![]() ![]() Each vertebra had pedicle screw instrumentation using both techniques by random assignment of the left and right pedicles. A 3.5 drill was then used to enlarge the trajectory, followed by pedicle screws from 5.5 to 8.5 mm.Įach resident was assigned one cadaver and provided with preoperative anteroposterior and lateral full size 17-inch scoliosis radiographs for familiarization of the underlying osseous pathology and pedicle morphology. A ball tip feeler was used to look for breaches in the pedicle wall. For drill technique Figure 1B), a 2.5 mm drill bit (Synthes, Monument, CO) on an Synthes drill driver was used to gain access to the pedicle. A tap between 4.5 to 7.5 mm was used following the trajectory, then a pedicle screw between 5.5 and 8.5 mm (1 mm larger than the tap) was inserted. For gearshift technique Figure 1A), a Lenke probe (Holmed LLC., Franklin, MA) was used to gain access to the pedicle and vertebral body. ![]() Starting holes were created using a high speed surgical burr (Midas Rex Legend, Medtronic, Minneapolis, MN) with a match head drill bit of 1.7 mm. 10 in thoracic spine, and Magerl 11 in the lumbar spine. Each resident was required to place 24 screws on the sawbone.Īll screws were placed using landmarks defined by Kim et al. This was followed by a hands-on training session using sawbone spines under the guidance of orthopaedic and neurosurgery attendings for both methods (gearshift and drill) before actual instrumentation. Accuracy of the instrumentation was evaluated by computerized tomographic (CT) scans of the cadavers.Īll residents underwent a didactic training session which included: anatomy, surgical concepts, and instructions on the gearshift and drill techniques for pedicle screw instrumentation by experienced spine surgeons. The resident surgeons had no prior experience with drill technique and had limited skills with the gearshift technique, thus allowing for an unbiased comparison. Grauer and colleagues 9 previously compared a modified drill (Safepath – a proprietary device) with traditional gearshift method in the cadaveric thoracolumbosacral spine and the modified drill technique performed better in the lumbar spine and significantly worse outcomes with the thoracic spine.Įxperienced spine surgeons use either of the techniques with good success rates the objective of our study, however, was to evaluate and compare the accuracy of these methods when employed by resident surgeons. 7, 8 Although these techniques are routinely used, there is limited information on the comparative evaluation of these methods. 5, 6 The drill technique is gaining popularity for pedicle screw instrumentation and there is published cadaveric and clinical evidence documenting the success of both these methods. The freehand funnel Gearshift technique is one of the traditional methods of pedicle screw placement and is routinely used to instrument the thoracolumbar spine using anatomical landmarks. Various techniques have been described for pedicle screw placement with established clinical and radiological success. 2– 4 Thus, it is of paramount importance to achieve maximum accuracy of screw placement. ![]() However, the procedure is also associated with complications arising from pedicle perforation such as neurological and vascular injuries. A recent meta-analysis 1 of 130 studies reported a high success rate of 91.3%. Pedicle screw fixation is widely used in spinal fusion and has been shown to have a high success rate. ![]()
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