Quantification of Segmental Flexibilities of Juvenile Lumbar Spinal Column Using a Three-Dimensional Finite Element Model (FEM)

TLDR: An anatomically accurate eight year old lumbar spine finite element model is developed and a generic flexibility comparison with scaled down Pediatrics and animal experiments showed that the flexibility responses was found to agree with literature projections.

Abstract: The growth changes in pediatric spine alter its biomechanical behavior. Thus characteristic responses become more age specific for pediatric spine as compared to an adult spine. The objective of this paper is to develop an anatomically accurate eight year old lumbar spine finite element model and make a comparative flexibility study. The finite element model of the eight year old female lumbar spine was developed from CT data. Since the current model belongs to the juvenile age group, an available 6 year old material model from the literature was adopted for various pediatric spine components. The anatomical differentiation of cortical and cancellous bone happens during early adolescence, however for the current 8 year old it was considered as vertebral centrum. The cartilage growth plate, posterior processes, and facet joints were also modeled. The disc with its fibre distribution in the annulus and the ligaments was also represented in the model. Pediatric Loading of 200N for axial compression and 500 Nmm for various range of motion was used for the study. The average end plate displacement of all the levels for the pediatric lumbar spine was 1.8mm under axial compression. During Flexion the maximum angular rotation was 2.3deg at L1/L2, under lateral bending the rotation was 2 deg at L4/L5 and with axial rotation it was 1.53 deg at L2/L3. Comparison of the increase in flexibility between pediatric and adolescent material property with that of adult on current juvenile geometry showed a maximum average ratio of 2.99 under axial rotation for the pediatric material model. A generic flexibility comparison with scaled down pediatric models and animal experiments showed that the flexibility responses was found to agree with literature projections.