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Congenital Spinal Deformity

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					Congenital Spinal Deformity
Synonyms and related keywords: hyperlordosis, lordosis, kyphosis,
scoliosis, congenital scoliosis, sacral agenesis, lumbosacral agenesis, cervical
spine anomalies, basilar impression, invagination, occipitalization of the atlas,
assimilation of the atlas into the occipital bone, occipitocervical synostosis,
odontoid anomalies, Klippel-Feil syndrome, Trisomy 21 syndrome, Down
syndrome, deletion 5p syndrome, chromosomal number 5 syndrome, Kabuki
syndrome, Noonan syndrome, Turnerlike syndrome, Aarskog syndrome,
cervico-oculo-acoustic syndrome, Wildervanck syndrome, MURCS association,
VACTERL association, Jarcho-Levin syndrome, spondylothoracic dysplasia,
proteus syndrome

AUTHOR INFORMATION

Author: Robert Mervyn Letts, MD, FRCSC, FACSC, Chief, Department of
Surgery, Division of Pediatric Orthopedics, Children's Hospital of Eastern
Ontario, University of Ottawa

Coauthor(s): Ayman Hussein Jawadi, MBBS, Pediatric Orthopedic
Consultant, Department of Surgery, King Fahad National Guard Hospital

Editor(s): Mininder S Kocher, MD, MPH, Assistant Professor of Orthopedic
Surgery, Harvard Medical School, Director, Orthopedic Institute for Clinical
Effectiveness, Children's Hospital of Boston; Consulting Surgeon, Department
of Orthopedic Surgery, New England Baptist Hospital; Francisco Talavera,
PharmD, PhD, Senior Pharmacy Editor, eMedicine; George H Thompson,
MD, Professor of Orthopedic Surgery and Pediatrics, Case Western Reserve
University; Director, Department of Pediatric Orthopedic Surgery, Rainbow
Babies and Children's Hospital; Dinesh Patel, MD, FACS, Associate Clinical
Professor of Orthopedic Surgery, Harvard Medical School; Chief of
Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts
General Hospital; and Dennis P Grogan, MD, Clinical Professor, Department
of Orthopedic Surgery, University of South Florida College of Medicine; Chief
of Staff, Department of Orthopedic Surgery, Shriners Hospital for Children of
Tampa

INTRODUCTION

Congenital deformities of the spine are caused by anomalous vertebral
development in the embryo. Minor malformations of the spine are seldom
apparent and often are identified only on routine chest films (see Image 1).
More severe congenital malformations resulting in progressive scoliosis are
even less common than are idiopathic scolioses (see Image 2). Congenital
anomalies of the spine may be simple and benign, causing no spinal deformity,
or they may be complex, causing severe spinal deformity or even cor
pulmonale or paraplegia.

The 3 major patterns of congenital spinal deformity are hyperlordosis (see
Image 3), kyphosis (see Image 4), and scoliosis (see Image 2). Congenital
scoliosis may have marked rotation (kyphoscoliosis) or true kyphoscoliosis in
which rotation is not a major component of the deformity.

For excellent patient education resources, visit eMedicine's Bone Health
Center and Back, Ribs, Neck, and Head Center. Also, see eMedicine's patient
education article Scoliosis.

Development of the spine

Molecular and cellular tissue interaction and increasing organ complexity
characterize the fundamental features of the embryonic developmental
process during axial embryogenesis. Alteration in the molecular and
macromolecular process may lead to structural defects involving the spine and
spinal cord. Such defects may occur prenatally, postnatally, or both. These
may be divided into 3 categories from the standpoint of basic developmental
pathogenesis: malformation, disruption, and deformation.

Malformation is a failure of embryological differentiation, development, or both
of a specific anatomic structure, causing it to be absent or improperly formed
before the fetal period commences. An example is the formation of
hemivertebra. Once it is anatomically established, the defect may continue to
adversely affect spinal development throughout the subsequent fetal and
postnatal periods. The eventual type of malformation and its severity depend
on the stage of the developmental or maturation cycle that is specifically
affected.

Disruption is a structural defect resulting from destruction of a part that formed
normally during the embryonic period. This mechanism involves the limbs
(amniotic band syndrome) more frequently than the spine during the fetal
stage.

Deformation is an alteration in the shape or structure of an individual vertebra
or of the entire spine during the fetal and/or postnatal periods, with the involved
region having initially differentiated normally (eg, infantile or adolescent
scoliosis). This is not a true congenital scoliosis. Deformation may be divided
into those that are intrinsically derived and those that are extrinsically derived.
Intrinsic deformation results from the reduced ability of the fetus or child to
move away from normal imposed forces and depends on the integrity of the
neuromuscular system to respond effectively. Extrinsic prenatal deformations
are the result of reduction in the amount of space in which a developing fetus
may move. Such reduction may be either physiologic or pathologic.

Physiologic structural deformations usually are limited and relatively reversible
once the constraining influences are removed. In contrast, pathologic
structural deformation is a more permanent process. Late gestational
deformations have an excellent prognosis. Approximately 90% of such
deformations noted at birth correct spontaneously. The earlier a deformation is
recognized, the greater the likelihood of correcting it or at least preventing
further deformation (eg, with early bracing for idiopathic scoliosis).

Embryogenesis

Gestation has been divided into the embryonic period and the fetal period. The
embryonic period is considered to be the time from fertilization to the end of
the eighth week of gestation. The reminder of gestation is called the fetal
period. The 5 major stages of embryonic development are fertilization,
cleavage, gastrulation, neurulation, and organogenesis. By the end of the
embryonic period, all of the major organ systems have been established, and
the basic body plan is complete.

Stages of embryonic development can be summarized as follows:

   •   Fertilization: Female and male gametes combine to form a zygote.



   •   Cleavage: The zygote divides into a ball of smaller cells, each receiving
       different parts of the maternal cytoplasm.



   •   Gastrulation: The cells migrate and proliferate to form the 3 primary
       germ layers, namely, the ectoderm, the mesoderm, and the endoderm.



   •   Neurulation: The notochord, the neural crest, and the precursors of the
       central and peripheral nervous system form.



   •   Organogenesis: Primary cell types differentiate to generate the organs.

The spine has its embryologic origins in the cell that is induced to migrate out
of the somite and toward the notochord and the neural tube (see Image 5). As
a mass of sclerotomal cells collects segmentally at the embryonic midline,
surrounding the neural tube and the notochord, the sclerodermal cells begin to
separate into a cranial portion and a caudal portion. The cranial portion of each
sclerotome recombines with the caudal portion of the directly superior
sclerotome in a resegmentation process known as metameric shift. After the
metameric shift, spinal nerves, which originally left the neural tube to go to the
center of the sclerotome, are able to pass between the precartilaginous
vertebral bodies to innervate the segmentation myotomes (see Image 6).

The atlas and axis form by a mechanism that is different from that of the other
vertebral bodies. Part of the first cervical sclerotome plus the cranial portion of
the second cervical sclerotome contribute cells, forming both the odontoid
process and the arch of the atlas. In the cervical region, the 8 cervical somites
generate 7 cervical vertebrae because the cranial portion of the first cervical
sclerotome contributes to the formation of the occiput, and the caudal portion
of the eighth cervical sclerotome contributes to T1. In this way, the 8 cervical
spinal nerves become associated with 7 cervical vertebrae (see Image 7). The
first cervical spinal nerve passes between the base of the skull and the first
cervical vertebra. The eighth cervical nerve exits below the seventh cervical
vertebra and above the first thoracic vertebra. The reminder of the nerve roots
exit below their corresponding vertebral bodies.

The intervertebral disks form in the area between the resegmented vertebral
bodies after the split of the sclerotomes. The nucleus pulposus originates from
cells of the notochord, whereas the annulus fibrosis originates from the
sclerotomal cell.

