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Computer Navigated Knee Replacement

Computer navigation in total knee replacement attempts to correct some of the problems faced in traditional total knee replacement. Accurate placement of a knee replacement is one of the most important predictors of longevity of knee replacement. Minor misalignment can lead to early loosening, early polyethylene wear and poor function. Until the advent of computer navigation, the only way to accurately assess the final position of the implanted prosthesis was with a post-operative x-ray. Computer navigation allows the surgeon to accurately check and adjust, if necessary, each step along the way, whilst performing the knee replacement, which still allows the surgeon to exercise his skill and judgement for optimal positioning of the implant.

The computer navigation system works by combining computers, infrared cameras and instruments that reflect infrared light back to the camera. The computer system creates an image of the knee joint during the operation, and it coordinates reference points on the natural knee to those on the new knee. This permits the surgeon to finely adjust the position of the new knee with certainty, so that he or she can orientate the replacement joint to function optimally with the bones, muscle, ligaments, and other structures around them. The surgeon is always in control of the operation and only uses the computer to provide information on where to place the new knee. When using the computer navigation system, pins are required, to be temporarily inserted into the bone; they are then removed once the new knee is inserted.

This requires two very small (half a cm long) cuts to be made on the skin over the shin bone in addition to the standard scar used to insert the new knee, which is over the front of the knee.

Traditional total knee replacement uses instruments temporary placed inside the thigh bone to assist with implant alignment and positioning. The computer navigation guides are placed directly onto your thigh bone and shin bone, and therefore do not require instrumentation of the bone canal, allowing for a potentially less invasive procedure.

Research has shown that the information from the computer navigation provides patients with a more precise operation to those performed with the standard instruments. Unfortunately, most surgeons still do not use this technology with only 3% of all knee replacements in England and Wales currently being completed with computer assistance. One of the main reasons why this technology is not more widespread is that initially it can take longer to perform the surgery using the computer navigation system, until the surgeon becomes skilled in using the information provided by the computer and the use of different instruments. However, this extra time is minimal once the surgeon becomes proficient and in Prof Davis’ practice he is able to perform the computer navigated knee replacement in just over 60 minutes, which is quicker than some surgeons who perform knee replacement using the conventional technique.