TKA without resurfacing carries sevenfold risk of patellar revision

A community-based joint registry study involving 95 surgeons and various designs showed better implant survival with routine patellar resurfacing during total knee arthroplasty compared with bicompartmental procedures without resurfacing.

For the study, Todd C. Johnson, MD, defined bicompartmental knee arthroplasty (BKA) as a total knee replacement (TKA) performed without resurfacing the patella.

“There was a significant difference in the cumulative patella revision rate between TKAs and BKAs, with the TKAs having a significantly lower cumulative risk of revision,” Johnson said during his presentation. “Similarly, when all revisions were considered, the TKAs once again had a lower cumulative risk of revision. In short, there was a seven times greater risk of patellar revision in BKAs and a 1.7 times greater risk for any revision in BKAs.”

Revision rates

Johnson and his colleagues compared more than 9,500 TKAs with cemented all-polyethylene patellas to 627 cemented BKAs performed without patellar resurfacing between September 1991 and December 2010.

“Our registry showed that resurfacing was performed in younger patients, had a later year of index procedure, and was performed more frequently over the course of the study,” Johnson said.

The study revealed that 23 BKAs underwent revision patella resurfacing. Of these, two were re-revised for any reason. Overall, progressive arthritis was the most common reason for the initial revision in the BKA group.

In the TKA group, 33 were revised due to issues with the patella. Of these, five were re-revised for any reason. Loosening, instability, fracture and mechanical failure were cited as the most common reasons for the initial revision.

“Cruciate retaining vs. sacrificing designs did not influence the revision risk,” Johnson said. Using peer-reviewed studies to categorize implants as having “patella-friendly” or less accommodating designs, the investigators found that these design characteristics did not impact the risk of revision.

Increase in resurfacing

Johnson highlighted that the postoperative complications of both resurfacing and not resurfacing patellas and the inability of surgeons to predict which patients will develop postoperative anterior knee pain as factors surrounding the higher revision rate for unresurfaced patellas.

“Also, secondary resurfacing is not a ‘no-brainer’, so to speak,” he said. “In one recent study looking at secondary patellar resurfacing, only 44% reported an improvement in knee pain and 30% had complications. Other studies have reported that only 52% of patients were satisfied with secondary resurfacing, confirming this coin-flip outcome.”

He noted selection bias as a limitation of the study.

“BKAs are more likely to be offered revision surgery if they describe anterior knee pain,” Johnson said. “We also noted that in our registry, patella resurfacing at the time of index procedure increased from 84% of all TKAs in 1991 to 98.1% in 2009.” – by Gina Brockenbrough, MA

Reference:

• Gioe TJ, Tatman P, Mehle SC, et al. Revision surgery for patellofemoral problems: Should we always resurface? Paper #588. Presented at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons. Feb. 15-19. San Diego.

• Todd C. Johnson, MD, can be reached at Department of Orthopedic Surgery, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157; 612-273-8043; email: joh03523@umn.edu.
• Disclosure: Johnson has no relevant financial disclosures related to this study.

Robert L. Barrack

The dramatic increased risk of revision for knees with unresurfaced patellae in this report is at odds with two major registry reports. The relative risk of revision reported by the Swedish registry is approximately 1.2 compared to resurfaced knees, and in Sweden about 90% of total knees are done without patella resurfacing in spite of this data. The Australian registry reports similar data with a relative risk of revision of approximately 1.3, and in Australia about 50% total knees are done without patella resurfacing.

Revision as an endpoint for a procedure that has a perceived easy bailout is prone to misinterpretation. Somewhere between 10% and 20% of total knees have persistent symptoms, dissatisfaction and anterior knee pain whether or not the patella is resurfaced. If the patella has not been resurfaced, surgeons will too frequently make the poorly advised choice of resurfacing the patella and most of these patients will not be improved, because the unresurfaced patella was not the problem to begin with.

Total knees with patellar resurfacing have as high an incidence of pain, dissatisfaction, and anterior knee pain; however, they are just asked to live with this since there is not a perceived easy option as with the unresurfaced patella.

— Robert L. Barrack, MD
Washington University School of Medicine,
Saint Louis, MO.
Disclosure:He received royalties in the past 12 months on THA products, but not resurfacing products, from Smith & Nephew. He is a consultant for Stryker and receives research support from Biomet, Medical Compression Systems, Smith & Nephew, National Institutes of Health, Wright Medical and Stryker.

Craig J. Della Valle

Whether the patella should be resurfaced at the time of total knee arthroplasty (TKA) continues to be controversial. The work presented adds further insight into this controversy, as unique and complementary information can be obtained from the review of a community registry. The authors’ findings mirror the results of many of the randomized controlled trials that have examined the same subject; leaving the patella unresurfaced leads to a higher rate of total reoperation, which is one of the most important measure of success or failure for both patients and surgeons.

As the authors allude to, however, surgeons evaluating patients with anterior knee pain following TKA may have a lower threshold to offer a revision procedure if the patella is unresurfaced. Unfortunately, as the authors relate, the results of this intervention can be erratic as anterior knee pain can have complex etiologies that are not necessarily related to an unresurfaced patella.

It would be interesting to determine in this cohort if the revision procedures were performed by the same surgeon who performed the index TKA or a different surgeon as a “second opinion” physician may be more likely to offer a revision. What may be most compelling is the trend over time in this community towards more routine resurfacing of the patella.

— Craig J. Della Valle, MD
Department of Orthopedic Surgery,
Rush University Medical Center, Chicago
Orthopedics Today Editorial Board member
Disclosure: He is a consultant to Biomet, Convatec and Smith & Nephew. He also receives research support from Smith & Nephew and Zimmer.