Journal List > J Korean Soc Spine Surg > v.20(4) > 1075999

Park, Kwon, and Yoon: Ideal Insertion Point and Angle of Cervical Pedicular Screws in Korean

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 3 rd to 7 th cervical spines was medially 3.3mm from lateral mass and downward 4.7mm from margin of upper facet. Mean insertion angles from 3 rd to 7 th cervical spines were 41.6° axially and 6.4° sagittally. Calculated safe insertion angles were 8° on medial and lateral sides and 14° 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.

REFERENCES

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Figures and Tables%

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
jkss-20-169f1.tif
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
jkss-20-169f2.tif
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
jkss-20-169f3.tif
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°
jkss-20-169f4.tif
Table 1.
Demographics
Range Male Female Total
Age
< 20 2 5 7
20 - 30 18 11 29
30 - 40 14 17 31
40 - 50 18 16 34
50 - 60 25 19 44
60 - 70 13 10 23
> 70 3 9 12
Average 46.5 47.1 46.8
Weight (Kg)
< 40 0 4 4
40 - 50 2 16 18
50 - 60 12 23 35
60 - 70 41 25 66
70 - 80 15 13 28
80 - 90 17 4 21
90 - 100 4 2 6
> 100 2 0 2
Average 70.4 59.9 65.1
Height (m)
< 1.4 1 2 3
1.40 - 1.50 0 19 19
1.50 - 1.60 10 36 46
1.60 - 1.70 32 24 56
1.70 - 1.80 41 6 47
1.80 - 1.90 9 0 9
> 1.90 0 0 0
Average 1.708 1.562 1.635
BMI (Kg/m2)
< 18.5 4 15 19
18.5 - 23 25 23 48
23 - 25 23 24 47
25 - 30 34 19 53
> 30 7 12 19
Average 24.11 24.43 24.27
Table 2.
Linear Parameters of Cervical Pedicle from C3 to C7
Pedicle Pedicle width (mm) Pedicle height (mm)
M F Total M F Total
C3
Average 4.8 4.6 4.7 6.8 6.7 6.8
Range 3.5-6.0 3.3-5.8 3.3-6.0 4.9-8.1 5.3-7.5 4.9-8.1
SD 0.6 0.7 0.7 0.8 0.9 0.9
C4
Average 4.7 4.6 4.7 7.0 6.9 7.0
Range 3.1-6.0 3.4-6.0 3.1-6.0 5.6-8.7 5.2-8.8 5.2-8.8
SD 0.7 0.7 0.7 0.8 0.8 0.8
C5
Average 5.8 5.6 5.7 7.2 7.0 7.1
Range 3.9-7.4 4.0-6.8 3.9-7.4 5.9-8.9 5.8-8.7 5.8-8.9
SD 0.7 0.8 0.7 0.9 0.9 0.9
C6
Average 6.0 5.8 5.9 7.4 7.3 7.4
Range 4.9-7.9 3.8-8.0 3.8-8.0 6.4-8.8 6.2-8.8 6.2-8.8
SD 0.8 0.8 0.8 0.8 0.8 0.8
C7
Average 6.5 6.4 6.5 8.0 7.8 7.9
Range 4.5-8.5 4.4-8.4 4.4-8.5 6.7-9.2 6.4-8.9 6.4-9.2
SD 0.9 1.1 1.1 0.7 1.0 0.9

M: male F: female

Table 3.
Linear Parameters of Cervical Pedicle from C3 to C7
Pedicle Pedicle length (mm) Total pedicle length (mm)
M F Total M F Total
C3
Average 15.0 14.8 14.9 29.5 28.1 28.8
Range 12.2-18.7 11.9-17.6 11.9-18.7 25.4-32.7 22.3-33.4 22.3-33.4
SD 2.1 2.6 2.5 2.5 2.7 2.6
C4
Average 15.4 14.7 15.1 30.7 29.3 30.0
Range 12.1-19.3 12.3-18.8 12.1-19.3 21.3-35.2 23.6-35.7 21.3-35.7
SD 1.9 2.1 2.0 2.6 3.1 3.0
C5
Average 15.8 15.0 15.4 32.1 30.3 31.2
Range 12.1-19.4 12.8-19.3 12.1-19.4 24.3-37.1 24.6-36.8 24.3-37.1
SD 2.0 1.8 1.9 3.3 3.1 3.3
C6
Average 16.3 15.5 15.9 32.8 32.0 32.4
Range 13.1-19.8 12.5-19.4 12.5-19.8 25.1-37.4 23.8-38.3 23.8-38.3
SD 2.2 1.7 2.1 3.5 3.4 3.4
C7
Average 16.3 15.4 15.9 33.9 33.5 33.7
Range 12.8-19.7 12.4-19.1 12.4-19.7 26.3-38.1 25.8-38.0 25.8-38.1
SD 2.3 1.8 2.1 3.1 3.2 3.2

