J Korean Orthop Assoc.  2007 Feb;42(1):98-105. 10.4055/jkoa.2007.42.1.98.

Scoliosis Correction with Thoracic Pedicle Screws: Posteroanterior C-arm Rotation Method

• Hwang C
• Lee CS
• Ahn YJ
• Kang SJ
• Kim JH
• Jeong KI
• Kim YT
• Lee DH

• KMID: 2106382
• DOI: http://doi.org/10.4055/jkoa.2007.42.1.98

Abstract

Purpose: This study evaluated a practical, safe and accurate method of thoracic pedicle screw insertion for the surgical treatment of scoliosis using the posteroanterior C-arm fluoroscopy rotation method.
Materials and Methods
A total of 611 thoracic pedicle screws were inserted in 45 patients using the posteroanterior (PA) C-arm rotation method. CT scans were taken postoperatively in the transverse and sagittal sections to evaluate the pedicle screw placement.
Results
A mean preoperative curve of 57.7o was corrected to 17.1o (range, 3o-45o) in the coronal plane. The postoperative CT scans revealed that 10 screws (1.6%) had penetrated the medial cortex by a mean distance of 3.0 mm and 56 screws (9.2%) penetrated the lateral cortex by a mean distance of 3.5 mm. No screw penetrated the inferior or superior cortex in the sagittal plane. However, 21 screws (3.4%) penetrated the anterior cortex. No neurological or vascular complications were encountered, and none of the screws required replacement.
Conclusion
Thoracic pedicle screw insertion in scoliosis patients using the posteroanterior C-arm rotation method is a practical, simple and safe technique that allows the en face visualization of both pedicles by rotating the C-arm to compensate for the rotational deformity.

Keyword

Scoliosis; Thoracic pedicle screw; C-arm fluoroscopy rotation method

MeSH Terms

Congenital Abnormalities
Fluoroscopy
Humans
Scoliosis*
Tomography, X-Ray Computed

Figure

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  Fig. 1 Positioning of the C-arm. Initially place it in the posteroanterior position. Rotate the C-arm according to the rotation of the pedicles until they are observed symmetrically on both sides. Most of patients require counterclockwise rotation when viewed from the feet and the largest rotation is usually required at the apical vertebra.

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  Fig. 2 (A) A case with a Cobb's angle of 69 degrees. (B) Without C-arm rotation, posteroanterior fluoroscopy reveals asymmetrical visualization of both pedicles with a Nash-Moe grade II deformity. (C) Counterclockwise rotation of the c-arm at 19 degrees provides en face visualization of both pedicles. This image is familiar to spine surgeons and the entry site for pedicle screw insertion can now be easily determined. Entry of the right pedicle at the 10 o'clock position and the left pedicle at the 2 o'clock position are designated.

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  Fig. 3 Pedicle screw trajectory can be evaluated by PA imaging because the insertion is performed with both pedicles en face. (A) Lateral deviation of the screw trajectory. (B) Proper trajectory. (C) Medial deviation. (D) Up-ward direction. (E) Correct trajectory.

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  Fig. 4 Comparison of screw insertion using biplanar radiographs and C-arm rotation. (A) With the C-arm rotated 15 degrees, both pedicles are symmetrical. A K-wire is inserted into the right pedicle at the 2 o clock position. The entry point and trajectory can be evaluated accurately. (B) Same K-wire without C-arm rotation. The entry point is 3 mm medial to the pedicle and the trajectory cannot be easily evaluated.

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  Fig. 5 A 16-year-old scoliosis patient in whom the rotating posteroanterior c-arm fluoroscopic guidance technique was used. (A) Preoperative radiographs show severe double major curves. (B) Pedicle screws were used to correct the deformity. (C) Thoracic and lumbar humps improved significantly after surgery.

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  Fig. 6 A 17 kg kyphosis patient in whom the rotating posteroanterior C-arm fluoroscopic guidance technique was used. (A) Preoperative radiographs show severe kyphoscoliosis. (B) An almost normal curvature after pedicle screw insertion and correction of the deformity.

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