Learning conditionally lexicographic preference relations

Richard Booth, Yann Chevaleyre, Jérôme Lang, Jérôme Mengin, Chattrakul Sombattheera

Abstract: Currently surgeons are unable to determine how much force is applied during scoliosis correction. The Gripper is a modified Moss Miami rod rotator with an instrumented sleeve that slips over the handle. This system is able to measure the force and resulting moment applied by the surgeon during the derotation maneuver of scoliosis surgery. The rigid frame of the hand grip is insensitive to the squeezing force and thus only the net forces and torque transmitted by the surgeon are recorded. The strain gauge data was sampled with a data acquisition system (DAQ 1200, National Instruments) and the voltage output was interpreted by MATLAB to calculate the forces and moments. Calibration showed that the system could calculate the forces accurately (R2=0.96) and to within ± 3 N. For scoliosis surgery, data were collected during the derotation of the rod, prior to fixation. Forces and moments were recorded for about 30 seconds at 10 samples per second. This system was tested on 4 subjects. The maximum forces applied by the surgeon ranged from 20 to 50 N with a torque of 4-11 Nm.