Abstract
Background: Knee osteoarthritis (OA) with extra‐articular deformity (EAD) is a rare condition for which achieving accurate alignment with total knee arthroplasty (TKA) is difficult. Extra‐articular corrective osteotomy may be necessary for severe deformities.Case Presentation: A 76‐year‐old man underwent TKA for knee OA with EAD due to malunion after fractures of the femur and tibia. The femoral varus and the tibial valgus/recurvatum deformities were mild and corrected by intra‐articular osteotomy using navigation (i.e., navigation‐assisted standard TKA). However, the femoral antecurvatum deformity was severe, and we performed extra‐articular corrective osteotomy simultaneously with TKA. Navigation was used not only for TKA but also for extra‐articular corrective osteotomies. The osteotomy site was fixed with a cemented stem and metaphyseal sleeve. The postoperative hip–knee–ankle angle was 1° varus, the femoral implant was implanted at 0.5° varus/0.5° flexion, and the tibial implant was implanted at 0.5° varus/0° posterior slope. Two years after surgery, improvements were obtained in the range of motion from 15°–95° to 0°–110°, the Knee Society Score from 39 to 92 points, and the functional score from 35 to 100 points.Conclusions: One‐stage TKA with extra‐articular corrective osteotomy achieved good clinical results due to accurate alignment using navigation and firm fixation of the osteotomy site using cemented‐stem and metaphyseal sleeve without any fixation devices.