For the 'LOP + paediatric cuff' group, cuff selection and application will be based on a standardized guide used to determine the most appropriate size and shape of cuff for the given limb. See cuff application guidelines (attached). Once the indicated cuff has been applied, the photoplethysmographic LOP sensor will be clipped to a toe of the affected leg, systolic blood pressure (SBP) will be recorded, and the automated LOP routine activated. LOP and recommended tourniquet pressure (RTP = LOP + predetermined margin) will be displayed within 1 minute and recorded. The limb will then be exsanguinated following the surgeon's usual procedure and the cuff inflated to the RTP.