Transpedicular spinal implants are known to be the most effective systems in the treatment of burst frac-tures. Hovvever, migration, pull out and pedicle screw breakage are the most troublesome issues of these systems. The İbn-i Sina universal transpedicular system is developed to overcome such difficulties. The an-terior portion of the pedicle screw of the İbn-i Sina instrument is specially designed to improve contact be-tween the spongious bone of the vertebral body and the posterior portion that will remain inside the pedicle is similar to a cortical screw. This modification is suspected to improve the stability of the system. Two types of the ibn-i Sina screws, mainly the original design and the AO type screvvs of three sizes (5.5 mm, 6.5 mm, 7.5 mm), vjere compared with the same size and length of Alıcı, Isola and TSRH pedicle screws. sizing of the screvvs was performed using the results of a previous anatomical study in vvhich the Standard of the pedicle sizes of the Turkish population was estimated. a quadrangular frame was developed to perform the experi-ments. The vertebral bodies vvere placed obliquely into the frame to allow the pedicle sere w to be pulled in the vertical direetion. Ali tests vvere performed on the M 30 K (Lloyd, UK) mechanical testing device. Pedicle screvvs of the above mentioned spinal systems vvere furthermore evaluated by photoelasticity after placing them into epoxy resin (Araldit D + HY 951, Ciba-Geigy, İstanbul). Early results of the experiment suggest that the ibn-i Sina type pedicular screws are as stable and povverful as any other universal sere w design. Loads up to 2500 N and 3000 N caused the pull out of the 6.5 mm AO type serevv and the original design İbn-i Sina serevv respeetively. The results suggest a slight improvement in the stability with the nevv design.

Transpedicular implants are effectively used in the maintenance of stability in spinal fraetures and defor-mities. A new spinal instrument, the so calied "İbn-i Sina Spinal İnstrument" is recently introduced and its screw design is evaluated by this study. Two different screvvs of the ibn-i Sina instrument vvere evaluated by the serevv pull-out tests and the results vvere compared to that of the TSRH instrument. The original design of the serevv was more effective than the AO design. the pull-out strength inereased as the diameter of the serevv inereased. The original design of the İbn-i Sina pedicle sere w is as effective as the TSRH transpedicular serevv occurred in the ibn-i Sina serevv. Further improvements in the metal of the screw is essential for the ibn-i Sina transpedicular serevv. A special frame was designed to be able to apply the pedicle serevv pull-out tests.

Keywords: Spine, Biomechanics, Pedicle Serevv, Pull-Out Test, İbn-i Sina İnstrument