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Denise asks about Stryker ABG 11 modular stem recall 22 August 21012

Have a question for Dr. Steve. What are your thoughts on the stryker ABG 11 modular stem recall and possible metal issues. I have this stem with a ceramic head and stryker dual mobility ADM cup. It seems to me stem is titanium, neck is co-cr and head is ceramic so not really a metal on metal problem. ADM has the ceramic head on poly shell, titanium cup. This stem was recalled with the rejuvanate which I bleiev has a metal ball which seems to be more of a problem. It seems to me the ABG was just bundled with the rejuvanate due to they are both modular. Thoughts on this? Can it be a problems. Your thought via email would be appreciated.

Dr Steve’s Reply – 25 August 2012

Styker (to my knowledge) never offered a metal-metal bearing hip other than marketing Corin’s resurfacing product in the US but their Rejuvatate stem is a problem with chrome-cobalt debris generated apparently at the modular connection between the stem body and the base of the femoral neck. At this junction the mated surfaces are both chrome-cobalt alloy. It is possible that similar debris might be generated at the modular head neck junction were the mated surfaces might be either chrome-cobalt on titanium or chrome-cobalt on ceramic. The potential problems at both junctions is likely increased if a larger head diameter is used, a longer neck is used, or if a “plus” head is used.

The mechanism by which metal debris is generated at these junctions can be both fretting (micro-motion) or galvanic corrosion. These problems are likely common stems of other brand that have stem/neck modularity (a handful of models and brands) or neck/head modularity with a head diameter of > 36 mm ( many ). Patients that have hips that generate this type of wear likely will not have the markedly high blood cobalt or chrome level that might result in outright systemic toxicity (cobaltism) manifest by damage to the mind (affective, memory, and learning problems ), hypothyroidism, or heart and vessel issues ( cardiomyopathy and hypertension ) but might have problem with tissue inflammation and tissue damage around the hip ( Adverse Reaction to Metallic Debris or ARMD).

ARMD reaction can be serious and might result in a difficult salvage situation for the patient that requires revision surgery and the surgeon that performs the revision. The major problem being the loss of ligaments, tendons, muscle, and bone. Many patients with severe loss of tissue will be condemned to a less than ideal result from their revision surgery with the most common problem being hip instability (dislocations). Most but not all patient with ARMD reactions will note pain and will have increased fluid or soft tissue masses about the hip – cystic (fluid) or solid psuedotumors -. These problem might not be apparent on plain X-ray but are usually found by ultrasound or metal suppression MRI, or CT exam.

Not all of the Rejuvanate stems had a modularity between the neck and the stem body, in the smaller sizes the stem body and the neck are one piece.

I am bothered by the Class Two recall designation. The product is silently removed from the market and surgeons that implanted the devices are notified by letter that there is a potential problem with the device that the surgeon should be aware of but it is not recommended that patients be notified and systematically brought in for review. I think many surgeons will be content to let sleeping dogs lie and not contact their patients and that some might have a smoldering problem in which the symptoms are not bad enough to cause them to contact their surgeon.

This type of recall seems to transfer the liability and responsibility from the manufactureur to the surgeon, to the determent of the patient. In my experience with this type of recall the representative of the company that made the implant is usually present at the time of revision surgery and will request that the explants be surrendered to him or her to be sent to the company’s lab for analysis. When this happens the surgeon and patient never see the explants again and if an inquiry is made as to the results of the “analysis” the answer is typically, “we could not find a problem with the device, the surgeon must have installed it wrong.”

I have been revising hips for twenty years and found and published on defects on implant designs (the combination of the Zimmer Trilogy acetabular shell with a thin cross-linked liner made of Longevity plastic). Though published this information never lead to a recall of any sort, this implant combination was quite common and likely hundreds of patients required revision because of failure of the liner (rim cracking). My paper may have contributed to the design of this product.

These flaws in implant design and the delayed nature of their discovery is being experienced now on a much larger scale with the resurfacing and modular bearing surface metal-metal hips. One system has been formally recalled (the Johnson and JohnsonDePuy – ASR), two others have had class 2 recalls, the Zimmer Durom (transient), and the modular Smith and Nephew metal-metal liners in their R-3 line.

It has been recommended by the British Orthopedic Association that surgeons stop implanting the modular metal-metal hips but most are still no the market. I think this is in essence a “silent recall” and is indicative of unbalanced industry influence on orthopedic professional organizations.

The FDA (US) and MHRA (UK) generally only accept input from orthopedic professional organizations, largely the same surgeons that are consultants to industry. For this reason I believe their response the complications of these devices is emblematic that these “regulatory agencies” are more protective of industry that of patients. This is not overt corruption, these agencies do not have the budgets to do independent pre or post market research. Almost all research on orthopedic devices is funded directly or indirectly by industry,

“He who takes the King’s coin whistles the King’s tune.

Regards,

Dr Steve

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