Overview
The pediatric cervical spine is subject to a broad variety of disorders that may affect function and may occasionally necessitate treatment. An understanding of the developmental anatomy, normal cervical and cervicocranial relationships, and common manifestations of pathologic processes is essential to the evaluation and treatment of these disorders. Although conditions of the cervical spine in children are traditionally discussed according to the anatomic location (e.g., occipitocervical, atlantoaxial, or subaxial) and the type of problem (e.g., instability, synostosis, stenosis, aplasia, or hypoplasia), a classification based on the clinical presentation may be more useful for understanding and treating cervical spine lesions. Such a classification also directs the evaluation and treatment of these disorders. The clinical presentations of cervical spine abnormalities include deformity, pain, limited motion, and neurologic compromise. Thus a patient who presents with a deformity but without pain or neurologic compromise would be evaluated for one set of cervical abnormalities, a patient with painful deformity would be evaluated for other conditions, and a patient presenting without a deformity but with neurologic symptoms would be evaluated for yet another set of conditions. Such a clinically derived classification promotes a unified understanding of cervical spine abnormalities and their underlying pathologic mechanisms.
Developmental Anatomy
The precise genetic control of cranial and cervical development remains unknown. However, two families of regulatory genes (the Hox and Pax genes) have been implicated in the processes of embryonic axial differentiation. The Hox genes specify the phenotype of vertebral morphology along the embryonic axis as an early controlled event, whereas the Pax genes contribute to the early development of the nervous system and are thought to establish the intervertebral boundaries of the sclerotomes. Targeted disruption of Hox genes may result in lethal skeletal dysplasia. Reduced or absent Pax expression correlates with fusions between adjacent vertebral primordia.
The development of the cervical region follows a pattern of craniocaudal resegmentation in which the eight pairs of embryonic cervical somites divide into cranial and caudal segments. Next, these primitive mesenchymal segments separate, and each vertebral anlage is then formed by the caudal half-sclerotome of one somite and the cranial half of the next lower one. The embryologic development of the occipitocervical junction is complex, with contributions from the fourth occipital and first cervical sclerotomes. The cranial half of the first cervical sclerotome remains as a half-segment (proatlas) between the occiput and the atlas proper and eventually becomes part of the occipital condyles and the tip of the odontoid. The atlas receives contributions from the fourth occipital and first cervical somites (two posterior arches). The axis receives contributions from the primitive second cervical somite (posterior arches), the cranial half of the first (tip of the odontoid), and the primitive centrum of the second (atlas), which becomes the body of the odontoid. In light of the complex origin of the cartilaginous anlagen of the craniocervical junction as well as the cervical vertebrae, it is not difficult to understand how anomalous development in the form of failure of segmentation and partial absences can occur and can produce numerous variations of odontoid morphology and the various fusions seen in Klippel-Feil syndrome.
Atlas
The atlas ultimately comprises three ossification centers, one for each lateral mass and one for the body, which does not appear until 1 year of age. The posterior arches fuse by approximately 3 or 4 years of age, and the lateral masses fuse to the body at the neurocentral synchondroses at age 7 years ( Fig. 11-1 ). As a result the final internal diameter of the atlas is present by approximately age 7 years, whereas further growth of the external diameter of the atlas occurs through appositional bone deposition.
Axis
The axis ultimately comprises five primary ossification centers (body, two neural arches or lateral masses, and two halves of the dens; Fig. 11-2 ). Persistence of the two halves of the odontoid is known as a dens bicornis. The body, or centrum, is connected to the adjacent lateral masses by neurocentral synchondroses and to the dens by the dentocentral synchondrosis. The dentocentral synchondrosis closes in most children by the age of 6 years. The tip of the odontoid, which appears at 3 to 6 years, usually fuses with the remainder of the odontoid by age 12 years. Occasionally fusion may fail to occur, and the tip of the odontoid is referred to as an ossiculum terminale persistens. Although occasionally mistaken for an os odontoideum, this finding is considered a normal anatomic variant and is not associated with instability.
Subaxial Cervical Spine
Each segment from C3 to C7 is made up of a centrum (body) and two posterior arches that arise from mesenchymal tissue migrating around each side of the neural tube ( Fig. 11-3 ). Secondary ossification centers for the superior and inferior ring apophyses ossify during late childhood and fuse to the vertebral bodies by 25 years of age. Other ossification centers for the transverse and spinous processes generally fuse by 3 years of age.
Unique Characteristics
The cervical spine of children younger than 8 years of age has unique anatomic features that influence the mobility of the cervical vertebrae and may affect the assessment of spinal stability. The facet joints initially are relatively horizontal and, during growth, gradually become more vertical, which enhances stability in flexion and extension. The vertebral bodies initially have an oval or wedge shape but gradually become fully ossified in a more rectangular configuration. In addition, a generalized ligamentous laxity, present in early childhood, combines with the vertebral and facet shapes to allow for physiologic cervical spine subluxation, termed pseudosubluxation, which may be seen in up to 40% of children younger than 8 years of age ( Fig. 11-4 ). This phenomenon occurs most commonly between the second and third cervical vertebrae and between the third and fourth cervical vertebrae. One case report noted physiologic anterior subluxation of C5-6 and C6-7 in a 9-year-old child. The spinolaminar line of Swischuk is helpful to differentiate between pseudosubluxation and true subluxation. This line is drawn along the posterior arch from the first cervical vertebra to the third. It should pass within 1.5 mm of the anterior cortex of the posterior arch of the second cervical vertebra during forward flexion. As long as the Swischuk line is maintained, as much as 4 mm of vertebral body subluxation can be accepted.