During the same time that the sclerotomes are undergoing shift to form the
vertebral bodies, the heart, kidneys, trachea, and esophagus are differentiating
so that a noxious influence during this time can affect all adjacent organs
developing at the same time. Hence, cardiac anomalies are often associated
with congenital scoliosis of the thoracic spine and renal anomalies are often
associated with congenital malformation of the lumbar spine. VACTERL
syndrome (ie, abnormalities of vertebrae, anus, cardiovascular tree, trachea,
esophagus, renal system, and limb buds) is the extreme example of
association of malformation in the embryonic stage.

Genetics

A family history of congenital spinal deformity is rare. Winter et al (1983) found
that only 13 of 1250 patients had a positive family history. Studies of twins
usually have shown that if one twin has an anomaly, the other does not, even if
the twins are identical. However, several investigators have described
hereditary congenital scoliosis. Most of the patients in those reports had
extensive defects of segmentation in association with spondylocostal,
costovertebral, or spondylothoracic dysplasia (Jarcho-Levin syndrome). In
addition to the defects of segmentation in the spine, such defects often occur
in the ribs, leading to a small stiff thorax and frequently to pulmonary
compromise. Such defects also may extend into the cervical spine as a
Klippel-Feil anomaly.

CONGENITAL SCOLIOSIS

Congenital scoliosis is a lateral curvature of the spine caused by congenital
anomalies of vertebral development. The vertebral abnormalities are present
at birth, but clinical deformity may not be evident until later in childhood, when
progressive scoliosis is evident. This type of scoliosis must not be confused
with infantile idiopathic scoliosis, which also can present as a deformity in early
childhood. However, the spinal radiograph shows that there are no vertebral
anomalies in the infantile form of idiopathic scoliosis. The male-to-female ratio
for congenital scoliosis is 1:1.4.

Classification, natural history, and prognosis

Congenital spine deformity is classified according to the types of anomalies.
The classification of MacEwen, advocated by the Scoliosis Research Society,
has been well accepted.

   •   Failure of formation (see Image 8)



          o   Partial failure of formation (wedge vertebra)



          o   Complete failure of formation (hemivertebra)



   •   Failure of segmentation (see Image 9)



          o   Unilateral failure of segmentation (unilateral unsegmented bar)



          o   Bilateral failure of segmentation (block vertebra)
   •   Mixed (see Image 10)



          o   Elements of both failure of formation and failure of segmentation

Defects of formation may be classified as follows:

   •   Anterior formation failure results in kyphosis, which is sharply angulated
       (see Image 4).



   •   Posterior formation failures are rare but can produce a lordotic curve.



   •   Lateral formation failure occurs frequently and produces the classic
       hemivertebrae of congenital scoliosis.

The scoliosis that develops may occur with kyphosis or lordosis, depending on
the precise location of the defects. Specific defects of segmentation may be
classified as follows:

   •   Anterior segmentation failure (anterior unsegmented bar) leads to
       progressive kyphosis owing to the absence of anterior vertebral growth
       (see Image 11).



   •   Posterior segmentation failure, if symmetrical, results in lordotic
       deformities.



   •   Lateral segmentation failure (unilateral unsegmented bar) often
       produces some of the worst and most unrelenting scoliotic curves (see
       Image 12).



   •   Total segmentation failure produces block vertebrae, which results in
       shortening of the spine.
   •   Posterolateral and anterolateral segmentation failures are rare but
       produce lordoscoliosis and kyphoscoliosis, respectively, when they do
       occur.

