J Korean Soc Spine Surg.  2013 Dec;20(4):169-177. 10.4184/jkss.2013.20.4.169.

Ideal Insertion Point and Angle of Cervical Pedicular Screws in Korean

• Park HJ
• Kwon KY
• Yoon WS

• KMID: 1896946
• DOI: http://doi.org/10.4184/jkss.2013.20.4.169

Abstract

STUDY DESIGN: A retrospective study.
OBJECTIVES
Using computed tomography, it is to measure pedicle size of lower cervical spine in Koreas to find ideal insertion point and angle in fixating pedicular screws. SUMMARY OF LITERATURE REVIEW: Although techniques in pedicular screw fixation and pedicle's anatomical shape in foreign populations have been well documented and studied, no anatomical study on lower cervical pedicle in Korean population has been reported.
MATERIALS AND METHODS
A total of 180 patients with computed tomography taken at our institution were selected for the study. Width, total length, and length of pedicle, insertion point and angle, and safe insertion angles were measured on axial view. On sagittal view, height of pedicle, insertion point and angle, and safe insertion angles were determined.
RESULTS
Mean height of study subject was 164.2cm. Mean width of pedicle was 5.5mm, mean height 7.2mm, mean total length 31.2mm, and mean length 14.8mm. Mean insertion point from 3rd to 7th cervical spines was medially 3.3mm from lateral mass and downward 4.7mm from margin of upper facet. Mean insertion angles from 3rd to 7th cervical spines were 41.6degrees axially and 6.4degrees sagittally. Calculated safe insertion angles were 8degrees on medial and lateral sides and 14degrees on superior and inferior sides.
CONCLUSIONS
Using computed tomography images, ideal insertion point and angle were measured for pedicular screw insertion, but, due to individual variation, preoperative measurement of insertion point and angle on computed tomography is necessary.

Keyword

Cervical spine; Pedicular screw; Insertion point; Insertion angle

MeSH Terms

Humans
Korea
Retrospective Studies
Spine

Figure

• 

  Fig. 1. Axial CT scan with diagram show measurements of the C3 - C7 pedicles. PL = pedicle length, TPL = total pedicle length, PW = pedicle width, ITA = injection trajectory angle, SAMe = the safe range of the inserting angle to medial side in the transverse plane, SALa = the safe range of the inserting angle to lateral side in the transverse plane, ED = the distance between the pedicle entry point and vertical line from the most outer margin of lateral, mass, EP = the entry point for screw insertion

• 

  Fig. 2. Sagittal CT scan with diagram show measurements of the C3 - C5. PH = pedicle height, ITA = injection trajectory angle, SAUp = the safe range of the inserting angle to upper side in the vertical plane, SALo= the safe range of the inserting angle to lower side in the vertical plane, ED = the distance between the pedicle entry point and transverse line from the most upper margin of lateral, mass, EP = the entry point for screw insertion

• 

  Fig. 3. Sagittal CT scan with diagram show measurements of the C6, C7. PH = pedicle height, ITA = injection trajectory angle, SAUp = the safe range of the inserting angle to upper side in the vertical plane, SALo= the safe range of the inserting angle to lower side in the vertical plane, ED = the distance between the pedicle entry point and transverse line from the most upper margin, of lateral, mass, EP = the entry point for screw insertion

• 

  Fig. 4. These figures show pedicles are cylinder as complete oval shape (A) In the transverse plane, tan α(SAMe) = 1.0/15, with diameter of screw is 3.5mm, ∴ α = 4°, (B) In the sagittal plane, tan ß(SAUp) = 1.85/15, with diameter of screw is 3.5mm, ∴ ß = 7°

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