The Effect of Lower Limb Cast Immobilization on Calf Muscle Pump Function

Abstract

Background: We have investigated the role of the calf muscle pump in casted patients. An audit of venous thromboembolism (VTE) in casted patients showed that the thrombosis occurred in the casted leg; this has not been previously assessed. We postulated that local factors play a major role, and we set out to assess the calf muscle pump in casted patients and to determine whether this can be optimized despite below-knee cast immobilization. Methods: We measured the flow in the popliteal vein using a validated method of Doppler ultrasound measurement of peak velocity with and without a below-knee plaster cast. Results: We demonstrated that a simple strategy of toe and ankle exercises can maintain venous return despite below-knee cast immobilization. Conclusion: This is the first study to examine the effect of the calf muscle pump in the presence of a plaster cast. Major muscle groups such as the flexor hallucis longus and gastrocsoleus extend beyond the field of control of the cast and can still be recruited. Clinical Relevance: We recommend that all patients treated with a below-knee cast be given a program of exercises that can be comfortably performed with the cast; this could provide a useful, inexpensive, and safe thromboprophylaxis strategy acting at the site of greatest risk and targeting a major cause of VTE.

The effect of active toe movement (AToM) on calf pump function and deep vein thrombosis in patients with acute foot and ankle trauma treated with cast – A prospective randomized study

“…This is the first study to examine the effects of active toe movement on DVT in patients with foot and ankle trauma treated with cast. Although we have previously shown that active toe movement (AToM) can influence calf pump function in healthy volunteers with below knee casts applied, we were unable to find any evidence that this reduces the incidence of DVT [8]. We anticipated that patients who performed regular active toe movements would have had improved venous calf pump function parameters, however this intervention had no significant effect.…”

“…Considering that active toe movement influences venous haemodynamics in healthy volunteers to a similar extent to intermittent pneumatic compression foot pump devices, we anticipated that this may also reduce asymptomatic DVT in patients with casts [8,21]. One of the main reasons why AToM failed to reduce DVT rates may relate to the relative infrequent performance of exercises by patients.…”

“…Patients with foot and ankle trauma treated with casts are also advised to participate in activities of early mobilisation and calf pumping exercises to reduce their risk of developing DVT [7]. Although we have previously shown that active toe movement increases venous velocities in the popliteal vein in healthy volunteers, even with a below knee cast applied, the clinical importance of these findings requires further investigation [8,9]. Most studies rule out mechanical thromboprophylaxis in patients with below knee casts for various reasons [10,11].…”

“…Peak velocity was then recorded during active toeplantarflexion. This method has previously been used to assess calf pump function in healthy volunteers with and without lower limb cast applied[8].…”

Hemodynamics and tolerability of lower-limb intermittent pneumatic compression devices and neuromuscular stimulation

“…The minimum hemodynamic effect of a device intervention to be DVT preventive is unknown. However, studies on hemodynamics during foot dorsiflexion may provide baseline data on blood flow during normal mobilization showing around at least a twofold increase in peak velocity, with results varying according to the type of exercise and body posture . Moreover, it is generally accepted that increased venous return leads to improved DVT prevention by correcting one of the three pathophysiological factors of thrombosis, the stasis, the other two being endothelial damage and increased coagulability, collectively known as the Virchow's triad.…”