The Safe Placement of Upper and Middle Thoracic Pedicle Screws in Pediatric Deformity

Abstract

A retrospective clinical study to discuss the diameter of pedicle screw used in upper and middle thoracic vertebrae of pediatric patients with spinal deformity. To determine the diameter of pedicle screw that can be accommodated in upper and middle thoracic vertebra fixation in the correction of pediatric spinal deformity. Internal pedicle screw fixation has been widely used in the treatment of pediatric spinal disorders, but the screw size is still a focus of debates in the application of internal pedicle screw placement in pediatric patients. From March 2004 to March 2008, 32 pediatric patients (aged from 6 to 12 y, mean age 9.2 y) with idiopathic and congenital kyphoscoliosis were treated with surgical correction of the deformity through posterior approach pedicle screw placement. Before operation, thin-slice computed tomography (CT) (1.0 mm) scan along the direction of the pedicle axis was done to scan the operative vertebra segments of all the patients. The transverse pedicle diameter was measured at the same time. When inserting thoracic pedicle screws, after having confirmed that the screw tract was completely contained within the pedicle walls, the surgeons gradually increased the pedicle screw diameter based on the transverse pedicle diameter measured before operation, and carefully sensed the differences in palpation accordingly, so as to determine the appropriate diameter of screws inserted. The position of screws was reevaluated by postoperative CT scan. The stability of internal pedicle screw fixation and neurologic functions of the patients were assessed in the follow-up. In this study, a total of 206 screws were placed into upper and middle thoracic pedicles (T1 to T8) of pediatric patients. Of them, the numbers of screws placed in pedicles T1 through T8 were 12, 36, 26, 22, 25, 23, 30, and 32, respectively. No screw was misplaced. The diameter of inserted pedicle screws ranged from 4.5 to 5.5 mm, 140.2%±19.2% that of the preoperative CT scan measurement of pedicles. The length of pedicle screws inserted varied from 30 to 40 mm. No postoperative neurologic deficit or vascular injury occurred. The period of follow-up was from 16 months to 36 months (22.7 mo on average). No loosening, deformation, breakage, or removal of inserted pedicle screws was reported in the follow-up. It is safe and feasible to use internal pedicle screw fixation to treat pediatric patients with upper and middle thoracic deformity in the process of screw placement, a pedicle screw with a larger diameter can be accommodated in upper and middle thoracic pedicles, if the axis of pedicle screw is confirmed within the pedicle walls. The most appropriate diameter of the screws can be determined concurrently by the palpation of the surgeon when placing the screw and referring to the pedicle screw diameter measured by CT before operation.