Choosing a knee implant is an important decision. The prosthesis will become a vital part of your anatomy, helping you to walk, sit, stand and move around. Not only that, but it will be with you for years to come – around 15+ is the usual lifespan for an artificial knee implant.
When you choose an orthopaedic surgeon to perform your knee replacement, alongside checking their credentials, experience and what their patients say about them, it is worth looking into what type of implants they use.
Carrothers Orthopaedics have been performing knee replacement surgery for many years and our preferred patient specific/customised knee prosthesis is made by Conformis.
Conformis customised artificial knee joints
The reason we choose them is because, unlike traditional, off-the-shelf implants, Conformis artificial knee joints are designed to precisely match the patient’s unique anatomy. The size and shape of each person’s knee is subtly different and using an off-the-shelf implant may mean having to compromise on the fit, alignment or rotation of the replacement joint.
This could account for the fact that one in five patients report being dissatisfied after total knee replacement surgery, according to Clinical Orthopaedics and Related Research conducted in 2010 by Bourne et al. Even the smallest amount of misalignment or compromise in relation to fit or rotation can lead to discomfort and pain.
For an artificial knee to operate smoothly, as your natural joint would, it needs to follow the shape and contour of your native knee precisely. This helps to prevent instability and results in a more natural feeling knee that allows you to regain the mobility that you have lost through disease or injury.
Arthritis and how the knee works
To fully understand why a personalised knee implant is so much better than an off-the-shelf one, it is helpful to understand how the knee works. The knee joint is where three bones meet – the thigh bone (femur), shin bone (tibia) and knee cap (patella). The bones form three compartments of the knee – the medial compartment on the inside of the knee, the lateral compartment on the outside of the knee and the patellofemoral compartment behind the knee cap.
When you have a degenerative disease like osteoarthritis, or if you severely injure your knee, the cartilage which cushions the articulating ends of the bones can wear away, which may cause the bones to rub together resulting in pain and loss of function.
If you have osteoarthritis in just one or two compartments of your knee, you may be able to have a partial knee replacement which offers faster recovery times. However, if all three compartments are affected you will need a total knee replacement.
Standard, off-the-shelf implants tend to come in six to 10 standard sizes. But when you consider how different people are in terms of their height, weight and shape, you can see why orthopaedic surgeons are forced to compromise to match off-the-shelf implants to the person’s anatomy.
Designing a custom implant
Conformis have developed the first customised total knee implant to be granted FDA approval. It is designed to follow the exact shape and contour of the individual’s knee so there is no compromise on fit or alignment. A CT scan is acquired of your knee and the Conformis iFit image-to-implant technology converts this into a 3D model. It is this model that is used to plan your surgery and create an anatomically unique implant for each patient.
The implants are based on the unique shape and bony curvatures of your knee so when the surgeon implants it into position it is virtually indistinguishable from your original knee joint – except that it is made from man-made materials rather than bone.
As much of your natural bone as possible can be preserved using this type of implant, which is an important advantage if you require revision replacement surgery in the future. This is surgery to replace a worn out implant, which can become necessary as most implants, depending on use and activities, last around 15 years.
Carrothers Orthopaedics believe that treating patients using customised patient specific knee implants gives the very best chance of smooth, pain-free movement and good quality of life for many years to come.
