Article Figures & Data
Figures
- Figure 1
Representative adequate dynamic x-ray images of a patient with cervical myelopathy depicting measurement of sagittal translational instability at C6-C7 level. Lines were drawn along the posterior border of the superior and inferior vertebrae, and the horizontal distance between the lines was measured. A difference of more than 3.5-mm translation or 20% was considered as sagittal translational instability.
- Figure 2
Representative dynamic x-ray images of a patient with cervical myelopathy depicting measurement of sagittal rotational instability at C4-C5 level. Lines were drawn along the inferior end plate of the superior vertebra and the superior end plate of the inferior vertebra, and the angle between these lines was measured. The difference in angles formed between these lines in flexion and extension views was measured. A difference of more than 12° was considered as sagittal rotational instability.
- Figure 3
Representative neutral T2-weighted sagittal magnetic resonance imaging image of the cervical spine depicting the measurement of disc height. Disc height was measured from the center of the inferior end plate of superior vertebra to the center of the superior end plate of the inferior vertebra.
- Figure 4
Representative neutral T2-weighted sagittal magnetic resonance imaging (MRI) images of the cervical spine depicting measurements for ligamentum flavum (LF) thickness and buckling. At the midlevel of the intervertebral disc, 2 linear lines were drawn. One line measured the distance from the posterior margin of the disc to the base of spinous process (A) and another line measured the distance from the posterior margin of the disc to the posterior border of the cerebrospinal fluid (b) in a flexion MRI. The difference in value obtained (A, B) represents the LF thickness in flexion. (C) and (D) represent similar measurements performed on an extension MRI. The LF thickness in extension is represented by value (c-d). The difference in LF thickness in flexion and extension (C, D-[A, B]) is considered as buckling.
- Figure 5
A flowchart depicting the selection of study samples utilized for the study.
- Figure 6
(A, B) T2-weighted magnetic resonance images showing the changes in ligamentum flavum (LF) with neck motion. As the neck goes into flexion (B) from extension (A), the distance between the origin (marked A) and insertion (marked B) increases and puts strain on the LF. (C) Representation of a typical stress-strain curve of a ligament. The x-axis represents the strain on the ligament, and y-axis represents the stress applied to the ligament. Within the elastic region, repeated increases or decreases in tension load will not change the ligament length. The elastic region represents the tension loads that occur within the physiological range of motion of the neck. Beyond a point, the curve tends to flatten, indicating that the ligament deforms more per given increase in tension load (ie, the ligament undergoes permanent deformation [plastic deformation]). This is called the yield point. After the plastic region, the sudden failure of the ligament occurs and stress disappears. This is called the failure point. With permanent deformation or lengthening of the ligament, the LF tends to buckle into the spinal canal in extension because of the closer contact between the laminae (points A and B in Figure 6A and B).
Tables
- Table 1
Descriptive statistics (mean ± standard deviation) according to the level. Analysis of variance (ANOVA) was used to compare the means of variables such as ligamentum flavum thickness/buckling across different cervical levels.
Characteristic C2-C3 C3-C4 C4-C5 C5-C6 C6-C7 C7-T1 P Valuea Thickness 0.26 ± 0.06 0.28 ± 0.07 0.29 ± 0.11 0.28 ± 0.09 0.27 ± 0.08 0.31 ± 0.08 <0.001 Buckling 0.03 ± 0.03 0.05 ± 0.05 0.10 ± 0.08 0.08 ± 0.09 0.05 ± 0.07 0.03 ± 0.04 <0.001 Disc height 0.71 ± 0.13 0.71 ± 0.21 0.72 ± 0.14 0.75 ± 0.15 0.72 ± 0.16 0.72 ± 0.20 0.331 Translation 0.26 ± 0.45 0.27 ± 0.35 0.27 ± 0.28 0.48 ± 0.63 0.30 ± 0.41 0.26 ± 0.25 <0.001 Rotation 3.03 ± 0.87 3.32 ± 1.53 4.02 ± 3.61 3.73 ± 1.77 3.27 ± 1.63 2.56 ± 1.22 <0.001 aRepeated measures ANOVA (Greenhouse-Geisser).
Level No. of Levels (%) Group A, Buckling≤0.1 mm (n = 798) Group B, Buckling>0.1 mm (n = 216) C2-C3 156 (19.5) 13 (6.0) C3-C4 136(17.0) 33 (15.3) C4-C5 97 (12.2) 72 (33.3) C5-C6 112 (14.0) 57 (26.4) C6-C7 148 (18.6) 21 (9.7) C7-T1 149 (18.7) 20 (9.3) - Table 3
Correlation analysis of buckling with age at different levels. Only C7-T1 level had correlation of ligamentum flavum buckling with age.
Age C2-C3 C3-C4 C4-C5 C5-C6 C6-C7 C7-T1 Pearson correlation 0.001 0.054 0.041 −0.129 −0.079 0.187a P value 0.986 0.487 0.594 0.095 0.310 0.015 aCorrelation is significant at the 0.05 level (2 tailed).
Level Group A, Buckling≤0.1 mm (n = 798) Group B, Buckling>0.1 mm (n = 216) P Value n Mean (SD) n Mean (SD) C2-C3 156 0.71 (0.14) 13 0.74 (0.09) 0.435 C3-C4 136 0.68 (0.13) 33 0.68 (0.13) <0.001 C4-C5 97 0.72 (0.71) 72 0.71 (0.11) 0.545 C5-C6 112 0.76 (0.17) 57 0.72 (0.10) 0.068 C6-C7 148 0.70 (0.17) 21 0.83 (0.02) <0.001 C7-T1 149 0.72 (0.19) 20 0.71 (0.28) 0.901
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