Evaluation of thoracic pedicle screw placement in adolescent idiopathic scoliosis |
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Authors: | Ahmet Y?lmaz ?arlak Bilgehan Tosun Halil Atmaca Hasan Tahsin Sarisoy Levent Buluç |
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Institution: | 1. Department of Orthopaedics and Traumatology, Kocaeli University, School of Medicine, Umuttepe Merkez Kampüsü, 41380, Umuttepe, Kocaeli, Turkey 2. Department of Radiology, Kocaeli University, School of Medicine, Umuttepe Merkez Kampüsü, 41380, Umuttepe, Kocaeli, Turkey
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Abstract: | Pedicle screw fixation is a challenging procedure in thoracic spine, as inadvertently misplaced screws have high risk of complications.
The accuracy of pedicle screws is typically defined as the screws axis being fully contained within the cortices of the pedicle.
One hundred and eighty-five thoracic pedicle screws in 19 patients that were drawn from a total of 1.797 screws in 148 scoliosis
patients being suspicious of medial and lateral malpositioning were investigated, retrospectively. Screw containment and the
rate of misplacement were determined by postoperative axial CT sections. Medial screw malposition was measured between medial
pedicle wall and medial margin of the pedicle screw. The distance between lateral margin of the pedicle screw and lateral
vertebral corpus was measured in lateral malpositions. A screw that violated medially greater than 2 mm, while lateral violation
greater than 6 mm was rated as an “unacceptable screw”. The malpositions were medial in 20 (10.8%) and lateral in 34 (18.3%)
screws. Medially, nine screws were rated as acceptable. Of the 29 acceptable lateral misplacement, 13 showed significant risk;
five to aorta, six to pleura, one to azygos vein and one to trachea. The acceptability of medial pedicle breach may change
in each level with different canal width and a different amount of cord shift. In lateral acceptable malpositions, the aorta
is always at a risk by concave-sided screws. This CT-based study demonstrated that T4–T9 concave segments have a smaller safe
zone with respect to both cord-aorta injury in medial and lateral malpositions. In these segments, screws should be accurate
and screw malposition is to be unacceptable. |
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Keywords: | Pedicle screws Thoracic spine Malposition Adolescent idiopathic scoliosis |
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