Biomechanical effects of different instrumented segments and trunk shifts on distal adjacent segments after congenital scoliosis posterior hemivertebrectomy: Preliminary results of a single case

Abstract

Objective: The present study aims to discuss the biomechanical effects of the sagittal vertical axis and different instrumented segments on distal adjacent segments after congenital scoliosis posterior hemivertebrectomy. Method: A case of congenital scoliosis caused by hemivertebra was selected for the reconstruction of the preoperative and postoperative 3D computed tomography data of the full spine. A finite element model of different fusion lengths and postoperative trunk shift (TS) values was established using the finite element method to compare the biomechanical effects of different models on the distal adjacent segment. Result: In the L1–L3 and T12–L1–L3–L4 fusion modes, the horizontal shift of the 1st vertebra below the lowest instrumented vertebra (LIV) increased with the trunk shift (TS) expansion after operation, and the imbalance between the left and right vertical stress of the 1st intervertebral disc below the LIV increased. With the decrease in fused segments in cases of TS = 10 mm and TS = 5 mm, the 1st vertebra below the LIV was subjected to a greater unbalanced force in the horizontal direction, and the 1st intervertebral disc below the LIV was subjected to a smaller imbalance between the left and right vertical stress after operation. Conclusion: When treating congenital scoliosis with hemivertebrectomy and pedicle screw fixation, fused segments can be properly extended and the postoperative TS shortened with a view of reducing the imbalance between the left and right stress of the 1st intervertebral disc below the LIV as well as the horizontal shift of the 1st vertebra below the LIV.

Keywords

• Congenital scoliosis
• Hemivertebra
• Biomechanics
• finite element analysis