Assessment of Magnetic Resonance Imaging in the diagnosis of lumbar spine foraminal stenosis -A surgeon's perspective

Detailed review

*Title: Assessment of Magnetic Resonance Imaging in the diagnosis of lumbar spine foraminal stenosis -A surgeon's perspective

요추 추간공 협착증 진단에서의 MRI의 측정 -외과의의 관점

*Author: Naftaly Attias, MD, Anne Hayman, MD, John A. Hipp, PhDz Philip Noble, PhD,

and Stephen I. Esses, MD

*Bibliography: J Spinal Disord Tech 2006;19:249-256

Study Design: A 2-part cadaveric study

Introduction:

1. Lumbar spine foraminal stenosis (LSFS) incidence >> 8% ~ 11%

2. Limitations of MRI itself for the diagnosis of LSFS

3. Not well understood about the effect of the variability on assessing LSFS

   1) Various Techniques

   2) Various Observers

4. No control over the final quality, or quantity of images provided to the surgeons

5. Glenn's words for size of a lesion in spine

   >> 1) normal, 2) slight, 3) mild, 4)moderate, 5) sever

6. Wildermuth et al's semi-quantitative classification system for grading LSFS

   1) On the basis of 'Open' MRI findings

   2) Grade 0 >> foramina without pathology

   3) Grade 1 >> slight foraminal stenosis

   4) Grade 2 >> marked foraminal stenosis

   5) Grade 3 >> advanced stenosis

7. About this study

   1) 2-part study to investigate the use of MRI in diagnosing LSFS

     ① Take MRIs of 3 cadavers in 3 centers, 8 spine surgeons to assess

       >> Reliability of Wildermuth semiquantitative classification system

       >> Variability in MRI examinations carried out in different institutions

     ② Compare MRI measurements vs. cadaveric slices to assess

       >> Differences between measurements from MRI vs. cadaveric specimens

Methods:

1. Fresh, frozen human lumbar spines (3 cadavers)

2. Examined with 3 different clinical MRI systems

3. Graded foramina by 8 surgeons on the basis of Wildermuth semiquantitative way

4. MRI measurements

   1) Foraminal height

   2) Superior foraminal width

   3) Middle foraminal width

   4) Posterior disc height

5. Specimen measurements

   1) Foraminal height

   2) Superior foraminal width

   3) Middle foraminal width

Results, Part 1:

1. 9set MRI scan review/total 72 foramina per one observer

2. Grading

   0) Grade 0 >> 222 foramina (39%)

   1) Grade 1 >> 201 foramina (35%)

   2) Grade 2 >> 127 foramina (22%)

   3) Grade 3 >>  26 foramina (04%)

   4) P = 0.15, nearly significant on the basis of paired t-tests

3. Level of interobserver agreement

   0) k grade 0 >> 0.13

   1) k grade 1 >> -0.01

   2) k grade 2 >> 0.06

   3) k grade 3 >> 0.11

   4) combined >> 0.07

   5) Most observers underestimated LSFS grade as compared with grading specimens.

   6) Preferred Method to assess the foramen >> T1 sagittal sequence

Results, Part 2:

1. MRI measurements

   1) Foraminal height >> 14.78mm (SD 4.53)

   2) Superior foraminal width >> 7.73mm (SD 1.77)

   3) Middle foraminal width >> 3.79mm (SD 1.68)

   4) Posterior disc height >> 5.55mm (SD 1.63)

   5) Correlation between MRI measurements and Actual dimensions in specimens >> Poor

2. Specimen measurements

   1) Measured 24 foramina and Graded according to Wildermuth classification

     Grade 0 >> 8 (33%)

     Grade 1 >> 3 (12%)

     Grade 2 >> 10 (42%)

     Grade 3 >> 3 (12%)

   2) Measurments of foraminal size

     Foraminal height >> 16.12mm (SD -3.11)

     Proximal foraminal width >> 8.99mm (SD -2.43)

     Middle foraminal width >> 4.76mm (SD -2.80)

Conclusion:

The parameters associated with the grade of stenosis assigned to the foramen were as follows: 

(1) the observer doing the grading

(2) the place it was imaged

(3) the location of the foramen.

There was poor correlation between measurements of the foramina carried out on MRI and the specimens.