The Visionaire Cutting Block System - An Outcome Study

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Currently knee replacement surgery is performed using alignment rods that correctly position the cutting blocks which guide bone cuts necessary to implant the metal and plastic total knee joint. Using a computer navigation system during surgery is considered the "gold standard" for guiding the cuts. Many surgeons however find this extends the time of the surgery for what is considered only a marginally better aligned knee and for much of the time the alignment is the same. These surgeons feel that the accuracy of the alignment of the total knee replacement without computer navigation is very good anyway and it is quicker to do. There is however new technology that has been developed that allows patient-specific cutting blocks, which are said to guide the cuts more accurately, to be manufactured based on a an MRI scan and x-ray of the affected knee taken before surgery. In this way it may be possible to have the accuracy of computer navigation in addtion to decreasing surgical time. This would be potentially good for the patients for a number of reasons including shorter operation time resulting in less chance of complications. In addition to this, less instuments will need to be used during surgery because the surgeon will already know the size of the knee replacement needed. This will reduce the cost of surgery while potentially increasing the accuracy. The current study will include 50 patients that have met the criteria for total knee replacement on the waiting list. The patients will require a pre-operative MRI and full-leg x-rays. Their surgery will be performed with the custom instrumentation. All bone cuts will be measured during surgery and compared to the bone cuts the MRI scan predicted. The surgeon can override the custom made blocks at any time and continue surgery in the conventional way if they feel the blocks are in any way inaccurate. The surgery time will vary but on average it should require approximately 80 minutes. The patients will require a post-operative computer tomography [CT] scan to evaluate the limb and implant alignment and information will be collected including pain levels, how far a person can walk and the affected knee's range of motion. This scan will be performed at least 6 weeks after surgery and the other information will be gathered before surgery and also at 3,6 and 12 months after surgery. Otherwise, the recovery and post-operative follow-up will be unchanged from that expected for routine knee replacement surgery. Our hypothesis is that the patient-matched instrumentation will align the bone cuts, implants, and the mechanical axis of the limb at least as well as would be expected using the conventional alignment rods, will cost less and on average speed up the surgery.

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