The patella in TKA: The North American view

In patients with knee arthritis, 80% have some degree of patellofemoral involvement.

Most North American surgeons resurface the patella. What are the advantages of doing it?

Javad Parvizi

First, the incidence of anterior knee pain is lower when the patella is resurfaced. Second, there are patients in whom the patellofemoral arthritis is the only compartment involved, which would make it difficult to replace the other two compartments without resurfacing the patella. Third, it is difficult to predict what the quality or thickness of the articular cartilage of the patella is at the time of knee arthroplasty and how long it is going to last. Hence, there might be arguments for resurfacing the patella and preventing the secondary resurfacing down the line.

Knee replacement is not a perfect procedure and there are patients who continue to experience pain following knee replacement regardless of whether the patella was or was not resurfaced. However, a patient presenting with anterior knee pain in whom the patella was not resurfaced generates an awkward situation. Surgeon and the patient both may “blame” the patella for the anterior knee pain.

Why not?

So why not resurface the patella and not worry about such situation that may arise down the line? There will be no second-guessing. The belief that patellar resurfacing is associated with increased complications is based mostly on literature evaluating the outcome of this procedure when an older generation of patellar prostheses was used.

I think one of the absolute indications for resurfacing the patella is inflammatory arthritis. One might argue that all arthritis is actually inflammatory. There has been recent research showing that there is ample interleukins and cytokines in osteoarthritis, also so it appears that even “run-of-the-mill” arthritis is also an inflammatory process.

The other absolute indication is, of course, patellofemoral arthritis, where other compartments may be spared. Another occasion is when the patient’s major symptom is anterior knee pain.

The arguments against resurfacing the patella include increased operative time, increased implant costs, and the concern that avascular necrosis is a complication that occurs only after patellar resurfacing. There are also concerns about resurfacing the patella when there is good articular cartilage. Cost is really not a real issue, at least not at some institutions, because some hospitals pay the same price for the implant regardless of whether the patellar component is used or not.

Literature and the law

There is plenty of published literature related to patellar resurfacing, some of which are level 1, randomized studies. Hence, you will find literature to support your opinion regardless of whether you are a resurfacer, selective resurfacer or nonresurfacer. The literature is, in other words, split. Even the level 1 studies differ in their conclusions. However, we know one thing: Resurfacing the patella with the modern-design prosthesis currently has few complications.

There may be legal issues related to patellar resurfacing. Unfortunately, there have been cases of legal suits against surgeons who did not resurface the patella and the patient required secondary resurfacing. The argument has been that failure to resurface the patella resulted in continued pain and “suffering” for the patient. I understand that there is little to no substance to such claims, but at the same time, there are patients who benefit from secondary resurfacing.

Just do it

I think the patella should be resurfaced because 5% of patients present with patellofemoral arthritis alone when the other compartments are spared. Patellar resurfacing is crucial for these patients, and 80% of patients who present with knee arthritis have some degree of patellofemoral involvement. In my opinion, it is better to resurface the patella in these patients and not have to deal with the consequences later.

We performed a meta-analysis of 158 publications, 14 of which were level 1 studies, and one strong and consistent finding of those studies was that failure to resurface the patella leads to an increased incidence of anterior knee pain, leading to a secondary resurfacing in 8.7% of patients.

The findings of our meta-analysis and others done subsequently are compelling enough to make me think that the patella should be resurfaced in all patients.

In order to perform an “optimal” resurfacing, certain caveats exist. First, you must measure the thickness of the patella in all four quadrants and you must try to reproduce the same thickness after resurfacing. Overstuffing is a problem. I irrigate the patella while I am cutting the bone and always use a sharp saw blade during resection to minimize heat generation. In addition, I always minimize excision of the fat pad around the patella, which carries some of the blood supply to the patella.

I also always use an all-polyethylene patellar component with three pegs, and I always check and double-check patellar tracking prior to closure to ensure no extensor mechanism problem exists.

For more information:

• Javad Parvizi, MD, FRCS, can be reached at the Rothman Institute, 925 Chestnut St., 5th Floor, Philadelphia, PA 19107, U.S.A.; +1-267-339-3617; e-mail: parvj@aol.com. He receives research support from and is a consultant to Stryker, he receives miscellaneous funding from Johnson & Johnson, and he is a consultant to Smith & Nephew.