Cervical Deformity: Torticollis
Torticollis (from the Latin meaning “twisted neck”) is a symptom of cervical spine abnormality. Its differential diagnosis may seem complicated at first glance, but it can be simplified by determining whether the deformity was present at birth (congenital) or was acquired and whether the deformity is painful or nonpainful ( Box 11-1 ).
Congenital—Nonpainful
Congenital muscular torticollis
Vertebral anomalies
Failure of segmentation
Klippel-Feil syndrome
Occipitalization of C1
Failure of formation
Congenital hemiatlas
Combined failure of segmentation and formation
Ocular torticollis
Acquired—Painful
Traumatic
Atlantoaxial rotatory displacement
Os odontoideum
C1 fracture
Inflammatory torticollis
Atlantoaxial rotatory displacement (Grisel syndrome)
Juvenile rheumatoid arthritis
Diskitis or osteomyelitis
Other infection in neck
Tumors
Eosinophilic granuloma
Osteoid osteoma or osteoblastoma
Calcified cervical disk
Sandifer syndrome
Acquired—Painful or Nonpainful
Paroxysmal torticollis of infancy
Tumors of the central nervous system
Posterior fossa
Cervical spinal cord
Acoustic neuroma
Syringomyelia
Hysterical torticollis
Oculogyric crisis (phenothiazine toxicity)
Associated with ligamentous laxity
Down syndrome
Spondyloepiphyseal dysplasia or mucopolysaccharidosis
Deformity Without Pain—Congenital Torticollis
Congenital Muscular Torticollis
The most common form of congenital painless torticollis is congenital muscular torticollis, or wry neck. The deformity is usually obvious at birth or shortly afterward. The child’s head is tilted toward the involved fibrotic sternocleidomastoid (SCM) muscle, and the chin is rotated toward the contralateral shoulder, thus producing the “cock robin” appearance ( Fig. 11-5, A ). The diagnosis is made on physical examination by detecting a mass or knot on the involved side of the neck in the body of the SCM muscle in the first 3 months of life ( Fig. 11-5, B ). The mass may regress after early infancy and be replaced by a readily palpable, fibrous contracted band that can be followed from its origin on the mastoid to the sternum and clavicular insertions. Although a mass may be undetected in as many as 80% of patients, the contracture is almost universally present after infancy.
The origin of congenital muscular torticollis remains unknown, but the condition likely results from local compartment syndrome or ischemia involving the neck that produces the fibrotic muscle. It is also almost certainly a “packing” problem, based on the high prevalence of breech positioning and primiparous birth order in this condition. It is hypothesized that the head becomes twisted and rotated in utero, and because of intrauterine crowding the position is maintained for a period of time before birth, with resulting ischemia, edema, and eventual fibrosis in the muscle. Evidence also indicates that progressive denervation of the muscle secondary to compression of the accessory nerve can exacerbate the fibrotic reaction. An increased incidence of congenital dislocation of the hip and of foot deformities (e.g., metatarsus adductus) in children affected by congenital muscular torticollis provides further support to the theory of intrauterine crowding as a cause of this condition. Although patients with torticollis may be at slightly greater risk for congenital dysplasia of the hip, we have not found anything more than routine neonatal examination and screening with ultrasonography to be appropriate. Prolonged observation for dysplasia in a child with torticollis does not appear warranted.
The clinical presentation varies from a simple head tilt with slight rotation and minimal restriction of motion to more severe plagiocephaly, which can be exacerbated by the positioning of the infant for sleep ( Fig. 11-5, C ). Flattening of the face on the ipsilateral side of the SCM lesion can be worsened by the prone position during sleep. The infant may also have a “bat” ear as a result of folding in utero. If infants are placed supine for sleeping, reverse modeling of the contralateral side of the skull can occur. Older children may be referred for scoliosis evaluation because of apparent elevation of the ipsilateral shoulder ( Fig. 11-6 ).
The differential diagnosis of congenital muscular torticollis includes congenital bony abnormalities producing the deformity. Therefore good-quality plain radiographs of the cervical spine are warranted if the typical SCM muscle contracture is absent. Because of difficulty in obtaining and interpreting such radiographs in a newborn or young infant, it is acceptable to forgo them if the clinical picture of an SCM mass and fibrosis is unmistakable, along with the plagiocephaly and other facial and ear abnormalities related to the packing problem. If, however, the deformity does not respond to the usual conservative measures, then radiographic evaluation is mandatory, along with ocular and central nervous system (CNS) evaluation.
Treatment
Nonsurgical.
