"Free-hand" technique for thoracolumbar pedicle screw instrumentation: critical appraisal of current "state-of-art".

Pedicle screws are widely used for instrumentation of the thoracolumbar spine. The anatomic studies performed in the last two decades, detailing the complex morphometry and three-dimensional anatomy of the thoracolumbar pedicles, have enabled the emergence of the so-called "free-hand" technique of pedicle screw placement based exclusively on anatomical parameters. However, in the thoracic spine, the benefits of pedicle screws have been tempered by its potential risks, such as, spinal canal violation, pedicle fracture, nerve root compression, and vascular lesions. Furthermore, the narrow and inconsistent shape of the thoracic pedicles, especially in spinal deformity, makes their placement technically challenging. In this article, the authors make a critical appraisal of current "state-of-art" of "free-hand" technique of pedicle instrumentation, analyzing its anatomical basis, surgical technique, present indications and limitations as well as the role of adjuvant image-guided and neurophysiological monitoring methods.