Variations of hemivertebrae are common, and prognosis depends on specific
patterns. Hemivertebrae also may be subclassified as incarcerated,
nonincarcerated, segmented, or nonsegmented (see Image 13). Incarcerated
hemivertebrae usually do not produce abnormal alignment because the
vertebral bodies above and below the abnormal segment are shaped so as to
accommodate the hemivertebrae. Nonincarcerated hemivertebrae lie at the
apex of a scoliosis, the curve magnitude depending on the size of the wedged
segment. A segmented or free hemivertebra has normal disks above and
below the defective body and is more likely to result in progressive curvatures
due to unbalanced growth from the wedge-oriented endplates. Nonsegmented
hemivertebrae lack disk spaces between the wedged and normal adjacent
vertebral bodies. Semisegmented hemivertebrae have a normal disk space on
one side and are nonsegmented at the opposite end.

Knowledge of the natural history of these congenital deformities is essential
because the natural history dictates the prognosis and treatment. The natural
history of congenital scoliosis has been described in several excellent studies.
The large study of McMaster and Ohtsuka of 202 patients is the best in this
regard. They found that only 11% of cases were nonprogressive, whereas
14% were slightly progressive, and the remaining 75% progressed significantly.
The prognosis for congenital scoliosis with regard to its rate of deterioration
and final severity depends on many factors, as follows:

   •   Type of vertebral anomaly: The type of anomaly that causes the most
       severe scoliosis is a unilateral unsegmented bar with contralateral
       hemivertebrae at the same level. Next in severity is a scoliosis caused
       by a unilateral unsegmented bar alone, followed by 2 unilateral fully
       segmented hemivertebrae, a single fully segmented hemivertebrae, and
       a wedge vertebra. The least severe scoliosis is caused by a block
       vertebra. Congenital scoliosis caused by unclassifiable anomalies can
       be difficult to predict and requires careful monitoring. The poor
       prognosis is associated with a unilateral unsegmented bar with or
       without contralateral hemivertebrae, which should be treated
       immediately without waiting for a period of observation (see Table
       below).

       Vertebral Anomalies Leading to Congenital Scoliosis


       Risk of Progression (Highest
                                                Curve Progression
                to Lowest)
       Unilateral unsegmented bar
                                          Rapid and relentless
       with contralateral hemivertebra

       Unilateral unsegmented bar         Rapid

       Fully segmented hemivertebra       Steady

       Partial segmented
                                          Less rapid
       hemivertebra

       Incarcerated hemivertebra          May slowly progress

       Nonsegmented hemivertebra          Little progression




   •   Site of the anomaly: The rate of deterioration of the resulting scoliosis is
       most severe in the thoracic and thoracolumbar regions and usually is
       less severe in the cervicothoracic and lumbar regions. On the other
       hand, a mild cervicothoracic curve may produce an unsightly
       appearance due to the head and neck tilt and elevation of the shoulder
       line. Lumbar curves do not cause much cosmetic deformity unless
       decompensation or pelvic obliquity occurs.



   •   Age of the patient at the time of diagnosis: Congenital scoliosis, like
       idiopathic scoliosis, tends to progress most rapidly during the
       preadolescent growth spurt, after age 10 years. Scoliosis presenting as
       a clinical deformity in the first few years of life has a particularly bad
       prognosis because this indicates a marked growth imbalance that will
       continue throughout the period of growth, resulting in severe deformity.



   •   Balance and pattern of the curve: In general, multiple balanced
       anomalies throughout the spine do not progress, and the cosmetic
       appearance is satisfactory. The more unbalanced the anomalies, the
       more likely the scoliosis is to progress.

Patient evaluation

Due to the very high frequency of associated anomalies both within and
outside of the spine, the evaluation of the patient who has a congenital spinal
deformity is very different from that of the patient who has the more common
idiopathic or neuromuscular spinal deformities. Letts and Bobechko (1974)
found that 82% of patients with congenital scoliosis had associated
malformation in 4 different organ systems. Beals and colleagues (1993) found
that 61% of patients with congenital scoliosis had abnormalities in 7 different
organ systems. Highest on the list were anomalies of the genitourinary tract.

Studies of patients with congenital scoliosis by MacEwen et al revealed a 20%
incidence of urinary tract anomalies detected on routine intravenous
pyelography, whereas the study by Hensinger et al on cervical spine
anomalies found a higher rate of 33%. Many of these were conditions such as
single kidneys, duplicate ureters, and crossed renal ectopia—conditions of
interest but not of potential danger to the child. However, in about 5% of the
patients, obstructive uropathy, most commonly urethrovesicular obstruction,
was present. Renal ultrasonography and MRI scan be used to accurately
diagnose renal anomalies.

A second area of great concern is cardiac anomalies. As many as 10-15% of
patients with congenital scoliosis have been noted to have congenital heart
defects. Murmurs should never be attributed to the scoliosis and must be
thoroughly evaluated.

Frequency of spinal dysraphism is high in patients with congenital scoliosis.
The prevalence of a dysraphic lesion was approximately 40% in 3 independent
studies. McMaster reported that about 20% of these patients with congenital
scoliosis had some form of dysraphism, such as diastematomyelia, tethered
spinal cord, fibrous dural band, syringomyelia, or intradural lipoma. Many other
anomalies can occur in addition to the above problems, such as Sprengel
deformity, Klippel-Feil deformity, Goldenhar syndrome (oculoauriculovertebral
dysplasia), and anal atresia.

Clinical evaluation

Taking a full detailed history and performing a full physical examination are
mandatory because associated anomalies of many organs are common.
Maternal perinatal history, family history, and developmental milestones must
be fully explored. A comprehensive review of systems includes evaluation for
hearing, visual, and dental problems; cleft palate and cleft lip; hernias,
anorectal abnormalities, and genitourinary problems; cardiac murmurs;
respiratory complaints; and neurologic disorders.

In the physical examination, the physician must not only explore the spinal
deformity but also focus particular attention on chest deformities and
cutaneous lesions (especially dimples and hair patches overlying the spine). A
detailed neurological examination should be performed. The genitalia should
be examined for maturity, epispadias, hypospadias, and the presence of
undescended testicles. The hand must be examined for clubhand, thenar
hypoplasia, or other more subtle anomalies. The feet must be studied for
clubfeet, cavus or varus deformities, vertical tali, clawing of the toes, or other
signs of motor weakness.

The spine is best examined with the patient fully disrobed and erect. Skin
dimples and hair patches should be documented. Shoulder and pelvic
levelness are assessed, and asymmetry and prominence of the scapulae are
noted. With the patient forward-flexed, rotational deformity is recorded as
centimeters of rib hump, and any lack of spinal motion is documented.

Radiographic evaluation

An accurate radiological evaluation is essential. Standard posteroanterior (PA)
and lateral views of the entire spine are used for the initial evaluation. Standing
films are customary, as they show the characteristics of the curve under
gravity with its compensation and torso-pelvic relationships. Supine
coned-down views of the anomalous region are especially helpful to visualize
defects and their patterns, while bending films allow evaluation of rigidity or
flexibility of the curves and their adjacent motion segments.

Convex growth is important. Therefore, the quality of the bone and disk spaces
on the convexity must be clearly visualized and inspected. If the disk spaces
are present and clearly defined and the convex pedicles clearly formed,
convex growth is possible, and the prognosis is poor. If the convex disks are
not clearly formed and the convex pedicles are poorly demarcated, less
convex growth potential is present, and the prognosis is not as bad.

In the first year to two years of life, cartilage forms a significant part of the
vertebra; thus, at this stage, prognostication is not as accurate as it is later in
childhood. Tomography (if available) is a useful technique for evaluating
congenital spinal deformities, especially for documenting the presence and
extent of unsegmented bars and incarceration of hemivertebra. Computed
tomography and MRI are particularly useful in detailing bony canal anatomy
and associated spinal cord dysraphism. These evaluations are mandatory
prior to surgical intervention because spinal cord tethering and
diastematomyelia must be identified and released prior to correction of the
curve.

