Does Main Curve Flexibility Affect Screw Insertion Accuracy Using a CT-based Navigation System in Adolescent Idiopathic Scoliosis Surgery?

Abstract

A retrospective single-center and single-surgeon study. This study investigated the screw perforation rate according to main curve flexibility in pedicle screw fixation using a computed tomography (CT) guidance for adolescent idiopathic scoliosis (AIS). The authors have been using a CT-based navigation system during pedicle screw insertion for AIS to avoid serious neurovascular or visceral structure injury but suspect that high main curve flexibility may account for some breaches. Seventy-two consecutive patients with AIS Lenke type 1 or 2 who had undergone pedicle screw fixation using a CT-based navigation system between February 2008 and April 2018 were retrospectively reviewed. The authors evaluated the perforation rate of pedicle screws inserted into the main thoracic curve between the upper-end and lower-end vertebrae for factors associated with screw violations using multivariate logistic regression mixed models. A total of 723 pedicle screws were inserted into the T4-T12 vertebrae with the aid of CT-based navigation. The respective grade 3 perforation rates according to main curve flexibility were 0%-30%: 3.2%; 30%-55%: 1.1%; 55%-75%: 5.2%; and 75%-100%: 5.5%. Main curve flexibility of ≥55% was significantly associated with grade 3 screw perforations (P=0.02). Main curve flexibility of ≥55% was significantly related to screw violation in AIS surgery. Greater care is thus advised for screw insertion using CT navigation in AIS with main curve flexibility ≥55%.