Accuracy of cannulated pedicle screw versus conventional pedicle screw for extra-pedicular screw placement in dysplastic pedicles without cancellous channel in adolescent idiopathic scoliosis: a computerized tomography (CT) analysis.

Abstract

This study aimed at studying the accuracy and safety of extra-pedicular screw insertion for dysplastic pedicles in AIS comparing cannulated screw system versus conventional screw system. 104 AIS patients with 1524 pedicle screws were evaluated using CT scan. 302 screws were inserted in dysplastic pedicles using fluoroscopic guidance technique. 155 screws were inserted using a cannulated system (Group 1), whereas 147 screws were inserted using standard screws (Group 2).The pedicle perforations were assessed using a classification by Rao et al.; G0: no violation; G1: <2mm perforation; G2: 2-4mm perforation; and G3: >4mm perforation). For anterior perforations, the pedicle perforations were assessed using a modified grading system (Grade 0: no violation, Grade 1: less than 4mm perforation; Grade 2: 4mm to 6mm perforation; and Grade 3: more than 6mm perforation). The perforation rate in Group 1 was4.5%and in Group 2 was15.6%(p=0.001). Most of the perforations were anterior perforations (53.3%). The anterior perforation rate in Group 1 was 1.9% compared to 8.8% in Group 2 (p=0.009). Group 1 has a medial perforation rate of 1.3% compared to Group 2, 6.1% (p=0.031). The rate of critical pedicle perforation in Group 1 was2.6%and in Group 2 was6.8%(p=0.102). InGroup 1, there wereno critical medial perforationbut there wasone G2 lateral perforation, one G2 superior perforation and two G3 anterior perforations. In Group 2, there werethree G2 medial perforations, one G2 lateral perforation, one G2 anterior perforation and five G3 anterior perforations. Usage of cannulated screw system significantly increases the accuracy of pedicle screw insertion in dysplastic pedicles in AIS.