Accuracy analysis of pedicle screw placement in posterior scoliosis surgery - Comparison between conventional fluoroscopic and computer-assisted technique

Study Design. The accuracy of pedicle screw placement was evaluated in posterior scoliosis surgeries with or without the use of computer-assisted surgical techniques. Objective. In this retrospective cohort study, the pedicle screw placement accuracy in posterior scoliosis surgery was compared between conventional fluoroscopic and computer-assisted surgical techniques. Summary of Background Data. There has been no study systemically analyzing the perforation pattern and comparative accuracy of pedicle screw placement in posterior scoliosis surgery. Methods. The 45 patients who received posterior correction surgeries were divided into 2 groups: Group C, manual control (25 patients); and Group N, navigation surgery (20 patients). The average Cobb angles were 73.7 degrees and 73.1 degrees before surgery in Group C and Group N, respectively. Using CT images, vertebral rotation, pedicle axes as measured to anteroposterior sacral axis and vertebral axis, and insertion angle error were measured. In perforation cases, the angular tendency, insertion point, and length abnormality were evaluated. Results. The perforation was observed in 11% of Group C and 1.8% in Group N. In Group C, medial perforations of left screws were demonstrated in 8 of 9 perforated screws and 55% were distributed either in L1 or T12. The perforation consistently occurred in pedicles in which those axes approached anteroposterior sacral axis within 5 degrees. The average insertion errors were 8.4 degrees and 5.0 degrees in Group C and Group N, respectively, which were significantly different (P < 0.02). Conclusion. The medial perforation in Group C occurred around L1, especially when pedicle axis approached anteroposterior sacral axis. This consistent tendency was considered as the limitation of fluoroscopic screw insertion in which horizontal vertebral image was not visible. The use of surgical navigation system successfully reduced the perforation rate and insertion angle errors, demonstrating the clear advantage in safe and accurate pedicle screw placement of scoliosis surgery.