Excellent results with massage and a stretching program can be achieved in approximately 90% of patients. This is the first treatment approach. At the time of diagnosis, the parents are instructed in the technique of stretching the contracted SCM muscle by rotating the infant’s chin to the ipsilateral shoulder and simultaneously tilting the head toward the contralateral shoulder. The exercises should be done gently but with the goal of attaining full passive range of motion—both rotation and tilting—as quickly as possible ( Fig. 11-7 ). Besides stretching, positioning toys and other maneuvers to solicit active rotation toward the involved side are important to actively overcome the fibrosis of the SCM muscle.
The plagiocephaly associated with congenital muscular torticollis garnered increased attention after the recommendations of the American Academy of Pediatrics in 1992 that infants be placed on their backs during sleep to reduce the risk of sudden infant death syndrome. Pressure exerted on the infant cranium in the supine position induces flattening of the parietooccipital region. This force is accentuated in congenital muscular torticollis because the infant consistently lies on one side, with a resulting compensatory anterior displacement of the ipsilateral ear and forehead. Natural history studies of the long-term consequences of such posterior positional plagiocephaly are sparse, but some investigators suggest that moderate to severe cases may result in facial asymmetry requiring maxillary osteotomies in adulthood. Two common forms of treatment for plagiocephaly include (1) repositioning of the neonate coupled with the organized stretching program for the torticollis and (2) external orthotic treatment with molding helmet therapy. Preliminary evidence suggests that infants with mild to moderate plagiocephaly may respond well to consistent repositioning and observation, whereas those infants who fail to respond to this form of treatment and who have moderate to severe deformity may be best treated with an orthotic helmet. However, controlled clinical trials are needed before any form of intervention can be verified as effective in the treatment of occipital plagiocephaly. Currently, this form of treatment is most commonly prescribed and monitored by craniofacial surgeons and neurosurgeons.
Surgical treatment of congenital muscular torticollis for infants and toddlers is rarely indicated. The natural history of the untreated deformity is benign; more than 90% of patients eventually develop an adequate range of motion and an adequate cosmetic appearance. Fewer than 10% of patients eventually require surgery. If a significant restriction of motion (lacking 30 degrees of full rotation or more) or facial asymmetry persists after the child achieves walking age, surgical intervention may be considered. However, surgical release has little advantage and much disadvantage in the young child, and we prefer to wait until just before school age before a decision on surgery is made.
The reasons for waiting are both technical and age related. Operative procedures include subcutaneous tenotomy, open tenotomy of the lower SCM insertions, bipolar tenotomy, and excision of part or all of the muscle. Although tenotomy or excision allows an immediate increase in head excursion, this procedure is more likely to lead to recurrent muscle contracture and a cosmetic deficit in the column of the neck resulting from the loss of muscle bulk. The earlier the surgical procedure is performed, the more technically difficult Z -plasty reconstruction will be because of the diminutive size of the structures.
The complications of surgery in infancy include scar formation, recurrent contracture with severe fibrosis, and, most important for this cosmetic deformity, unacceptable cosmetic appearance because of removal of the SCM column of the neck line, which produces an unsightly “hole” at the distal insertion in the sternum and clavicle, an outcome reported in 40% to 90% of patients. Because of the excellent results that can be obtained if surgery is delayed until the child is older, there is simply no urgency for surgery in infancy for congenital muscular torticollis.
Surgical.
Most authors favor surgery, when indicated, by 6 years of age. Others have extended this period upward to age 12 years and beyond. Functional outcome, as judged from range-of-motion evaluation, is not different for surgery performed between the ages of 1 and 6 years, and the disadvantages of early surgery (poor cosmesis, recurrence) decrease as the age of the child increases. Poorer results, primarily related to intractable facial asymmetry or some limitations of motion, are restricted to the most severe cases, although the benefits of later surgery in correcting head tilt and overall cosmesis are well established.
We prefer the bipolar lengthening technique of Ferkel and associates for patients needing surgery ( Video 11-1 ). 
The release of the SCM muscle includes careful reconstruction of the “column” of the SCM by either of the following procedures: (1) performing Z -plasty of the clavicular insertion and releasing the sternal insertion from bone; or (2) transecting the sternal portion of the muscle 1 to 2 cm proximal to its insertion, releasing the clavicular insertion from bone, and transferring the latter to the remaining distal sternal portion ( Fig. 11-8 ). Such a Z -plasty reconstruction is technically difficult to perform in the infant or toddler, and this explains why early release produces cosmetically unappealing results. Release at the mastoid process allows more vigorous and complete release of the patient’s head so that postoperative physical therapy can be more effective. The mastoid release should be performed at the bony insertion to avoid possible injury to the spinal accessory nerve. Skin incisions should never be placed over the clavicle because of unaesthetic scar spreading.
The results of surgical release in older children have also been satisfactory ( Fig. 11-9 ). There is therefore little to criticize in benign neglect of the young child, with surgical release, if indicated, performed sometime between 5 and 12 years of age.
