In parallelism with advance instrumentation technology, pedicular screw usage increased at thoraco-lumbar area. Thus, neural and bonerelated complication of these screws decreased within last few decades. The reason of above mentioned situation adequate surgical approach as well as usage of appropriate size of screws

Studies related to appropriate screw length for Turkish community is limited. In addition, the trials for morphometric analysis of adolescent age group are also limited. Therefore, the diameters of thoracic 12 (T-12) and lumbar 1 (L- 1) measured within MRI studies and average values determined for 50 male (ages between 20-40) and 50 female (ages between 10-18) healthy volunteers. When all patients included, average diameter of pedicle and possible length of screws (PLS) detected 4.90 ± 1.31 mm and 39.40 ± 6.20 mm for T-12 , and 43.35 ± 6.25 mm 5.21 ± 1.56 mm and 43.35 ± 6.25 mm for L1. It is also determined that there is no significant difference between T-12 and L-1 values on the basis of left-right measurements (p>0.05). On the contrary, there is a significant difference between pedicle diameters and PLS values for males and females for same age group and also difference between adolescent females and adult females as adolescent males with adult males reported (p<0.05).

As a result, on the basis of the outcomes of this study, Turkish people require different length and diameter of screws from available instrument systems at market for both adolescents and adults. As these screws about to produce, it is obtained an idea of use with close length as 3.5 and 4.5 mm screws for adolescent males and females, and 4.5 and 5.5 mm screws for adult males and females, respectively.

Keywords: Thoracolumbar area, pedicle morphology, morphometric measurements, lengths of transpedicular screws,