.

The authors of this study conclude that doctors need a rigorous follow-up strategy for MoM THA patients in order to identify and treat implant failure early on.

Introduction

When MoM THA implants were first introduced, they were thought to have a lot of benefits and quickly became popular. However, multiple studies have shown that MoM devices shed metal debris into patients’ bodies, causing many painful and dangerous complications such as pseudotumors and elevated levels of metal ions (cobalt and chromium) in the blood and serum.

Pseudotumor formations can lead to the early failure of hip implants, and there are many risk factors that make people more likely to develop pseudotumors, ranging from the positioning of the implant to the gender of the patient. Because of the well-documented negative consequences of MoM hip implants, the Netherlands recalled these devices and ordered active follow-ups of all patients who received them. This study analyzes the patients who came for follow-ups after the recall.

Materials and Methods

All patients received the Biomet Magnum (M2a-Magnum) prostheses with Recap cup and Taperloc (Taperloc®Hip Stem) or Mallory stem (Mallory®).

All patients had their cobalt and chromium blood levels tested; normal cobalt levels were considered to be below 40 nmol/l. Patients were also asked to complete the Harris Hip Score (HHS) survey. The HHS asks a series of questions that are intended to measure how well an implant is working; after answering these questions, the patient is given a score ranging from 0-100 to rank how well the implant is working. In addition to these examinations, the patients got X-rays, MARS-MRI scans, and CT scans.

Results

In total, this study looked at 160 MoM implants from 150 patients; 10 patients had bilateral MoM implants (meaning they had implants on both hips).

From this group of 160 hips, a total of 15 implants (9.4%) had to be revised. Revisions occurred, on average, 3.7 years after implantation, but some revisions occurred in as little as 6 months after implantation.

Seven of the revision patients experienced groin pain, but 21 of the non-revised patients also experienced groin pain. Additionally, two revisions were conducted due to the loosening of the implant device. Finally, a total of 14 implants developed pseudotumors.

All patient statistics considered, the authors conclude that the survival rate of the large-head Biomet MoM THA device at 5 years is 93.1%.

The patients with revised implants had an average HHS score between 70-80, which is considered “fair.”

The X-rays did not show any bone loss, bone resorption, or fracture. An important finding in this study is that patients with pseudotumors had much higher levels of cobalt in their blood.  Finally, 26 patients had abnormal fluid around their joints.

Discussion

Many studies have shown that large-head MoM THA devices fail early on, develop pseudotumors, and have high revision rates. For instance, one study showed that Biomet implants tend to fail specifically because of their cup, which is a component in the device that’s implanted in the pelvis. Another study found that the Biomet M2a-Magnum had a survival rate of 88% after 3.6 years.

When it comes to pseudotumors, there is some confusion in the literature. Some authors believe that any patient with a pseudotumor should undergo revision surgery, while other authors believe that a pseudotumor alone is not a sufficient reason to revise an implant. It is also unclear whether pain in the hip always indicates the presence of a pseudotumor.

In this study, a total of 14 hips developed pseudotumors after 6.1 years, meaning that patients had an 8.75% chance of developing pseudotumors. Some warning signs of pseudotumors include pain and discomfort in the groin, deafness, fear, and dizziness.

This study also found that patients with pseudotumors experienced more pain in the groin and had lower HHS scores. However, the authors note that they may have missed pseudotumors in patients who did not show any pseudotumor symptoms because some patients did not receive CT scans.

The authors of this study also found that pseudotumors are linked to higher levels of cobalt and chromium in the blood.

The authors believe that large-head MoM devices and high inclination angles are more likely to result in elevated cobalt and chromium blood levels because they cause the implants to shed metal debris more quickly.

The effects of metal debris on the body are not completely understood yet. Some studies have shown that women are more likely to develop pseudotumors than men, and they tend to have higher serum levels of cobalt and chromium.

The authors end their study with multiple recommendations. First, they conclude that doctors should follow up with their patients frequently and measure their metal ion levels each time because these are useful in determining the presence of pseudotumors. They also recommend that patients with pseudotumors undergo revision surgery in order to prevent future complications. Additionally, the authors state that doctors should follow-up very closely with patients who are experiencing pain. Next, they recommend close follow-ups for patients with non-MoM hip devices because those can also have negative side-effects. Finally, they discourage the use of MoM implants outside of a research setting.

