Patellar resurfacing in posterior cruciate ligament retaining total knee arthroplasty (PATRES): design of a randomized controlled clinical trial

Background: Anterior knee pain may occur after total knee arthroplasty (TKA). Patellar resurfacing, which is considered to lower the incidence of anterior knee pain after TKA, remains controversial. In the present study clinical and radiological outcomes after TKA performed on patients with clinical and radiological signs of femorotibial and patellofemoral osteoarthritis (OA) with and without patellar resurfacing will be compared. Methods/design: Fifty patients will be included in a randomized controlled trial. Patients scheduled for TKA with clinical and radiological signs of femorotibial and patellofemoral OA will be included. Arthritis of the patellofemoral joint was determined based on the preoperative Baldini and Merchant X-ray views, which is assessed by the orthopaedic surgeon who treats the patient. Exclusion criteria are rheumatoid arthritis, history of patellar fracture, tuberosity transposition, high tibial osteotomy (HTO), hip arthroplasty and posterior cruciate ligament insufficiency. Patients will be randomized to undergo TKA either with or without patellar resurfacing. Outcomes will be assessed preoperatively, at 6 weeks and at 6, 12, 18 and 24 months postoperatively. Primary outcome measure is the patellofemoral scoring system according to Baldini. Secondary outcome measures are the Knee Society clinical rating system (KSS) and the Knee Osteoarthritis Outcome Scale (KOOS) scores. Conventional weight-bearing radiographs, and views according to Baldini will be used to asses component loosening, wear, and patellofemoral problems including fracture or loosening of resurfaced patellae, subluxation and wear of non-resurfaced patellae. Discussion: There is no consensus regarding patellar resurfacing during primary TKA. Current prospective studies fail to determine any differences in clinical outcome among patients after TKA with or without patellar resurfacing. This randomized controlled trial has been designed to determine the effectiveness of patellar resurfacing during TKA in patients undergoing TKA who have clinical and radiological signs of tibiofemoral and patellofemoral OA, using a specific patellofemoral outcome measurement.