Mother is having a revision surgery on her knee replacement. Evidently it has cracked and come loose both. What's involved in something like this?

Revision (second) surgeries may be done when a joint replacement (implant) fails or the patient has knee pain that doesn't go away with exercise. As you might imagine, the surgeon can't just go into the operating room and take the old implant out without some serious planning and preparation ahead of time. First, the patient must be examined. There may be some biomechanical reasons why the implant didn't hold up well. Joint alignment is important in making sure the load placed on and through the joint is evenly distributed and not stressing one part of the implant more than any other. X-rays, MRIs, CT scans, bone scans and other imaging studies are used to help determine what's going on. Lab tests will probably be done to make sure there isn't any infection in that knee. When revision surgery is called for, the surgeon must go back to the medical records and find out what type of implant was used. The patient's alignment and muscle control must be examined to look for uneven pull on the joint or other problem areas related to bone and soft tissues. These must be corrected during the revision procedure. Next, the surgeon must decide what surgical technique would be best for each patient. What kind of incision is needed for the intended procedure? A larger incision is required when the surgeon has to clean out the entire joint from infection and get a good look at the condition of the bone. Should the incision be straight or curved? Is more than one incision needed? Can the incision from the first surgery be re-used for the revision surgery? Remember, the implant was put into the joint with the intent to stay. It doesn't just pop out. Special surgical tools such as high-speed drills, surgical hammers, and small oscillating saws are used to separate the implant from the bone. Sometimes it's impossible to keep from removing additional bone and that can affect both the revision and the patient's leg length. The next step is to reconstruct the joint. Taking the implant out is only a small part of the procedure. Now the bone is reshaped, bone grafts may be added, bone defects filled in with cement, and a new implant put into place. Selecting the right implant for the revision requires an additional set of decisions based on analysis of patient factors such as age, condition of the bone, diagnosis, activity level, and so on. Throughout the revision process, the surgeon is evaluating joint angles, alignment, muscle balance, leg length, and the need to fill in or augment where there has been an excess loss of bone. The goal is to make sure the joint line (where the two halves of the joint meet) is at the same level on both knees. Each patient comes with his or her own unique circumstances, risk factors, and functional needs. All of these are taken into consideration not only before the procedure during pre-op evaluation and planning but also during the revision and afterwards during the post-operative period.

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