Fig. 3

Illustration of FCPSI Design and application process. (A) (B) The metallic wires in different directions are added into the regular design as fluoroscopy calibration markers. According to the preoperative plan, an AP marker should be presented as a point on the AP view to achieve a true AP view on fluoroscopy. Then OP marker served as a reference to accurately place the guide on the coronal plane. The distal end of an OP marker should be aligned with the joint surface (the line between the distal end of medial and lateral condyles). (C) The FCPSI was initially assembled with the bone model. (D-F) Subsequently, the surgeon acquired a true AP X-ray image of the FCPSI. The position of C-arm was adjusted to achieve a position where the AP marker appears as a dot. With meticulous calibration to the optimal position (F), all markers adhered precisely to the preoperative planning as shown in (A)