Predictive factors of symptomatic lumbar canal stenosis in patients after surgery for cervical spondylotic myelopathy

Figures & data

Figure 1 Measurement of AP diameter of cervical canal and spinal cord compression on T2 sagittal MR imaging.

Notes: D1–D4 were diameters of cervical canal at the mid-vertebra level from C4 to C7. AP diameter of cervical canal (mm)=(D1+D2+D3+D4)/4. a and b are the spinal cord diameters of narrowest part and the C2/C3 intervertebral level. Spinal cord compression (%)=a/b.
Abbreviations: AP, anteroposterior; MR, magnetic resonance.

Figure 2 The lumbar canal was calculated by a ratio of the mid-sagittal spinal canal diameter at the level of the intervertebral disc to the spinal canal diameter at the mid-vertebra level of the upper vertebral body.

Note: The percentage of lumbar canal stenosis (%)=(a/A+b/B+c/C+d/D)/4.

Table 1 Classification system for lumbar spinal stenosis based on MR images

Type I	Normal spinal canal
Type IIa	Tapering of the spinal canal with gradual narrowing from the thoracolumbar junction to a peak area of stenosis at L5–S1
Type IIb	Hourglass stenosis with a canal that begins to narrow at the thoracolumbar junction down to a peak area of stenosis, typically at the L3–L4 level, and then widens again caudally
Type III	Global stenosis with a symmetrically narrow canal throughout all lumbar segments with little to no spinal fluid surrounding the conus

Abbreviation: MR, magnetic resonance.

Figure 3 Kaplan–Meier survivorship curve for symptomatic LCS after CSM surgery.

Abbreviations: CSM, cervical spondylotic myelopathy; LCS, lumbar canal stenosis.

Table 2 Patients’ demographic and baseline data for two groups

Variables	LCS patients (N=39)	Non-LCS patients (N=278)	P-value
Age (years)	65.1±8.6	63.7±7.0	0.195
Gender
Male	22	186	0.211
Female	17	92
BMI (kg/m^2)	24.8±6.1	25.9±6.7	0.332
Preoperative JOA score (points)	9.5±2.5	9.8±2.2	0.434
Sagittal alignment
Kyphosis	6	34	0.606
Lordosis	33	244
Levels with CSM
Single level	13	153	0.016
Multiple level	26	125
AP diameter of cervical canal (mm)	12.7±1.4	14.9±1.6	,0.001
Cervical cord compression (%)	76.3±8.1	78.2±6.9	0.117

Abbreviations: AP, anteroposterior; BMI, body mass index; CSM, cervical spon-dylotic myelopathy; JOA, Japanese Orthopedic Association; LCS, lumbar canal stenosis.

Figure 4 Scatter diagram showing the relationship between AP diameter of cervical canal and severity of LCS.

Abbreviations: AP, anteroposterior; LCS, lumbar canal stenosis.