Tianhao Wang1, Zhihua Cai2, Yongfei Zhao3, Wei Wang2, Guoquan Zheng3, Zheng Wang3, Yan Wang4. 1. Department of Orthopaedics, Southwest Hospital, Third Military Medical University, Chongqing, China; Department of Orthopaedics, General Hospital of Chinese People's Liberation Army, Beijing, China. 2. School of Electromechanical Engineering, Hunan University of Science and Technology, Xiangtan, China. 3. Department of Orthopaedics, General Hospital of Chinese People's Liberation Army, Beijing, China. 4. Department of Orthopaedics, General Hospital of Chinese People's Liberation Army, Beijing, China. Electronic address: yanwang_301@126.com.
Abstract
OBJECTIVE: To develop finite element models of spine following osteotomy and evaluate the effect of number and location of cross-links (CLs) on long-segment instrumentation. METHODS: A finite element model of instrumented spine following osteotomy was created from computed tomography images of a postoperative male patient with thoracolumbar kyphotic deformity. Five fixation models were established to simulate different number and location of CLs. Four loading conditions (flexion, extension, lateral bending, and axial rotation) were applied on the models. Range of motion (ROM), maximum value and distribution of stress on implants, and stress on vertebrae were compared between models. RESULTS: With increased number of CLs, average ROM of instrumented segments was reduced by 2.37%, 1.89%, and 2.49% in flexion, extension, and lateral bending. ROM was reduced by 21.98% in loading axial rotation condition. With increased number of CLs, ROM tended to be limited. Peak stresses were located on rods during axial rotation, on proximal pedicle screws during flexion, and on the osteotomy site during extension and lateral bending. CLs had an effect of dispersing stress concentration. CONCLUSIONS: The application of CLs enhanced the rigidity of the construct. With increased number of CLs, ROM of the construct was decreased, especially in axial rotation. CLs can also disperse the stress concentration. After comparing various CL configurations in different motion conditions, we believe that the optimal method is to place 2 CLs at the osteotomy site and the proximal segment.
OBJECTIVE: To develop finite element models of spine following osteotomy and evaluate the effect of number and location of cross-links (CLs) on long-segment instrumentation. METHODS: A finite element model of instrumented spine following osteotomy was created from computed tomography images of a postoperative male patient with thoracolumbar kyphotic deformity. Five fixation models were established to simulate different number and location of CLs. Four loading conditions (flexion, extension, lateral bending, and axial rotation) were applied on the models. Range of motion (ROM), maximum value and distribution of stress on implants, and stress on vertebrae were compared between models. RESULTS: With increased number of CLs, average ROM of instrumented segments was reduced by 2.37%, 1.89%, and 2.49% in flexion, extension, and lateral bending. ROM was reduced by 21.98% in loading axial rotation condition. With increased number of CLs, ROM tended to be limited. Peak stresses were located on rods during axial rotation, on proximal pedicle screws during flexion, and on the osteotomy site during extension and lateral bending. CLs had an effect of dispersing stress concentration. CONCLUSIONS: The application of CLs enhanced the rigidity of the construct. With increased number of CLs, ROM of the construct was decreased, especially in axial rotation. CLs can also disperse the stress concentration. After comparing various CL configurations in different motion conditions, we believe that the optimal method is to place 2 CLs at the osteotomy site and the proximal segment.