This study was conducted to determine the external and internal biomechanical responses of the one, three and six year old paediatric cervical spine structures under varying severities of combined compression-flexion and compression-extension, and axial tension load vectors. The authors' existing one, three and six year old paediatric lower cervical spine finite element models (FEM's) were used. The models in the three age groups were developed by incorporating the characteristic developmental paediatric anatomy such as the variations in the ossification patterns. The three-dimensional (3D) models were exercised using the principles of geometrical and material nonlinear analyses. The resulting external and internal biomechanical responses were expressed in terms of the overall flexibilities. The intrinsic stresses in the bone and intervertebral anulus, and pressures in the nucleus and facet joints were determined under each load vector. All these output were compared with respect to the adult human spine. In general, decreases in the flexibilities were apparent with increasing age. This was independent of the load vector. However, the magnitudes of the decrease were nonuniform with respect to the age group, and the type and severity of the external load vector. The differences with respect to the age and loading mode found may assist to explain the intrinsic load sharing among the developing paediatric components, and provide a likely explanation for the mechanisms of injury.
Abstract