[Efficacy analysis of 3D printing prefixed nail path model assisted lumbar and sacral hemivertebra orthopaedic surgery].

Objective: To analyze the safety and effectiveness of 3D printing prefabricated nail path model assisted lumbosacral hemivertebra orthopaedic surgery.

Methods: A retrospective analysis was performed on 8 patients with lumbosacral hemivertebra deformity admitted from January 2016 to July 2021, including 3 males and 5 females, aged 6 to 15 at the time of surgery. The hemivertebra of 4 cases located on the left side and 4 cases on the right side. The hemivertebra of 1 case located at L, 2 cases at L, 2 cases at L, and 3 cases at LS. Four cases were fully segmented hemivertebra and 4 cases were incomplete segmented hemivertebra. The patient CT data was imported into Mimics 21.0 software for modeling, and then the model data was imported into 3-Matic software. The vertebra requiring screw placement was selected to simulate the optimal screw placement angle and length, and the model was printed for preoperative planning and intraoperative guidance. All patients underwent orthopedic surgery with the aid of 3D printing preset nail path model. The safety and effectiveness of the 3D printing prefabricated nail tunnel model assisted lumbosacral hemivertebra orthopaedic surgery was evaluated by comparing the imaging parameters of the patients. The main outcome measures were the Cobb angle of the main curve, the Cobb angle of the proximal compensatory curve, the coronal balance index C plumb line-center sacral vertical line(CPL-CSVL), the accuracy of nail placement, and the correction rate of scoliosis before surgery, 1 week and 1 year after surgery.

Results: All of 8 patients were followed up for 13 to 31 months. A total of 98 pedicle screws were placed in 8 patients. The number of pedicle screw grades A, B, C, D, E was 38, 46, 10, 4, 0 screws. The screws of grade A and B were defined as good position, the accuracy rate of screw placement was 85.7%. The Cobb angle of the main curve were 21° to 38° before operation, 5° to 11° at 1 week after operation, 7°to 12° at 1 year after operation. The Cobb angle of the proximal compensatory curve were 16° to 39° befoer operation, 7° to 12 °at 1 week after operation, 7° to 14° at 1 year after operation, the correction effect remained good with no correction loss. The coronal balance index C7PL-CSVL were 20 to 35 mm before operation, 11 to 18 mm at 1 week after operation, 10 to 16 mm at 1 year after operation, the coronal imbalance improved. The scoliosis correction rate was 65.6% to 84.2% 1 week after surgery, and 61.9% to 81.6% 1 year after surgery.

Conclusion: The use of 3D printing prefixed nail tunnel model in lumbosacral hemivertebra osteotomy is safe and effective, and can significantly improve patients' local deformities. It is a reliable method to assist lumbar sacral hemivertebra osteotomy.