2013년 9월 16일 월요일

Lumbar intervertebral foramens-An in vitro study of their shape in relation to intervertebral disc pathology -Spine (Phila Pa 1976). 1991 May;16(5):525-9.

Title: Lumbar intervertebral foramens-An in vitro study of their shape in relation to intervertebral disc pathology


Introduction

1. Variations in the size & shape of foramens in lumbar region
   >> Often associated with symptoms of nerve root compression
   >> Inverted Pear Shape (IPS)
   >> Oval Shape (OS)
   >> Auricular Shape (AS)
   >> Range of foraminal height in L-Spine: 11-19mm and 13-15mm
   >> Foraminal width, average size = 7mm
   >> Occupation of nerve root in area of the foramen = over 50%

2. What is the problem?
   >> Limited observation methods
   >> So, no consideration of variation in form of the intervertebral disc
   >> Radiographs not allowing for the changing orientation of foramens from a horizontal and lateral direction in the upper lumbar spine to an anterior and caudal direction in the sacrum

3. The purpose of the study
   >> Measure the dimensions accurately
   >> Outline the shape of 5 pairs of foramens of L-Spine
   >> Asses the accuracy of some radiological measurements
   >> Determine the effect of abnormalities of the intervertebral disc on foraminal shape

*Figure 1














*Figure 2














Materials and Methods

1. Subjects
   >> Lumbosacral region of vertebral column
   >> From 20 cadavers
   >> Age: 16~88y

2. Radiographs and Cadaver Measurements
   >> Anteroposterior and Lateral
   >> Various measurements
      1) Interpedicular Height (IH)
      2) Foraminal height (FH)
      2) Foraminal width (FW)
    


Results

1. Foraminal Shape (normal disc), 194 foramens examined

 1) 3 types of shape
   >> Round or Oval type: 81 (42%)
   >> Auricular type: 95 (50%)
   >> Teardrop-shaped type: 15 (8%)

 2) Normal intervertebral disc
   >> Round or Oval type: 56%
   >> Auricular type: 39%
   >> Teardrop-shaped type: 5%

 3) According levels
   >> L1/2: never observed the oval and teardrop shape
   >> L2/3: Oval shape 56%, Auricular shape 32%
   >> L3/4: Oval Shape 53%, Auricular shape 39%
   >> L4/5: Oval Shape 31%, Auricular shape 59%, non of the teardrop shape
   >> L5/S1: Oval shape 59%, Auricular shape 41%

2. Foraminal Size (normal disc)
   >> Great variation in foraminal size at each level
   >> L1/2 normal: 80.4
   >> L2/3 normal: 95.0
   >> L3/4 normal: 96.2
   >> L4/5 normal: 87.3
   >> L5/S1 normal: 103.6

3. Foraminal Shape (abnormal disc), markedly differed from the normal pattern

 1) Abnormal intervertebral disc
   >> Round or Oval type: 22%
   >> Auricular type: 66%
   >> Teardrop-shaped type: 12%

2) According levels
   >> L1/2: Oval shape 30%, Auricular shape 70%
   >> L2/3: Oval Shape 17%, Auricular shape 78%
   >> L3/4: Oval Shape  8%, Auricular shape 67%,
   >> L4/5: Oval shape 12%, Auricular shape 67%, Teardrop shape 21%
   >> L5/S1: Oval shape 50%, Auricular shape 44%

4. Foraminal Size (abnormal disc)
   >> L1/2 normal: 91.2
   >> L2/3 normal: 101.3
   >> L3/4 normal: 92.1
   >> L4/5 normal: 92.1
   >> L5/S1 normal: 99.3

5. Radiologic Measurements
   >> No difference between radiologic measurements and corresponding dimensions from sectioned foraminal models




Discussion

1. Disc degeneration continued
   >> reciprocal encroachment into posterior foraminal boundary by hypertrophied superior articular facet converted the auricular into a teardrop-shaped foramen

2. Uppermost 2 levels
   >> In abnormal disc, auricular foramen predominated, but not decreased height and area
   >> May explain why pathology is rarely seen at uppermost 2 levels

3. L3-4 level
   >> Showed a fall in height and area with a greater proportion of auricular foramens

4. L4-5 level
   >> No change in area or height even with abnormal disc
   >> More often shape in abnormal is the teardrop.
      > indicated that here degeneration did not cause collapse of the foramen
      > but rather alteration in its outline, affecting the lower part of the foramen

5. Lumbosacral level
   >> Abnormal disc: decreased foraminal area unlike the height
   >> Increased proportion of auricular foramens
   >> Demonstrated the greatest deformation from the abnormal disc

Conclusion

1 .Foraminal Height varies from 10 to 19mm
2. Foraminal area varies from 40 to 160

3. Disc degeneration alters the foramen shape from relatively round structure to auricular shape.