March 01, 2018
3 min read

Always resurfacing the patella in TKR is no longer a reasonable practice

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What would happen if the U.S Secretary of Health met the Minister of Health of Norway and the topic was total knee replacement and patellar replacement, in particular? With more than 600,000 TKRs done per year in the United States and an estimated cost of $300 U.S. for a patellar button, about $150 million U.S. could be saved annually by not using a patellar button, the Norwegian health minister would probably say.

What would happen if a patient with patellar replacement with complications, such as fracture, loosening or osteonecrosis, meets a patient who has done well without patellar resurfacing during TKR? Would the first patient who underwent patellar replacement blame the surgeon for unnecessary surgery?

Jan Verhaar, MD, PhD
Jan Verhaar

I wonder why the controversy about patellar resurfacing has gone on for so long?

Practices in Europe

Europe has championed the setting up of implant registries and after the start in Sweden, many other countries followed including other Scandinavian countries, the United Kingdom, the Netherlands and recently Germany. The European Federation of National Associations of Orthopaedics and Traumatology has formed a platform for exchange of registry data called NORE. I was happy to read the study by Fraser and colleagues from 2017 entitled “International rates of patellar resurfacing in primary total knee arthroplasty” based on registry data during the period of 2004 to 2014. Average rates of patellar resurfacing in this period ranged from 4% in Norway to 82% in the United States. Three countries (Denmark, Norway and Sweden) showed a decreased rate of patellar resurfacing during this time. There were, however, two countries — Australia and England — that demonstrated an increased rate of resurfacing.

How is so much practice variation possible between countries? In my view, the literature is clear. Many recently published studies show no difference in Knee Society Scores and KOOS measures from joint injury for osteoarthritis scores or satisfaction levels for an unresurfaced patella. Good quality studies also show no difference in rates of anterior knee pain between resurfaced and unresurfaced patellae.

Therefore, the only remaining argument concerns the suggested increased rate of revision in unresurfaced patellae. However, the 2014 Swedish Knee Arthroplasty Registry Annual Report reported patella resurfacing had led to an increased risk of revisions with a relative risk of 1.2 compared with unresurfaced patellae in primary TKR. Others argue that even if the revision rate would be higher in a patient with a non-resurfaced patella, this may be caused by bias similar to the increased revision rate discussed related to unicompartmental knee arthroplasty. Patients without resurfacing can be offered a revision in cases of continued complaints, but a resurfaced patient with identical symptoms of anterior knee pain may not be offered surgery. In addition, there are several studies reporting a success rate of patellar revision for pain after not replacing the patella in TKR of about 50%, which suggests the cause of the pain was not the unresurfaced patella.


Comparative studies, patient factors

Many studies have compared “always resurfacing the patella” with “never resurfacing the patella.” Others have tried a more selective approach. These surgeons take into consideration several patient factors, which they assume to be important like age, sex, obesity and operative diagnosis, but also the size and the thickness of the patella, quality of the articular cartilage and the grade of tibiofemoral OA. A study by Maradit-Kremers and colleagues in 2017 that was based on data from the Mayo Clinic concluded that selectively not resurfacing the patella yielded similar results to those of routine resurfacing. Selectively not resurfacing offers a compromise that avoids potential complications associated with unnecessary resurfacing, the authors concluded. However, this research did not answer the question of whether the resurfaced group in this series would have shown similar results if they were not resurfaced.

Although there is extensive evidence that in most patients patellar resurfacing is not necessary and potentially harmful, the study from 2017 by Fraser and Spangehl showed that in the countries they studied there was hardly any change in the percentage of resurfacing of the patella in TKR surgery during the years. I wonder how that is possible.

Surgeons may base their decision to resurface the patella on medicolegal or economic concerns and prefer to follow the national consensus. Others may be influenced by device manufacturers. Some surgeons may prefer to practice as they were trained, ignoring scientific data and experiences outside their country. The choice for resurfacing the patella seems to be more cultural than scientific-related. When orthopaedic surgeons claim to practice evidence-based medicine and use appropriate criteria for the indications and techniques used for their surgery, there is a need for change in patellar resurfacing.

From a European perspective, there is no place for always resurfacing the patella in TKR. Based on the data from Sweden and Norway, there may be no indication at all for patellar replacement. There could be a small place for selective replacement but for the moment, we have no scientific data to support that option. Non-resurfacing the patella would be cheaper, better for the patient and show that this orthopaedic practice has a scientific basis. Will we take up this challenge?

Disclosure: Verhaar reports no relevant financial disclosures.