Treatment

The primary goal of treatment of congenital scoliosis is to prevent the
development of a severe deformity. Do not wait until a severe deformity has
developed and then attempt to perform a major and dangerous corrective
procedure. For patients with a marked spinal growth imbalance, no treatment
is perfect. The best result that can be achieved is spinal growth that is
balanced on the convexity. In these circumstances, the optimum result is a
short relatively straight spine rather than the severely crooked spine that would
have developed without treatment. Three key factors exist in achieving an
optimum result in patients with congenital scoliosis, as follows:

   •   Early diagnosis: If the diagnosis is made early, while the curvature is
       still small, an opportunity exists for prophylactic surgery to balance the
       growth of the spine.



   •   Anticipation: The prognosis for deterioration of congenital scoliosis can
       be anticipated based on the amount of spinal growth remaining, the
       type and site of the vertebral anomaly, and the degree of growth
       imbalance it produces. This requires careful study of good quality spinal
       radiographs and knowledge of the natural history of the condition.



   •   Prevention of deterioration: It is easier to prevent a severe spinal
       deformity than to correct one. A unilateral unsegmented bar, with or
       without contralateral hemivertebrae, is associated with a bad prognosis
       such that no period of observation is necessary. It requires immediate
       surgical treatment no matter how young the patient. Other types of
       congenital scoliosis may be observed, but one of the most common
       errors is to fail to recognize slow and relentless progression until it is too
       late for prophylactic treatment. Therefore, all patients require
       radiological assessment at 4- to 6-month intervals, and once
       progression is established, immediate treatment is necessary to prevent
       further deterioration.

Nonoperative treatment

Observation

The most common nonoperative management in congenital scoliosis is mere
observation, monitoring the curves for progression. Patients are observed in
cases in which the natural history is not known. No role for mere observation
exists in a patient with an unsegmented bar because this condition uniformly
progresses, but mere observation does have a role in the management of
hemivertebrae and in mixed deformities. Radiographs are obtained at regular
visits (every 4-6 mo). The same vertebrae are measured on each radiograph,
using exactly the same vertebral landmarks, and the current film is compared
to the film from the last visit and the original film. These comparisons are
necessary because progression is slow. The two periods of rapid growth are
during the first 4 years of life and during adolescence, with the adolescent
growth spurt. More frequent visits are necessary during these periods.

Orthotic treatment

Unlike idiopathic scoliosis, for which bracing can be effective, very few cases
of congenital scoliosis lend themselves well to brace treatment because the
primary deformity in congenital scoliosis is in the vertebrae, rather than in the
soft tissues, and the curves tend to be rigid. In addition, in cases in which the
natural history indicates a poor prognosis, orthotic treatment is contraindicated.
Thus, short stiff curves, an unsegmented bar, congenital lordosis, and
congenital kyphosis all are contraindications to orthotic treatment. The only
congenital scoliosis in which bracing does well is that of long curves that have
good flexibility, which is best determined by bending or by traction radiographs,
and unbalanced scoliosis secondary to an unbalanced hemivertebrae at the
T12 or L5 level.

The brace of choice is the Milwaukee brace for high thoracic curves (apex T6
or above), because it avoids the constriction of the thorax that may occur with
an underarm brace, and the thoracolumbosacral orthosis (TLSO) for lower
curves. Winter et al indicated that certain patients did well in the Milwaukee
brace for many years, and a few could even be permanently treated with an
orthosis and avoid surgery. The best results were in patients with mixed
anomalies that were flexible and in patients with a progressive secondary
curve. Braces are unlikely to be effective if the scoliosis is more than 40° or if
less than 50% flexibility is established using side bending or distraction
radiographs.

