Abstract
Various tests are used preoperatively to differentiate patients who require an above-knee amputation (AKA) from those whose vascular supply is adequate to heal a below-knee procedure (BKA). This 15-month study of 109 amputations compared four of these methods: segmental Doppler systolic pressure measurements, transcutaneous oxygen measurement (tcPo2), fluorescein angiography, and skin thermometry. There were 66 BKAs (85% healed primarily) and 43 AKAs (93% healed primarily). The actual level of amputation was determined by the operating surgeon without consideration of the preoperative test results, and the incidence of healing was then related to the test parameters. The average skin temperature at the amputation site was higher (93.7° F) in the group that healed primarily compared with those who required operative stump revision (89.9° F) (p < 0.001). The mean midcalf tcPo2 was also higher in the BKA group that healed (Po2 = 36.6 mm Hg) compared with those who failed (Po2 = 16.4 mm Hg) (p < 0.001). Qualitative skin fluorescence was less successful in differentiating success from failure. Of the 63 BKAs that fluorescein predicted would heal, eight failed (13%). Doppler pressures at the thigh, popliteal, midcalf, or ankle level were unreliable in predicting healing of a BKA. Formulation of indexes relating absolute pressures to the brachial systolic pressure did not improve the value of this examination. From this review it is concluded that the skin temperature and tcPo2 obtained at the site of proposed amputation were the most reliable prognostic noninvasive examinations. Depending on which test was used, routine application of the noninvasive predictors in this study as the sole determinant of amputation level would have resulted in an AKA in 17% to 60% of patients whose amputations otherwise would have healed at a lower level. Objective data can supplement clinical judgment but not replace it.