A COMPARISON OF PULLOUT STRENGTH OF PEDICULAR SCREWS BETWEEN DIFFERENT METHODS OF SCREW INSERTION IN POSTERIOR FIXATION OF THORACIC SPINE

Abstract- Pedicle screws provide rigid fixation for instabilities in the lumbar and lumbosacral spine. Anatomical consideration and potential risk of neurologic complications are the reasons to hesitate using pedicle screws in the thoracic spine. Twenty moulages similar to human vertebrae were instrumented with Cotrel-Dubousset (CD) system pedicle screw by intratransverse process, extrapedicular and intrapedicular methods and pullout strength was measured. There was statistically significant difference between three techniques. By increasing the length of screw in any method, pullout strength increased. Average pullout strength in extrapedicular technique was less than two other techniques in dynamic state. The strongest technique for screw placement was intratransverse process technique. It seems that intratransverse process technique is safe for posterior fixation of spine