Does Screw Size or Insertional Technique Matter in the Thoracic Spine?

· (a – DePuy AcroMed, Johnson & Johnson)

PURPOSE: To biomechanically compare thoracic pedicle screws placed traditionally or laterally.

METHODS: Cadaveric thoracic vertebrae were divided into 3 groups (A: T1-T2; B: T3-T6; C: T7-T12). Screws were tested in 3 sizes (4.75, 5.5, 6.25 mm) and inserted using either a traditional approach within the pedicle, or a lateral approach. Screws were pulled in axial tension until failure.

RESULTS: Group A: highest absolute values for pullout strength (>1000N) and insertional torque (2.25Nm). Groups B & C: no significant differences in pullout strength. Significant differences were detected in insertional torques with larger screws and traditional insertions.

CONCLUSIONS: Group A: Use traditional approach only. Larger screws increase insertional torque. Group B: Both techniques equivalent; Larger screws demonstrated no benefit. Group C: Pedicle screws should be used in groups A and C and either approach for Group B.

· If noted, the author indicates something of value received. The codes are identified as: a-research or institutional support; b-miscellaneous funding; c-royalties; d-stock options.