Measured distance from posterior tibia to popliteal artery increases with flexion and subluxation of the knee.

Purpose: Popliteal artery laceration is a devastating complication in total knee arthroplasty (TKA). Its anatomic position relative to the tibia has been studied using ultrasound or magnetic resonance imaging. This is the first study performed in a laboratory using radiographic measurements to determine if increased flexion and subluxation of the knee increase the distance between the tibia and popliteal artery.

Methods: The femoral artery was infused with radiopaque dye in six cadavers. The knee was placed in two different degrees of flexion and three of subluxation. The radiographic distance between standardized markers in the posterior tibia and popliteal artery was measured.

Results: The average distance from the tibial peg to the popliteal artery at 90° of flexion increased from 0% to 50% to 100% subluxation. The increase was statistically significant (Friedman test  = 0.016). The contrast between neutral and 100% subluxation was statistically significant (Sign test  = 0.031). At 115° flexion, average distance from the peg to popliteal artery significantly increased as subluxation increased (Friedman test  = 0.05). In three specimens, at 115° of flexion and 100% subluxation, a line perpendicular to the axis of the tibia, failed to intersect the popliteal artery. The measured distance increased from 90° to 115° of flexion at a given degree of subluxation, but this difference did not reach statistical significance.

Conclusions: Increasing flexion and subluxation of the tibia results in increasing distance between the cut plane of the tibial plateau and popliteal artery and decreases risk of laceration.

Level Of Evidence: Not applicable.