A significant shoulder elevation is best treated with a shoulder ring attached to
the Milwaukee brace, and head support pads can be added to create a neutral
head position if the patient has a head tilt. Only the Milwaukee brace and its
modifications can control high curves. The physician must recognize the role of
the orthosis and must carefully monitor the curves clinically and
radiographically. If the patient's curve progresses despite the orthosis, fusion
must be performed without further delay. Orthosis treatment should be
continued only if the orthosis successfully controls the curve. After surgery,
however, a brace may be required to help control spinal alignment and the
development of compensatory curves that were not included in the fusion.

No other known form of nonoperative treatment has any effect on congenital
scoliosis. Exercises, manipulation, and electrical stimulators all have failed
completely.

Operative treatment
Surgery is the most effective treatment for severe or progressive congenital
scoliosis. Many different forms of operative treatment exist for congenital
scoliosis, and all have their place. No single operative procedure can be
applied to all types of deformities. The method of surgery selected depends on
the age of the patient, the site and type of vertebral anomaly, the size of the
curvature, and the presence of other congenital anomalies. Successful
surgical treatment depends on selecting the right procedure and applying it at
the right time.

Progressive curves should be treated surgically, especially if they do not
respond to orthotic treatment. For example, if a 25° curve in a 3-year-old child
progresses to 35° by age 6 years, the curve requires surgical treatment. The
tendency is to avoid surgery at this age for fear of stunting the child's growth,
but in reality, the child will grow taller if the curve is fused than if a progressive
deformity occurs because the anomalies are devoid of normal vertical growth
potential.

There are 4 basic procedures for the surgical treatment of congenital scoliosis,
namely, convex growth arrest (anterior and posterior hemiepiphysiodesis),
posterior fusion, combined anterior and posterior fusion, and hemivertebra
excision. The fusion can be in situ or with correction by traction, bracing, or
instrumentation, although instrumentation should be used only to maintain
correction and not to produce correction.

Convex growth arrest

The prophylactic convex growth arrest procedure was first described by
MacLennan in 1922 and subsequently was described by Roaf and others. It
was designed to arrest the excessive convex growth and allow the concave
growth to occur and correct the deformity. Therefore, it is indicated in cases
with a progressive scoliosis or marked scoliosis with single or adjacent convex
hemivertebrae and a chance for concave growth with normal or near normal
concave growth plates. This procedure is best applied to a patient younger
than 5 years when there is growth potential on the concavity, as evidenced by
healthy-appearing growth plates, and a short curve of less than 60°.
Theoretically, this should allow the scoliosis to slowly correct by means of the
continuing growth on the concavity.

This is a relatively safe procedure. The only disadvantage is the slow and often
uncertain correction due to the unpredictable growth potential on the concavity
of the curve. However, even if the deformity does not correct at all, a convex
growth arrest often is sufficient to stabilize the deformity. This procedure is
contraindicated if any kyphosis is present in the area of the anomaly as the
anterior portion of the fusion may aggravate the kyphosis.
The surgery is performed in 2 stages that usually are carried out under the
same anesthetic. The spine is first approached anteriorly on the convexity of
the scoliosis. The lateral half of the disks and their adjacent endplates are
removed at the site of hemivertebra and at one intervertebral level above and
below. This removes the anterior growth plates at the site of the anomaly,
which is the main cause of the increasing scoliosis. In older or larger children,
this procedure may be able to be performed thoracoscopically, avoiding a
thoracotomy for thoracic level curves. The second stage of the procedure is
performed through the separate posterior exposure of the convexity of the
curve at the site of the hemivertebra. The paraspinal muscles on the concavity
of the curve should not be stripped. A posterior convex fusion is performed to
one level above and below the hemivertebra.

The child is placed in a postoperative body cast, and the cast is trimmed
appropriately so that the chest tube (inserted more anteriorly than normal) can
be removed from under the cast. The child is kept nonambulatory for 3-4
months, at which time the cast is removed and the child is placed in a
well-fitting spinal orthosis that is worn full time for 12-18 months. This
protection actually is necessary in all cases of fusion in the young child.
Reports of this combined growth arrest procedure show that the best results
are achieved with surgery at a younger age and with lumbar anomalies.

