title: Navigation-assisted total knee arthroplasty for patients with extra-articular deformity.
abstract: OBJECTIVE
  Since the existence of an extra-articular deformity seriously alters the normal geometry and kinetics around the knee joint, difficulties are often encountered in total knee arthroplasty (TKA) using a standard surgical technique. The purpose of this study was to evaluate the usefulness of surgical navigation system as a treatment option for osteoarthritic knees with extra-articular deformity.
  
  
  METHODS
  The authors retrospectively reviewed medical records of the patients who underwent primary TKA between 2007 and 2012. Knees with preoperative radiography showing an angular deformity within the region from the middle third of the femur to the middle third of the tibia in the ipsilateral limb of the arthritic knees were considered as cases having extra-articular deformity. Thirteen knees of the 13 patients were found to have undergone TKA using a navigation system for osteoarthritis with ipsilateral extra-articular deformity. The hip-knee-ankle angle, Knee Society score (KSS), and range of motion were measured before and after the operation to evaluate the improvement.
  
  
  RESULTS
  The mean hip-knee-ankle angle in the coronal plane was improved to 0.2°±4.5° in valgus alignment postoperatively. The KSS was improved to 89.6±4.6 points postoperatively at the last follow-up, with over 90% of good and excellent results. The range of motion was improved to 118.5°±10.5° postoperatively.
  
  
  CONCLUSIONS
  Navigation-assisted TKA is a good treatment option of osteoarthritic knees with extra-articular deformity.
authors.affiliation: Department of Orthopedic Surgery, Pusan National University Hospital, Busan, Korea.
authors.forename: Seung Joon
authors.initials: SJ
authors.lastname: Rhee
authors.affiliation: Department of Orthopedic Surgery, Pusan National University Hospital, Busan, Korea.
authors.forename: Chang Hyo
authors.initials: CH
authors.lastname: Seo
authors.affiliation: Department of Orthopedic Surgery, Pusan National University Hospital, Busan, Korea.
authors.forename: Jeung Tak
authors.initials: JT
authors.lastname: Suh
keywords: Arthroplasty; Deformity; Extra-articular; Knee; Navigation