J Korean Soc Spine Surg.  2011 Sep;18(3):111-116.

Measurement of Canal Encroachment Using Axial and Sagittal-Reconstructed Computed Tomographic Images in Thoracolumbar Burst Fractures

• Kim JH
• Chung NS
• Lim OK
• Roh HR
• Jeon CH

Abstract

STUDY DESIGN: A retrospective study.
OBJECTIVES
The aim of this study was to examine the usefulness of axial and sagittal-reconstructed CT images in the evaluation of spinal canal encroachment by thoracolumbar burst fractures. SUMMARY OF LITERATURE REVIEW: The dimensions of spinal canal encroachment by burst fractures have been described using axial CT images in the thoracolumbar region and sagittal-reconstructed images in the lower cervical region. However, the validity and reliability, depending on the measuring method, have not been fully evaluated.
MATERIALS AND METHODS
A hundred and ninety-nine patients, who had diagnosed as a thoracolumbar burst fracture, were included in this study. Three orthopedic surgeons independently measured the canal encroachment of the burst fragment in the axial CT images and the sagittal-reconstructed images using the ratio of spinal length (method 1) and the ratio of area (method 2). The validity for the evaluation of the deformity and fracture stability was evaluated. In addition, the reliability of each method was assessed.
RESULTS
Sixty-seven stable burst fractures and 132 unstable burst fractures were assessed. The mean kyphotic angle of stable and unstable burst fracture were 11.89 +/- 8.49degreesand 15.90 +/- 9.63degrees(P=0.005). The mean canal encroachment ratios of stable fracture were 17.21 +/- 15.82 % (axial-method 1), 16.71 +/-16.49 % (axial-method 2), 19.54 +/- 17.03 % (sagittal reconstructed-method 1), and 11.75 +/- 12.33 % (sagittal reconstructed-method 2). The mean canal encroachment ratios of unstable fracture were 31.54 +/- 17.10 % (axial-method 1), 29.67 +/- 18.47 % (axial-method 2), 28.53 +/- 18.60 % (sagittal reconstructed-method 1), and 21.20 +/- 15.11 % (sagittal reconstructed-method 2). There was no relationship between the fracture deformity and the canal encroachment ratio in all 4 methods. All ratios in the 4 method showed significant differences in the evaluation of fracture stability. All methods except method 1 in the sagittal-reconstructed images showed significant differences in the assessment of neurologic compromise.
CONCLUSIONS
The measurement of a canal encroachment area using axial and sagittal-reconstructed images was valid in the description of fracture stability.

Keyword

Thoracolumbar; Burst fracture; Canal encroachment; Computed tomography

MeSH Terms

Congenital Abnormalities
Humans
Orthopedics
Reproducibility of Results
Retrospective Studies
Spinal Canal

Figure

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  Fig. 1. Measurement of coronal and sagittal deformity using Cobb method.

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  Fig. 2. Canal encroachment ratio was calculated by the upper and lower adjacent levels (A) using the length ratio on the axial images, (B) using the area ratio on the axial images, (C) using the length ratio on the sagittal-reconstructed images, (D) using the area ratio on the sagittal-reconstructed images

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  Fig. 3. Paired t-tests revealed that the canal encroachment ratio using the area ratio on the sagittal-reconstructed images was different from those of other methods.

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