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Joseph H. Saunders
Joseph H. Saunders
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New Medical Study Supports Stryker Rejuvenate AGB II Lawsuits

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A peer reviewed medical study published in the March 19, 2014 edition of The Journal of Bone & Joint Surgery concluded that the Stryker Rejuvenate modular-neck stems were failing at an alarming rate. The medical study found that from June 2009 to July 2012 the 104 patients that were reviewed had a 28% revision rate. All of these patients had hip implants by the same surgeon who was skilled and well respected at Houston Methodist Hospital in Houston, Texas. The study is titled: Early Corrosion-Related Failure of the Rejuvenate Modular Total Hip Replacement.

Study Concluded that Corrosion at Rejuvenate Neck Joint Caused Failures

The doctors conducting the study measured the metal ion levels of the patients to compare their chromium and cobalt blood levels. They used the metal ion levels as a surrogate marker of corrosion wear.  High metal levels indicate corrosion of the implant. Metal levels were found to be higher in younger and more active patients.

The study described the likely mechanical causes of the corrosion in the hip implants. The metal parts of the implant have a hard and finished surface that resists corrosion. When the surface of the metal becomes fretted or scratched allowing bodily fluids to interact with the metal under the finished surface of the metal it allows the corrosion to begin. This fretting or scratching of the surface of the metal parts is caused by micro motion of the different joints rubbing against each other and scratching the surfaces of the metal. The study refers to this as crevice corrosion at the neck stem junction.

The Rejuvenate has a modular neck with a joint inserted into the femoral stem on one end and into the ball on the other end. Traditional artificial hip implants only have one joint since the femoral stem is connected directly to the ball.

Mismatch of Metals by Stryker May Cause Corrosion

It is a basic principle of chemistry that placing different metals in contact with each other can cause corrosion of the metals. Different metal don’t like each other chemically. The study observed that one important cause for the increase in chromium and cobalt levels in patients with a Rejuvenate stem could be the metallurgy mismatch between the modular neck and the stem. A titanium alloy is used to make the femoral stem and the modular neck that is inserted into the stem is made from cobalt and chromium.

Improper Taper Fit between the Neck and Stem May Contribute to Corrosion

If the joint between the neck and the stem is not tight and very slight motion called micro motion occurs allowing the metals to move against each other, the surfaces get fretted or scratched leading to corrosion. This is a defect in the design of the Stryker modular neck implants. The Study listed inadequate taper fit as one of the possible causes of the corrosion.

I have heard from orthopedic surgeons helping me with my cases that the design of this joint required that the neck be hammered in with significant force to achieve a tight fit. Surgeons by training and experience are hesitant to use such force because it might fracture the femur. This would be a design defect that Stryker should have anticipated. The Study did not mention this issue but I think it may be a significant legal issue showing defective design or negligence on Stryker’s part.

Study is Legal Evidence that Helps Lawsuits

Peer reviewed medical literature is an important part of proving a legal product liability lawsuit. Published medical literature is relied on by experts testifying for injured persons to prove that a medical product is defective and that the defect is caused the injury. Here, the new study published in The Journal of Bone and Joint Surgery provides accepted medical science to help attorneys for injured hip implant patients prove these cases in court. The literature can be used as a foundation to show that the expert witnesses have solid medical evidence to back up testimony. Judges require such a showing to qualify experts to give testimony in court.

My law firm is handling a number of these Stryker lawsuits in both federal and state courts. The Stryker Rejuvenate and AGB II was recalled in 2012.

I would be happy to answer individual questions about this article or about individual cases.

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