Dalley, 10th Edition

Chapter 2 ■ Back

112

this displacement dislocates and fractures the articular fac ets between the two vertebrae and ruptures the interspinous ligaments. Irreparable injuries to the spinal cord accompany most severe exion injuries of the vertebral column. Sudden, forceful extension of the neck can also injure the vertebral column and spinal cord. Head butting or illegal face blocking in football may lead to a hyperextension injury of the neck (Fig. B2.16A). Such violent hyperextension is most likely to injure posterior parts of the vertebrae, frac turing by crush or compression of the vertebral arches and their processes. Fractures of cervical vertebrae may radiate pain to the back of the neck and scapular region because the same spinal sensory ganglia and spinal cord segments receiving pain impulses from the vertebrae are also involved in supplying neck muscles. Severe hyperextension of the neck (“whiplash” injury) also occurs during rear-end motor vehicle collisions (Fig. B2.16B), especially when the head restraint (head rest) is too low. In these types of hyperextension injuries, the an terior longitudinal ligament is severely stretched and may be torn. Hyper exion injury of the vertebral column may also occur as the head “rebounds” after the hyperextension, snapping the head forward onto the thorax. “Facet jump ing” or locking of the cervical vertebrae may occur because of dislocation of the vertebral arches (see the Clinical Box “Dislocation of Cervical Vertebrae” in this chapter). Severe hyperextension of the head on the upper neck may, in addi tion to producing a cervical spondylolysis or hangman’s frac ture (see the Clinical Box “Fracture and Dislocation of Axis” in this chapter), rupture the anterior longitudinal ligament and the adjacent anulus brosus of the C2–C3 IV disc. If this injury occurs, the cranium, C1, and the anterior por tion (dens and body) of C2 are separated from the rest of the axial skeleton (Fig. B2.16C), and the spinal cord is usu ally severed. Persons with this severe injury seldom survive. Football, diving, falls (e.g., from a horse), and motor vehicle collisions cause most fractures of the cervical region of the vertebral column. Symptoms range from vague aches to pro gressive loss of motor and sensory functions. The transition from the relatively in exible thoracic region to the much more mobile lumbar region occurs abruptly. Consequently, vertebrae T11 and especially T12 (which participates in rotatory movements superiorly but only exion and extension movements inferiorly) are the most commonly fractured noncervical vertebrae. Dislocation of vertebrae in the thoracic and lumbar re gions is uncommon because of the interlocking of their articular processes. However, when spondylolysis —frac ture of the column of bones connecting the superior and inferior articular processes (the pars interarticularis or in terarticular part)—occurs, the interlocking mechanism is broken (Fig. B2.17). Subsequently, dislocation between adjacent vertebrae, known as spondylolisthesis , may occur. Failure or fracture of the interarticular parts of the vertebral laminae of L5 ( spondylolysis of L5 ) especially may result in

Fracture of posterior arch elements (pedicle, spine)

Crush or compression fracture

Intervertebral disc injury

Lateral view

(A) Hyperextension of neck

“Tear drop” fracture and dislocation of vertebrae

Torn anterior longitudinal ligament

Median section

(B) Hyperextension (whiplash) injury

C1

C1

C1

C1

C2

C2

C3

C2

C2

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C3

C4

(C) Left lateral radiograph, h angman's fracture with disruption of C2/C3 disc and anterior longitudinal ligament

FIGURE B2.16. Extension injuries of cervical vertebrae.