Reference

Koper M., Mathijssen N., Vehmeijer, S. “A 5-year survival analysis of 160 Biomet Magnum M2 metal-on-metal total hip prostheses.” Hip Int 2016; 26(1): 50-56.

Want to Discuss Your Metal on Metal Hip Case?

Maglio Christopher and Toale, P.A. is a national leader in metal on metal hip lawsuits. We have contacts within the orthopedic community and extensive medical and technical knowledge about these defective orthopedic hip replacements.

Our attorneys have sued almost all of the manufacturers in the orthopedic industry. In fact, our firm filed the FIRST metal-on-metal hip lawsuit in the United States.

Contact us at 888-952-5242 or fill out the online form below. Our Firm will review your information to determine if we can represent you.  We might even be able to review some of your medical information over the phone.

Continue Reading ~9% Chance of Pseudotumors 5 Years After Biomet Magnum M2a Hip

Monitor for Cobalt Chromium Levels and Pseudotumors Very Early On

Title: Clinical and Wear Analyses of 9 Large Metal-on-Metal Total Hip Prostheses

Abstract

All patients in this study had the Biomet Magnum (M2a-Magnum™) hip implant with a Recap cup and Taperloc (Taperloc1 Hip Stem) or Mallory stem.

This study attempts to figure out the underlying reasons for implant failure by looking at the wear analyses and clinical symptoms of 9 patients with revised Metal-on-Metal (MoM) total hip arthroplasty (THA) implants.

The authors conclude that is very important for doctors to monitor the indicators of implant failure very early on; these include pain, decreased range of motion, and high levels of cobalt and chromium in the blood. The long-term effects of keeping failed implants in place can seriously decrease a patient’s quality of life.

Introduction

All MoM hip implants were recalled in 2011 in the Netherlands. This decision was made after many studies showed MoM THA implants had high rates of revision and caused pseudotumors. Despite this, MoM hip implants remained quite popular in the United States and England.

MoM THA implants shed metal debris into the body, which in turn can lead to high levels of cobalt and chromium in the blood. This can also lead to the formation of pseudotumors around the implant. Pseudotumors are enlargements of tissue that resemble tumors.

The positioning of the implant can impact the amount of wear suffered by implants. For instance, cup inclination angles greater than 55 degrees are known to increase wear due to edge loading. Edge loading occurs when the cup is malpositioned on the head, causing excessive stress and friction, which leads to higher rates of wear.

The wear rates of MoM bearings in this study varied a lot. The authors of this study tried to relate each bearing’s wear rate to its patient’s symptoms in order to understand the underlying mechanisms of implant failure.

Materials and Methods

Of the 9 implants in this study, 7 were revised due to pseudotumor formation. Two of them were revised because of increasing pain. Six of the patients were female, and the average age of the patients was 57.

This study had two main parts: patient examinations and implant wear analysis.

The patient exams consisted of X-rays, MARS-MRI scans, CT scans, ultrasounds, cobalt and chromium serum measurements, and the Harris Hip Score (HHS) survey. The HHS has a series of questions that are intended to measure the performance of an implant; after answering these questions, the patient is given a score from 0-100 to describe how well an implant is working.

Implant wear analysis involved studying the implants themselves after they were removed from the patients in order to determine how much metal was lost by each component of the implant.

Results

The patients’ average HHS score was “fair” (in the 70-80 range). Patients whose implants were revised due to pain had lower HHS scores (in the 60-70 range). Seven patients experienced groin pain, and 2 patients noticed their hip joint was swollen. None of the patients had any neurological problems, deafness, or dizziness.

Four of the patients with pseudotumors experienced groin pain, while three of the patients with pseudotumors (all females) did not experience any groin pain.

According to the X-ray scans, only two patients appeared to have loose cups. Additionally, no patients suffered from bone loss, bone resorption, or fractures. The median inclination angle of the implant cup was 41.2 degrees. However, for the patients with pseudotumors, the median inclination angle of the implant cup was much higher at 47.7.

