Hey Everyone,
I have been monitoring the posts about this topic for weeks now, and tried to avoid commenting too much about the topic, Now I think it is time to set the record straight officially and talk about the Stryde recall, its causes and the future. Let it be known that I am in no way shape or form a NuVasive consultant, that except for using some of their implants in my limb lengthening clinical practice, I have no financial affiliation with them. This post comes from my own initiative.
(If you do not want to read this long post, go straight to the end for the conclusions )
Let's start by generally talking about orthopedic implants. Most orthopedic implants, whether used in joint replacement, fracture fixation, or deformity correction, have mechanical as well as chemical properties. None is completely inert and they all interact with the human body it is in contact with. The body is a very complex machine with chemical properties, also submitted to mechanicals principles. Our body is quite corrosive in itself! we are like a big saline water container.
Here are a few examples of corrosion in orthopedic implants:
- Junction between head and neck of a Hip Replacement
- Metal on Metal hip replacement coupling (more surface wear than corrosion)
- junction between screws and metal plates/nails in fracture fixation
- Spine fusion rods
I am sure there are 100 more examples i'm forgetting, but you get the point. All those mechanical implants achieve their objective, the task for which they have been conceived, with a small compromise of corrosion. Corrosion that is mostly asymptomatic , that is noted during implant removal surgery, and is likely to never cause any further issue. It is a known fact and none of those devices are pulled from the market. During orthopedic training, material properties is part of the standard curriculum.
So what causes corrosion? When metal has tiny microscopic scratches, and body fluids are pumped into these scratches, 2 pieces of metal touching will start transferring ions .That reaction transforms a refined piece of metal(stainless) into a ''more chemically stable metal'' (that reddish residue we call rust, or corrosion). It is typical of stainless steel and can be accelerated by other materials such as silicon. The nail is literally bathing in a bucket of salt water when it is sitting inside of the bone. Patients want weight bearing implants, and stainless steels are, for now, the only good material that can provide weight bearing.
Even if we venture in the world of other stainless steel internal lengthening rods, we know that STRYDE is not the only one to create corrosion! There are other nails that have been around for literally decades, with the same problem. But because it does not create any significant issue, (no cancer, no metal toxicity, no adverse effects), they have remained on the market and deemed effective and safe. Corrosion at the same male-female junction has been found upon removal of other internal lengthening rods.
So what is the status with the Stryde recall?
The recall of all stainless steel implants was done COMPLETELY VOLUNTARILY by NuVasive to address physican and patient concerns, investigate the reaction, its significance, and improve the product to eliminate de problem. I have read all kind of ominous threads out there and it is time to demystify them:
What is the underlying issue?
An inflammatory reaction in the bone at the male-female junction (where the small piece comes out of the bigger piece) was noticed that in 10-15% of patients with stryde, 6 to 9 months after the initial surgery. This seems to occur slowly enough that the bone has time to repair itself faster without breaking. This reaction completely disappears when the nail is removed. To be completely clear, Dr. Herzenberg who was part of the design team for the PRECICE nail, has always advocated for implant removal, even when he was using ISKD! So the concept that nail removal is pushed by surgeons due to this reaction with completely ridiculous. Any reasonable surgeon should consider removing lengthening implants.
What is that reaction?
From taking biopsies of the bone reaction after nail removal in our center, the current most likely working hypothesis is that the reaction seen on xray is just a manifestation of the body's defense mechanisms (white blood cells) against the corrosion. Remember, the body is a complex machine that always interacts with metal implants, so this is not entirely abnormal.
Can I suffer from Metal poisoning with a lengthening rod?
We have also been drawing Chromium and Cobalt levels in our patients with Stryde nails. Normal levels of Chromium are below 1ng/ml (there is chromium in your drinking water !) The levels of cobalt were normal in our patients and chromium levels never rose beyond 1.5ng/ml (highest safest concentration is 15ng/ml, which is 10folds those levels).
Would you still implant a Stryde nail in your family member if it were necessary?
Yes. Understand me well here: I am not minimizing the fact that Stainless lengthening nails create some amount of corrosion. I believe this needs to be investigated further and that actions should be taken to solve the issue. As a rule of thumb we should always try to improve our technology. But I believe the implant to be safe and reliable, and that it is only a matter of time before we can start using weight bearing implants again.
CONCLUSIONS?
all orthopedic implants have mechanical and chemical properties.
They all interact with the corrosive and alive human body.
Stainless steel lengthening nails may create corrosion where 2 pieces of metal rub against each other. Stryde is not the only one.
The body tries to protect itself by creating a healing reaction around it. It seems to be benign and self limiting, but we are all actively researching this.
NuVasive is doing its due dilligence and addressing the problem to find solutions. We should all be happy and encouraged about that.
Engineers are smart. We are all confident that Nuvasive will find a fix and that Stryde will be back on the market soon.
Bottom line is: Whether we like it or not, the world is made of compromises. Any implant designed to defy nature and lengthen a limb, replace an articulation, fix a fracture, enhance bodily features (i'm including all cosmetic fillers, neurotoxins and prosthetics AND medications) , has the potential to create some problems. If one is not willing to risk complications or problems, one should avoid any kind of surgery altogether.
"For every action, there is an equal and opposite reaction"
- my main man Sir Isaac Newton
Clarifications about the Stryde recall
Thanks for your detailed and thorough perspective. I think the most important unknown most of us are wondering currently is, "When will this be an option again?" and the most critical part of your reply would then be:
Quote from: Michael J. Assayag, MD on March 13, 2021, 06:29:38 PMThe recall of all stainless steel implants was done COMPLETELY VOLUNTARILY by NuVasive to address physician and patient concerns, investigate the reaction, its significance, and improve the product to eliminate the problem.
