case_images: PMC11300108_01
case_images: Preoperative radiograph. (a) Lateral view: Femoral deformity is 25  antecurvatum; tibial deformity is 7  recurvatum. (b) Anteroposterior view: Hip-knee-ankle angle is 21.7  varus, femoral deformity is 7  valgus, and tibial deformity is 7  valgus.
case_images: CRIOR2024-6699418.001.jpg
case_images: PMC11300108_01_CRIOR2024-6699418.001.jpg
case_images: fig1
case_images: Due to postfracture malunion, the overall alignment of the lower limb revealed a hip-knee-ankle angle of 21.7  varus, the femoral deformity was 7  varus in the coronal plane/25  antecurvatum in the sagittal plane, and tibial deformity was 7  valgus in the coronal plane/7  recurvatum in the sagittal plane (Figure 1). First, navigation-assisted distal femur osteotomy was performed with the aim of achieving a neutral position of the varus/valgus and 25  of flexion (Figure 3, Line 1).
case_images: Preoperative planning using a 3D digital template. (a) The femoral implant is placed in line with the distal femoral axis. (b) The femoral implant is placed in line with the femoral mechanical axis.
case_images: CRIOR2024-6699418.002.jpg
case_images: PMC11300108_01_CRIOR2024-6699418.002.jpg
case_images: fig2
case_images: Regarding the sagittal alignment of femoral component, when the femoral implant was placed in line with the distal femoral axis in the sagittal plane, an extension deficit of 25  could develop (Figure 2(a)). When the femoral implant was placed in line with the femoral mechanical axis in the sagittal plane, a notch was observed (Figure 2(b)). The amount of bone resection was determined by the point at which the two osteotomy lines were crossed, just at the posterior cortex of femur (Figure 3, Lines 2 and 3).
case_images: Osteotomy lines. Line 1: Distal femur osteotomy has been performed to fix the varus/valgus to a neutral position with 25  of flexion. Lines 2 and 3: A 25  closed-wedge extension corrective osteotomy. Gray line: mechanical axis on the sagittal plane after corrective osteotomy. *Distal femoral reference point.
case_images: CRIOR2024-6699418.003.jpg
case_images: PMC11300108_01_CRIOR2024-6699418.003.jpg
case_images: fig3
case_images: During the registration process of the navigation system, we registered the distal femoral reference point as the distal endpoint of the expected mechanical axis in the sagittal plane after corrective osteotomy to enable navigation use after corrective osteotomy (Figure 3). First, navigation-assisted distal femur osteotomy was performed with the aim of achieving a neutral position of the varus/valgus and 25  of flexion (Figure 3, Line 1). The amount of bone resection was determined by the point at which the two osteotomy lines were crossed, just at the posterior cortex of femur (Figure 3, Lines 2 and 3).
case_images: Extra-articular osteotomy using navigation. Extra-articular corrective osteotomy was performed at the deformity apex using the Stryker Precision  Oscillating Tip Saw (Stryker, New Jersey, United States) mounted with a navigation tracker.
case_images: CRIOR2024-6699418.004.jpg
case_images: PMC11300108_01_CRIOR2024-6699418.004.jpg
case_images: fig4
case_images: The Stryker Precision  Oscillating Tip Saw (Stryker, New Jersey, United States) was mounted with the tracker of navigation (Figure 4), and the osteotomy was performed without a cutting guide.
case_images: Postoperative radiograph. (a) Lateral view: Femoral and tibial implants are implanted at 0.5  varus. (b) Anteroposterior view: Hip-knee-ankle angle is 1  varus, the femoral implant is implanted at 0.5  flexion, and the tibial implant is implanted at 0  posterior slope.
case_images: CRIOR2024-6699418.005.jpg
case_images: PMC11300108_01_CRIOR2024-6699418.005.jpg
case_images: fig5
case_images: 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 (Figure 5).