J Korean Soc Spine Surg.  2005 Jun;12(2):123-131. 10.4184/jkss.2005.12.2.123.

Thoracic Pedicle Screw Insertion in Scoliosis Using Posteroanterior C-arm rotation Method

• Ahn YJ
• Lee CS
• Kim JH
• Jeong KI
• Kim YT

• KMID: 1583455
• DOI: http://doi.org/10.4184/jkss.2005.12.2.123

Abstract

STUDY DESIGN: A prospective study of the accuracy of thoracic pedicle screws inserted in scoliotic patients.
OBJECTIVES
To evaluate and present a practical, safe and accurate method for thoracic pedicle screw insertion in the surgical treatment of scoliosis using the posteroanterior c-arm fluoroscopy rotating method. SUMMARY OF LITERATURE REVIEW: Previous studies have emphasized the clinical importance, yet difficulty, of accurate thoracic pedicle screw insertion in scoliotic patients. Three-dimensional alterations in the pedicle orientation of scoliotic patients makes the accurate insertion challenging. No reports exist on the accuracy and benefits of posteroanterior c-arm fluoroscopy, which is rotated to allow visualization from en face, in real patients.
MATERIALS AND METHODS
A total of 350 thoracic pedicle screws were inserted in 29 patients, including 24 with idiopathic scoliosis, using the posteroanterior (PA) c-arm rotation method. The smallest patient weighed 14 kg, and the next smallest 17 kg. The average preoperative curve was 60.9 degrees(range, 45 degrees~101 degrees). CT scans were taken, postoperatively, in the transverse and sagittal sections to evaluate the pedicle screw placement.
RESULTS
The mean preoperative curve of 60.9 degrees was corrected to 15.4 degrees(range, 3 degrees~45 degrees) in the coronal plane, a correction of 74.7%. A mean of 12.1 thoracic screws were inserted per patient. On analysis of the postoperative CT scans, 39(11.1%) of the 350 screws penetrated the medial or lateral pedicle cortices, 8(2.3%) into the medial cortex and 31(8.9%) into the lateral cortex, by mean distances of 3.3 and 3.6 mm, respectively. No screws penetrated the inferior or superior cortices in the sagittal plane, but 16(4.6%) penetrated the anterior cortex. No neurological or vascular complications were encountered, and none of the screws required subsequent replacement.
CONCLUSIONS
Thoracic pedicle screw insertion in scoliotic patients, using a posteroanterior c-arm rotation method, allows the en face visualization of both pedicles by rotating the c-arm to compensate for rotational deformity, which makes it a practical, simple and safe method.

Keyword

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

MeSH Terms

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

Figure

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  Fig. 1. Positioning of the c-arm. (A) Place in the posteroanterior position. (B) Rotate the c-arm according to the rotation of the pedicles until they are seen symmetrically on both sides. Most patients require counter-clockwise rotation (when viewed from the feet). (C) More counter-clockwise rotation is usually required at the apical vertebra.

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  Fig. 2. (A) Case with a 69 degrees Cobb’s angle. (B) Without c-arm rotation, posteroanterior fluoroscopy reveals asymmetrical visualization of both pedicles with a Nash-Moe grade II deformity. (C) 19 degrees counter-clockwise rotation of the c-arm pro-vides en face visualization of both pedicles. This image is familiar to spine surgeons and entry sites for pedicle screw insertion is now easily determined. Entry of the right pedicle at 10 o’ clock and the left pedicle at 2 o’ clock is initiated.

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  Fig. 3. Pedicle screw trajectory can be evaluated with the PA imagery because insertion is performed with both pedicles en face. (A) Axial image revealing: lateral deviation of 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 and a K-wire is inserted into the right pedicle at 2 o’ clock. The entry point and trajectory can be accurately evaluated. (B) Same K-wire without no c-arm rotation. The entry point is 3 mm medial to the pedicle and the trajectory can not be easily evaluated.

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  Fig. 5. A 14 kg scoliosis patient using the rotating posteroanterior c-arm fluoroscopic guidance technique. (A) The patient with severe imbalance and a Cobb's angle of 100 degrees. (B) Pedicle screws used to correct the thoracic curve. (C) Improvement of truncal imbalance post-operatively.

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  Fig. 6. A 17 kg kyphosis patient using the rotating posteroanterior c-arm fluoroscopic guidance technique. (A) The patient with 95 degrees kyphosis and 47 degrees scoliosis of the thoracic spine. (B) An almost normal curvature after pedicle screw insertion and correction of T4-L4.

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