Minimum thickness of all-poly tibial component unicompartmental knee arthroplasty in patients younger than 60 years does not increase revision rate for aseptic loosening

PURPOSE:Management of unicompartmental knee osteoarthritis in middle-aged patients is a challenging problem. Despite its functional advantages, UKA still raises questions concerning implant survivorship and an increased revision risk for aseptic loosening mainly due to polyethylene wear. The main purpose of the present study was to investigate whether using the minimum thickness of an all-poly tibial UKA in patients under 60 years of age increases the revision rate for aseptic loosening. The secondary purposes were to compare implant survivorship with data reported in literature and to prospectively evaluate the clinical outcome in this selected group of patients.METHODS:Thirty-three consecutive patients under 60 years of age at the time of surgery with isolated medial compartment osteoarthritis underwent a unilateral medial UKA from 2002 to 2005 and were prospectively followed. A Kaplan-Meier analysis was performed to determine the 8-year implant survivorship with revision for any reason as endpoint. KSS, WOMAC, Tegner-Lysholm, Tegner and VAS scores were prospectively evaluated at 3- to 8-year follow-up. Weight-bearing radiographs were collected pre-operatively and at 3- to 8-year follow-up to prospectively evaluate hip-knee-ankle angle (HKA), femoro-tibial angle (FTA), tibial plateau angle and posterior tibial slope.RESULTS:The 8-year Kaplan-Meier survivorship with revision for any reason as endpoint was 83 %. Five failures were reported, and in 3 patients' aseptic loosening of the tibial component was the reason for failure. All clinical scores significantly improved at 3-year follow-up, and no further modification was demonstrated up to 8-year follow-up. HKA, FTA and TPA had a significant difference at 3-year follow-up with respect to pre-operative values (p < 0.01) and no further difference at 8-year follow-up was found.CONCLUSIONS:The present study failed to demonstrate an increased revision rate for aseptic loosening of the implant in patients under 60 years of age, who received an all-poly tibial component UKA using the minimum thickness of the implant in all cases.