Total Knee Replacement Techniques – How can it be done
Whilst a total knee replacement is a successful operation, the current literature supports that only 80% of patients are truly Good or Excellent when questioned. With the recovery time for a total knee replacement getting quicker and quicker, even after 1 year, having 1 in 5 patients who isn’t good or excellent can pose a problem. The development of various knee replacement techniques have allowed surgeons to refine how they are placing total knee replacements in a more accurate way.
Conventional Method (Instrumented)
In the traditional method of knee replacement techniques, once the knee is opened, a surgeon drills a hole in the femur (Thigh bone) and tibia (Leg bone) and inserts a long rod (Approximately 30cm) into the bone. This is used to approximate the shaft of each bone, which then relates to how much the first cuts are angled. This relies on an accurate Xray from the hip to the ankle, taken with the perfect alignment, to ensure that any pre-operative calculations are transferred to the operating table. This has been shown to be an accurate way of performing total knee replacements in general. There is bleeding from the drill holes in the bone, which are then filled with left over bone to stop the bleeding from entering the knee.
During surgery, the surgeon inserts pins through the bone, away from the surgical site. This is then sensed by a computer looking over the surgeons shoulder. The surgeon then maps out the bone using a probe and sends this information back to the computer. Once the calculations are performed, the surgeon uses the computer to help make accurate cuts of the knee for the final implant. This can be extremely accurate, but is dependent on the method of mapping used on the surface of the knee, and relies on the correct information being inputted prior to cutting.
A pre-operative scan is taken of the knee, and the robot then determines where the cuts will finish. Guided by the surgeon, the robotic arm burrs away the bone, rather than cutting it. The surgeon moves the robotic arm around, which limits any false moves from the surgeon. This is different to the Da Vinci robot, which can be performed from another room,m or even another country. In total knee replacement surgery, this technique relies upon the similar mapping of the knee as navigation, but also uses the pre-operative scan to improve the alignment further. In Adelaide, it is only a new technology, available for partial knee replacements only.
Patient Specific Technology
Every knee is different, and patient specific technology relies upon a detailed 3 dimensional scan of the hip, knee and ankle, to obtain a true 3 dimensional picture of where the knee sits, its overall alignment from the hip to the ankle, and also any detailed abnormalities with the knee joint itself. The information is checked and custom made cutting blocks are created, which are used during surgery as cutting guides. This does not rely on any pins placed onto the bone, or rods drilled into the bone, and therefore is a fast, accurate and reproducible way to provide a customised solution to patients. One of the excellent features of surgery of this kind, is that the surgery is effectively performed in virtual space, long before a patient is due for their operation. This means that a surgeon can determine the best alignment and cuts to perform without needing to do this during the operation itself, making it a reassuring way of performing total knee replacement surgery.
Current research suggests that the accuracy of the implantation of a total knee replacement is very important. This means that the Hip, Knee and Ankle should align perfectly, as close to a straight line as possible. Any deviation more than 3 degrees from this line, usually results in more problems with the knee. As knee replacement techniques improve, patients are likely to obtain the best result possible out of their total knee replacement.
Dr Liew uses only Patient Specific Technology as he believes it to provide customised solutions for each patient, as every knee is different.
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