Background: Unicompartmental knee arthroplasty( UKA) has become a treatment of choice for many patients with isolated unicomparmental arthritis due to its specific advantages over total knee anthroplasty, but few studies have compared conventional and navigational UKA with similar instrumentation on mid- to long-Lerm results. We investigated whether the use of imageless navigation can improve implant positioning and clinical outcomes of UKA at a long term follow-up compared to the conventional technique. Methods: We prospectively studied clinical and radiological results in 68 patients with an average age of 64.0 years (range, 50 to 81 years) who received UKA between January 2003 and December 2005 using the conventional or navigational technique. Clinical evaluations were performed preoperatively and the last follow-up included knee range of motion, Hospital for Special Surgery (HSS) scores, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores and Visual Analogue Scale (VAS) pain score. For radiologic evaluation, the mechanical alignment of the lower limb was measured using mechanical femoro-tibial angle (mFTA) and Kennedy protocol. Results: Alter an average 9-year follow-up (range, 7.4 to 103 years), the navigation group showed better coronal alignments of the components, fewer radiological out-liers and better clinical scores, but similar estimated 10-year prosthesis survival rates. Conclusion: This study indicates that the use of navigation significantly contributes to the desired mechanical axis and improved component placement as compared to the conventional technique.
