Dalley, 10th Edition

93

Vertebrae

Zygapophysial joints

ANTERIOR

S i

S i

Normal

C6

LEFT

i

C7

S i

i

i

S

RIGHT

S

S

2

Following bilateral dislocation

POSTERIOR

Facet jumping (C6 “jumped”

(G) Transverse scan with schematic

anteriorly over C7, red arrow )

i S

Inferior articular processes of C6 Superior articular processes of C7

C6

C7

Normally, the superior articular processes are anterior to the inferior processes, with their flat articular facets in contact as a zygapophysial joint.

(F) Median MRI with schematic

FIGURE B2.5. F. MRI of a stage IV dislocation with cord injury. The body of C7 is fractured ( open white arrowheads ). The ligamentum avum is disrupted ( curved black arrow ), and the spinous process is avulsed ( straight black arrow ). G. CT of same individual shown in F . The articular processes of the C6 and C7 vertebrae are reversed due to “facet jumping.” ( continued )

Lumbar Spinal Stenosis

Tip of conus medullaris

Lumbar spinal stenosis describes a stenotic (narrow) vertebral foramen in one or more lumbar vertebrae (Fig. B2.6B–D). This condition may be a hereditary anomaly that can make a person more vulnerable to age-related degenerative changes such as IV disc bulging. Lumbar spinal nerves increase in size as the vertebral column descends, but paradoxically, the IV foram ina decrease in size. Narrowing is usually maximal at the level of the IV discs (see Fig. 2.4). However, stenosis of a lumbar vertebral foramen may cause compression of one or more spinal nerve roots occupying the inferior vertebral ca nal. When IV disc protrusion occurs in a patient with spinal stenosis (Figs. B2.6B and C), it further compromises a ver tebral canal that is already limited, as does arthritic prolif eration (Fig. B2.6D), ligamentous degeneration, and vertebral malalignment (Fig. B2.6C). Surgical treatment of lumbar stenosis may consist of decompressive laminectomy (see the Clinical Box “Laminectomy” in this chapter).

Nerve roots of cauda equina

Region of lumbar spinal stenosis ( arrow )

Sacrum

(C) Median MRI

Common iliac arteries L4/L5 IV disc

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Psoas major muscle Nerve roots of cauda equina and lateral recess stenosis ( arrow ) Arthritic hypertrophy of facet joint and ligamentum flavum

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Superior views

(B) Stenotic vertebral foramen (D) Transverse MRI FIGURE B2.6. Lumbar spinal stenosis. A and B. Normal ( A ) and stenotic ( B ) vertebral foramina ( asterisks ) are compared. C and D. Lumbar MRIs demonstrate a high-grade stenosis ( red arrows ) caused by hypertrophic articular processes and ligamenta ava and moderate peripheral bulging of the L4–L5 IV disc. (A) Normal vertebral foramen