How Much Surface Registration Accuracy is Required Using Ct-based Navigation System in Adolescent Idiopathic Scoliosis Surgery?

Study Design: Retrospective, single-center, single-surgeon study. Objective: This study investigated screw perforation rate according to surface registration accuracy in pedicle screw fixation using a CT-based navigation system for adolescent idiopathic scoliosis (AIS). Summary of Background data: Posterior spinal fusion for scoliosis correction using pedicle screws is widely adopted but carries a risk of serious neurovascular or visceral structure events. To attempt to avoid these complications, we have been using a computed tomography (CT)-based navigation system during screw insertion, although insufficient surface registration accuracy may be a reason for some screw perforations. Methods: We evaluated 116 AIS patients (9 male and 107 females; mean +/- standard deviation age: 15.2 +/- 2.3 y) who had received pedicle screw fixation guided by a CT-based navigation system between August 2007 and December 2017. Screw perforation rate was evaluated in relation to surface registration accuracy and cut-off values were determined by receiver operating characteristic (ROC) curves. Results: A total of 1553 pedicle screws were inserted into T2-L4 vertebrae using CT-based navigation system. The respective overall perforation rates for grade 2 or 3 and grade 3 perforations by surface registration accuracy were 0.2 mm: 0% and 0%; 0.3 mm: 3.5% and 0%; 0.4 mm: 3.5% and 0.8%; 0.5 mm: 8.0% and 3.5%; 0.6 mm: 6.7% and 2.7%; 0.7 mm: 8.9% and 3.8%; 0.8 mm: 9.3% and 6.7%; and 0.9 mm: 9.3% and 4.7%. ROC curve analysis revealed a cut-off surface registration accuracy of 0.5 mm. The major screw perforation rate for a surface registration accuracy of >= 0.5 mm was significantly higher than that for <0.5 mm (P<0.01). Conclusions: Analysis of screw perforation rate according to surface registration accuracy demonstrated a clinical cut-off of 0.5 mm. Thus, surface registration accuracy should optimally be <0.5 mm for scoliosis surgery with CT-based navigation system.