Postoperative care of the patient who has undergone bipolar release includes reinstitution of stretching exercises as soon as pain has abated and the surgical incisions have adequately healed. Historically, postoperative treatment included the use of all types of braces and cast correction, but we have found that active range-of-motion exercises produce excellent results, and the use of postoperative immobilization is somewhat obsolete. Residual fascial bands can lead to recurrence of deformity. These bands are best avoided by delaying the surgical procedure until the recommended age of at least 5 years.
Klippel-Feil Syndrome
A second form of painless congenital torticollis is associated with congenital osseous fusions (synostosis) and failure of segmentation of the cervical spine. Such fusions can involve the craniocervical junction (occiput-C2), the subaxial cervical spine, or both, and they typically result in the appearance of a short, webbed neck combined with a low posterior hairline. An associated head tilt and loss of cervical motion complete the clinical triad commonly referred to as Klippel-Feil syndrome ( Fig. 11-10 ). In practice, the term is used to describe any failure of segmentation in the cervical spine. Some series report the full triad in only half the patients with the diagnosis. The loss of motion, particularly rotation, associated with torticollis brings attention to the abnormality.
Frequently the neck webbing appears to produce the head tilt or deformity, and, as such, the torticollis has the appearance of being secondary to the soft tissue abnormality, as opposed to the actual underlying cause, the skeletal abnormality. Simple failure of segmentation of the vertebral bodies or posterior elements may not produce true head tilt or rotation, but frequently an asymmetry of fusions or an additional congenital unilateral fusion in the subaxial or cervicothoracic area produces the torticollis. These fusions result from abnormal embryologic formation of the cervical vertebral mesenchymal anlagen. Not only does failure of normal segmentation of the cervical somites between the third and eighth weeks of gestation explain the cervical synostoses and anomalies, but also, because of the scapular differentiation from mesenchymal tissue at the C3-4 level that occurs simultaneously, Sprengel deformity, seen in up to 50% of patients with Klippel-Feil syndrome, is an expected anomaly accompanying the congenital fusions ( Fig. 11-11 ). The well-known omovertebral bone connecting the scapula and cervical spine in Sprengel deformity is further evidence of a failure of segmentation underlying the entire process. The cause of such failures of segmentation is believed to be either toxic or ischemic (anomalous vertebral artery development), and because of the timing in embryologic development, the extent of the embryologic insult is also believed to result in abnormalities of other organ systems.
As mentioned, other anomalies also appear, resulting from the global nature and timing of the postulated fetal insult. In children with Klippel-Feil syndrome, genitourinary anomalies are estimated to occur in 25% to 35%, congenital heart disease in 14% to 29%, deafness in 15% to 35%, and synkinesis or mirror movements in 15% to 20%. Various congenital limb deficiencies have been associated with Klippel-Feil syndrome, including longitudinal distal radial deficiencies and longitudinal combined humeroulnar deficiencies. The defect producing the combination of Klippel-Feil syndrome and upper limb deficiency is thought to occur between the fourth and fifth weeks of gestation and primarily to affect sclerotome 6.
Scoliosis, either congenital or idiopathic-like, occurs in 60% of patients with Klippel-Feil syndrome, and the congenital fusions involving the cervical and cervicothoracic junctions are most troublesome in producing this deformity. One study found that the severity of the scoliosis, which occurred in 70% of the patients in their series, could be correlated with the type of Klippel-Feil syndrome. Patients with type I (fusion of cervical and upper thoracic vertebrae) had a 31-degree Cobb angle, compared with patients with type II (isolated cervical spine fusions), who had only a 9-degree Cobb angle. Rib anomalies often accompany both congenital fusions and Sprengel deformity (see Fig. 11-11, A ). Syndromes producing all the aforementioned anomalies include the VACTERL ( v ertebral anomalies, a nal atresia, c ardiac defect, t racheo e sophageal fistula, r enal abnormalities, and l imb abnormalities) association, Goldenhar syndrome, and fetal alcohol syndrome.
Clinical Features
The newborn or young infant with the classic triad of a low hairline, webbed neck, and limited motion with or without torticollis presents no problem in diagnosis (see Fig. 11-10 ). Patients with less obvious signs of classic Klippel-Feil anomalies are usually diagnosed on the basis of the restricted motion associated with vertebral fusions. The finding of an abnormal head position, true torticollis, and restricted range of motion, without an obvious SCM contracture, should prompt radiograph evaluation of the cervical spine. Screening for other vertebral anomalies is appropriate if any cervical fusions are found.
Once vertebral fusions in the cervical spine are documented, a general pediatric evaluation should be undertaken to rule out congenital cardiac or other neurologic abnormalities. Renal ultrasonography is an appropriate screening test to diagnose genitourinary anomalies. Magnetic resonance imaging (MRI) of the cervical spinal cord and craniocervical junction is recommended whenever any orthopaedic procedure is contemplated, and it certainly is indicated for evaluation of symptoms related to spinal cord compression or stenosis or instability.
Patients with Klippel-Feil anomalies present at a young age for evaluation of deformity, which is managed in a fashion similar to that for congenital scoliosis. Because the cervical spine has no room for a compensatory curve to develop to keep the head upright and compensated, any progression of cervical scoliosis as the cause of a patient’s head tilt and torticollis must be aggressively treated to avoid head tilt that is not correctable or severe compensatory scoliosis that decompensates the trunk ( Fig. 11-12 ).
