Date of download: 6/22/2016 Copyright © ASME. All rights reserved. From: A Multiaxis Programmable Robot for the Study of Multibody Spine Biomechanics Using a Real-Time Trajectory Path Modification Force and Displacement Control Strategy J. Med. Devices. 2013;7(3): doi: / Spine Robot configuration. Diagram of 4-DOF robotic system developed in the current study. The manipulator was comprised of a series assembly of a vertical translational z-axis, horizontal translational x-axis (via moving carriage), and rotational pitch and roll axes orthogonally applied through a triangular biaxial gimbal joint. Six axis load sensors were mounted to the manipulator/gimbal assembly (GLS) and to the testing frame base (BLS). Figure Legend:

Date of download: 6/22/2016 Copyright © ASME. All rights reserved. From: A Multiaxis Programmable Robot for the Study of Multibody Spine Biomechanics Using a Real-Time Trajectory Path Modification Force and Displacement Control Strategy J. Med. Devices. 2013;7(3): doi: / Testing system and specimen mounting. (Left) Photo of assembled 4-DOF manipulator within tripod support frame. (Right) Antero- lateral view of human cadaveric cervical spine (C2–T1) mounted in the testing frame with midsagittal plane aligned with the robot x– z plane. The potted rostral end was rigidly affixed to the six-axis gimbal load sensor, and potted caudal end affixed to the base six- axis load sensor and frame. Dashed arrow schematically illustrates flexion path. Figure Legend:

Date of download: 6/22/2016 Copyright © ASME. All rights reserved. From: A Multiaxis Programmable Robot for the Study of Multibody Spine Biomechanics Using a Real-Time Trajectory Path Modification Force and Displacement Control Strategy J. Med. Devices. 2013;7(3): doi: / Spinal end body forces. Applied rostral–caudal (Fz) and antero–posterior (Fx) spinal forces were determined with respect to the moving gimbal load sensor reference frame. Spinal end forces were corrected for the influence of pot weight and changes in gimbal load sensor readings due to changes in orientation. Figure Legend:

Date of download: 6/22/2016 Copyright © ASME. All rights reserved. From: A Multiaxis Programmable Robot for the Study of Multibody Spine Biomechanics Using a Real-Time Trajectory Path Modification Force and Displacement Control Strategy J. Med. Devices. 2013;7(3): doi: / Force control algorithm. Algorithm derived to control spinal end forces by issuing a real-time trajectory path modification command every 4 ms (inner RTTPM loop) according to force control criteria. A separate software looping structure was nested inside a programmed point to point continuous motion path loop to achieve this task. Figure Legend:

Date of download: 6/22/2016 Copyright © ASME. All rights reserved. From: A Multiaxis Programmable Robot for the Study of Multibody Spine Biomechanics Using a Real-Time Trajectory Path Modification Force and Displacement Control Strategy J. Med. Devices. 2013;7(3): doi: / Spinal shear forces during force controlled pure moment pilot test. Programmed spinal shear force (Fx = 0 N) at the rostral specimen end (gimbal load sensor: programmed) is shown in comparison with actual shear forces applied (gimbal load sensor: applied) during flexion and extension. Ideal projected forces expected at the specimen caudal end based on programmed Fx and Fz forces (base load sensor: programmed Ideal) are also shown in comparison with shear force values measured caudally (base load sensor: measured). Figure Legend:

Date of download: 6/22/2016 Copyright © ASME. All rights reserved. From: A Multiaxis Programmable Robot for the Study of Multibody Spine Biomechanics Using a Real-Time Trajectory Path Modification Force and Displacement Control Strategy J. Med. Devices. 2013;7(3): doi: / Axial spinal forces during force controlled pure moment pilot test. Programmed axial spinal force (Fx = 5 N) at the rostral specimen end (gimbal load sensor: programmed) is shown in comparison with actual axial forces applied (gimbal load sensor: applied) during flexion and extension. Ideal projected forces expected at the specimen caudal end based on programmed Fx and Fz forces and a 16 N potted specimen weight (base load sensor: programmed ideal) are also shown in comparison with actual axial forces measured caudally (base load sensor: measured). Figure Legend:

Date of download: 6/22/2016 Copyright © ASME. All rights reserved. From: A Multiaxis Programmable Robot for the Study of Multibody Spine Biomechanics Using a Real-Time Trajectory Path Modification Force and Displacement Control Strategy J. Med. Devices. 2013;7(3): doi: / Global spinal flexibility during force controlled pure moment pilot test. Global spinal flexibility determined from applied bending moment values at the rostral end of the test specimen (gimbal load sensor: applied) is shown in comparison with flexibility determined from bending moment values recorded at the caudal specimen end (base load sensor: measured) during flexion and extension. Figure Legend:

Date of download: 6/22/2016 Copyright © ASME. All rights reserved. From: A Multiaxis Programmable Robot for the Study of Multibody Spine Biomechanics Using a Real-Time Trajectory Path Modification Force and Displacement Control Strategy J. Med. Devices. 2013;7(3): doi: / Percent contribution of MSU rotations to global rotation during pure moment pilot test. Individual motion segment unit percent contributions to global spinal rotation during force controlled pure moment pilot test in flexion and extension. Figure Legend: