Abstract: BACKGROUND: Adult idiopathic scoliosis is a common clinical disease leading to adult spinal deformity. Surgical correction is an effective means to treat the disease, but the choice of surgical timing and surgical correction strategy poses a challenge to clinicians.
OBJECTIVE: To follow up the same Lenke 3 adult idiopathic scoliosis volunteer and carry out finite element modeling and simulated posterior orthopedic surgery before and after 5 years, so as to understand the disease progression of this type of adult scoliosis, the biomechanical changes of spinal column and implant, and the changes of orthopedic effects of different orthopedic methods, and to provide data reference for the treatment of this type of disease.
METHODS: A typical Lenke 3 adult idiopathic scoliosis volunteer, male, aged 28 years old, was selected as the research object. The volunteer’s spine was scanned by continuous CT. The original image was imported into the finite element software for modeling, and the model was further cleaned. After optimization, a complete Lenke 3 adult idiopathic scoliosis finite element model including thoracic structure was established, and finite element surgical simulation was carried out on this model. Case 1: bilateral screw placement from the upper to lower vertebrae and removal of the corresponding posterior joint capsule to achieve the purpose of joint release; Case 2: posterior key vertebrae were nailed and the corresponding segments of posterior joint capsule were removed for joint release; Case 3: posterior key vertebra nailing, removal of posterior joint capsule of corresponding segments, and release of thoracic vertebrae at anterior scoliosis; Case 4: posterior key vertebra nailing, removal of posterior joint capsule of corresponding segments, and release of lumbar spine at anterior scoliosis; Case 5: posterior key vertebra nailing, removal of posterior joint capsule of corresponding segments, and release of the thoracic and lumbar spine at the anterior scoliosis. Five years later, the volunteer’s scoliosis was modeled again by finite element method and simulated surgery, so as to understand the disease progression, biomechanical changes of spine and implant, and the changes of orthopedic effects of different orthopedic methods.
RESULTS AND CONCLUSION: (1) On the scoliosis model established five years later, the surgical correction scheme for Case 1-Case 5 was successfully completed. The correction rates of thoracic scoliosis were 56.8%, 48.9%, 49.8%, 55.9%, and 57.0%, and the correction rates of lumbar scoliosis were 33.0%, 36.9%, 29.4%, 30.0%, and 34.3%. The orthopedic effects of simulated surgery of Cases 3 and 5 were significantly lower than those 5 years ago. At the same time, the maximum screw stress area and the minimum screw stress area were different. (2) The lumbar scoliosis deformity of Lenke 3 adult idiopathic scoliosis volunteers increased with age, but there was no significant progress in thoracic scoliosis. Five years later, the correction rate and effect of each operation scheme on thoracic and lumbar scoliosis decreased significantly, and the area with the largest screw stress under each operation also changed.

Key words: adult idiopathic scoliosis, long-term follow-up, biology, pedicle screw technique, spinal orthopedics, orthopedic implants, finite element analysis, timing of operation