Inflating a thigh tourniquet anteriorly displaces the popliteal artery relative to the posterior tibial cortex: an in vivo magnetic resonance imaging study

Background Previous work has demonstrated that with increasing knee flexion angles, the popliteal artery is located further away from the posterior tibial cortex (PTC), thus offering a safer position for procedures about the knee. Prior studies did not, however, incorporate the use of a surgical thigh tourniquet, a device commonly used by orthopaedic surgeons. Thigh tourniquet effect on popliteal spatial anatomy will be assessed in this study. Methods Using 3 Tesla magnetic resonance imaging, 6 volunteer knees were evaluated in both full extension and 90 degrees (°) of flexion, with and without a thigh tourniquet inflated to 200 millimeters of mercury. Axial images at the level of the posterior cruciate ligament (PCL) tibial insertion were obtained. The distance of the popliteal artery from the PCL tibial insertion and the PTC at this level were calculated. Results Without a tourniquet, at 0° and 90° of flexion, the mean distance between the popliteal artery and the PTC was 6.9 and 9.4 millimeters, respectively. With a tourniquet, at 0° and 90° the mean distance between the popliteal artery and the PTC decreased to 6.2 (-0.7) and 8 (-1.4) millimeters, respectively. These reductions in distances with inflating the tourniquet were statistically significant (p<0.05). The distance between the artery and the PCL attachment did not change with and without inflating the tourniquet. Conclusions Inflating a thigh tourniquet moves the popliteal artery approximately 1 millimeter (8.5 percent) anterior towards the PTC and has no effect on the relationship between the popliteal artery and PCL insertion.