New York University Langone Orthopedic Hospital has halted the use of the Stryker Tritanium hip implants. This action was based upon findings in a new study published in June 2018 by doctors and scientists at the hospital.
The study documented several performance failures of the Stryker Tritanium hip device compared to other hip implant devices on the market. The problem that was documented in the study was an abnormally high rate of the implants coming loose. When implants come loose surgery is required to remove the implant and replace it with a new implant. This is called a revision surgery. Revision surgeries are more complicated and more prone to complications than initial implant surgeries. After revision surgeries patients are more prone to functional limitations in walking and other activities than after an initial implant.
The Study is entitled: Early Aseptic loosening of the Tritanium Primary Acetabular Component with Screw Fixation was published in Arthroplasty Today. The study notes that hip implants should function well for many years. Sources cited in the study document survival rates of hip implants generally to be 90% still functional at a 10 year follow up and 85% at a 15 year follow up.
So the concern of the investigators in the study was that NYU hospital was seeing the Tritanium implants coming loose within a few years after implant. Implants can and do become loose and fail early in a small number of cases which should be under 1% per year. Some implants come loose for unknown reasons and some can be due to infections. But these background loosenings are accounted for in the 1% per year failure standard. When the number of loosenings on a particular device start to exceed 1% per year that calls for an inquiry as to whether there is a defect in the design of the device. That is what this study was assessing.
As the title to the study indicates the authors were looking at aseptic loosening. Aseptic means that there was no infection. Infections can occur in patients with hip implants for a number of reasons that are generally not the fault of the manufacturers or the surgeons and many infections may be unavoidable. An implant device does not have blood flow within it so bacteria in the body from the blood stream can collect on the implant. Bacteria can get in the blood stream from dental work or even vigorous teeth brushing, cuts, or bearing down on a bowel movement. Infected implants usually have to be removed but sometimes can be treated with IV antibiotics.
By excluding cases with infections the authors could focus on failures that might relate to the design of the implant device. Most hip implant cups including the Tritanium are designed to fit tightly into the pelvis into a recess that is reamed out by the surgeon and then designed to allow the bone from the pelvis to grow into the back of the cup that is porous. Different manufacturers use different materials for this porous backing of the cups. Some materials have been proven better than others at allowing or stimulating this bony ingrowth into the back of the cup.
The authors of this study found that the Stryker Tritanium cup had a higher failure rate than the Trident cup which is also made by Stryker. The authors also found that the Tritanium cup designed for initial implant which is call a primary cup had a higher failure rate than the Tritanium cup designed for revision surgery. They compared the manufacturing process and the materials used in the primary titanium cup with the revision titanium cup and found significant differences which they believe is the cause of the loosening failures in the Tritanium primary cup. They concluded that “the pore structure and polymeric binding agent used in the Tritanium primary cup may be directly related to its increased tendency to fail in comparison with the revision cup.”
The study was a case review of a series of 5 cases at the hospital and a medical literature review of some prior papers that came to conflicting conclusions. Therefore, the authors of this study are conducting a larger more comprehensive study to further assess the problem with the Stryker Tritanium cup but they believed that the results of this study justified halting the use of this device at NYU hospital to protect patient safety.
Our law firm and others are preparing product liability lawsuits against Stryker to further investigate the failures of these devices and to seek compensation for those who had to have a revision surgery to have the Tritanium devices removed. We are accepting these cases for legal review.
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