M: male F: female

Table 4.
Angular parameters of cervical pedicle from C3 to C7
Pedicle Injection Trajectory angle(°) on Axial cut Injection Trajectory angle(°) on Sagittal cut
M F Total M F Total
C3
Average 44.3 45 45 11.2 10.3 10.8
Range 40.5-50.1 41.3-50.3 40.5-50.3 5.6-17.9 6.1-17.1 5.6-17.9
SD 3.5 3.7 3.6 2.3 3.4 3.1
C4
Average 42.2 43.1 42.7 9.7 10.7 10.2
Range 38.1-48.4 37.1-49.7 37.1-49.7 3.8-20.1 2.1-18.3 2.1-20.1
SD 3.2 3.4 3.4 3.5 4.2 4
C5
Average 43.1 42.2 42.7 10.7 7.3 9.1
Range 38.6-49.8 37.3-49.1 37.3-49.8 2.0-19.3 3.8-16.8 2.0-19.3
SD 4.3 3.9 4.2 6.3 3.5 5.7
C6
Average 41.7 40.1 40.9 2 3.4 2.7
Range 36.2-48.4 35.1-47.6 35.1-48.4 -7.6-11.2 -8.3-12.1 -7.6 -12.1
SD 3.4 3.6 3.5 4.3 3.8 4.1
C7
Average 38.1 36.6 37.3 -3.7 0.5 -1.3
Range 30.8-47.9 28.4-47.2 28.4-47.9 -15 - 10 -13 - 12.1 -15 – 12.1
SD 4.8 3.8 4.5 3.8 4.1 4
Total
Average 41.8 41.4 41.6 6.0 6.6 6.4
Range 30.8-50.1 28.4-50.3 28.4-50.3 -15 – 20.1 -13 – 18.3 -15 – 20.1
SD 5.3 6.1 5.8 6.2 6.3 6.3

M: male F: female

Table 5.
Anatomic relations of entry point to reference lines by CT Measurement from C3 to C7
Pedicle Entry point to horizontal line(mm) Entry point to vertical line(mm)
M F Total M F Total
C3
Average 2.8 2.5 2.7 4.7 3.8 4.3
Range 1.7-4.0 1.6-4.0 1.6-4.0 1.5-7.6 1.9-5.1 1.5-7.6
C4 SD 0.7 0.8 0.8 1.6 1.3 1.5
C4 Average 3.1 2.7 2.9 5.2 4.3 4.8
Range 1.5-4.3 1.7-3.9 1.5-4.3 2.6-8.4 2.5-5.5 2.5-8.4
SD 0.8 0.7 0.8 1.6 1.5 1.6
C5 Average 3.7 3.4 3.6 4.9 4.4 4.7
Average Range 3.7 1.6-4.2 3.4 2.1-5.1 3.6 1.6-5.1 4.9 3.7-7.1 4.4 2.8-6.2 4.7 2.8-7.1
SD 0.8 1 0.9 1.4 1.4 1.4
C6
Average 3.7 3.4 3.6 4.1 4.8 4.4
Range SD 2.3-5.6 0.9 2.4-5.6 0.9 2.3-5.6 0.9 2.6-5.4 1.1 2.8-6.8 1.8 2.6-6.8 1.6
C7
Average 4.1 3.6 3.9 5.4 5.3 5.4
Range 2.4-5.9 2.1-6.1 2.1-6.1 3.4-7.3 2.6-7.3 2.6-7.3
Total SD 0.7 1.1 1.0 0.9 1.4 1.2
Total Average 3.4 3.1 3.3 4.8 4.5 4.7
Range 1.5-5.9 1.6-6.1 1.5-6.1 1.5-7.3 1.9-7.3 1.5-7.3
SD 0.9 1.2 1.1 1.7 1.8 1.7

M: male F: female

Table 6.
Angular parameters of cervical pedicle from C3 to C7
Pedicle Safe Angle(°) on Axial cut Safe Angle(°) on Sagittal cut
Lateral Medial Total Upper Lower Total
C3
Average 5.8 3.8 4.8 6.9 7.7 7.3
Range 3.9-7.8 2.5-4.1 2.5-7.8 5.3-9.7 5.5-10 5.3-10
SD 1.4 0.8 1.3 0.9 1 1
C4
Average 10.3 4.1 7.3 7.2 8.6 7.9
Range 7.8-13.1 2.1-7.6 2.1-13.1 5.2-10.6 5.9-11.7 5.2-11.7
SD 0.8 1.2 1.1 1.2 1.6 1.5
C5
Average 10.2 4.8 7.6 4.9 6.7 5.8
Range 8.3-13 3.1-7.8 3.1-13 3.4-7.2 5.1-9.6 3.4-9.6
SD 1.2 0.7 1.0 0.9 0.8 0.9
C6
Average 8.2 5.5 6.9 6.2 5.8 6.0
Range 4.1-11.6 3.1-7.8 3.1-11.6 5-8.9 4.2-9.2 4.2-9.2
SD 1.7 1.3 1.5 0.8 0.8 0.8
C7
Average 10.2 8.2 9.2 8.6 8.6 8.6
Range 5.1-13.3 5.1-13.5 5.1-13.5 7-11.2 5.9-12.9 5.9-12.9
SD 1.3 2.1 1.8 0.9 1.3 1.2
Total
Average 8.9 4.4 7.2 6.8 7.5 7.1
Range 3.9-13.3 2.1-13.5 2.1-13.5 3.4-11.2 4.2-12.9 3.4-12.9
SD 1.4 2.3 2.3 1.4 1.8 1.8
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