What Is a Knee Replacement?
When a total knee replacement (TKR) fails the next step may be a fusion or arthrodesis. In the late 1970s fusion rates were fairly low post-TKR (64%). It wasn't a very successful operation. Since that time new fusion methods have been developed. In this report, surgeons review the advantages and disadvantages of fusion methods used today in patients with a failed TKR that can't be revised.
According to today's research results, there still isn't a "best method" for knee arthrodesis. Each one has its good points and bad points. The two main ways to perform the arthrodesis are internal and external fixation. With internal fixation a long pin or "nail" is used down through the center of the thigh, knee, and lower leg bone.
The results are better with this method than with external fixation. Studies show a 95 percent fusion rate for internal fixation compared to 64 percent for external. Internal fixation is useful when the patient has lost a lot of bone from the insertion and removal of the TKR. This type of nail can't be used when the patient has a hip replacement on the same side or when there is active infection around the site of the TKR.
External fixation uses a variety of different pins, rods, rings, and frames outside the leg. One problem with this treatment method is that fractures and infection can occur at the pin sites. The pins can come loose before fusion takes place. The device is very bulky. Early weight-bearing for walking is an advantage. Bone grafting isn't needed. The fusion is solid in about six months.
The authors conclude for some patients with a failed TKR, knee fusion or arthrodesis can reduce pain and avoid a long rehab program. Fusion is considered a "salvage" procedure. It saves the leg from amputation but does not preserve full function. The surgeon must be familiar with the details of both types of surgery. Choosing the right one for each patient is very important.
James H. MacDonald, MD, et al. Knee Arthrodesis. In Journal of the American Academy of Orthopaedic Surgeons. March 2006. Vol. 14. No. 3. Pp. 154-163.'