Biomechanical analysis and activity study of Lenke-Silva type Ⅵ degenerative scoliosis with different internal fixation methods

English Keywords:Scoliosis  Orthopedic  Biomechanics  Finite element analysis

English Abstract:

  【Abstract】 Objectives: A three-dimensional finite element model after degenerative scoliosis correction was established and simulated analysis was performed to obtain the stress distribution of the nail-rod system. The patient′s postoperative activity was determined based on the yield strength of the titanium alloy nail rod. Methods: Four patients who had undergone orthopedic surgery but the nail rods were not removed were selected. Four patients underwent A, B, C and D internal fixation schemes. Innovative solution of satellite rod technology, A, T10-S1 17 screws were fixed, the horizontal connection was located above the orthopedic area; B, L2-S1 12 screws were fixed; C, T10-S1 14 screws were fixed, the horizontal connection was located below the orthopedic area; D, T10-S1 19 screws were fixed, the satellite rod was fixed and strengthened across L1-S1, and the horizontal connection was located above the orthopedic area. CT scans were performed on the spine of 4 patients, and a complete three-dimensional finite element model was established based on the CT images. The three-dimensional model was loaded to simulate six conditions: forward-backward bending, left-right bending and left-right rotation. Stress distribution of the nail-rod system. The sensitivity analysis was performed on the nail rod, and the postoperative mobility of the patient was determined according to the yield strength and sensitivity curve of the titanium alloy nail rod. Results: A three-dimensional finite element model after degenerative scoliosis correction was successfully established, the stress on the nail rod was concentrated at the junction of the nail tail and the nail body and the junction of the nail tail and the orthopedic rod. The activities of the four schemes(A, B, C and D) under the six operating conditions were as follows, forward-backward bending was 22°, 30°, 45°, 30°; left-right bending was 19°, 28°, 34°, 32°; left-right rotation was 21°, 20°, 42°, 24°, respectively. Conclusions: The establishment of finite element model and stress analysis after degenerative scoliosis correction can provide reference for the biomechanical research of degenerative scoliosis, and provide a certain theoretical basis for the formulation of surgical plans and postoperative mobility of patients.