Anterior dual rod instrumentation in idiopathic thoracic scoliosis: a computed tomography analysis of screw placement relative to the aorta and the spinal canal.
METHODS
Axial computed tomography scans (CT) in 20 consecutive patients with idiopathic right thoracic scoliosis and anterior correction and fusion with a dual rod dual screw system.


OBJECTIVE
CT evaluation of screw position in anterior dual rod instrumentation relative to the aorta and the spinal canal.


BACKGROUND
In anterior scoliosis surgery, bicortical screw purchase is used to increase pullout strength. However, impingement of the aorta due to excessive contralateral screw penetration has been reported, especially after endoscopic instrumentation. Data on the accuracy of dual screw instrumentation in thoracic scoliosis are missing.


METHODS
All 20 patients underwent an identical anterior surgical technique with double thoracotomy approach and dual rod instrumentation of the primary curve. Postoperative sequential CT scans were analyzed with respect to following parameters: vertebral body width and depth, diameter of the aorta, distance from the aorta to the closest point of the vertebral body cortex, distance between the tip of the screws and the aorta, distance between the screw and the spinal canal, and the amount of contralateral screw penetration. A total amount of 226 screws were evaluated.


RESULTS
All screws were placed correctly without any critical proximity to the aorta or spinal canal. A total of 198 of 226 screws (88%) had a bicortical purchase. Thirteen screw tips (5.8%) were within 1 to 3 mm proximity to the aorta. All other screws were more than 3 mm distant from the aorta. The closest proximity of the screw tips to the thoracic aorta was found at the upper end vertebrae (T5, T6, or T7). There were no screws perforating the spinal canal.


CONCLUSIONS
Anterior instrumentation and correction of thoracic scoliosis with a dual rod dual screw system enable a correct and safe screw placement using a standard open approach. Excessive bicortical screw perforation should be avoided in order not to endanger the thoracic aorta.
Bullmann
Viola
V
Department of Orthopaedics, University Hospital of Muenster, Muenster, Germany. bullmanv@uni-muenster.de
Fallenberg
Eva M
EM
Meier
Norbert
N
Fischbach
Roman
R
Schulte
Tobias L
TL
Heindel
Walter L
WL
Liljenqvist
Ulf R
UR
D000293:Adolescent; D000328:Adult; D001027:Aortography; D001858:Bone Nails; D001863:Bone Screws; D002648:Child; D004867:Equipment Design; D005260:Female; D006801:Humans; D016268:Internal Fixators; D008297:Male; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000601:surgery*; D013115:Spinal Canal / Q000000981:diagnostic imaging*; D013123:Spinal Fusion; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D014057:Tomography, X-Ray Computed