Can the failure of a below-knee amputation be predicted? Predictability of below-knee amputation healing

The predictability of below-knee amputation healing was evaluated in 69 patients with severe distal ischaemia with or without diabetes mellitus. A special attempt was made to find out predictors of amputation failure. Of 71 amputations performed 20 failed. Preoperative systolic blood pressures and skin perfusion pressures were significantly higher at the level of amputation in patients whose amputations healed than in those whose amputations failed, mean 69.5 (SD 33.4) mmHg and 55.9 (SD 27.0) mmHg vs. 41.5 (SD 31.6) mmHg (p less than 0.01) and 35.6 (SD 13.9) mmHg (p less than 0.05), respectively. There was, however, considerable overlapping and only if calf systolic blood pressure was unmeasurable did below-knee amputations always fail. PVR and skin perfusion pressure data were useful in disclosing falsely high calf systolic blood pressures apparently caused by mediasclerosis. When these patients with pseudohypertension were excluded the presence of diabetes did not affect the pressure readings. The blood viscosity as indicated in this study by pre- and postoperative haemoglobin levels did not affect amputation healing. The present results suggest that vascular laboratory data are useful as supplementary information in the assessment of below-knee amputation healing but it can predict amputation failure only when no Doppler signals are present at the ankle level.