Patients with Klippel-Feil anomalies may also present at an older age with pain, radiculopathy, or myelopathy secondary either to spinal cord compression in a congenitally anomalous, narrow canal or to instability or hypermobility at unfused levels. Torticollis may or may not be present, or it may have been recently acquired at the time of symptom appearance when it was previously absent. Patients with extensive vertebral fusions, often extending up to C3, may also have occipitoatlantal fusion, producing hypermobility at an unfused C1-2 or C2-3 level (see Fig. 11-11 ). Any unfused segment adjacent to extensive synostosis may eventually become hypermobile, with or without neurologic symptoms. Thus an adolescent with mild nonprogressive deformity may develop symptomatic hypermobility after years of being asymptomatic, although hardly ever before 13 years of age. Degenerative changes at the hypermobile segments may produce just enough spinal cord or nerve root impingement in a young adult to produce radiculopathy and myelopathy. Degenerative stenosis without hypermobility may result in subaxial cervical segments when osteophytes and disk degeneration progress in adult life.
Depending on the site and type of stenosis (anterior or posterior) and anatomic level, motor and sensory deficits and reflex changes may occur, as well as paresthesias in the occiput, neck, and upper extremities. If the cerebellar tonsils are compressed or herniated (Arnold-Chiari malformation), neurologic findings, including ataxia, dizziness, and nystagmus, may occur. Cranial nerve changes from brainstem compression (difficulty swallowing, disturbed phonation) or hydrocephalus from obstruction of cerebrospinal fluid flow (blurred vision, headache) by invagination of the odontoid into the foramen magnum (basilar impression) can be observed. Less commonly, vertebral artery involvement can produce syncope, seizures, or ataxia because of brainstem ischemia. Any of these varied neurologic signs and symptoms must be investigated in a patient with known cervical anomalies.
Radiographic Findings
Imaging studies of the cervical spine, especially of the craniocervical junction, are crucial in the management of patients with Klippel-Feil anomalies. Besides defining the often bizarre, mixed anomalies, neuroradiologic evaluation is mandatory in patients who experience neurologic compromise. Positioning for imaging studies may be problematic because of the shortened neck and relative lack of motion. Overlapping shadows from the mandible and occiput can confound interpretation of plain radiographs. A lateral radiograph of the skull, rather than of the cervical spine itself, best demonstrates the presence of occipitocervical bony abnormalities by eliminating some of the obliquity and rotational overlapping seen with torticollis. If C1 has been assimilated into the occiput, the lateral skull film is helpful in determining whether C1-2 has any pathologic process. Once anomalous osseous structures are visualized on a screening radiograph, further studies by computed tomography (CT), with or without three-dimensional reconstruction, and MRI to evaluate the brainstem and cervical spinal cord are recommended.
Besides symptoms of instability, patients with Klippel-Feil anomalies and neurologic symptoms must also be evaluated for basilar impression. A good-quality lateral radiograph shows the upward migration of atlantoaxial structures, particularly the odontoid, into the foramen magnum, and knowledge of the traditional radiographic lines (Chamberlain, McRae, and McGregor) is useful in screening for the presence of basilar impression. The McGregor line, drawn from the upper surface of the posterior edge of the hard palate to the most caudal point of the occiput, is the best screening line because of the reproducibility and clarity of these radiographic landmarks ( Fig. 11-13 ). The McRae line defines the opening of the foramen magnum and truly defines basilar impression because the odontoid projects above this line in patients who are symptomatic. Modern imaging studies, such as CT with sagittal or three-dimensional reconstruction, show the osseous relationships more clearly. If any question of neural impingement exists, MRI is the more revealing study.
Equally important is the determination of impending stenosis or cord impingement by evaluating the space available for the cord (SAC) and its corollary measurement at C1-2, the atlantodens interval (ADI) ( Fig. 11-14 ; also see Fig. 11-11 ). These intervals are usually determined on lateral flexion-extension radiographs, generally obtained with the patient awake and voluntarily flexing the head. The SAC is measured as the distance between the posterior edge of the dens and the anterior edge of the posterior ring of the atlas or the foramen magnum. An SAC of 13 mm or less is associated with neurologic compromise. In patients with hypermobility, as suggested by an ADI of more than 4.5 mm between flexion and extension, measurement of the SAC gives a reasonable evaluation of how tenuous the neurologic situation may be. Up to 4.5 mm of motion at the ADI is considered normal in children younger than 8 years of age, whereas older children and adolescents should have an ADI of less than 2 mm.
