Total number of cases: 60
Cases with transitional LSV (Case group): 30
- Cases with Sacralization: 20
- Cases with Lumbarization: 10
Cases without transitional LSV (Control group): 30
Demographics:
Gender: 31 males (51.6%) and 29 (48.4%) females.
Age: 18-64 (mean age 46)
Piriformis muscle topmost attachment:
Piriformis Attachment site |
Normal |
Sacralization |
Lumbarization |
S1 |
0 |
0 |
0 |
S2 |
16 |
20 |
0 |
S3 |
14 |
0 |
9 |
S4 |
0 |
0 |
1 |
In the case and control groups the Piriformis muscle was attached at S2 and S3 vertebral levels.
In the control group percentage of cases where the Piriformis muscle attached at S2 and S3 were 53.3 % and 46.7% respectively,
while in the case group it was 66.7% and 36% respectively.
There was no statistical difference between the cases and the control groups (P value of 0.282).
However,
the topmost piriformis slip attachment was at the higher level (S2) in 100% cases of sacralization; and at lower levels (S3 in 90% and S4 in 10%) in lumbarization.
Psoas Major muscle topmost vertebral attachment level:
Psoas Muscle lowest attachment |
Normal |
Sacralization |
Lumbarization |
T12 |
0 |
6 |
0 |
T12/L1 |
7 |
6 |
0 |
L1 |
21 |
8 |
5 |
L1/L2 |
2 |
0 |
3 |
L2 |
0 |
0 |
2 |
Most cases in both groups showed that Psoas Major topmost attachment was to L1 vertebra followed by T12-L1 levels.
In the control group percentage of cases attached at L1 and T12-L1 are 70 % and 23.3 % respectively,
while in the case group it is 40% and 20% respectively.
There is no statistical difference between case and control groups (P value of 0.038).
However,
higher level of topmost psoas attachment at T12/L1 or T12 level was seen in 60% of sacralization cases (and none in lumbarization); and lower level of attachment (L1/L2 or L2) in 50% of lumbarization cases (and none in sacralization). Both sacralization (40%) and lumbarization (50%) had topmost psoas attachment at L1 level.
Iliac crest corresponding vertebral level:
Iliac Crest |
Normal |
Sacralization |
Lumbarization |
L4 |
1 |
17 |
0 |
L4/L5 |
1 |
2 |
0 |
L5 |
27 |
1 |
6 |
L5/S1 |
1 |
0 |
2 |
S1 |
0 |
0 |
2 |
In the control group 90% of cases have L5 verterba corresponded to the iliac crest level on coronal localizor images.
In case group Iliac crest corresponded to L4 vertebra level in 56.7%,
but this higher level majority was contributed solely by the sacralization cases.
We noticed that in the case group the iliac crest corresponding vertebral level have a different pattern between lumbarization and sacralization. In sacralization the iliac crest corresponded to L4 in 56%; whereas in lumbarization it corresponded to L5 in 60%.
There was a statistical significance between case and control groups (P value of <0.001).
However,
this landmark is not reliable due to the anatomical variant pattern of distribution of cases and control groups (Figure 3).
A notable feature was that sacralization corresponded to a much higher level of the iliac crest in coronal images (85% at L4,
10% at L4-5,
only 5% at L5 and none below that); whereas lumbarization corresponded to a lower level of the iliac crest (none above L5,
60% at L5,
20% at L5-S1 and 20% at S1).
Iliolumbar ligament (ILL) verterbal attachment level:
Iliolumbar lig attachment level |
Normal |
Sacralization |
Lumbarization |
L4 |
0 |
19 |
0 |
L5 |
30 |
1 |
2 |
S1 |
0 |
0 |
3 |
L4/L5 |
0 |
0 |
0 |
L5/S1 |
0 |
0 |
5 |
The ILL originated from L5 vertebra in 100% of the controls.
On the other hand,
only 10% of the transitional LSV case group originated from L5 vertebra.
The case group had a different attachment level for lumarization and sacralization.
The main attachment level in sacralization was L4 in 95%. The main attachment level for lumbarization was L5/S1 which was seen in 50%.
The ILL was always present and its origin was related to the last lumbar/mobile vertebra in the control group,
sacralization and part from the lumbarization group.
In Lumbarization mixed attachment pattern was observed with ILL originating from L5 on one side and S1 on the other.
There was statistical significance between case and control groups (P value of <0.001).
However,
ILL is always related to last lumbar/mobile vertebra so knowing if it L4,
L5 or even S1 is not constant making this landmark unreliable.
In sacralization, ILL originated at higher level (95% at L4,
only 5% at L5 and none below that); whereas in lumarization ILL originated at lower level (none above L5,
20% at L5,
50% at L5/S1,
and 30% at S1).