Impact of Active Ankle Movement Frequency on Velocity ofLower Limb Venous Flow following Total Hip Arthroplasty

Although active ankle movement plays a predominant role in mechanical thromboprophylaxis following total hiparthroplasty (THA), the most effective frequency of movement remains unclear.Materials and Methods.In 29 consecutive patientsundergoing THA, the velocity of blood flow in the profunda femoris was measured after various frequencies of ankle movementtwo days after THA using a pulse wave Doppler ultrasound system. To test the interobserver reliabilities for the velocity measuredwith Doppler ultrasound system, the intraclass correlation coefficient was calculated based on the measurement in 10 limbs ofhealthy volunteers.Results.At 0, 1, and 2 minutes after ankle movement, the velocity after movement at 60 contractions per minutewas significantly faster than that after movement at 40 or 80 contractions per minute (𝑝=0.0007, repeated-measures analysisof variance). The intraclass correlation coefficient score in two investigators was 0.849 (95% confidence interval, 0.428 to 0.962).Conclusions.Active ankle movement at 60 contractions per minute is recommended in patients receiving THA to obtain optimalvenous blood flow