Placement of thoracolumbar pedicle screws using three-dimensional image guidance: experience in a large patient cohort

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Abstract
The goal of this study was to analyze the placement accuracy and complications of thoracolumbar pedicle screws (PSs) inserted using 3D image guidance in a large patient cohort. The authors reviewed the charts of 220 consecutive patients undergoing posterior spinal fusion using 3D image guidance for instrumentation placement. A total of 1084 thoracolumbar PSs were placed using either the BrainLAB Vector Vision (BrainLAB, Inc.) or Medtronic StealthStation Treon (Medtronic, Inc.) image guidance systems. Postoperative CT scanning was performed in 184 patients, allowing for 951 screws to be graded by an independent radiologist for bone breach. All complications resulting from instrumentation placement were noted. Using the intraoperative planning function of the image-guided system, the largest diameter screw possible in each particular case was placed. The screw diameter of instrumentation placed into the L3-S1 levels was noted. No vascular or visceral complications occurred as a result of screw placement. Two nerve root injuries occurred in 1084 screws placed, resulting in a 0.2% per screw incidence and a 0.9% patient incidence of nerve root injury. Neither nerve root injury was associated with a motor deficit. The breach rate was 7.5%. Grade 1 and minor anterolateral "tip out" breaches accounted for 90% of the total breaches. Patients undergoing revision surgery accounted for 46% of the patients in this study. Accordingly, 154 screws placed through previous fusion mass could be evaluated using postoperative CT scanning. The breach rate in this specific cohort was 7.8%. A total of 765 PSs were placed into the L3-S1 levels in this study; 546 (71%) of these screws were > or = 7.5 mm in diameter. No statistical difference in breach rate was noted in PSs placed through revision spinal levels versus nonrevision spinal levels (p = 0.499). Additionally, no increase in breach rate was noted with placement of 7.5-mm-diameter screws. Three-dimensional image guidance is a useful adjunct to placement of spinal instrumentation. The complication rate in this study was low, and accurate placement of instrumentation was achieved despite the high percentage of revision surgery cases in our patient population. Additionally, because active fluoroscopy was not used for instrumentation placement, there was minimal to no radiation exposure to the surgeon or operating room staff.