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Results of Three Patellar Treatments After Total Knee Replacement

There remains much debate about what should be done with the patella or kneecap during total knee replacement (TKR). TKR doesn't always include removing and replacing the patella.

There are three treatment options for the patella. First, the patient's natural patella can be left alone or unchanged. Second the patella can be removed and replaced with an implant. And third, the patella can be spongialized. It's unclear if one of these methods is better than the others.

Spongialization is a new way to resurface joints damaged by osteoarthritis. The worn cartilage and layer of bone underneath are removed. A soft layer of bone is left exposed. Blood to the area helps new tissue form.

In this article, surgeons review the benefits and drawbacks of these three treatment methods. They also report on the results of the different treatment options for the patella. They were able to examine the surfaces of 11 patellae during revision surgery years after the primary TKA.

Tissue samples were taken and examined under a microscope. This is called a histologic study. They found the following results:

  • Patellar revision with an implant was stable. There was only a small area of wear. The surface of the implant (made of polypropylene or plastic) was covered with granulation tissue. There was a rich blood supply and many new cells forming.
  • The unchanged patella had advanced osteoarthritic changes. Bone spurs were seen around the edges of the patella. The cartilage was softened with many tiny fibers loose from a surface that should have been smooth.
  • Changes to the joint surface were seen in patients who had spongialization. The surface was covered with a thick white tissue. Small bone spurs seen on X-ray formed around the rim of the patella. This fibrocartilage tissue helped balance any uneven surfaces between the patella and the implant in the knee.

    The authors suggest that leaving the patella alone may not be the best treatment option during TKR. Spongialization appears to have better short-term results over patellar revision with a new implant. More studies are needed with a larger number of patients to see what the long-term results are for spongialization versus revision.

    • Reference: 

    Peter Dömös, MD, et al. The PatellarSurface After Different Treatment Options in TKA. In Orthopedics. August 2006. Vol. 29. No. 8. Pp. 685-688.

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