Pedal Musculovenous Pump Activation Effectively Counteracts Negative Impact of Knee Flexion on Human Popliteal Venous Flow

Abstract

Knee scooters are commonly used for mobility instead of other devices. However, passive popliteal venous flow impedance has been observed with knee scooter usage ostensibly as a result of deep knee flexion. This study aimed to characterize the magnitude of impact knee flexion has on popliteal venous flow in relation to the degree of knee flexion when walking boot immobilized. Furthermore, the countervailing effect of standardized pedal musculovenous pump (PMP) activation was observed. Popliteal venous diameter and flow metrics were assessed with venous ultrasonography in 24 healthy individuals. Straight leg, crutch, and knee scooter positioning while wearing a walking boot and non–weight-bearing were compared. Flow was assessed with muscles at rest and with PMP activation. Of 24 participants, 16 (67%) were female. Twelve limbs (50%) were right sided. The mean age was 21.9 (SD = 3.0) years, and the mean body mass index was 21.9 (SD 1.9) kg/m2. Observer consistencies were excellent (intraclass correlation range = 0.93 to 0.99). No significant differences in mean vessel diameter, time-averaged mean velocity, and total volume flow occurred (all P > .01). Corresponding knee flexion effect sizes were small (range = −0.04 to −0.26). A significant decrease (−24%) in active median time-averaged peak velocity occurred between upright and crutch positions (20.89 vs 15.92 cm/s; P < .001) with a medium effect size (−0.51). PMP activation increased all flow parameters (all P < .001), and effect sizes were comparatively larger (>0.6) across all knee flexion positions. Clinical Significance: Knee flexion has a small to medium impact on popliteal venous return in healthy patients. Active toe motion effectively counters the negative effects of gravity and knee flexion when the ankle is immobilized. Levels of Evidence: Therapeutic, Level IV

EMG Activity With Use of a Hands-Free Single Crutch vs a Knee Scooter

“…26 The authors go on to identify that the knee position and lack of muscle contraction with the use of standard axillary crutches led to significantly decreased activation of the pedal musculovenous pump stimulated time-averaged peak velocity, which could potentiate venous stasis. 26 The lack of cyclic muscle contraction and pedal musculovenous pump activation with standard axillary crutches is also consistent with our previous study that clearly established minimal EMG activity while using standard axillary crutches as compared to an HFSC. 11…”

Popliteal Blood Flow With Lower-Extremity Injury Mobility Devices

“…11 Previous investigations highlight a negative effect of knee flexion on venous flow when standing still, but neither HFC nor MKS affected venous flow compared to baseline in this study despite a flexed knee position. 21 Venous dimensions are not influenced by knee flexion in other reports, perhaps because of lack of ambulation. 6 However, in the current study, use of the MKS elicited a larger venous diameter than baseline and AC but lower venous flow than walking, supporting previous evidence that weightbearing with a straight knee stimulates venous flow more than weightbearing on a flexed knee.…”

“…Baseline and post-mobility device popliteal hemodynamics were collected on the right lower limb (disuse limb) via duplex ultrasonography (Terason uSmart 3300, Terason, Burlington MA, USA) of the popliteal fossa while prone on a training table with the ankle propped to set the knee angle between 15 and 20 degrees of flexion. 21 Vessels were imaged longitudinally with a 15L4 linear transducer. Doppler was superimposed over 2D imaging to measure velocity (cm/s).…”

“…Sample size for the study was estimated above previous studies on blood flow in ambulatory conditions. 6,21 A retrospective power analysis for our main dependent effects of popliteal venous and arterial flow determined that the sample size of 40 participants was above 85% power at an alpha level of 0.05.…”

“…Alternatively, ambulation devices and unloading conditions may also influence local blood flow. 6 , 14 , 21 , 28 Venous thromboembolism, which may present as deep vein thrombosis (DVT), is a consequence of prolonged immobilization and is a concern for patients and clinicians. Incidence of DVT following foot and ankle surgery has been elusive to determine but may range from 0.22% up to 32%.…”