What to Do with the Patella in TKA

By: Jennie McKee

Jennie McKee

Two studies presented yesterday may result in a simpler total knee arthroplasty (TKA) procedure. Based on the results of a British retrospective, comparative cohort study, it may not be necessary to resurface the patella during TKA. And, when the patella is not resurfaced during TKA, circumferential denervation may not be indicated, based on the results of a second, independent study also conducted in the United Kingdom.

To resurface or not to resurface
British researchers, using prospectively collected national outcome data based on pre- and postoperative questionnaires, analyzed the outcomes of 23,393 TKA patients.

By accessing Patient Reported Outcome Measures (PROMs) data linked to the appropriate National Joint Registry record, researchers were able to link outcome data to the relevant demographic and surgical data for each individual patient.

The researchers’ goal was to determine whether patella resurfacing influences knee function, general health status, and patient-reported satisfaction using validated, prospectively collected PROMs for primary TKA patients. PROMs included validated assessments of knee function using the Oxford Knee Score (OKS), which measures knee pain and function. Investigators also collected data using the EuroQol-5D (EQ5D), a validated measure of general health status. Finally, they collected patient reports of satisfaction/success with surgery using a 5-point Likert scale.

Of the 23,393 TKA patients whose outcomes were analyzed, 8,103 patients (34.6 percent) underwent patella resurfacing and 15,290 patients (65.4 percent) did not undergo resurfacing. Mean time from surgery to postoperative assessment was 7 months (range: 6 to 12 months) and was similar for both groups.

Researchers found that the mean improvement in the OKS was similar for both groups (resurfaced = 15.1; non-resurfaced = 15.2; mean difference 0.1, with 95 percent confidence interval, P = 0.69). In addition, they did not detect any significant differences in any of the five EQ5D domains between the two groups. Improvements in the EQ5D index and EQ5D health scale were comparable. Patient satisfaction with the surgery was high; 92.3 percent of patients with resurfaced patellas and 91.8 of patients with no resurfacing rated their surgeries as successful. The rate of wound problems was also similar—12.1 percent among patients with resurfacing and 12.0 percent among patients without resurfacing.

“We found no clinically significant differences between TKAs with and without patella resurfacing for improvements in knee function, general health, and patient-reported satisfaction and success related to the surgery,” noted the researchers, adding that they “question the efficacy of routine resurfacing in TKA for improving overall patient satisfaction and functional outcomes.”

They added, however, that differences they found in the improvement of the OKS depending on implant type “must be considered when designing and reporting future trials assessing the role of patella resurfacing and when interpreting prior analysis of trials involving only one implant type.”

Is patella denervation needed?
The goal of patella denervation is to reduce the incidence of patellofemoral pain. A double-blind, randomized trial conducted in the United Kingdom evaluated whether any evidence exists to support this practice during a TKA if patella resurfacing is not performed.

Between April 2009 and June 2010, 126 patients undergoing primary TKA at the researchers’ institution were randomized into two equal groups. Patients in Group A (n = 63) would undergo circumferential denervation; patients in Group B (n = 63) would not undergo circumferential denervation. All patients in both groups had varus osteoarthritis and received a cruciate-retaining implant.

After the surgeon had determined the patella did not require resurfacing, patients were randomized using sealed envelopes. All surgeries were performed directly by or under the direct supervision of two experienced surgeons. For the duration of the study, patients and assessors were blinded regarding denervation status.

Three independent practitioners performed preoperative assessments and outcome analysis at 3 months and 12 months, using questionnaires and physical assessment. The following outcomes measures were used: OKS, Knee Society Score (KSS), and Knee Society function score, as well as the Bartlett score and Activities of Daily Living (ADL) score. Routine demographic data, including age, gender, side of surgery, and body mass index, were collected prior to surgery.

Researchers found no differences in demographics and preoperative scores between groups. Patient satisfaction, however, was higher in the denervation group (47 excellent, 9 good, 7 fair/poor, 1 patient lost to follow up) than in the non-denervation group (32 excellent, 16 good, 14 fair/poor). In addition, flexion was better in the denervation group (104 degrees vs. 99 degrees).

“We found no statistically or clinically significant differences in OKS, KSS, Bartlett scores, or ADL scores during the follow-up period,” noted the researchers. No complications or additional surgical procedures were required during the follow-up period, they added.

They acknowledged that “circumferential denervation of the patella during primary TKA without patellar resurfacing appears to be a safe procedure that may improve patient satisfaction and range of flexion at 1 year postoperatively.”

They concluded, however, that because they did not find evidence of clinically or statistically significant improvements based on standard validated outcome measures, “the evidence is not strong enough to state that denervation should be performed when the patella is not resurfaced.”

The lead researcher of paper 013, “Comparison of Patient Reported Outcomes following Total Knee Replacement with and without Patella Resurfacing,” is Paul Baker, MBBS, MSc, FRCS (no conflicts). Additional researchers include Daniel J. Dowen, MBBS, MRCS (no conflicts); Simon Jameson, MBBS, MRCS (no conflicts); Mike R. Reed, FRCS, MD (Biomet, Heraeus Medical, Carefusion, Ethicon, Stryker); David Deehan, FRCS, MSc, MD (no conflicts); and Paul J. Gregg, FRCS, MD (no conflicts).

This study was funded by a fellowship from the National Joint Registry.

The lead researcher of paper 002, “Patella Denervation in Primary TKA: A Double Blind, Randomized Study” is George J. McLauchlan, FRCS. Additional researchers include Videsh Raut, FRCS; and Ramnadh S. Pulavarti, FRCS. All report no conflicts.