J Korean Orthop Assoc.  2007 Apr;42(2):255-263. 10.4055/jkoa.2007.42.2.255.

Morphologic Feasibility of Pedicle Screw Insertion in Korean

• Ahn MW
• Han JH
• Koo JW
• Chung SM
• Cho JH

• KMID: 854596
• DOI: http://doi.org/10.4055/jkoa.2007.42.2.255

Abstract

PURPOSE: This study examined the morphological characteristics of the thoracic and lumbar vertebrae of normal Koreans and the factors causing breakage of the pedicular wall by measuring the thoracolumbar vertebrae relative to the pedicle screw insertion. MATERIALS AND METHODS: The effect of the pedicle screw shape on the pedicle wall integrity of 56 normal Koreans was examined by performing a computer simulation of the inserting pedicle screws into the pedicle wall by superimposing the graphical images of the screws onto the CT scan images. RESULTS: Because the inner pedicle diameters of the most thoracic vertebrae from T4 to T10 were <5 mm, most pedicles of the thoracic vertebrae were expected to be broken after inserting the 5 mm-diameter cylindrical screws. The pedicles of the thoracic and lumbar vertebrae were classified into 6 groups by performing the cluster analysis using morphometric parameters. Group 1 was labeled "relatively narrow". Group 2 "moderate". Group 3 "wide and angular". Group 4 "severly narrow and short", Group 5 "long", and group 6 "relatively wide and angular". The simulation showed the pedicles of groups 1 and 4 to be too narrow for the 5 mm-diameter cylindrical screws to preserve the pedicular wall integrity. CONCLUSION: The pedicles of the vertebra of Koreans are similar in size to those of Caucasians. Personal morphological characteristics of the pedicles as well as their sizes and levels of the vertebrae are believed to be the significant factors that can cause the breakage of the pedicular wall.

Keyword

Thoracolumbar spine; Morphology of pedicle; Pedicle screw

Figure

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  Fig. 1 Distribution of the slices of the axial CAT images.

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  Fig. 2 Morphometric parameters of the vertebrae.

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  Fig. 3 Status of the pedicular wall during the insertion of screw into the pedicle.

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  Fig. 4 Inner and outer diameter of the pedicular isthmus from T4 to L5.

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  Fig. 5 Morphologic characteristics of each cluster. Group I was characterized by the severe narrowing of the inner and outer pedicular diameters and the short pedicular length. Group II was characterized by the narrow pedicular canal. However, the pedicular length and insertion angle had increased. The pedicular canal and insertion angle had increased the most in Group III. Group IV was characterized by it's the largest decrease in the pedicular canal and length. The pedicular length had increased the most in Group V. Its pedicular canal was relatively wide. In Group VI, the pedicular canal was wide and its length and insertion angle had increased compared with those of the other groups.

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