The effect of increased hip flexion using stirrups on lower-extremity venous flow: a prospective observational study

BackgroundPatient positioning during surgeries for colorectal cancer may represent an unrecognized risk factor for deep venous thrombosis.MethodsTwelve healthy control patients were positioned supine with knee flexion at 90°. Duplex ultrasound examined common femoral vein (CFV) and proximal femoral vein diameter, peak systolic velocity, and volume flow with hip flexion at 0°, 30°, 60°, and 90°. Data were analyzed using the paired t test.ResultsIn the CFV, hip flexion to 90° was associated with a significant increase in mean volume flow when compared with hip flexion at 0° (.59 vs .36 L/min; P = .05) and 30° (.59 vs .35 L/min; P = .038). In both the CFV and proximal femoral vein, increased hip flexion was associated with significantly reduced vessel diameter and increased peak systolic velocity.ConclusionsIntraoperative positioning of the lower extremities represents a modifiable risk factor for deep venous thrombosis. When stirrups are used, hip flexion of 90° maximizes venous drainage from the legs.