Kinematic Alignment for Total Knee Replacement
In general, total knees are implanted using either Mechanical Axis (MA) alignment OR Kinematic Alignment (KA) Principles. Historically, most total knee replacements were implanted using the mechanical axis method. This method basically cuts every patients knee at the same angles. In other words, the bone cuts around the knee are intended to effectively make every patients knee/leg perfectly straight.
The trouble with this approach, is that we know from decades of research and doing knee replacements, along with the CT scan data of tens of thousands of knee patients, that most patients legs are NOT perfectly straight. Many patients are varus (bow-legged) for most of their life, while some are valgus (knock-knee). The soft-tissues, ligaments, and patella (kneecap) are used to functioning at these pre-existing positions and angles. If we ignore these angles (Mechanical Axis Alignment) and cut every patient perfectly straight, a certain percentage of these patients continue to have pain, swelling and trouble with their knee replacements despite our best efforts.
For these reasons, we have transitioned over the years towards Kinematically Aligned (KA) Total Knee Replacement. Dr. Stephen Howell, our friend and colleague, has been instrumental in teaching knee surgeons around the world the benefits of Kinematically Aligned Total Knee Replacement. Since 2015, we have been following these KA principles and have seen a tremendous benefit in our patients.
In Kinematic Alignment Total Knee Replacement, we insert the knee in the EXACT position that matches the position of the native knee BEFORE the patient developed arthritis. Effectively, we remove the exact same thickness of bone that matches the thickness of the new metal knee placing the new metal knee in the same position of the original knee. We use our pre-operative CT scan to assist with this planning, however, we have specialized instruments and measuring devices that allow us to do it in the event we cannot get a CT done before surgery. We literally measure each small cut of bone to the millimeter to ensure an accurate reconstruction!