Normal range of motion at the atlantooccipital joint has not been defined. The occiput-C1 articulations are primarily saddle-shaped, elliptic surfaces that allow flexion and extension but little rotation or lateral flexion. Instability of this joint, which is much less common than instability of C1-2, is not well described. According to Tredwell and colleagues, posterior subluxation of the atlantooccipital joint in extension of more than 4 mm suggests instability. This can be measured from the excursion of the basion or occipital condyles in relation to a fixed point, usually the posterior edge of the anterior ring of C1 during flexion and extension ( Fig. 11-15 ). The Power ratio identifies anterior occiput-C1 instability, but because most instabilities are more obvious in extension, this ratio may not be as useful. Normal occiput-C1 translation should be no more than 1 mm in adults, and thus the importance of measuring the SAC on either plain radiographs or flexion-extension CT or MRI scans may be more critical at the atlantooccipital joint.
Treatment
Treatment of Klippel-Feil syndrome and other synostotic anomalies must take into consideration both the deformity and any existing or potential neurologic deficit. Management of the deformity is considerably simplified if no neurologic deficit is present. The treatment of occipitocervical junctional abnormalities in the presence of neurologic deficit is fraught with the potential for significant morbidity and even mortality because of the proximity of the cervical spinal cord and brainstem. In such a situation, the combined efforts of both orthopaedists and neurosurgeons may be required.
Halo Fixation.
Deformity management involving head tilt or rotation frequently requires the use of a halo to obtain and maintain correction. The halo is the one device that allows simultaneous correction and repositioning of the skull and upper cervical spine and then provides the external immobilization necessary to protect a decompression and achieve spinal fusion. The device also has the advantage of avoiding skin complications around the mandible or occiput, the bane of most occipital-mandibular devices (e.g., Minerva brace or four-poster brace) when applied to children (see Fig. 11-10 ). Access to cervical incisions and freedom of the mandible for eating are important advantages of the halo, and because a halo ring and vest usually do not need to be removed or adjusted once applied, early mobilization of the patient is improved.
Reluctance to use halo fixation in young children stems from fear that the pins could penetrate the cranial vault and result in epidural abscess or osteomyelitis. In fact, pin loosening is a far more common problem. Because of variation in skull thickness and suture formation, CT of the skull has been recommended, but in practice we have not found that CT findings significantly alter intended pin placement. For immobilization of young children, halo pins are placed in safe areas of the skull that are considered to have appropriate bone stock. These sites include the frontal areas approximately 0.5 to 1 cm above the supraorbital rim. Care must be taken to avoid the thin temporal bone and the supraorbital rim that borders this safe area laterally and medially, respectively. Posterior pin placement is directed at the parietooccipital region below the equator of the skull to avoid superior dislodgment of the halo. Decreased insertional torque is used, depending on the child’s age, with a general rule of 1 lb of torque per year of age up to age 6 years, whereas in children older than 10 years of age it is reasonable to follow adult halo guidelines, by using four halo pins with an application torque of 6 to 8 in-lb. Halo wrench accuracy and reliability have been shown to vary significantly among wrenches that have settings that allow the low application torques of 1 to 6 in-lb used in small children. Osteology studies have shown variable skull thickness in the safe areas up to 10 years of age, with thicknesses as little as 2 mm being identified. To accommodate for this variation, multiple pin constructs are used to achieve enhanced pin-skull fixation without excessive force of insertion. We use every possible hole in the halo ring so that a maximum number of pins is placed, with the goal of at least six pins used in patients younger than 6 years of age. Placing pins as perpendicular to the skull as possible also increases pin stability. With such a regimen, pin loosening and infection are manageable, with minimal morbidity.
The major contraindication to the use of halo fixation in infants and young children is the presence of abnormally wide sutures or fontanelles, which allow the bones of the skull to move away from the tips of the pins during insertion and result in loss of fixation. The presence of a significant metabolic bone disease, such as renal osteodystrophy or osteogenesis imperfecta, is a relative contraindication to use of the halo device. A basilar impression may be secondary to the pathologic bone. Longitudinal traction with the halo device in an attempt to reduce such a basilar impression may not be possible in children with porotic or dysplastic skulls.
Surgical Treatment
Indications.
One indication for surgical treatment in patients with Klippel-Feil syndrome or other cervical anomalies is progression of head tilt or rotation that is not passively correctable by positioning. If the anomalies producing deformity (hemivertebra, unsegmented bar) are in the subaxial cervical spine or cervicothoracic junction, the patient will develop head tilt toward the concavity of the deformity that results from an insufficient number of cervical vertebrae cephalic to the deformity to develop a compensatory curve (see Fig. 11-12 ). Increasing rigidity and inability to correct the head tilt are crucial indications of the need for surgical treatment. The fusion should include all vertebrae involved in the primary curvature. The halo is used to maintain the correction of the head tilt during healing of the fusion. Depending on the patient’s age, both anterior and posterior fusion procedures (the former to eliminate a possible crankshaft phenomenon) may be necessary to eliminate further growth of the anomalous vertebra. Because fusion to halt progression is almost always undertaken in young children in whom a fixed deformity is developing, anteroposterior arthrodesis is indicated in most instances.
In the case of torticollis produced by upper cervical anomalies, posterior fusion alone, in association with halo correction of the deformity, is usually sufficient. In congenital unilateral absence of C1 (hemiatlas), the deformity is present at birth and often progresses, and posterior fusion from the occiput to C2 is recommended between 5 and 8 years of age. Because of the limited amount of growth of the upper cervical vertebrae, recurrence caused by the crankshaft phenomenon does not appear possible.
