I overheard my surgeon telling someone that they can expect more blood loss when a cementless implant is used for a total knee replacement. I have a cementless knee implant but I don't remember anyone mentioning blood loss. What causes this problem?

Patients are always advised that complications can occur with surgery. Some of those problems are standard and can develop no matter what kind of surgery is done -- for example, poor wound healing, infection, formation of blood clots, even death. Blood loss is another common event in many operations. Total knee replacement can involve quite a bit of blood loss. Sometimes it's even necessary to transfuse the patient with additional units of blood. Researchers are trying to figure out just what is causing so much bleeding during this procedure. They know that cutting into the bone is a major source of blood loss. But there might be other factors such as age, sex (male versus female), or the overall health of the patient. One group of orthopedic surgeons from France investigated whether or not blood loss was linked to the type of fixation used to hold the implant in place. In a recent study, surgeons from France took a look at fixation methods as a potential risk factor for bleeding. Fixation refers to the way in which the implant is placed and held in the bone. Some implants can be put in place without cement to hold them there. This method is called a press-fit fixation. The bone is cut and the implant pressed into the bone in such a way that it holds without cement. The other most common fixation method is with cement. There's been some suggestion that blood loss is more likely with cementless implants. That's because once the bone is cut, there is quite a bit of bleeding and nothing to stop it. The exact mechanism by which cemented implants might reduce bleeding isn't completely clear. Some experts suggest that when cement is used to hold the implant against the bone, the cement itself may plug some of the bleeding vessels. Others propose that heat released by the cement coming in contact with the bone might cauterize bleeding blood vessels. Based on the results from that study, it did not appear that cementing the implant in place influenced how much blood was lost during the knee replacement procedure. Surgeons still have to plan for blood transfusions in patients having a total knee replacement but it won't be because of the type of fixation used. Some other factor may yet need to be discovered.

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