This is the key point from my perspective. NuVasive reps have been trying to sell the line that they are just doing the recall for "testing and review" which would allow it to come back in just a few months. I doubt that same as you do. I think they are recalling to try to fix the problem, and fixing the problem may take longer. Re-engineering anything in the span of just a few months might be doable but if they intend to perform re-testing or make multiple designs to attempt different approaches to fixing it that will all obviously take some work.
Without insider info from NuVasive though we're all guessing about that.
I did see one x-ray on the forum from someone with a Stryde who had what looks to me like some pretty significant heterotopic ossification around the distraction point and was told by his surgeon to "push it back towards the bone" and try to massage it to break it up. I'm sure that's been rare, but there was then definitely something a bit unusual about the Stryde and this issue, as I've never seen or heard of that with the Betz/Guichet steel nails.
Here you can see his x-rays:
http://www.limblengtheningforum.com/index.php?topic=64978.msg187526#msg187526
Thank you doctor, that was really useful.
Quote from: maximize on March 13, 2021, 06:46:36 PM
I did see one x-ray on the forum from someone with a Stryde who had what looks to me like some pretty significant heterotopic ossification around the distraction point and was told by his surgeon to "push it back towards the bone" and try to massage it to break it up. I'm sure that's been rare, but there was then definitely something a bit unusual about the Stryde and this issue, as I've never seen or heard of that with the Betz/Guichet steel nails.
Here you can see his x-rays:
http://www.limblengtheningforum.com/index.php?topic=64978.msg187526#msg187526
You are very welcome.
What you see on that xray is not related to the implant itself. It is a possible complication of limb lengthening surgery. I lack detail of the surgical technique, do not know about the patient nor have I seen any other xray (in orthopedics we tend to say "1 view is no view") to reliably comment on that out of control bone formation.
however I can guarantee that the comment made in the thread that
Quotei mark. The issue you experienced with the tumour-like outgrowth of the bone onto the side of the nail is now a reason why Stryde has been suspended in the UK for now.
is completely false.
Quote from: Michael J. Assayag, MD on March 13, 2021, 06:59:38 PMYou are very welcome.
What you see on that xray is not related to the implant itself. It is a possible complication of limb lengthening surgery. I lack detail of the surgical technique, do not know about the patient nor have I seen any other xray (in orthopedics we tend to say "1 view is no view") to reliably comment on that out of control bone formation.
however I can guarantee that the comment made in the thread that
is completely false.
Right. Fair enough. I suppose the theoretical concern is if the device is chewing itself up and corroding from poor mechanics shedding metal into the soft tissue this could trigger inflammation which would then lead to increased risk for heterotopic ossification like this. In which case there could be a link. Or as you said it could have nothing to do with the Stryde and be a patient factor that he would have had in his case either way (or a surgeon factor).
With an N of 1 obviously no way to know that for sure. Maybe NuVasive has more info on this. If they're seeing it in a higher number of cases than the Precice it might suggest a link. Someone on here claims Paley has seen more cases of this with Stryde but that is hearsay and I don't know if he really did:
Quote from: one on March 11, 2021, 07:02:41 AMPaley has announced that 60% of people have had odd bone formation possibly due to corrosion.
The other example of concern on this forum I have seen was this case, where his chromium levels were 2-3 times the norm, suggesting there likely was a significant amount of flaking/breakdown/leaching/corrosion:
http://www.limblengtheningforum.com/index.php?topic=66149.msg189943#msg189943
I agree entirely there's no reason for anyone to automatically worry for people who already had the Stryde. Maybe just check your chromium levels and as long as you're healing well you're probably fine. For my own benefit, I wish they didn't pull it at all. The abnormal ossification is the only thing I would worry about as that can cause chronic pain after. If you dodge that or there's truly no connection it's probably still the best device even with these flaws.
Very helpful doc!
QuoteThe body tries to protect itself by creating a healing reaction around it. It seems to be benign and self limiting, but we are all actively researching this.
Is this something to research specifically with limb lengthening and Stryde? If corrosion is a common phenomenon with many implants, then the healing reaction should have happened with other implants too isn't it? And the benignity of such healing reactions should have also been researched, right?
Thank you very much for the detailed response Dr. This kind of information is very helpful to us all.
Excellent post doctor, as always from you.
Thank you with all the knowledge you offer to us.
I have a question though. Could the corrosion of steel (or any metal in orthopaedic nails, plates etc), except from poisoning which you mentioned that is not the case, increase the possibilities of a tumor in bone or other organs?
This is the most important thing for me and I would like a clear answer if you can.
Quote from: Body Builder on March 13, 2021, 07:54:18 PMExcellent post doctor, as always from you.
Thank you with all the knowledge you offer to us.
I have a question though. Could the corrosion of steel (or any metal in orthopaedic nails, plates etc), except from poisoning which you mentioned that is not the case, increase the possibilities of a tumor in bone or other organs?
This is the most important thing for me and I would like a clear answer if you can.
This is highly unlikely.
The only orthopedic implants known to have precipitated what we call Pseudotumor (which is not cancer) are certain types of Metal on Metal coupling hip replacements. However hip replacements move constantly and were creating more than a thousandfold the amount of metal debris.
as for the bone formation reaction i mentioned before, everyone please note that it is not reported at the regenerate site, but at the telescopic junction of the nails.
As for corrosion in orthopedic implants , it is very well documented and has been extensively studied .
How does corrosion affect health in general
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