EFFECT OF ANKLE POSITION AND A PLASTER CAST ON INTRAMUSCULAR PRESSUREIN THE HUMAN LEG

Intramuscular pressure was measured with transducer-tipped catheters t hat had been inserted into the anterior and deep posterior compartment s of the leg in seven healthy adults. Intramuscular pressure increased three to sevenfold (depending on the position of the ankle) in both c ompartments after the application of a plaster cast from the proximal part of the thigh to the malleoli. While the cast was in place, the ba seline intramuscular pressure was elevated by the inflation of a tourn iquet, which was located on the proximal part of the thigh, to a press ure of sixty millimeters of mercury (8.00 kilopascals). The intramuscu lar pressure in both the anterior and the deep posterior compartments was found to be lowest when the ankle joint was between the neutral an d the resting positions (between 0 and 37 degrees of flexion). After t he cast was bivalved and the opening on each side was spread approxima tely one-half centimeter, there was a significant decrease in intramus cular pressure of 47 per cent in the anterior compartment and of 33 pe r cent in the deep posterior compartment (p < 0.05 for both). CLINICAL RELEVENCE: The application of a plaster cast after an injury can incr ease the risk of compartment syndrome in the anterior and deep posteri or compartments of the leg. The best compromise in order to achieve th e lowest intramuscular pressure in both compartments, if both are enda ngered, is for the ankle to be immobilized between the resting and the neutral positions. A combination of bivalving of the cast and spreadi ng of the opening on each side can reduce the pressure in these compar tments.