Comparison of functional deficits in the rabbit tibialis anterior following tourniquet ischemia and tourniquet compression.

The purpose of this study was to measure the contractile properties of skeletal muscle after direct compression with a tourniquet and to compare these properties with those found after a similar period of tourniquet ischemia. A rabbit model of tourniquet compression of the tibialis anterior was developed and tested for this investigation. Fifty-seven animals then were divided into four protocol groups: (a) thigh tourniquet (ischemia) at 350 mm Hg (46.7 kPa), (b) leg tourniquet (compression) at 350 mm Hg (46.7 kPa), (c) leg tourniquet at 125 mm Hg (16.7 kPa), and (d) controls. A significant decrease in maximum tetanic tension was demonstrated in all three experimental groups. Direct compression at 350 mm Hg resulted in the greatest decline in maximum tetanic tension (22.6% of control), followed by compression at 125 mm Hg (30.5%) and ischemic injury (40.2%). In addition, direct compression at 350 mm Hg resulted in a significantly greater loss of force-generating capacity when compared with the ischemic group (p < 0.01). A similar pattern was noted for the rate of rise in maximum tetanic tension. Gross histologic examination of the tibialis anterior sections was consistent with the results of functional testing, with the more severe abnormalities noted in the compressed specimens. These results clearly demonstrate that tourniquet compression injury results in a more significant loss of functional strength and contractile speed than tourniquet ischemia. Further investigations on the safe limits of tourniquet use thus should be directed toward measuring the effect of the pneumatic tourniquet on the underlying soft tissues.