Knee replacement implants are designs that use a metal shell that covers the ends of the thigh bone (the femur) and the top of the shin bone (the tibia) with a plastic insert placed between. It is important that the metal shell closely replicates the normal anatomy of the knee joint. Implants that are too thick or not properly sized to the patient can cause limitations in joint mobility and lead to stiffness after the knee replacement.
Gender-Specific Implants
A gender-specific total knee replacement implant is a prosthesis that is specifically designed either for a male or a female. The size of the implant is slightly different to accommodate the slightly different average size of the bones between males and females. Most knee replacements marketed as gender-specific are specially designed to fit a woman’s knee joint anatomy.
Traditionally, implant designs have been made using “average” size data. This means that the designers of implants tried to find the “average” size at a joint, and then design implants that are both slightly larger and slightly smaller than the average. As one might expect, the average size of a woman’s knee joint is different from the average size of a man’s knee joint.
Gender-specific implants are designed in a similar way, except that the “average” is different for a man’s bone and a woman’s bone. The idea behind doing this is that by better replicating the normal anatomy, the joint replacement implants may allow for better function, as well as improved durability.
Effectiveness and Durability
There is no data to suggest that creating a gender-specific implant design will help achieve the goals of better function or improved durability. Most orthopedic surgeons will tell you that implants already come in a variety of sizes that will accommodate almost any patient’s anatomy.
It is clear that orthopedic implant companies are looking for ways to distinguish themselves. Sometimes solutions are created for problems that don’t necessarily exist. Only time will tell if a gender-specific implant is actually a better, or worse, implant design.
Currently no evidence exists to suggest that it is an important determinant of a patient’s satisfaction or outcome following joint replacement surgery.
What Should You Do?
Many people who are considering joint replacement surgery may be interested in a specific brand or type of implant. They may have heard about a particular implant material from a friend, an advertisement, or someone they know in the medical field. So what should you do? Is it appropriate to ask your surgeon to use a particular type of implant?
It is always appropriate to discuss with your surgeon any questions, concerns, or interest that you have in joint replacement surgery. That said, it is also important to be willing to listen to your surgeons’ preferences regarding surgery. Most surgeons will not offer to use an implant that they do not know well, but some might. Having familiarity with a particular implant, and the instruments used to implant it within the body is a critical part of the surgery.
If you are interested in a particular implant or material, ask your surgeon to explain more about it. Your surgeon should be able to answer your questions and also explain why they may or may not recommend that particular implant. Keep in mind, implant companies often want you to believe that a newer implant is far superior, but that is not always the case. There is tremendous value in the utilization of implants that have an excellent long-term track record, and the use of implants that have less of a track record can present the potential for problems.
