Characterization of Correction Forces in Spinal Fusion Surgery

In 1880, Messerer initiated the research in mechanical behavior by studying the strength of vertebrae and since then, the complex mechanical system of human spine was one of the main areas to be studied. Most of this research was conducted using adult cadaver spines or animal spines. However, it was difficult to find any previous research on the mechanical behavior of the adolescent spine or child spine. This research paper aimed to assist the surgical procedure by identifying the significant correction forces for scoliosis spinal fusion surgery. The objective was to investigate the forces acting on the child/pediatric spine with Scoliosis. Scoliosis is a medical condition where the spine is deformed from the normal frontal axis of the body caused by the lateral displacement and rotation of the vertebral bodies. A three dimensional diagnostic method was developed for a number of different scoliosis conditions using design software Pro-Engineer. Based on the analysis, the most common region affected was the middle thoracic region (T4-T8) and hence this research was carried out on this region. An artificial spine was constructed using polyurethanes and silicones materials. The biomechanical tests were conducted using the six degree freedom spine simulator from the Bionix Servo Hydraulic Test System machine from MTS. The results indicate a probability of difference mechanical behavior acting on adult and child spine but one similarity could be observed on the flexibility of spine motion segments whereby it is more flexible in the flexion compared to extension.