The accuracy of pedicle screw placement in the thoracic spine using the "Funnel Technique": part 1. A cadaveric study.

A cadaveric study using the "funnel technique" to probe thoracic pedicles was conducted. The results (location, level, and perforation rate) of three spine surgeons of varying experience were compared. The objectives were to evaluate the reliability and accuracy of the funnel technique for the placement of thoracic pedicle screws and to describe the technique. Nine fresh cadavers (216 thoracic pedicles) were used for pedicle screw placement using the funnel technique. The study was conducted by three spine surgeons with a significantly different level of experience in thoracic pedicle screw placement (72 thoracic pedicles each). Critical and noncritical perforations were recorded. The perforation rate was 6% (13 of 216 pedicles). Of this, only 0.4% (1 of 216) was a critical perforation (a contact with T8 nerve root). The junior spine surgeon who had no previous experience with thoracic pedicle screw placement had a 12.5% (9 of 72) perforation rate, the surgeon very familiar with the technique had a 5.5% (4 of 72) perforation rate, and the senior author who originated this technique had a 1.4% (1 of 70) perforation rate. All perforations made by the junior spine surgeon occurred in his first 24 pedicles; none occurred in his last 48 pedicles. The reliability of the funnel technique in placement of thoracic pedicle screws was proven in our cadaveric study. It provided even an entry-level surgeon with a safe way to identify and place thoracic pedicle screws. The funnel technique is a simple, safe, and cost-effective alternative to any other currently recommended techniques for pedicle screw placement.