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SICOT e-Newsletter

Issue No. 41 - February 2012

Scientific Debate

Patellar Resurfacing in Total Knee Arthroplasty for Osteoarthritic Knees

The decision to resurface patella or to leave it unresurfaced during total knee arthroplasty (TKA) in an osteoarthritic knee remains controversial. This has led to many randomised control trials. However, none of them provide any consistent result in short- or long-term follow-ups. As an initiative of the young surgeon's group of SICOT, we attempt to discuss both aspects of this situation. The following debate is a personal opinion of each author based on his experiences and interpretation of literature; and in no way should be considered as an absolute guideline for management.

PATELLA SHOULD BE RESURFACED ROUTINELY

SR: Resurfacing of patella is usually associated with a low complication rate and has a predictable postoperative result with less anterior knee pain [1,2]. Anterior knee pain is usually attributed to patellofemoral joint and the incidence has been variably shown to be between 5% and 47% in the unresurfaced patients [3].

Studies have also shown a lower rate of reoperation following TKA with patellar resurfacing as against TKA without patellar resurfacing [3,4,5]. The relative risk of the rate of reoperation related to the patellofemoral joint in the patellar resurfacing group has been shown to be about 0.37 times lower than that of the patellar non-resurfacing group [3]. These large relative risk estimates clearly show that patellar non-resurfacing in TKA can significantly reduce the rate of reoperation for patellofemoral joint problems.

Proponents of not resurfacing patella during TKA frequently cite the fact that studies comparing post-operative knee scores after TKA in patella resurfacing and non-resurfacing groups have been inconclusive. Nevertheless, there is not a single study to our knowledge showing better knee scores following unresurfacing of patella (as compared to resurfacing) in TKA. On the contrary, some authors have clearly shown significantly better post-operative Knee Society Scores in patients undergoing resurfacing of patella during TKA as compared to the unresurfacing group [6,7]. This reminds me of a famous English saying: "There's no smoke without fire!!"

Although unresurfaced patella can function well when applied to a femoral surface that is designed to minimise articular pressure, such prosthetic designs are not yet uniformly available. Non-resurfacing of patella leads to high incidence of poor results when applied to the commonly available femoral component with a high, wide intercondylar notch and a shallow patellar groove [4].

Some authors prefer to perform patelloplasty instead of patellar resurfacing, which helps get rid of the pathological cartilage. Although there is limited literature on efficacy of the procedure, it seems to be definitely beneficial. Various studies showing comparable results in resurfaced and non-resurfaced groups usually include patients undergoing patelloplasty in the patellar non-resurfacing group. Aggregating patients without patellar resurfacing and those receiving patelloplasty could potentially introduce a selection bias in case patelloplasty were proved to be a more effective intervention than leaving the patella unresurfaced. While patelloplasty might be a useful procedure, leaving an osteoarthritic patella totally untouched does not make any sense at all.

To conclude, patellar resurfacing is a successful procedure and patients undergoing patellar resurfacing have uniformly shown high satisfaction and a decreased risk of reoperation and anterior knee pain. As such, there should not be any hesitation in the mind of a surgeon to resurface the patella when faced with an osteoarthritic patella femoral joint.
  

PATELLA SHOULD NOT BE RESURFACED ROUTINELY

KB: The issue of the patellofemoral joint in TKA surfaced in the 1970s because of the high rate of anterior knee pain associated with early implant designs [3]. The subsequent incorporation of patellar resurfacing into TKA instrumentations lowered the AKP rate. However, the increasing rate of patella resurfacing-related complications has led us to reconsider the indication for routine patellar resurfacing. With the improvement in component designs, the issue of anterior knee pain associated with unresurfaced patella in TKA seems to have been virtually resolved.

Patellar resurfacing is definitely associated with a increased risk of post-resurfacing complications such as patellar fracture (0.05–8.5%) [8,9], avascular necrosis (0.05–2%) [6,9], patellar tendon injury (1–2%) [10,11], and instability requiring reoperation (1–25%) [8,9] after resurfacing. Patellar component loosening is another definite risk and studies have shown it to be a major culprit behind revision of a TKA. Several factors probably contributing to patellar instability include malposition of components, soft tissue imbalance, excessive femoral component size, polyethylene wear and inadequate patellar resection. Contributing factors for tendon injury are excessive dissection and knee manipulation, and trauma.

Some studies show lower rate of reoperation following resurfacing in TKA. Nevertheless, the absolute risk difference for reoperation has been shown to be very small. Various recent meta-analyses have shown that around 25 to 33 patellae resurfacing would have to be done to avoid one reoperation for patellofemoral-related complications [2-5]. Furthermore, not all patients with patellofemoral problems after unresurfaced patella TKA will benefit from a secondary resurfacing procedure.