In patients with congenital occipitocervical fusion (synostosis), deformity (head tilt, torticollis) may be the only sign of neurologic compromise secondary to irritation of neural tissue, usually from either C1-2 instability or basilar impression. The atlantooccipital assimilation may be a relatively isolated finding (see Fig. 11-15 ), or it may be part of a wide spectrum of congenital synostoses in a patient with obvious Klippel-Feil anomalies. In other situations, neck pain and frank neurologic deficit may develop as a result of encroachment of the odontoid into the foramen magnum or instability at the C1-2 articulation (see Fig. 11-11 ). Arnold-Chiari type I malformation is also associated.
Treatment for neurologic compromise, either irritative (pain, deformity) or a frank deficit, invariably involves extension of the atlantooccipital fusion to include the axis or perhaps C3, depending on whether the decompression is necessary. Transoral resection of the odontoid is the logical choice for anterior cord or brainstem impingement, whereas posterior craniectomy or C1 laminectomy is logical for posterior compression associated with anterior C1-2 instability.
Techniques for Upper Cervical Fusion.
Because of cervical spine and craniofacial abnormalities, airway management may be difficult in patients with Klippel-Feil syndrome. According to a report by Stallmer and associates of 11 cervical spine fusions in 10 patients with Klippel-Feil syndrome, however, 5 of 6 tracheal intubations were easily achieved, and 4 laryngeal mask airways (Orthovent Intafix, Maidenhead, UK) were placed without difficulty. Only one patient had a “difficult” intubation. The investigators concluded that difficult airway management may not be as common in patients with Klippel-Feil syndrome as previously thought, but careful preoperative evaluation still is necessary, including preoperative imaging and a comprehensive airway examination to determine the potential for difficulty or risk of neurologic injury.
As delineated in the previous sections, occipitocervical arthrodesis is required to correct deformity or instability involving the craniocervical junction. Because of the significant forces producing movement between the skull and the cervical spine, fixation of an upper cervical–to-occiput fusion is crucial to achieve arthrodesis. Immobilization with a halo device is strongly recommended, but additional internal fixation and specific bone grafting techniques are important to achieve the highest rate of fusion. Burr holes can be placed near the foramen magnum so that wire or heavy suture (in the case of young infants or children) can be passed either from burr hole to burr hole or from the burr hole through the foramen magnum and then fixed distally to the desired cervical level. Equally important is the creation of a shaped corticocancellous bone graft, either a one-piece or bilateral graft, that can be compressed against decorticated occipital bone and the cervical laminae ( Fig. 11-16 ). This graft is preferentially obtained from the posterior iliac crest. Alternatively, ribs can be harvested in young children. The graft is shaped to lie against the decorticated occipital surface, and in the case of suboccipital craniectomy for decompression, it may be more convenient to cut the graft into two separate rectangular pieces to be placed on each side of the foramen magnum. The graft is fixed to the occipital bone by tightening wires over it, or a small hole may be placed in the graft so that wire or suture exiting a burr hole can be placed through the graft for fixation (see Fig. 11-16 ). Caudally, the graft is compressed to the cervical laminae, either by using a sublaminar wire passed through the small holes in the graft and tightening against the lamina or by using a wire or suture fixed to the base of the spinous process or to a threaded Kirschner wire ( K -wire) through the base of the spinous process (Dewar technique; see Fig. 11-16, C and D ). Such an approach has resulted in a high rate of fusion.
For atlantoaxial arthrodesis in children with C1-2 instability, standard techniques such as those of Gallie, Brooks, and Magerl ( Fig. 11-17 ) can be used, depending on the experience of the surgeon and the bony anatomy available. Transarticular screw fixation is biomechanically the stiffest of these methods and is recommended whenever possible because of its enhanced stability in the setting of C1-2 instability. Gulf and Brockmeyer reported placement of 127 C1-2 transarticular screws in 67 patients ranging in age from 18 months to 16 years. Fusion was successful in all patients, with no screw backout or breakage. Two patients had vertebral artery injuries during screw placement, but neither had permanent neurologic deficits. Multiplanar CT reconstructions were used to determine the best path for screw placement in all patients.
For patients with incomplete posterior elements who are too small for transarticular screws, suggested alternatives include constructs using C1 lateral mass screws, C2 pars screws, and/or C2 laminar screws. An analysis of 23 cervical CT scans of healthy children determined that the C2 laminae were more likely to be suitable for placement of a 3.5-mm screw (65%) than were C2 pedicles (24%); 80% of C2 laminae were suitable for 3.0-mm screw placement compared with 41% of C2 pedicles, and 95% of C1 lateral masses were deemed suitable for 3.5-mm screw placement.
As another alternative, arthrodesis in situ with halo immobilization may be appropriate. Alternatively, in patients with incomplete or cartilaginous posterior spinous processes, the Dewar technique, using a K-wire across the posterior laminae above the dura, is an excellent method for anchoring wire or suture that cannot be passed beneath the lamina (see Fig. 11-16, D ). In patients younger than 9 years of age who are undergoing any posterior cervical fusion, this technique has been recommended to avoid pulling of wire through a possible cartilaginous spinous process.
