Growth-preserving spinal surgery suffer from high complications rate. A recent bipolar instrumentation using two anchoring points (thoracic and pelvic) showed lower rates, but its biomechanical behaviour has not been characterised yet. The aim of this work was to combine in vitro and in vivo data to improve and validate a finite element model (FEM) of the spine, and to apply it to compare bipolar and classical all-screws implants.

Spinal segments were tested in vitro to measure range of motion (ROM). Thoracic segments were also tested with bipolar instrumentation to measure ROM and rod strain using a strain gage.

A subject-specific FEM of the spine, pelvis and ribcage of an in vivo asymptomatic subject was built. Spinal segments were extracted from it to reproduce the in-vitro mechanical tests. Experimental and simulated ROM and rod strain were compared. Then, the full trunk FEM was used to compare bipolar and all-screws instrumentations.

The FEM fell within 1° of the experimental corridors, and both in silico and in vitro instrumentation rods showed 0.01% maximal axial strain. Bipolar and all-screws constructs had similar maximal Von Mises stresses.

This work represents a first step towards subject-specific simulation to evaluate spinal constructs for neuromuscular scoliosis in children.

脊柱保生长手术并发症发生率高。最近使用两个锚定点（胸部和骨盆）的双极器械显示出较低的比率，但其生物力学行为尚未表征。这项工作的目的是结合体外和体内数据来改进和验证脊柱的有限元模型 (FEM)，并将其应用于比较双极和经典全螺钉植入物。

体外测试脊柱节段以测量运动范围（ROM）。还使用双极仪器测试了胸段，以使用应变计测量 ROM 和杆应变。

建立了体内无症状受试者的脊柱、骨盆和胸腔的受试者特定 FEM 。从中提取脊髓节段以重现体外机械测试。比较了实验和模拟的 ROM 和杆应变。然后，使用完整的躯干 FEM 来比较双极和全螺钉仪器。

FEM 落在实验走廊的 1° 范围内，并且在硅胶和体外仪器棒中都显示出 0.01% 的最大轴向应变。双极和全螺钉结构具有相似的最大 Von Mises 应力。

这项工作代表了针对特定主题的模拟评估儿童神经肌肉脊柱侧弯的脊柱结构的第一步。