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Lumbar zygapophyseal joint angle* *In relation to the sagittal plane. †Joint space oriented parallel to sagittal plane. ‡Joint space perpendicular to sagittal plane. From Bogduk N, Twomey L: Clinical anatomy of the lumbar spine, ed 3, London, 1997, Churchill Livingstone. March 26, 2003 -- This article is the 14th in our series of white papers on radiologic patient positioning techniques for x-ray examinations. If you'd like to comment on or contribute to this series, please e-mail . The most common routine cervical projections are the anteroposterior (AP), AP open mouth, and lateral. Oblique projections of the cervical spine are not routinely obtained, although they may be called for to help visualize obscure fractures of the neural arch and abnormalities of the neural foramina and apophyseal joints. Structurally, the first and second cervical vertebrae possess anatomic features distinct from those of the remaining five cervical vertebrae. The first cervical vertebra, C-l or atlas, is a bony ring consisting of anterior and posterior arches connected by two lateral masses. The atlas has no body; its main weight-bearing structures are the lateral masses, also called articular pillars. The second vertebra, C-2 or axis, is a more complex structure whose distinguishing feature is the odontoid process, also known as the "dens" (tooth), projecting cephalad from the anterior surface of the body. The vertebrae C-3 to C-7 exhibit identical anatomic features and are more uniform in appearance, consisting of a vertebral body and a posterior neural arch, including the right and left pedicles and laminae, which together with the posterior aspect of the body enclose the spinal canal. Extending caudad and cephalad from the junction of the pedicle and lamina on each side are superior and inferior articular processes, which form the apophyseal joints between the successive vertebrae. Extending laterally from the pedicle on each side is a transverse process, and in the posterior portion, a spinous process extends from the junction of the laminae in the midline. Lateral projection of the cervical spine Radiographic examination of a patient with cervical spine trauma may be difficult and is usually limited to one or two projections. Frequently the patient is unconscious, there are associated injuries, and unnecessary movement risks damage to the cervical cord. The single most valuable projection in these instances is the lateral view, which may be obtained in the standard fashion or with the patient supine, depending on their condition. This projection suffices to demonstrate most traumatic conditions of the cervical spine, including injuries involving the anterior and posterior arches of C-l; the odontoid process, which is seen in profile; and the anterior atlantal-dens interval. The bodies and spinous processes of C-2 to C-7 are fully visualized, and the intervertebral disk spaces and prevertebral soft tissues can be adequately evaluated. The lateral view can also be obtained in flexion and extension of the neck, which is particularly effective in demonstrating suspected instability at C-1 to C-2 by allowing evaluation of the atlanto-odontoid distance. It is of the utmost importance on the lateral projection of the cervical spine that the C-7 vertebra be visualized, as this is the most commonly overlooked site of injury. Technical factors
Positioning for a lateral projection of the cervical spine
Evaluation criteria
Cervicothoracic (swimmer’s view) lateral projection of cervical spine Special projections may occasionally be required for sufficient evaluation of the structures of the cervical spine. The swimmer’s view may be employed for better demonstration of C-7, T-1, and T-2 vertebrae, which on the standard lateral projection are obscured by the overlapping clavicle and soft tissues of the shoulder girdle. Technical factors
A: For a swimmer’s view projection, the arm adjacent to the vertical grid is elevated and flexed, resting the forearm on the head for support, while the other arm is depressed and moved slightly anterior to place the vertebral head anterior to the vertebrae. The CR is centered to T1 and directed perpendicular to the shoulder. B: A swimmer’s view projection can also be taken with the patient placed prone on the table with the left hand abducted 180° and the right hand to the side, as if swimming. The cassette is placed against the right side of the neck. Image courtesy of Dr. Naveed Ahmad. Positioning for swimmer’s view lateral projection of the cervical spine
Evaluation criteria
AP axial projection of the cervical spine On the AP view of the cervical spine the bodies of the C-3 to C-7 vertebrae (in young patients the C-l and C-2 vertebrae may be visible) are well demonstrated, as are the uncovertebral (Luschka) joints, and the intervertebral disk spaces. The spinous processes are seen almost on end, casting oval shadows that resemble teardrops. Technical factors
Positioning for an AP projection of the cervical spine
Evaluation criteria
AP "open-mouth" projection of the cervical spine This variant of the AP projection, also known as the "open-mouth" view, may be obtained as part of the standard cervical spine examination. This view provides effective visualization of the structures of the first two cervical vertebrae. The body of C-2 is clearly imaged, as are the atlantoaxial joints, the odontoid process, and the lateral spaces between the odontoid process and the articular pillars of C-l. Technical factors
Positioning for open-mouth projection of the cervical spine
Evaluation criteria
A: For the erect lateral view of the cervical spine, the patient is standing or sitting, with head straight in neutral position. The CR is directed horizontal to the center of C-4 vertebra (at the level of the chin). B: For the AP view of the cervical spine, the patient is either erect or recumbent. The beam is directed toward the C-4 vertebra (at the Adam's apple) at an angle of 15°-20° cephalad. C: For the open-mouth view, the patient is positioned in the same manner as for the supine AP projection; the head is straight, in the neutral position. With the patient's mouth open as wide as possible, the CR is directed perpendicular to the midpoint of the open mouth. D: For the oblique view of the cervical spine, the patient may be erect or recumbent. The patient is rotated 45° to the left, to demonstrate the right-side neural foramina. The CR is directed to the C-4 vertebra with 15°-20° cephalad angulation. Image courtesy of Dr. Naveed Ahmad. By Dr. Naveed AhmadAuntMinnie.com contributing writer March 26, 2003 Copyright © 2003 AuntMinnie.com What type of CR angulation is required for the AP axial projection for the cervical spine?C-Spine positioning. How much angulation is required for the routine AP axial cervical spine?B: For the AP view of the cervical spine, the patient is either erect or recumbent. The beam is directed toward the C-4 vertebra (at the Adam's apple) at an angle of 15°-20° cephalad.
How many degrees and in which direction should the CR be directed for AP axial projections of the coccyx?Lumbar,sacrum, and coccyx by merrils. Where is the CR centered for an AP axial projection of the sacrum?The CR is centered 1.5 inches inferior to the iliac crest and 2 inches posterior to the ASIS.
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