TABLE 21.1 Axial Skeletal Malformations Due to Genetic Abnormalities
as the distance between the anterior margin of the condyles at the base of the skull and the sharp contour of the anterior aspect of the concave joint of the atlas anteriorly, or as the distance between the occipital protuberance and the superior arch of the atlas posteriorly. Another method to measure posterior subluxation of the atlantooccipital joint is that of Wiesel and Rothman (42) (Fig. 21-5). With this technique, occiput-C1 translation from maximum flexion to maximum extension should be no more than 1 mm in normal adults. These norms in children have not yet been established.
FIGURE 21-4. Lateral (A) flexion and (B) extension radiographs of an 11-year-old boy with Down syndrome. The child presented with loss of hand control when flexing his neck. Using the method of Tredwell et al. (41), the atlantooccipital distance is measured as the distance between the anterior margin of the condyles at the base of the skull and the sharp contour of the anterior aspect of the concave joint of the atlas. More than 4 mm of posterior translation is abnormal. The atlantooccipital distance (arrows) measured 10 mm in extension and 1 mm in flexion. The ADI was 1 mm in extension and 6 mm in flexion, for a total of 5 mm of motion (arrowheads). The SAC was 17 mm in flexion and 20 mm in extension. Both occipitoatlantal instability (more than 4 mm posterior translation) and atlanto-dens hypermobility (5 mm ADI in flexion) were present.
FIGURE 21-5. The method of measuring atlantooccipital instability according to Weisel and Rothman (42). The atlantal line joins points 1 and 2. A perpendicular line to the atlantal line is made at the posterior margin of the anterior arch of the atlas. The distance (x) from the basion (3) to the perpendicular line is measured in flexion and extension. The difference between flexion and extension represents the AP translation at the occipitoatlantal joint; in normal adults, this translation should be no more than 1 mm. (From Gabriel KR, Mason DE, Carango P. Occipito-atlantal translation in Down’s syndrome. Spine 1990;15:996-1002, with permission.)
of age, when this distance is largest at C5-C6 (34). The AP displacement, from hyperflexion to hyperextension, decreases from C2-C3 to C6-C7. The angular displacement is greatest (15 degrees) at C3-C4 and C4-C5 for children 3 to 8 years of age, is greatest (17 degrees) at C4-C5 for children 9 to 11 years of age, and is greatest (15 degrees) at C5-C6 for children 12 to 15 years of age.
The differential diagnosis of torticollis is large and can be divided into osseous and nonosseous types. In a recent large series from a tertiary care pediatric orthopaedic center (49), a nonmuscular etiology of torticollis was found in 18% of patients, most frequently the Klippel-Feil syndrome or a neurologic disorder (ocular pathology, or central nervous system lesion).
Arnold-Chiari malformation; transoral anterior decompression was reserved for those with an associated Arnold-Chiari malformation (84). These are general statements, and each case must be considered individually. Secondary basilar impression tends to progress despite arthrodesis (61).
suboccipital pain, decreased cervical motion, or a clunking of the upper cervical spine.
with an anterior shift of 5 mm or less, type III is rotary displacement with an anterior shift >5 mm, and type IV is rotary displacement with a posterior shift. The amount of anterior displacement considered to be pathologic is >3 mm in older children and adults and >4 mm in younger children (33). Flexion and extension lateral-stress radiographs are suggested to rule out the possibility of anterior displacement.
FIGURE 21-20. The four types of atlantoaxial rotary displacement. (From Fielding JW, Hawkins RJ. Atlanto-axial rotatory fixation. J Bone Joint Surg Am 1977;59-A:37-44, with permission.)
the side of the long sternocleidomastoid muscle because the muscle is attempting to correct the deformity, unlike congenital muscular torticollis where the muscle causes the torticollis. If the deformity becomes fixed, the pain subsides but the torticollis persists, along with decreased neck motion. In longstanding cases, plagiocephaly and facial flattening may develop on the side of the tilt.
FIGURE 21-21. A 5-year-old boy developed an atlantoaxial rotary subluxation after an upper respiratory viral infection (Grisel syndrome). It rapidly resolved after treatment with a soft collar and mild doses of diazepam.
FIGURE 21-22. The child in Figure 21-19 had a fixed deformity that occurred 6 months earlier, immediately after reconstructive maxillofacial surgery for Goldenhar syndrome. It did not respond to traction, including halo traction. She underwent a posterior C1-C2 (Gallie-type) fusion. A solid fusion was present 9 months later; clinically, the patient achieved 80 degrees of rotation to the left and 45 degrees of rotation to the right.
FIGURE 21-23. The most common arthrodesis of the cervical spine is between the axis and the atlas because of the numerous congenital and developmental problems that affect this region. Although several techniques have been advocated to achieve arthrodesis of these vertebrae, the technique attributed to Gallie (130) is the most reliable and the easiest to apply in children. In this technique, the wire not only helps to pull C1 back into position and hold it there but also holds the bone graft firmly in place (131, 132). Occasionally, the posterior arch of C1 is not formed completely, making this technique impossible; in these cases other techniques need to be used, such as only grafting with halo immobilization (104).
In cases in which there is a great deal of instability with chance for neurologic injury, it is preferred to place the patient in a halo vest or cast first. This can be done under local or general anesthesia, as needed. Reduction is achieved and confirmed by radiographs. If the halo was applied with the patient awake, anesthesia is then induced and the child turned prone for the posterior fusion. No head rest is necessary, and there is little danger of neurologic injury while carefully intubating and moving the patient with the halo vest in place.
The occipital region of the skull is shaved, and the posterocervical area and the posterior iliac crest are prepared and draped. The incision extends in the midline from the base of the skull to the spinous process of C4. Dissection is carried down to the tips of the spinous processes. At this point, a metal hub needle is placed in the spinous process of C2 and a lateral radiograph is taken. This is done to positively identify the correct vertebrae for exposure. In the young child, exposure of the base of the skull or any additional vertebrae may result in “creeping fusion.”
FIGURE 21-28. In children, the spinous process of C2 is often small and does not provide much strength for fixation of the wire. The spinous process K-wire technique is an alternative technique (133). A threaded K wire of appropriate size is passed through a small stab wound on the side of the neck and through the paravertebral muscles and is drilled through the spinous process of C2. It is cut so that approximately 1 cm is protruding on each side.
neck (138, 156). Radiographs of the cervical spine should be obtained to rule out associated congenital anomalies. Plain radiographs of the cervical spine in children with muscular torticollis are always normal, aside from the head tilt and rotation. If any suspicion exists about the status of the hips, appropriate imaging (e.g., ultrasonography, radiography) should be done, depending on the age of the child and the expertise of the ultrasonographer.