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

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Abstract
Clinical and vascular laboratory data on 126 patients with below-knee or forefoot amputation were evaluated. 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 < 0.005), an ankle systolic pressure > 30 torr yielded 91% (39/43) success (P < 0.025), and an ankle systolic pressure > 0 yielded an 87% success (P < 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 < 0.025); 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 < 0.025). For the 72 forefoot amputations, an ankle systolic pressure > 70 torr yielded a 65% success (P < 0.025). The sensitivity of an ankle systolic pressure > 70 torr was 80% (32/40) and an ankle systolic > 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; 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.