The Role of Vascular Laboratory Criteria in the Selection of Patients for Lower Extremity Amputation

We evaluated clinical and vascular laboratory data on 126 patients with below-knee or forefoot amputation. Vascular laboratory examination included Doppler systolic blood pressure and arterial wave form analysis using the segmental plethysmograph. Fifty-four patients had below-knee amputation. A calf systolic pressure greater than 70 torr was associated with 97% (33/34) success (p less than 0.005), an ankle systolic pressure greater than 30 torr yielded 91% (39/43) success (p less than 0.025), and an ankle systolic pressure greater than zero yielded an 87% success (p less than 0.005). In the absence of each of the above criteria, the predictive value of a negative test was only 32%, 40%, and 52%, respectively. The presence of a popliteal pulse was associated with 97% success (p less than 0.025); however, 88% of those with an absent popliteal pulse also achieved successful healing of below-the-knee amputations. Prior vascular reconstructive surgery was detrimental to healing of below-knee amputations. with 33% failure rate (p less than 0.025). For the 72 forefoot amputations, an ankle systolic pressure greater than 70 torr yielded a 65% success (p less than 0.025). The sensitivity of an ankle systolic pressure greater than 70 torr was 80% (32/40) and an ankle systolic greater than 35 yielded a sensitivity of 95% (38/40). The specificity was low for both of these reference values. Clinical and vascular laboratory criteria can identify patients who will have a successful below-knee amputation; however, because of the high false negative rate, patients should not be denied below-knee amputation solely on the basis of Doppler systolic pressure. Vascular laboratory criteria for predicting healing of forefoot amputations are also limited by the high rate of false positive and false negative results.