Deformity With Pain
Acquired Torticollis
Atlantoaxial Rotatory Displacement
The most common condition associated with acquired painful torticollis is atlantoaxial rotatory displacement (AARD). Because of the relative frequency of upper respiratory infections, inflamed adenoids, and other oropharyngeal sources of invasive bacterial infection and the association of such sources of inflammation with Grisel syndrome, children frequently present with an acquired torticollis that, when manipulated to correct the deformity, elicits significant pain and resistance. The pathophysiology of spontaneous atlantoaxial displacement is probably inflammation of adjacent neck tissues resulting from a direct connection between the periodontoidal venous plexus and the pharyngovertebral veins of the posterosuperior pharynx. This connection provides a route for hematogenous transport of bacteria to the upper cervical spine region and leads to inflammatory hyperemia, which then produces ligamentous laxity at the atlantoaxial articulation. The venous anatomy described by Parke and colleagues offers an explanation for the occurrence of AARD after upper respiratory infection, ear-nose-throat procedures, and other forms of oropharyngeal surgery. The rotatory laxity at C1-2 can then progress to a fixed position or torticollis.
A traumatic origin of AARD has also been proposed. Meniscal-like folds of synovium in the atlantooccipital and atlantoaxial joints, which can then be infolded during a sudden rotatory displacement (trauma), may actually prevent relocation of the atlantoaxial joints.
Fixed dislocation of the atlantoaxial joint (and thus rigid torticollis) is seen in only a small percentage of rotatory displacements. The milder forms of rotatory displacement probably resolve spontaneously without coming to medical attention because the rotated displacement spontaneously reduces when the inflammatory process recedes. Fixed displacement is characterized by rigid torticollis, with the SCM muscle on the contralateral side, away from the head tilt, in spasm and prominent, as if the muscle were trying to correct the deformity ( Fig. 11-18 ). This is in contrast to the physical findings in congenital muscular torticollis. Besides the “cock robin” tilt of the head and the finding of a prominent, contracted SCM muscle on the long side of the deformity, range of motion is markedly decreased, and the patient may experience pain at rest as well as increased pain with head manipulation. Plagiocephaly is usually not present unless the deformity has persisted for years. In posttraumatic cases, the inciting incident is often subtle and unknown to the parents and in fact may never be identified.
Radiographic Finding.
As with any torticollis, radiographs of the cervical spine and occipitocervical junction are often difficult to interpret. Malalignment of the head, along with the inability to position the patient comfortably, makes it difficult to assess this area adequately and thus delays the diagnosis. Anteroposterior or open-mouth views of C1-2 are not useful because it is impossible to differentiate the apparent facet subluxation seen in a normal child whose head is rotated from fixed subluxation produced by AARD. The head tilt produces distortion of the normal appearance of the C1-2 joint on a routine lateral radiograph, and thus a true lateral view of the skull is recommended. It is believed that the ring of C1 moves with the occiput. Consequently, tilting of the head tilts C1, and a true lateral view of C1 is seen on a true lateral view of the skull. Such a radiograph usually demonstrates an increased ADI resulting from the rotatory displacement (see Fig. 11-18, D ) and thus gives the best plain radiographic evidence of AARD.
Cineradiography was used in the past to demonstrate the rotatory fixation, but this older technique was superseded by CT. The diagnosis of rotatory fixation rests on the demonstration of a fixed rotation between C1 and C2 when the head is rotated maximally to the right and to the left and shows no motion or reduction of the rotatory displacement. Although this form of dynamic CT is helpful, in practice it may be difficult to obtain because of the relative discomfort and limited neck mobility of the patient. Under these circumstances a static CT scan is carefully analyzed for the relationship between C1 and C2. Investigators suggested that it is probably not necessary to obtain CT scans (static or dynamic) in patients with acute torticollis at the time of initial presentation. In a series of 33 consecutive pediatric patients, the investigators were unable to demonstrate AARD or atlantoaxial rotary fixation initially, a finding suggesting that the phenomenon may not be present in this subset of patients and may be identified only in the more chronic setting.
Rotatory displacement has been classified into four types : type 1, a simple rotatory displacement without anterior shifting of C1; type 2, rotatory displacement and an anterior shift of 5 mm or less; type 3, rotatory displacement with an anterior shift of more than 5 mm; and type 4, rotatory displacement with a posterior shift. Anterior displacement of more than 3 mm in older children and more than 4 mm in younger children is considered pathologic. Such displacement can usually be discerned on the true lateral view of the skull, but it is definitively seen on CT. Type 1 is by far the most frequent in the pediatric age group and is the most benign form, often resolving by spontaneous relocation of the facet joints. Types 2 and 3 ( Fig. 11-19, C ), in which some anterior shift is present, are the more severe, fixed rotatory displacements; because of the decreased SAC, these displacements raise the potential for neurologic compromise, which fortunately is rare in this condition, presumably because of the normally large diameter of the cervical spinal canal.
