Anatomical characteristics of thoracic vertebrae for safe pedicle screw placement：comparison between normal adolescents and adolescent idiopathic scoliosis patients / 中国组织工程研究

ABSTRACT

BACKGROUND:Pedicle screw is the major instrumentation of surgery in thoracic spine. However, there have been few reports about pedicle morphology relevant to screw insertion tracts, and few reports comparing the normal adolescents and adolescent idiopathic scoliosis patients. OBJECTIVE:To compare the morphologic characteristics of the thoracic pedicle with regard to safe thoracic pedicle screw placement in normal adolescents and adolescent idiopathic scoliosis patients. METHODS: Thoracic pedicles of thirty-five normal adolescents and thirty-five adolescent idiopathic scoliosis patients were measured with three-dimensional reconstruction CT images. Measured parameters include (1) critical distance: the shortest distance from an entry point to the ventral cortex of the lamina. (2) Safe distance: the distance from the entry point to the tangent of the spinal canal at the medial wal of the pedicle. (3) Pedicle screw length. (4) Pedicle width. (5) Pedicle transverse angle. The dangerous area was defined as the distance between the critical distance and the safe distance. RESULTS AND CONCLUSION: The mean critical distance was (9.2±1.0) mm for the normal adolescents, and (9.4±1.2) mm for the adolescent idiopathic scoliosis patients. Safe distances were significantly less in normal adolescents (14.7±0.8) mm than that of the adolescent idiopathic scoliosis group (15.4±1.4) mm (P < 0.001). The dangerous area was (5.4±0.7) mm for the normal adolescents, which was significantly less than that of the adolescent idiopathic scoliosis patients (6.0±1.0) mm (P < 0.001). Pedicle screw length was (36.6±4.1) mm for the normal adolescents and (37.1±5.3) mm for the adolescent idiopathic scoliosis patients. Pedicle width was (5.8±1.2) mm for the normal adolescents and (5.7±1.7) mm for the adolescent idiopathic scoliosis patients. No significant difference in critical distance, pedicle screw length and pedicle width was found between the two groups (P=0.382, 0.135, 0.293). Pedicle transverse angle decreased gradualy from T1 to T12 in both groups. These results verify that pedicle morphology of many parameters is different between normal adolescents and adolescent idiopathic scoliosis patients, especialy in the apical area of the thoracic curve.