Thoracic pedicle: Surgical anatomic evaluation and relations

This anatomic study investigated the thoracic pedicle and its relations. Th e objective was to emphasize the importance of the thoracic pedicle for tra nspedicular screw fixation to avoid complications during surgery. Twenty ca davers were used to observe the cervical pedicle and its relations. The ist hmus of the pedicle was exposed after removal of whole-posterior bony eleme nts, including spinous processes, laminas, lateral masses, and the inferior and superior facets. The pedicle width and height, inter pedicular distanc e, pedicle-inferior nerve root distance, pedicle-superior nerve root distan ce, pedicle-dural sac distance, root exit angle, and nerve root diameter we re measured. There was no distance between the pedicle and dural sac in eig ht specimens. There was, however, a short distance in 12 remaining specimen s in the upper and lower thoracic regions. The distances between the thorac ic pedicle and the adjacent nerve roots ranged from 1.5 to 6.7 mm and 0.8 t o 6.0 mm superiorly and inferiorly at all levels. The mean pedicle height a nd width at T1-T12 ranged from 2.9 to 11.4 mm and 6.2 to 21.3 mm, respectiv ely. The interpedicular distance decreased gradually from T1 to T5 and then increased gradually to T12. The mean root exit angle decreased consistentl y from 104 degrees to 60 degrees. The nerve root diameter was between 2.3 a nd 2.5 mm at the T1-T5 level and then increased consistently from 2.5 to 3. 7 mm. All significant differences were noted at p < 0.05 and p < 0.01. The following suggestions are made based on these results. 1) More care should be taken when a transpedicular screw is placed in the horizontal plane. 2) Improper medial placement of the pedicle screw, especially in the middle th oracic spine, should be avoided, and the anatomic variations between indivi duals should be considered. 3) Because of substantial variations in the siz e of thoracic pedicles, utmost attention should be given to the findings of a computed tomographic evaluation before thoracic transpedicular fixation is begun.