The effects of pedicle screw adjustments on neural spaces in burst fracture surgery.

Abstract

An in vitro biomechanical study of experimental burst fractures and a pedicle screw device. To investigate the effects that adjustments of a pedicle screw device have on the neural spaces of the burst fracture. Decompression of the neural spaces is important for the recovery of neural function after a burst fracture. No studies, experimental or clinical, are available that have attempted to relate the pedicle screw device adjustments to the decompression of the neural spaces. Burst fractures were produced at L1 vertebra in nine human lumbar spine specimens. Pedicle screw devices were attached to T12 and L2. Eight device adjustments, consisting of pure translations (distraction or compression), pure extension, and combinations of translation and extension were applied. The dimensional changes in the canal and the superior and inferior intervertebral foramens were measured. Functions of restoration and improvement were determined for the adjustments to evaluate the effects of each adjustment and to determine the optimal adjustment. Analysis of variance was used to find statistically significant differences, with significance set at P values less than 0.05. Significant differences were observed in the results of the eight adjustments. The most effective adjustments were the combination of 5-mm distraction with 6 degrees extension or 10-mm distraction alone. The worst adjustment was 5 mm of compression. Restoring compromised neural spaces in a patient with burst fracture is necessary. The choice of a device adjustment was found to be an important factor in the decompression of the neural spaces after the burst fracture. Combined distraction with extension and distraction alone were found to decompress the canal andintervertebral foramens maximally in a burst fracture.