Moreover, eight patients received ultrasounds. Pseudotumors were visible in 2 ultrasounds. Liquid accumulations in the hip joint were visible in 4 ultrasounds.

In this study, the median cobalt levels were 24.8 nmol/l, and median chromium levels were 47.3 nmol/l. However, patients with pseudotumors had median cobalt levels of 53.8 nmol/l and median chromium levels of 63.0 nmol/l.

A total of 6 MARS-MRIs and CT scans were obtained. Two CT scans showed possible pseudotumors. Five MARS-MRI scans showed possible pseudotumors.

In addition to assessing the patients, the authors of this study also looked at the implants themselves in order to measure the level of wear in each implant. Wear indicates the amount of metal that was shed from a particular component of an implant. Overall, the amount of wear differed a lot from one bearing to another, ranging from 0 mm³ to 24.424 mm³ in the heads, and 0 mm³ to 20.575 mm³ in the cups, and 0 mm³ to .172 mm³ in the tapers. Severe wear was seen in only one bearing.

Discussion

Large-head MoM THAs frequently lead to early failures and pseudotumor formations. However, wear rates and pseudotumor formations vary widely. A better understanding of the relationship between wear rates and pseudotumor formations is needed in order to predict the outcome of MoM THAs in the future.

Some studies have found a link between high wear, patient’s metal sensitivity, and the appearance of pseudotumors. However, other studies have found that pseudotumors can still occur without a lot of wear. In these patients, it is possible that a hypersensitivity to metal caused the implant failure. In hypersensitive patients, reducing the amount of wear experienced by their implant could possibly prevent the implant from failing.

The most important predictor of a bearing’s wear rate is a type of wear called edge loading. Edge loading is caused by a lot of factors, the most significant of which is high cup inclination.

The effects of metal wear particulars and elevated levels of cobalt and chromium have been documented, but they are still not completely understood.

This study did not find a clear relationship between serum metal ion levels and wear rates. However, this study did show a correlation between high cup inclination and increased metal ion levels. For instance, two patients had a cup inclination angle over 55 degrees, and these patients also had the highest amount of wear in their cups.

The patients with the highest amount of head wear also had increased levels of cobalt and chromium in their serum. These findings show that implant positioning is very important in preventing high metal ion levels.

All patients had high levels of cobalt and chromium in their serum. Two patients also had very elevated levels of titanium in their serum. Elevated titanium levels indicate the presence of trunniosis, which is wear of the femoral head–neck interface. It is only seen in large-diameter head bearings. Trunniosis is typically only seen in head bearings larger than 40mm in diameter.

The exact causes of implant failure and pseudotumor formation are not yet known. They could be caused by high cup inclination, edge loading, trunniosis, patient characteristics, or a combination of all of these factors.

The authors provide some recommendations to doctors who treat people with MoM hip implants. They first recommend very close and frequent monitoring of patients with MoM implants. Doctors should not just ask the patient questions to determine if their implant is working; they should also measure patients’ cobalt, chromium, and titanium levels, take X-rays, and conduct MARS-MRI scans. More information is needed to understand the relationships between failed implants, metal ion levels, pseudotumor formations, and patient symptoms.

Reference

Koper, M.C., Mathijssen, N.M.C., Witt, F., Morlock, M.M., Vehmeijer, S.B.W. Clinical and Wear Analyses of 9 Large Metal-on-Metal Total Hip Prostheses. PLoS ONE 11(10):e0163438. doi:10.1371/journal.pone.0163438 (2016).

Want to Discuss Your Metal on Metal Hip Case?

Maglio Christopher and Toale, P.A. is a national leader in metal on metal hip lawsuits. We have contacts within the orthopedic community and extensive medical and technical knowledge about these defective orthopedic hip replacements.

Our attorneys have sued almost all of the manufacturers in the orthopedic industry. In fact, our firm filed the FIRST metal-on-metal hip lawsuit in the United States.

Contact us at 888-952-5242 or fill out the online form below. Our Firm will review your information to determine if we can represent you.  We might even be able to review some of your medical information over the phone.

Continue Reading Monitor for Cobalt Chromium Levels and Pseudotumors Very Early On

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