Geometry, Growth, and Shape of the Normative Pediatric Thoracic and Lumbar Spines and Rib Cage
Monday, November 27, 2017
1:00 PM-3:00 PM
BIOMED PhD Thesis Defense
Geometry, Growth, and Shape of the Normative Pediatric Thoracic and Lumbar Spines and Rib Cage and Comparisons with Adolescent Idiopathic Scoliosis
James Peters, PhD Candidate, School of Biomedical Engineering, Science and Health Systems
Sriram Balasubramanian, PhD, Associate Professor, School of Biomedical Engineering, Science and Health Systems
Previous studies of pediatric vertebrae and rib morphology use varying measurement techniques to collect geometric dimensions from nonhomogeneous samples and few of these studies evaluate growth or possible vertebral level and sex-related differences in the pediatric morphology. Detailed morphology data on the pediatric vertebra and ribs may provide insights into the progression of spinal deformities like adolescent idiopathic scoliosis (AIS). AIS is a complex three-dimensional (3D) deformity of the thoracic and lumbar spines and rib cage. Classification schemes like the Lenke system have been developed to help categorize scoliotic deformities and provide guidance for surgical interventions, and Lenke-types 1, 2, and 5 represent approximately 83 percent of cases requiring surgery. The standard surgical treatment for AIS is posterior spinal fusion (PSF) ; however more recent techniques rely on growth modulation and require knowledge about how mechanical forces impact development of the spine. Such investigations can be conducted using finite element (FE) models and while previous FE models of the spine have simulated growth of the vertebral bodies, growth of the posterior elements (pedicles, facets, and major processes) is largely ignored due to a lack of data describing their development.
In this thesis, pediatric vertebrae and rib morphology data were collected from 3D reconstructions of 202 skeletally normal subjects between the ages of 1 and 19 years. This normative data was compared with that of 36 Lenke-type 1, 2, and 5 subjects to quantitatively assess the deformity in each and evaluate vertebral remodeling following PSF. Finally the pediatric growth data was integrated into a growing FE model and used to assess the impact of vertebral growth on a simulated PSF construct.
Growth of the vertebra and ribs was found to vary across vertebral levels; however, few differences between sexes were observed for the vertebral bodies and pedicles. Remodeling of the vertebrae following PSF was found for Lenke-type types 1, 2, and 5 suggesting continued growth for the structures after surgery. Finally growth of the posterior vertebral elements was determined to have a significant effect on the stresses induced in the simulated PSF construct.
In addition to improving FE models of the growing spine, the normative and Lenke-type-specific morphology data presented here can be used to optimize the timing and duration of growth modulating devices and develop novel techniques for the treatment of AIS.