Anatomy Atlas and Interpretation of Spine Surgery

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J.-g. Shi et al.
hypoglossal
nerve
body of axis
lateral mass
of axis
Atlantoodontoid
process
cephalad
lateral
mass of
atlas
axis
hypoglossal
nerve
spinal
dura sac
cephalad
Fig. 1.32 Removal of the anterior tubercle of the atlas by Kerrison’s
rongeur to expose the odontoid process
Fig. 1.34 Removal of the tectorial membrane to expose the dural sac
hypoglossal
nerve
body of
axis
lateral
mass of
axis
transverse
ligment
cephalad
lateral
mass of
atlas
Fig. 1.33 Excision of the odontoid process with a high-speed drill
Tectorial membrane: a continuation of the posterior
longitudinal ligament and a wide and strong ligament.
Its superficial layer is above the foramen magnum and
is attached to the skull and merges with the dural sac of
skull. Its deep layer is composed of a strong central
band and two side bands. The central band runs upward
to the foramen magnum, and the two side bands run to
the foramen magnum and merge with atlantooccipital
joint capsule (Figs. 1.35 and 1.36).
Cruciate ligament of the atlas: composed of the
transverse ligament and longitudinal ligament. The
transverse ligament is wide and strong, about 2 cm
long, with both sides arising from the axial lateral
mass which arches across the back of the odontoid
process and serves as an important structure for stabilizing
the atlantoaxial joint. The superior border of the
transverse ligament emits a tough central longitudinal
ligament, which runs upward to the base of the occipital
bone between the apical odontoid ligament and tectorial
membrane. The bottom of the transverse
ligament also emits a thin longitudinal ligament that
ends at the posterior border of the axis. The transverse
ligament divides the atlantoaxial canal into an anterior
and a posterior section, where the anterior section consists
1/3 of the canal including the odontoid process,
while the posterior section consists 2/3 of the canal
including the spinal cord and its membranes (Fig. 1.37).
Alar ligament: arises from the posterolateral side of
the tip of the odontoid process to the medial rough surface
of the occipital condyle and is about 1 cm long.
The main function of alar ligament is to restrict contralateral
rotation of the atlantoaxial joint (Fig. 1.38).
Apical odontoid ligament: extends from the tip of
the odontoid in the shape of a sector to the anterior
margin of the foramen magnum through the alar ligaments
(Figs. 1.38, 1.39, 1.40, and 1.41).