Kinematic alignment refers to a method of placing the femoral and tibial implant in a total knee replacement so that they better replicate the native joint axis. This contrasts with the traditional technique of mechanical alignment where the implants are placed at a perpendicular to a line from the center of the hip to the center of the ankle. Proponents of the mechanical axis technique have argued that this perpendicular placement is better for the loading mechanics of the implant which reduces shear forces on the fixation to bone and improves implant longevity. Because mechanical alignment is not truly anatomic relative to the knee joint line and flexion axis, the use of off-the-shelf implants placed by this method can lead to kinematic abnormalities which may manifest themselves as stiffness, instability or pain. In many cases, releases of the soft tissues (usually the medial or lateral collateral ligament) are necessary to balance the soft tissues around the implant throughout the range of motion.
In theory, by placing the implant in a manner that more closely mimics the normal joint line and flexion axis, kinematic alignment may reduce the need for soft tissue releases and provide for a more stable and natural feeling knee. Recently there has been growing interest in this technique as surgeons look for ways to improve outcomes and speed recovery.
Conformis Inc., a manufacturer of patient-specific, custom total knee replacements, offers a unique solution that provides the best of both worlds. Each iTotal Identity implant is made to fit the respective patient’s native anatomy. In other words, the shape of the implant is custom fit to the patient’s anatomy. By doing so, and by providing 3D printed cutting jigs that ensure proper implant placement, Conformis allows the surgeon to replicate kinematic alignment with precision. Furthermore, the shape of the plastic insert is also customized to restore the joint line axis allowing the tibial component to be placed in mechanical alignment while still allowing a kinematic alignment at the articular surface. This provides the benefit of optimized implant fixation and loading along with optimized soft tissue balance and joint function.
Conformis is the only company that currently provides customized joint replacement implants. Other novel technologies such as robotics continue to use non-custom implants that may not well fit a particular patient’s anatomy. The value proposition of Conformis with its anatomic replication, kinematic alignment and precision instrumentation cannot be beaten by any other product including a robotic total knee. When combined with the benefits of our AVATAR rapid recovery program, great results can be achieved.