Direct vertebral rotation significantly decreases the pullout strength of the pedicle screw: a biomechanical study in adult cadavers

The pullout strength of the pedicle screws after direct vertebral rotation (DVR) maneuver is not known. This biomechanical study was performed to quantitatively analyze the pullout strength of a pedicle screw after DVR maneuver using human cadaveric vertebrae. Thoracic vertebral bodies from three cadavers were harvested and stripped of soft tissues. Thirty pedicles of 15 vertebrae were separated into two groups after bone mineral density measurements. Polyaxial 5.5 mm pedicle screws with appropriate length were inserted with a freehand technique for each pedicle. One Kirschner wire was inserted to the anterior part of each vertebral corpus the half depth of each corpus was embedded into PVC pipes using polyester paste. In the DVR group, each screw was pulled horizontally with 2 kg (~20 N) load over a screwdriver rigidly attached to the screw, and a DVR maneuver was simulated. The control group did not load with a DVR maneuver. Samples were placed on a universal testing machine and pullout loads were measured. The Mann–Whitney U test was utilized, and the P value
Source: Journal of Pediatric Orthopaedics B - Category: Orthopaedics Tags: Spine Source Type: research