Effect of Foot Stato-Dynamic Disorders on hemodynamics of the lower limb using strain-gauge plethysmography.

BACKGROUND: The plantar venous pump PVP, composed of deep plantar veins, is the most distal contributor to venous return from the lower limbs. There is still a pressing need to assess how plantar muscles contraction and gait affect its function, how foot stato-dynamic disorders FSD can contribute to venous insufficiency, and how it can be optimally stimulated.

OBJECTIVE: Our first objective is to compare venous blood hemodynamics in lower limb between healthy subjects having FSD and healthy subjects without FSD to understand the influence of foot morphology in the performance of the PVP. Our second objective is to evaluate whether the PVP function varies modifying plantar pressures.

PATIENTS/METHODS: Fifty-two healthy volunteers - twenty-six feet with normal arch (control group) and twenty-six feet with dysmorphy (thirteen flat feet, thirteen hollow feet) - were included. Strain-gauge plethysmography was performed 8 cm above the medial malleolus during different conditions of PVP stimulations: (1) with toe flexions, (2) with Intermittent Pneumatic Compression (IPC) with and without insole, (3) with 3 km/h-speed walking on a treadmill barefoot, with shoes, and with shoes and insoles. From the strain-gauge plethysmography, we measured venous blood ejection fraction (EF,%). From the pressure sensor placed at midfoot on the plantar arch during IPC, we obtained maximal pressure (N/cm2 ).

RESULTS: Toe flexion allowed ejecting in average 20% of the total venous volume in both groups whereas IPC and gait generated mean EF superior to 100% of the available venous volume. The Pmax applied at midfoot during IPC was lower than the pressure set. No significant difference of EF and Pmax was observed between the two groups. The mean EF was not significantly impacted in pronator and supinator walkers compared to subjects with normal walking dynamics. Wearing shoes did not significantly impact the mean EF whereas wearing insoles during gait significantly increased venous return in feet with plantar dysmorphy.

CONCLUSION: This clinical study is the first one to assess the PVP function in 52 healthy volunteers with and without foot stato-dynamic disorders. The study showed that wearing shoes did not significantly impact the PVP efficiency while wearing morphological adapted insoles significantly improved the venous return in dysmorphic feet. In this sample of healthy volunteers, the differences observed between control group and feet with FSD were not significant.