There is a lack of literature demonstrating any significant difference between the resurfaced and unresurfaced groups as far as anterior knee pain is concerned. Anterior knee pain following TKA could have multiple aetiologies and unresurfaced patella should not be considered as a sole cause of this problem. Furthermore, isolated revision of the patella component has been reported to be fraught with complications and there are fewer options available for the treatment of anterior pain in a knee with a patella already resurfaced [12].

Although there are isolated studies showing higher postoperative knee function scores in resurfaced patella groups, the majority of the studies have shown no statistical significance. Furthermore, the patient satisfaction score, widely regarded as an index of success of TKA, have uniformly been comparable in the two groups. Routine patellar resurfacing lacks sufficient supporting evidence. As such, the additional cost, increased operative time, and the complications involved with patellar resurfacing procedure cannot be fully justified.

To conclude, patellar retention should be considered as a reasonable option in all the patients undergoing TKA for osteoarthritis. Nevertheless, the patients must accept the increased risk of reoperation for which quantitative evidence-based support is mild.
  

References:

  1. Clements WJ, Miller L, Whitehouse SL, Graves SE, Ryan P, Crawford RW. Early outcomes of patella resurfacing in total knee arthroplasty. Acta Orthop. 2010;81(1):108-13.
  2. Helmy N, Anglin C, Greidanus NV, Masri BA. To resurface or not to resurface the patella in total knee arthroplasty. Clin Orthop Relat Res. 2008;466(11):2775-83.
  3. Li S, Chen Y, Su W, Zhao J, He S, Luo X. Systematic review of patellar resurfacing in total knee arthroplasty. Int Orthop. 2011;35(3):305-16.
  4. He JY, Jiang LS, Dai LY. Is patellar resurfacing superior than nonresurfacing in total knee arthroplasty? A meta-analysis of randomized trials. Knee. 2011;18(3):137-44.
  5. Fu Y, Wang G, Fu Q. Patellar resurfacing in total knee arthroplasty for osteoarthritis: a meta-analysis. Knee Surg Sports Traumatol Arthrosc. 2011;19(9):1460-6.
  6. Schroeder-Boersch H, Scheller G, Fischer J, Jani L. Advantages of patellar resurfacing in total knee arthroplasty. Two-year results of a prospective randomized study. Arch Orthop Trauma Surg. 1998;117(1-2):73-8.
  7. Kordelle J, Schleicher I, Kaltschmidt I, Haas H, Grüner MR. Patella resurfacing in patients without substantial retropatellar knee pain symptoms? Z Orthop Ihre Grenzgeb. 2003;141(5):557-62.
  8. Grace JN, Rand JA. Patellar instability after total knee arthroplasty. Clin Orthop Relat Res 1988;237:184–9.
  9. Ortiguera CJ, Berry DJ. Patellar fracture after total knee arthroplasty. J Bone Joint Surg Am. 2002;84:532–40
  10. Feller JA, Bartlett RJ, Lang DM. Patellar resurfacing versus retention in total knee arthroplasty. J Bone Joint Surg Br. 1996;78:226–8.
  11. Keblish PA, Varma AK, Greenwald AS. Patellar resurfacing or retention in total knee arthroplasty: a prospective study of patientswith bilateral replacements. J Bone Joint Surg Br. 1994;76:930–7.
  12. Barrack RL, Bertot AJ, Wolfe MW, Waldman DA, Milicic M, Myers L. Patellar resurfacing in total knee arthroplasty. A prospective, randomized, double-blind study with five to seven years of follow-up. J Bone Joint Surg Am. 2001;83(9):1376-81.

   
About the Authors:

SR: Saurabh Rawall, MBBS, MS (ortho), FNB (spine), is an orthopaedic surgeon trained in India and currently working as a clinical fellow in the Department of Orthopaedics, University of Calgary, Alberta, Canada. His career interests include spine and arthroplasty surgery.

KB: Kamal Bali, MBBS, MS (ortho), DNB (ortho), is an orthopaedic surgeon trained in India and currently working as a fellow in knee surgery at the North Sydney Orthopaedic Sports Medicine Centre, New South Wales, Australia. His career interests include arthroplasty and sports surgery.

The readers are kindly requested to send their "verdict" and opinions related to the above topic of debate directly to edsecr@sicot.org. These would be published in the debate section of the upcoming issues of the e-Newsletter.