Experimental Analysis of Fabricated Synthetic Midthoracic Paediatric Spine as Compared to the Porcine Spine Based on Range of Motion (ROM)

Abstract

The present study is aimed at investigating the mechanical behaviour of fabricated synthetic midthoracic paediatric spine based on range of motion (ROM) as compared to porcine spine as the biological specimen. The main interest was to ensure that the fabricated synthetic model could mimic the biological specimen behaviour. The synthetic paediatric spine was designed as a 200% scaled-up model to fit into the Bionix Servohydraulic spine simulator. Biomechanical tests were conducted to measure the ROM and nonlinearity of sigmoidal curves at six degrees of freedom (DOF) with moments at ±4 Nm before the specimens failed. Results were compared with the porcine spine (biological specimen). The differences found between the lateral bending and axial rotation of synthetic paediatric spine as compared to the porcine spine were 18% and 3%, respectively, but was still within the range. Flexion extension of the synthetic spine is a bit stiff in comparison of porcine spine with 45% different. The ROM curves of the synthetic paediatric spine exhibited nonlinearities for all motions as the measurements of neutral zone (NZ) and elastic zone (EZ) stiffness were below “1.” Therefore, it showed that the proposed synthetic paediatric spine behaved similarly to the biological specimen, particularly on ROM.

Finite Element Modelling of a Synthetic Paediatric Spine for Biomechanical Investigation

“…As presented in Figure 5, the ROM from experimental data increased significantly (by 50%) from ±2 Nm to ±3 Nm loads, which suggested that the synthetic paediatric spine was more flexible after the ±2 Nm loads. Further analysis of the synthetic FE model was carried out to compare the ROM against the experimental data [17]. Based on the average percentage differences, the synthetic FE model ROM at ±2 Nm loads for the flexion/extension and lateral bending movements were the closest to the experimental result of paediatric ROM.…”

“…Further analysis of the synthetic FE model was carried out to compare the ROM against the experimental data [ 17 ]. Based on the average percentage differences, the synthetic FE model ROM at ±2 Nm loads for the flexion/extension and lateral bending movements were the closest to the experimental result of paediatric ROM.…”

“…Based on the data reported from previous works on similar topics, a moment of ±0.5 Nm was considered as paediatric loading, in order to obtain the correct paediatric ROM without failure [ 13 , 23 ]. Next, the final loading mode was applied the same as the experimental loads of ±2 Nm and ±3 Nm for all six motions, for comparison with the experimental data of previous work [ 17 ]. The bottom endplate and posterior were fixed, and the ROM (angular displacements) variable was measured as displayed in Figure 3 .…”

“…For validation of synthetic paediatric FE model, comparison of the ROM between the synthetic paediatric FE model and the synthetic paediatric spine (that was obtained from the experimental data [ 17 ]) was conducted. The objective for the experimental procedure was to ensure that the fabricated synthetic model could mimic the biological specimen behaviour as tested using the Bionix Servohydraulic spine simulator [ 17 ]. The ROM curves obtained from a synthetic paediatric spine exhibited nonlinearities for all motions, because the measurements of neutral zone (NZ) and elastic zone (EZ) stiffness were less than “1”.…”

“…Hence, the authors are currently working on a project to create a working paediatric mid-thoracic (T4–T8) spinal segment model. The fabricated synthetic paediatric spine has been compared with the porcine spine on the ROM and the results suggested that the synthetic paediatric spine ROM was acceptable, as it was in good agreement with lateral-bending and axial rotation [ 17 ]. The next step is to investigate if the synthetic paediatric spine can obtain the acceptable value of ROM under certain child loading conditions using finite element analysis.…”