J Korean Fract Soc.  2007 Apr;20(2):115-122. 10.12671/jkfs.2007.20.2.115.

Upper Sacral Morphology Related to Iliosacral Screw Fixation in Korean

• Kim JJ
• Jung CY
• Oh HK
• Yang BS
• Chang JS

• KMID: 2295567
• DOI: http://doi.org/10.12671/jkfs.2007.20.2.115

Abstract

PURPOSE
To evaluate upper sacral morphology and anatomy of safe zone related to iliosacral screw fixation in Korean.
MATERIALS AND METHODS
100 patients performed pelvis 3D CT scan were evaluated. We used 16 channel CT and analyzed reconstructed image (shaded-surface display, transparent image and reformat image). RESULT: The angle between superior aspect of S1 body and iliac cortical density is 27.3°, between anterior cortical line of S1,2 body and horizontal plane 24.6°, and between superior aspect of S1 body and horizontal plane is 39.7°. The axis of S1, S2 pedicle is 32.5° and 15.6° toward anteromedial. The area of S1 pedicle according to sagittal plane and sagittal-oblique axis is 310.7 mm2 and 384.8 mm2. Also, S2 pedicle area is increased 163.1 mm2 to 188.4 mm2. The average depth of ala indentation is 5.1 mm and the maximal value is 9.5 mm. Distinct upper sacral dysplasia is 22%, transitional form is 32%.
CONCLUSION
We measured Korean upper sacrum with 3D-CT, found out dysplasia come up to 54%. Considering the frequency of dysplasia, the investigation of anatomy and technique is essential to sacroiliac screw insertion.

Keyword

Sacrum; Dysplasia; Iliosacral screw; Safe zone; 3D-CT

MeSH Terms

Humans
Pelvis
Sacrum
Tomography, X-Ray Computed

Figure

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  Fig. 1 Angle A is angle between superior aspect of S1 and iliac cortical density (ICD) line.

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  Fig. 2 Angle B is angle between anterior cortical line of S1, 2 vertebral body and horizontal plane; Angle C is angle between superior aspect of S1 vertebral body and horizontal plane.

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  Fig. 3 Cross line shows the cutting plane of Ap1S and Ap2S.

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  Fig. 4 Cross line shows cutting plane of Ap1Ax and Ap2Ax.

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  Fig. 5 The example demonstrates how to measure Ap1Ax (area of S1 pedicle in pediculsr axis, arrow) and its long and short axis.

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  Fig. 6 The image of transparent inlet view and the illustration show alar indentation (maximal depth of anterior alar concavity) and alar length (length of anterior sacral ala).

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  Fig. 7 The schematic illustration shows safe zone in sacral pedicle. True safe zone in sacral pedicle is not obtainable in one cut image (The image is modified and cited from "The vestibule concepts"2)).

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  Fig. 8 Anterior protrusion (white arrow) of safe zone (Ap1Ax) crosses the anterior sacral body after extension of Ap1Ax to the S1 body.

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  Fig. 9 Superior protrusion (white line) of safe zone (Ap1Ax) crosses the S1 superior end plate after extension of Ap1Ax to S1 body.

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