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.
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