Page 19 - ISAKOS Newsletter 2016 Volume 1

Patellar Resurfacing: Where Are We Now?
Michelle L. Cameron-Donaldson, MD Northern Montana Hospital Havre, MT, UNITED STATES
The appropriate management of the patella during primary total knee arthroplasty remains elusive. The earliest knee replacements focused entirely on the tibio-femoral joint. The patello-femoral joint was not addressed in the first generation of knee arthroplasty. With the success of the first generation of knee arthroplasty and recognition of significant complications with the patello-femoral joint, advances were made in joint design, including more attention to the patella. The addition of a trochlear flange to the femoral component to accommodate the native patella improved outcomes. The next major design advancement occurred in the 1980’s with the introduction of resurfacing. However, as patellar resurfacing was accepted as a crucial portion of total knee arthroplasty, a unique set of complications was identified. The metal backed patella was introduced during this time, and resulted in catastrophic failures. Historically, the patella accounted for up to 50% of total knee replacement failures in the 1980’s and 90’s. This led to significant rethinking of the necessity of patellar resurfacing. The debate over how to address the patella has continued for three decades.
International Perspective
The controversy in patella resurfacing is demonstrated by the wide divide in international approaches to the patella during total knee arthroplasty. In North America, greater than 90% of surgeons routinely resurface the patella. Vielgut et al published an interesting review of eight European joint registries in International Orthopaedics in 2013 and noted wide differences in patellar resurfacing. In Scandinavian countries there are dramatic differences in the approach to the patella. The Danish joint registry shows that 76% of patellae are resurfaced, whereas in Norway and Sweden, only 2% are resurfaced. Australian surgeons resurface approximately 50% of patellae. The English and Welsh registry showed a 30% rate of patellar resurfacing.
The Portuguese registry showed a 65% resurfacing rate. In New Zealand 30% are resurfaced and in Canada almost 60% are resurfaced. Reviewing the revision rates of these same registries, there appears to be no correlation with patellar resurfacing.
Current Approaches to Patellar Management in Total Knee Arthroplasty
As of 2016, there are three camps in the approach to patellar resurfacing; routine resurfacing, no resurfacing and selective resurfacing.
Routine Resurfacing
Proponents of routine resurfacing cite reduced post-operative anterior knee pain, higher patient satisfaction, better overall function and low complication rates. Revision rates for resurfaced patellae have decreased from 50% in the 1980s and early 90’s to approximately 10% in the current literature. Complications associated with resurfacing include patella fracture, maltracking, soft tissue impingement, patellar ligament rupture, polyethylene fracture, polyethylene wear, component loosening and component dissociation. In total, the risk of all of these complications is low with most studies citing individual complication risks in the 1% range.
No Resurfacing
Clinicians who favor retaining the native patella argue that clinical results between patients with and without resurfacing are similar to resurfacing. The reported rate of secondary resurfacing due to recalcitrant anterior knee pain is 10-12% based on multiple studies. The non-resurfacing camp claims preservation of patellar bone, more normal patello-femoral kinematics, and ease of resurfacing if recalcitrant anterior knee pain develops. Furthermore, they emphasize the avoidance of post- operative complications attributable to resurfacing.
Selective Resurfacing
Proponents of selective resurfacing attempt to identify patients at risk for recalcitrant anterior knee pain or poor clinical function. Broad guidelines for patellar resurfacing are pre-operative anterior knee pain, inflammatory arthritis, crystalline disease, and evidence of Outerbridge grade IV changes, patellar maltracking, subluxation or dislocation.
CURRENT CONCEPTS
ISAKOS NEWSLETTER 2016: Volume I 17