Selection of amputation level and prediction of healing using transcutaneous tissue oxygen tension (PtcO2)

Pre-operative measurement of transcutaneous tissue oxygen tension (PtcO2) by reflecting oxygen delivery at proposed amputation sites may allow accurate prediction of post-operative healing. Thirty-eight patients requiring amputation had PtcO2 measured with a Clark electrode on the foot, anteriorly and posteriorly below knee and above the knee while lying supine. PtcO2 greater than 24 mmHg was chosen to predict healing and indicated 13 above-knee (AK) and 25 below-knee (BK) amputations. Clinical criteria indicated 12 AK and 26 BK amputations. PtcO2 and clinical judgement differed on five occasions, a lower amputation was indicated by PtcO2 twice and by clinical selection three times (PtcO2 16 mmHg). Amputation was performed at the more distal level indicated (25 BK, 13 AK). Foot PtcO2 in both groups did not differ significantly, 4.08 +/- 2.00 mmHg (BK) and 3.9 +/- 1.29 mmHg (AK) (p greater than 0.5), nor did above knee PtcO2 (p greater than 0.3). Anterior below knee PtcO2 in both groups differed significantly, 34.92 +/- 10.84 mmHg (BK) and 9.5 +/- 5.60 mmHg (AK) (p less than 0.001). Likewise, posterior PtcO2, 39.64 +/- 6.85 mmHg (BK) and 14.1 +/- 4.43 mmHg (AK) (p less than 0.001). Amputation sites healed primarily within two weeks except the site with a pre-operative PtcO2 of 16 mmHg, where healing was delayed and occurred by second intention. These results indicate that PtcO2 is a valid predictor of primary healing following amputation.