Leonardo da Vinci’s famous depiction of The Vitruvian Man demonstrates the importance of proportion in the human body and the interdependence of form and function. These concepts especially hold true in the knee joint where the shape of the bones and the function of the joint are tightly wedded.
The knee joint has a flexion axis that is determined by the shape of the femur bones and the level of the joint line. The medial and lateral collateral ligaments have their insertion sites at fixed points relative to the flexion axis and if this axis is not restored to the proper position by the implant, these ligaments may not provide stability throughout the full range of motion. This can lead to a common occurrence call flexion instability which is one of the most frequent reasons for revision knee replacement surgery.
Knee implants have to placed at a precise location to properly restore the flexion axis of the knee in a way the keeps the ligaments stable throughout flexion and extension. Conventional implants that do not mimic the natural shape of a patient’s knee, may fail to properly restore the relationship between fit and function. The mismatch between the knee’s natural shape and the shape of the implant may account for the substantial percentage of patients who continue to manifest symptoms of pain, stiffness, swelling or instability after conventional knee replacement.
The Conformis “Image to Implant” process creates a patient-specific custom implant for each patient based on precise imaging data obtained from a CT scan. This data can not only be used to define the optimal shape of an implant that restore the natural shape of the joint, but also to engineer cutting blocks that ensure the implants are placed in the correct position to restore the alignment of the leg from hip to ankle. The image to the right shows a mesh reconstruction of a knee from which the curvature of the joint surface and be measured to create a custom implant that mirrors this shape.
Custom instruments are also 3D printed to fit the patient’s bone, allowing a smooth surgical process that is efficient and accurate. Both the implant, the instruments and the trials come in a single box that reduces the number of instruments in the operating room, thereby reducing operative time and lowering the risk of infection. The image to the right shows all of the custom components that allow a surgeon to perform a Conformis total knee replacement
3D design and fabrication of the implants is a revolutionary advancement that will come to define the industry in the future. Custom manufacturing of implants to provide a more perfect fit for individual patients is a profound innovation for knee replacement that will continue to perfect this operation so that patients can perform high demand activities with comfort and confidence.
Dr. Parsons has performed several hundred Conformis knee replacements and introduced the iTotal to New Hampshire after which several other surgeons followed suit. For patients considering knee replacement surgery, this technology makes so much sense, it is almost hard to believe why every surgeon does not use this implant.
If you have interest in learning more about the Conformis knee, please contact us at [email protected].
Also see our comprehensive overview of the benefits of this system here: