Technical note Routine spinal navigation for thoraco–lumbar pedicle screw insertion using the O-arm three-dimensional imaging system improves placement accuracy Ji Min Ling a , Shree Kumar Dinesh a , Boon Chuan Pang a , Min Wei Chen a , Heng Lip Lim a , Danny T. Louange b , Chun Sing Yu b , Chee Meng Ernest Wang a,⇑ a Department of Neurosurgery, National Neuroscience Institute, Singapore 11 Jalan Tan Tock Seng, Sinagpore 308433, Singapore b Department of Orthopaedic Surgery, Tan Tock Seng Hospital, Singapore, Singapore article info Article history: Received 17 September 2012 Accepted 20 February 2013 Keywords: Navigation O-arm Pedicle screw Stereotaxy abstract Modern image-guided spinal navigation employs high-quality intra-operative three dimensional (3D) images to improve the accuracy of spinal surgery. This study aimed to assess the accuracy of thoraco- lumbar pedicle screw insertion using the O-arm (Breakaway Imaging, LLC, Littleton, MA, USA) 3D imaging system. Ninety-two patients underwent insertion of thoraco–lumbar pedicle screws guided by O-arm navigation over a 27 month period. Intra-operative scans were retrospectively reviewed for pedicle breach. The operative time of patients where O-arm navigation was used was compared to a matched control group where fluoroscopy was used. A total of 467 pedicle screws were inserted. Four hundred and forty-five screws (95.3%) were placed within the pedicle without any breach (Gertzbein classification grade 0). Sixteen screws (3.4%) had a pedicle breach of less than 2 mm (Gertzbein classification grade 1), and six screws (1.3%) had a pedicle breach between 2 mm and 4 mm (Gertzbein classification grade 2). The grade 2 screws were revised intra-operatively. There was no incidence of neurovascular injury in this series of patients. The mean operative time for O-arm patients was 5.25 hours. In a matched control group of fluoroscopy patients, the mean operative time was 4.75 hours. The difference in the mean oper- ative time between the two groups was not statistically significant (p = 0.15, paired t-test). Stereotactic navigation based on intra-operative O-arm 3D imaging resulted in high accuracy in thoraco–lumbar ped- icle screw insertion. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Modern image-guided spinal navigation employs high-quality intra-operative three dimensional (3D) images to improve the accuracy of spinal surgery. Such systems are founded on the con- cepts of stereotaxy, which has been crucial in the advancement of neurosurgical procedures and techniques over the last 2 decades. 1 In cranial procedures, neuro-navigation has become fun- damental in many procedures. It is now commonplace in planning surgical incisions and approaches, brain biopsies, skull base surger- ies, neuro-endoscopy and neuro-oncology. 2–4 In spinal surgery, modern image-guided surgery has clear advantages when precise surgical instrumentation is necessary, such as pedicle screw place- ment in the cranio–cervical region or in the thoracic region where pedicles are thinner 5 and visualisation is difficult with conven- tional two dimensional (2D) fluoroscopy. However, its routine use in spinal instrumentation has not been well demonstrated. The O-arm (Breakaway Imaging, LLC, Littleton, MA, USA) is a mobile cone beam imaging system. It can function both as a 2D fluoroscopy device or collect 3D volumetric imaging data. Equipped with a flat panel detector, it is able to produce near CT scan quality images. We therefore studied the clinical utility and efficacy of adopting a 3D spinal navigation system as a routine imaging tool in thoraco–lumbar spinal instrumentation. 2. Method Patients who underwent spinal surgeries involving thoraco– lumbar pedicle screw insertion and O-arm navigation from Feb- ruary 2009 to April 2011 at Tan Tock Seng Hospital, Singapore were retrospectively reviewed. Data collected included demo- graphic details of patients, indication for surgery, duration of surgery, intraoperative findings and neurological examination findings before and after surgery. O-arm images acquired intra- operatively were reviewed for accuracy of pedicle screw placement. 0967-5868/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jocn.2013.02.034 ⇑ Corresponding author. Tel.: +65 6357 7191; fax: +65 6357 7137. E-mail address: ernest@wangsonly.com (C.M.E. Wang). Journal of Clinical Neuroscience 21 (2014) 493–498 Contents lists available at SciVerse ScienceDirect Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn