Evaluation of Accuracy of Preoperative Planning of the Femurofibular Angle in Open-Wedge High Tibial Osteotomy for Mild Medial Knee Osteoarthritis

Figure 1

Preoperative planning of FFA. (a) A primary mechanical axis line was drawn from the femoral head center to the ankle joint center on a full-length anteroposterior radiograph of the lower limb. Intersecting point (55%) and intersecting point (57.5%) of the targeted mechanical axis from the medial border of the tibial plateau surface were marked. (b) A corrective mechanical axis line connecting the femoral head center to intersecting point and intersecting point was drawn and extended to the level of the ankle joint (defined as mechanical axis and axis ). (c) A frame was created to encircle the predicted osteotomy plan, enclosing the tibia and fibula. The frame was then rotated and moved until the ankle joint center was on the targeted mechanical axis . (d) A similar frame was created and rotated until the ankle joint center was on the targeted mechanical axis . (e) A distal femoral condyle line and a proximal fibula axis line were drawn, and the angle between these two lines was measured and designated as the FFA. The FFA was 91° based on the targeted mechanical axis . (f) The FFA was 93° based on the targeted mechanical axis .

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