Mean tourniquet time was 118.6 mins (range 98–143 mins) in the navigation/robotic group, which was significantly longer than the conventional group (mean 96.2 mins and range 61–131 mins). Blood loss as estimated from the difference between pre and post op haemoglobin measurements was 3.2 g/dl (range 0.2–6.2 g/dl) in the navigation/robotic group as compared to 3.1 g/dl (range 1.0–6.6 g/dl) in the conventional group. Mean length of stay was 8.7 days post op and 8.9 days post op in the navigated/robotic and conventional groups respectively. There were no physical surgical complications in the navigated/robotic group and 3 in the conventional group (1 superficial cellulitis, 1 haematoma and 1 case of temporary sensory loss to the sole of the foot). 3 cases from the navigated/robot-assisted group had to be completed with the conventional technique due to software/hardware failure intra-operatively. Other factors to consider, which are difficult to quantify, but which were noted in the navigated/robotic group are:
Training of the surgeon Training of the theatre personnel Cost of the system Cleaning/sterilisation burden of the robot and tools, which have stringent requirements and long turn around times Requirement of technical assistance with equipment and software Radiographic assessment (need long leg films to accurately assess alignment)
