ANATOMY
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Fracture of the dens of the axis with
posterior dislocation may crush the spinal cord at the level of the
-?-first
cervical vertebra with terminal paralysis of respiratory musculature.
The cruciform ligament is the principal
structure preventing subluxation at the atlantoaxial joint because the
articular surfaces between the axis and
-?-atlas
are nearly horizontal and there is no intervertebral disk.
Herniation usually occurs in the fourth or
fifth intevertebral disks because of the pronounced lumbar curvature and the
considerable body mass
-?-superior
to this region.
The anterior and posterior longitudinal
ligaments reinforce the underlying annulus fibrosus but do not meet
-?-posterolaterally, resulting in a
weak area predisposed to herniation.
Lumbar puncture and intrathecal anesthesia
should be introduced below the third lumbar vertebra as the spinal cord usually
-?-terminates
between the first and second lumbar vertebrae.
Posterolateral disk prolapse impinges upon
the spinal nerve of the next lower vertebral level, causing symptoms associated
with the -?-dermatomic
and myotomal distribuations of that nerve.
| Hernia | Involvement | Signs | Reflex Test |
|---|---|---|---|
| C3-C4 | -?-C4 (Phrenic, C3-C5) | Weak diaphragmatic Respiration | |
| C4-C5 | C5 (Suprascapular, C4-C6) | -?-Weak arm abduction | |
| C5-C6 | C6 (Musculocutaneous, C5-C6) | Weak forearm flexion | -?-Biceps |
| -?-C6-C7 | C7 (Radial, C6-C8) | Weak forearm extension | Triceps |
| C7-C8 | -?-C8 ( Ulnar, C7-T1) | Weak thumb adduction | |
| L1-L2 | L2 (Genitofemoral, L1-L2) | -?-Weak hip flexion | Cremaster |
| L2-L3 | -?-L3 (Obturator, L2-L4) | Weak knee extension | |
| L3-L4 | L4 (Femoral, L1-L4) | Weak leg extension | -?-Knee jerk |
| -?-L4-L5 | L5 (Fibular, L4-S1) | Weak dorsiflexion | |
| L5-S1 | S1 (Tibial, L5-S2) | -?-Weak plantar flexion | Ankle jerk |