Cervical and high thoracic ligamentum flavum frequently fails to fuse in the midline.
BACKGROUND
Cervical and high thoracic epidural anesthesia and analgesia have gained increasing importance in the treatment of painful conditions and as components of anesthetics for cardiac and breast surgery. In contrast to the hanging-drop technique, the loss-of-resistance technique is thought to rely on the penetration of the ligamentum flavum. However, the exact morphology of the ligamentum flavum at different vertebral levels remains controversial. Therefore, the aim of this study was to investigate the incidence and morphology of cervical and high thoracic ligamentum flavum mid-line gaps in embalmed cadavers.


METHODS
Vertebral column specimens were obtained from 52 human cadavers. On each dissected level, ligamentum flavum mid-line gaps were recorded and evaluated with respect to shape and size.


RESULTS
The following variations were encountered: complete fusion in the mid-line, mid-line fusion with a gap in the caudal part, mid-line gap, and mid-line gap with widened caudal end. The incidence of mid-line gaps at the following levels was: C3-C4: 66%, C4-C5: 58%, C5-C6: 74%, C6-C7: 64%, C7-T1: 51%, Th1-Th2: 21%, Th2-Th3: 11%, Th3-Th4: 4%, Th4-Th5: 2%, and Th5-Th6: 2%. The mean width of mid-line gaps was 1.0 +/- 0.3 mm.


CONCLUSIONS
In conclusion, the present study shows that gaps in the ligamenta flava are frequent at cervical and high thoracic levels but become rare at the T3/T4 level and below, such that one cannot always rely on the ligamentum flavum as a perceptible barrier to epidural needle placement at these levels.
Lirk
Philipp
P
Department of Anesthesiology and Critical Care Medicine, University of Innsbruck, Austria. plirk@mcw.edu
Kolbitsch
Christian
C
Putz
Guenther
G
Colvin
Joshua
J
Colvin
Hans Peter
HP
Lorenz
Ingo
I
Keller
Christian
C
Kirchmair
Lukas
L
Rieder
Josef
J
Moriggl
Bernhard
B
D002574:Cervical Vertebrae / Q000033:anatomy & histology*; D006801:Humans; D017843:Ligamentum Flavum / Q000033:anatomy & histology*; D013904:Thoracic Vertebrae / Q000033:anatomy & histology*