The selection of amputation level: an approach using decision analysis.

The choice of level for a major amputation of the leg depends upon the careful balancing of the advantages of preserving the knee joint against the risks of failure to heal and subsequent revision of the amputation stump. A study has been carried out to measure the values that health care professionals put upon different levels of disability resulting from amputation. The results show that the reduction of quality of life is thought to be 5-10% and 10-20%, respectively, for ambulation upon a below-knee and above-knee prosthesis and about 50% for failure to mobilise on an artificial limb. These utilities have been incorporated into a decision analysis to determine the optimum strategy for evaluation of amputation level, with other probabilities obtained from published data. The results demonstrate the advantage of attempting to preserve the knee joint, even if the chance of primary healing is as low as 20%. Tests of likely healing are most useful if the sensitivity is high, with specificity being less important, and the advantages may be outweighed by the costs of false negatives if sensitivity is below 90%. Sensitivity analysis shows that these findings remain valid over a wide range of possible values. Further research is required to gain more accurate information on which to base decisions, but on current evidence a policy of below-knee amputation in all cases of clinical doubt may be preferable to the use of currently available tests.