The Safety and Accuracy of Freehand Pedicle Screw Placement in the Subaxial Cervical Spine

Abstract

Retrospective cohort study. To assess the safety and accuracy of subaxial cervical pedicle screw placement with freehand technique and to report the technical nuances. Although the efficacy and safety of freehand screw fixation in thoracic and lumbar vertebrae is proven, reports on this technique of screw insertion in the subaxial cervical spine are lacking. From March 2012 to September 2013, 45 consecutive patients underwent posterior cervical fusion. The diagnoses were trauma (22 patients), degenerative disease (18 patients), discitis/osteomyelitis (2 patients), pathological fracture (2 patients), and postlaminoplasty kyphosis (1 patient). Preoperative computed tomography (CT) was performed in all patients. We included patients whose outer diameter of the pedicle was greater than 3.0 mm. The standard entry points were modified according to the CT anatomy of each patient. A small pilot hole was fashioned at a predetermined entry point. Then, a 2.5-mm diameter curved pedicle probe was slowly inserted with a medial trajectory into the pedicle. After ball-tip probing and tapping, the screw was inserted. If ball-tip probing was suggestive of risk to neurovascular structures, conversion to a lateral mass screw was performed. Postoperatively, a CT scan was performed in all patients and the conversion rate from pedicle to lateral mass screw was recorded. The breech rate of pedicle screws was also analyzed. There were 256 planned pedicle screws and 20 incidences (7.8%) of conversion to lateral mass screws. Lateral wall violation was observed in 14 pedicle screws (accuracy rate: 94.1%) on the postoperative CT scan. No medial, superior, and inferior pedicle wall violations were observed. There was no patient who developed symptoms related to vertebral artery stenosis. Adherence to the surgical tips presented in this article may lead to safe and effective freehand placement of cervical pedicle screws. 3.