Affiliations: [a] Biomedical Engineering, Department of Electrical Engineering, Technical University of Denmark, Ørsteds Plads B349, Kongens Lyngby, Denmark 2800 | [b] JJ X-Ray A/S, DTU Scion, Science and Technology Park, Technical University of Denmark, Diplomvej B377, Kongens Lyngby, Denmark 2800 | [c] Laboratory of Biomechanical Design, Division of Human Mechanical Systems and Design, Faculty of Engineering, Hokkaido University, North 13 West 8 North Ward, Sapporo, Japan 060-8628 | [d] Department of Orthopaedic Surgery, Eniwa Hospital, Kogane-cho 2-1-1, Sapporo, Japan 061-1449 | [e] Advanced Medicine for Spine and Spinal Cord Disorders, Graduate School of Medicine, Hokkaido University, North 15 West 7 North Ward, Sapporo, Japan 060-8638
Correspondence:
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Corresponding author: Remel Alingalan Salmingo, PhD, JJ X-Ray A/S, DTU Scion, Science and Technology Park, Technical University of Denmark, Diplomvej B377, Kongens Lyngby, Denmark 2800. Tel.: +45 2824 5523; E-mails: [email protected], [email protected], [email protected].
Abstract: Treatment for severe scoliosis is usually attained when the scoliotic spine is deformed and fixed by implant rods. Investigation of the intraoperative changes of implant rod shape in three-dimensions is necessary to understand the biomechanics of scoliosis correction, establish consensus of the treatment, and achieve the optimal outcome. The objective of this study was to measure the intraoperative three-dimensional geometry and deformation of implant rod during scoliosis corrective surgery. A pair of images was obtained intraoperatively by the dual camera system before rotation and after rotation of rods during scoliosis surgery. The three-dimensional implant rod geometry before implantation was measured directly by the surgeon and after surgery using a CT scanner. The images of rods were reconstructed in three-dimensions using quintic polynomial functions. The implant rod deformation was evaluated using the angle between the two three-dimensional tangent vectors measured at the ends of the implant rod. The implant rods at the concave side were significantly deformed during surgery. The highest rod deformation was found after the rotation of rods. The implant curvature regained after the surgical treatment. Careful intraoperative rod maneuver is important to achieve a safe clinical outcome because the intraoperative forces could be higher than the postoperative forces. Continuous scoliosis correction was observed as indicated by the regain of the implant rod curvature after surgery.
Keywords: Orthopaedic biomechanics, dual camera system, scoliosis, rod deformation, 3D reconstruction
