Typically, the patient is positioned supine on a radiolucent table with a bump under the ipsilateral hip to avoid excessive external rotation of the distal femur. The C-arm is brought from the contralateral uninjured side. Obtaining appropriate imaging before the surgery is critical. Before prepping and draping, the contralateral limb is imaged for rotational purposes (Figure 1). An radiograph of the knee is first obtained with the patella centered. Without changing tilt and rotation, an radiograph of the lesser trochanter is then obtained. This "lesser trochanter profile" can be used as a template when assessing the rotation of the injured limb. In addition, a reproducible anterior-posterior (AP) image (which may be defined as showing 50% overlap of the fibular head by the tibial metaphysis) of the uninjured knee should be obtained. This radiograph will reveal the anatomic contour of the trochlear notch in the uninjured knee, which can be used as a template for the injured side when assessing whether the articular block is hyperextended relative to the shaft (a hyperextended articular block will have a trochlear notch that appears "larger" than the contralateral uninjured side, Figure 2). Finally, an overlapping femoral condyle lateral of the uninjured knee can be obtained to characterize the native anatomy between the condyles and the shaft. This is often a useful template for reduction because posterior comminution may prevent the use of the posterior cortex as a key in reestablishing the shaft-articular block relationship.
Fluoroscopic images showing the assessment of rotation and alignment. Fluoroscopic images of the uninjured knee and hip (top left) obtained without changing the C-arm rotation are compared with images of the injured knee and hip (top right) and demonstrate a similar appearance of the lesser trochanter with similar knee rotation, confirming that a rotational malreduction has not occurred. AP fluoroscopic images of the hip, ankle, and knee with a bovie cord spanning from the femoral head to the middle of the ankle (bottom row) confirm that the mechanical alignment of the knee is anatomic after reduction and fixation.
Radiograph showing the hyperextension of the articular block relative to the shaft. The contour of the trochlea in the postoperative AP image (left) is larger in height compared with the contour of the trochlea in the contralateral AP image (right), suggesting hyperextension of the articular block. Hyperextension is confirmed with comparison of the postoperative lateral image (left) with the contralateral lateral image (right). Plate-bone mismatch is also seen on the postoperative AP image because of the posterior condyles being anteriorly translated, increasing the distance from the shaft to the plate.
J Am Acad Orthop Surg. 2021;29(18):770-779. © 2021 American Academy of Orthopaedic Surgeons