The Role of Near Infrared Spectroscopy in Diagnosing Stump Ischaemia in Patients with Below Knee Amputation: Case Reports

INTRODUCTION: Functional near infrared spectroscopy (fNIRS) can be used to quantify stump oxygen saturation (SaO(2)) as one of many possible causes of pain following major amputation. Although commonly used for cerebral perfusion monitoring during carotid or cardiac surgery, it can also be used to monitor tissue perfusion in the lower limb and predict healing following below knee amputation (BKA). The aim of this study was to measure the SaO(2) trend as there is no validated oxygen threshold to diagnose insufficient flow into the arterial collateral network currently. REPORT: NIRS was used to measure SaO(2) while performing treadmill exercise. Two BKA patients with chronic stump pain were asked to perform treadmill exercise while using their prosthesis and NIRS optode applied to the posterior stump to monitor SaO(2). Cases 1 and 2 showed a decline in SaO(2) of 25% and 18%, respectively, while walking on the prosthesis. After superficial femoral artery (SFA) recanalisation and stenting, Case 1 showed improvement by maintaining SaO(2) between 54% and 60% throughout treadmill exercise. In Case 2, perfusion could not be further improved, and the patient underwent through knee amputation. DISCUSSION: fNIRS detected compressive ischaemia and exercise induced ischaemia as mechanisms of stump pain. Findings provided the multidisciplinary team with objective information, aiding decision making to treat stump pain.