A person usually opts for a total knee replacement (TKR) to regain their quality of life lost due to degenerative bone disease, joint damage caused by arthritis or injury. It is one of the most successful procedures in all of medicine and the Arthritis Foundation estimates TKRs will exceed 3 million by 2030.
The demand is forcing the medical community to consider alternative products that will increase operational efficiency, including relying more heavily on high-viscosity cement (HVC). The Orthopaedic Research Society explains that researchers deem HVC less effective than low- or medium-viscosity bone cement (non-HVC).
Studies show that HVC increases the risk of failure, even when used in combination with a previously well-performing implant. Then, the patient needs a revision, ultimately delaying them from achieving improved quality of life.
Bone cement, or epoxy, is used to attach components of the new knee joint to the femur (thigh bone) and tibia (shin bone). It includes a powder and a liquid that must be combined. Viscosity refers to the epoxy’s thickness or consistency after it is mixed.
Varying viscosity levels yield different product qualities. Surgeons can apply HVC epoxy earlier in the procedure because it takes less preparation time and takes longer to harden – giving the surgeon more time to work. However, the differences between HVC and non-HVC epoxies may play a significant role in the strength of the cement’s bond with both the bone and implant.
The National Center for Biotechnology Information (NCBI) reports that in 2016 researchers evaluated 13 cases where the implant debonded or failed to adhere to the cement along the edge of the shin bone. Researchers believe the use of HVC in those cases is linked to the implant failures. Similar procedures using non-HVC showed no signs of debonding. Similarly, NCBI notes a 2013 study revealed that out of 3,048 TKRs, only nine failed – all of which involved the use of HVC.
Manufacturers enhanced the push to use HVC by fast-tracking the Food and Drug Administration’s (FDA) approval. They claimed HVC was “substantially equivalent” to epoxies on the market, which allowed it to be approved through the 501k process. The fast-track approval does not require products to demonstrate their safety and effectiveness.
Normally, a TKR dramatically reduces knee pain and improves quality of life, but by using a less effective product, patient benefits are often sacrificed.
Orthopaedic Research Society
National Center for Biotechnology Information
U.S. Food and Drug Administration