Fate of the Unrevised All-Polyethylene Patellar Component in Revision Total Knee Arthroplasty

Background: During revision total knee arthroplasty, the alternatives for addressing the well-positioned and secure all-polyethylene patellar component with minimal or no wear include retention, revision, and resection. The purpose of the present study was to determine the intermediate-term fate of all-polyethylene patellar components that were left in situ at the time of revision tibiofemoral arthroplasty.

Methods: We retrospectively reviewed the results of 202 revision total knee arthroplasties, performed at four centers, in which a well-fixed, well-positioned all-polyethylene patellar component with minimal wear was retained. Clinical evaluation was performed to identify the presence of anterior knee symptoms or patellar failures, and the Knee Society clinical scores were recorded.

Results: Sixty-eight percent of the revision tibiofemoral components were from a different manufacturer than the retained patellar component. Twenty-one patients (twenty-one knees; 10%) reported anterior knee pain at a mean duration of follow-up of seven years (range, two to fourteen years). Eleven of the twenty-one knees with anterior knee pain had evidence of component loosening, excessive wear, or delamination either on follow-up radiographs or on direct inspection at the time of reoperation. In the other ten knees, the findings were attributable to osseous impingement on the femoral component or soft-tissue dysfunction (including soft-tissue impingement, subluxation, and scarring). Seventeen of the twenty-one patients with anterior knee pain underwent additional surgery to address the source of the pain. Failures due to loosening or wear occurred only in patients in whom the patellar component had been sterilized with gamma irradiation in air; these failures occurred at a mean 7.3 years after revision (eleven years after primary total knee arthroplasty). The likelihood of patellar component failure was significantly greater when the component had been gamma irradiated in air than when it had been sterilized with another method (p = 0.0008). The average knee score increased from 42 to 86 points, and the average function score increased from 46 to 70 points.

Conclusions: Retaining a well-positioned, stable all-polyethylene patellar component at the time of revision tibiofemoral arthroplasty can be successful, provided that the polyethylene has not oxidized. Manufacturing mismatch is acceptable with most contemporary designs provided that the patellar component articulates appropriately with the femoral implant.

Level of Evidence: Therapeutic study, Level IV (case series [no, or historical, control group]). See p. 2 for complete description of levels of evidence.