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2013년 9월 15일 일요일

Factors affecting dynamic foraminal stenosis in the lumbar spine

2nd journal review

*Title: Factors affecting dynamic foraminal stenosis in the lumbar spine

*Author: Vijay Singh,MD, Scott R. Montgomery,MD, Bayan Aghdasi,BA, Hirokazu Inoue,MD,PhD, Jeffrey C.Wang,MD, Michael D. Daubs,MD

*Bibliography: 2013 Sep;13(9):1080-7.


Background Context: Minimal in vivo data exists quantifying changes in foraminal area(FA) as the spine moves from flextion to extension in the lumbar spine.

Purpose: To evaluate the relationship between foraminal stenosis and lumbar segmental 1)angular motion, 2)translational motion(TM), 3)disc bulge migration.

Study design: A retrospective radiographic study.

Patient sample: 45patients undergoing kMRI for symptoms of low back pain of radiculopathy(44years).

Outcome measures: MRI measurements of FA, angular motion, TM, disc bulge migration.

Methods:
>Study population
-45patients with clinically symptomatic low back pain or radiculopathy were reffered to lumbar kMRI.  (2011.03~2011.06)
-sex: 27males / 18females
-age: 44.7 years
-exclusion criteria: patients with unclear foraminal margins owing to rotation or scoliosis and with previous surgery, trauma, tumor, and infection.
    total 204 foramina met the inclusion criteria for analysis...

>MRI imaging protocol
-MRI of lumbar spine was performed using a 0.6-T Upright Multi-Position MRI (Fornar Corporation, Melville, NY, USA).

>MRI measurements
-Foraminal Area
1) The FA was calculated after outlining the perimeter of the neural foramen on parasagittal images using Image J software (ver. 1.45, US, National Institutes of Health, Bethesda, MD, USA)

2) assessed qualitatively using a modification of the grading system published bt Wildermuth et al.
Grade 1: normal foramina with normal foraminal epidural fat.
Grade 2: slight foraminal stenosis and deformity of epidural fat with remaining fat still completely surrounding the exiting nerve root.
Grade 3: marked foraminal stenosis with epidural fat only partially surrounding the nerve root or complete stenosis of foraminal epidural fat.

-Angular motion, TM, disc bulge
Images were evaluated with digital imaging software(MR Analyzer, ver. 2.0; TrueMRI Corporation, Bell-flower, CA, USA).
1) segmental angular motion: defined as the difference in intervertebral angles between two adjacent vertebrae from flextion to extension.
2) TM: calculated as the amount of anteroposterior movement at each vertebral level (flex to ext).
3) disc bulge: measured as the difference in the amount of disc bulging in the foramen from posterior vertebral margins at the level of foramina (flex to ext).

>Statistical analysis
-disc bulge, TM, angular motion data underwent statistical significance testing using the Shapiro-Wilk test and Mann-Whitney U test, Bonferroni inequality (p<0.05).

Results:
-There was a significant decrease in the FA from flx to neutral at all levels except L5-S1 and from neutral to ext at all levels.
-The average percent decrease in FA was 30.0%.
-Greatest decrease from flx to ext at L2-L3.
-Smallest change at L5-S1.
-The magnitude of change in FA increased as angular motion at a segment increased.
-The mean change in FA was 32.3㎟ when angular motion was less than 5º and was 75.16㎟ when angular motion exceeded 15º.
-The extent of disc bulging posteriorly in the neural foramen was also correlated with the reduction in the FA from flx to ext, but TM had no effect.

Conclusions:
-Foraminal area decreased significantly in extension compared with flexion and neutral on MRI.
-Disc bulge migration and angular motion at each level contributed to the decrease in FA(from flx to ext).
-TM was not strongly correlated to changes in FA.