Abstract
Introduction: Unicondylar knee arthroplasty (UKA) has seen a resurgence in the past decade. Perpetuation of this trend can only be supported through prospective demonstration of efficacy with validated outcomes measures.
Materials & Methods: Thirty-three consecutive cemented medial Miller-Galante UKA’s (Zimmer, Warsaw, IN) were performed in 32 patients (7 males/25 females; mean age of 67 ± 9 years). Average weight, height, and body mass index (BMI) of the patient population was 189 ± 31 lbs (Range, 145–293), 65 ± 4 in (range, 60–75), and 33 ± 5 BMI (range, 25–43), respectively. Average polyethylene thickness (as labelled) for this cohort was 8.3mm (range, 8–12mm). Outcomes were prospectively assessed via the SF-12, WOMAC, and Knee Society Score (KSS). No patients were lost to follow-up. Kaplan-Meier survivorship and Student’s t-test were performed using GraphPad Prism 4 software (GraphPad Software Inc., San Diego, CA).
Results: Minimum follow-up was 39 months with a mean follow up period of 49 (range, 39–59) months. One knee was converted at 6 months at another institution to a TKA. Kaplan-Meier survivorship analysis reported 97% survivorship at 59 months (95% CI). Of the 32 knees remaining, mean preoperative KSS and WOMAC pain scores improved significantly from 52 ± 7 (range, 37–67) to 89 ± 9 (range, 67–100) (p< 0.0001) and from 40 ± 22 (range, 0–80) to 93 ± 14 (range, 35–100) (p< 0.0001), respectively. Additionally, average SF-12 Physical Component scores significantly increased from 30 ± 7 (range, 18–51) at baseline to 49 ± 10 (range, 28–59) at time of follow-up (p< 0.0001). Overall stiffness and physical function assessed via the WOMAC index also exhibited statistically significant improvement, bettering from mean baseline scores of 54 ± 24 (range, 0–100) and 52 ± 19 (range, 25–87) to 84 ± 19 (range, 50–100, p< 0.0001) and 88 ± 15 (range, 44–100, p< 0.0001), respectively. No significant cement/bone interface radiolucencies were found upon thorough radiographic review at 3 years post UKA.
Discussion & Conclusion: The significant improvements observed in knee function & stiffness, and decreases in pain at a mean of 4 years after medial UKA are encouraging. Coinciding results from the physical component of the SF-12 assessment indicate reassurance of physical improvements regarding patient lifestyle. 97% survivorship in the short term would be discouraging if not for the specific circumstances of the sole conversion to TKA. This specific patient went against the advice of the operative surgeon and solicited services at an outside institution in conversion to a TKA despite markedly improved function (Pre-op/3 month post-op WOMAC and KSS of 30/75 and 60/91). Clinical and radiographic follow-up will continue in order to assess the long-term efficacy of medial UKA with the Miller-Galante prosthesis using strict patient selection criteria.
Correspondence should be addressed to ISTA Secretariat, PO Box 6564, Auburn, CA 95604, USA. Tel: 1-916-454-9884, Fax: 1-916-454-9882, Email: ista@pacbell.net
