The Effect of Lower Limb Cast Immobilization on Calf Muscle Pump Function: A Simple Strategy of Exercises Can Maintain Flow

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.