Posterior fusion

The aim of a posterior fusion is not curve correction, but rather curve
stabilization with the prevention of further curve increase. Posterior spine
fusion without instrumentation is the basic criterion standard for congenital
scoliosis surgery, but in the past 10 years, the combined anterior and posterior
approach has been used more commonly. It is the usual surgical procedure for
an older child with a moderately severe curve that still is relatively flexible. The
fusion must cover the entire measured curve and extend to the central gravity
line. Although it usually is not possible to obtain correction at the site of the
anomalous vertebrae, moderate correction may be achieved at the relatively
normal vertebral levels that lie above and below this area and are still within
the scoliosis.

The child should be immobilized completely with an appropriate molded Risser
cast or with a well-fitting Milwaukee brace until the fusion is absolutely solid.
Although a soft fusion may occur in 4-6 months, a strongly trabeculated fusion
will not occur for about 1 year, particularly if bank bone has been used as it
takes longer to incorporate into the body.

The use of posterior spinal instrumentation to correct a congenital scoliosis at
the time of the spinal fusion has several advantages. Posterior spinal
instrumentation achieves a moderately better correction and reduced
incidence of pseudoarthrosis compared with a posterior spinal fusion in a
Risser jacket alone. Spinal instrumentation is, however, associated with a
greater risk of producing neurologic complications due to the effect of
distraction on the spinal cord while the patient is anesthetized. A preoperative
MRI scan is necessary when instrumentation is planned, to exclude any spinal
dysraphism. Spinal cord monitoring using evoked potentials is essential, but,
unfortunately, it is not completely reliable.

The wake-up test should be performed immediately following correction of the
deformity. This test monitors only the current neurologic status, and neurologic
abnormalities can develop at a later stage in the operative procedure and even
in a delayed manner postoperatively. Because many types of instrumentation
are available today, the surgeon should choose the system that best fits the
child, the deformity, the safety factors, and the surgeon's experience.

Combined anterior and posterior fusion

Combined anterior and posterior fusion has become an increasingly performed
procedure for congenital scoliosis. It is used for thoracic, thoracolumbar, or
lumbar curves with a poor prognosis (ie, good convex growth potential). The
multiple diskectomies provide an anterior growth arrest, which reduces or
eliminates any bending of the fusion (crankshaft effect). This is far less
frequent in congenital scoliosis than in juvenile idiopathic scoliosis due to the
very abnormal growth plates and more rigid curvature. In addition, because of
the combined approach, the pseudoarthrosis rate is lower. This usually is
performed under the same anesthetic.

It is preferable to perform the anterior procedure first by removing an
appropriate rib to expose the area of the curvature and then by removing the
disk and growth plates. This provides greater mobility in the curvature, allowing
a better correction. The removed rib is placed in a trough that has been
created in the vertebral bodies with a rongeur, and the periosteum is resutured.
This provides a greater assurance of solid fusion without pseudoarthrosis. A
thoracoscopic procedure can also be used in older children. A chest tube is
inserted, the chest is closed, the patient is turned prone, and the standard
posterior spine fusion is performed with or without instrumentation, depending
on the circumstances.

The one circumstance in which anterior fusions are contraindicated is in the
very young child with a kyphotic deformity, in whom the anterior growth plates
are maintained to continue growth in the face of the solidly fused spine
posteriorly.

Hemivertebra excision
Hemivertebra excision was first performed in 1921 in Australia by Royle.
Despite this long period of experience with the procedure, very few reports
exist of significant follow-up until fairly recently. The only exception is the
excellent paper by Leatherman and Dickson.

Excision of a fully segmented hemivertebra is theoretically attractive as a
prophylactic procedure because it removes the primary cause of the scoliosis,
which is the enlarging wedge of the convexity at the apex of the curve.
Remember that the entire curve must always be fused after the wedge
osteotomy. Hemivertebra excision is indicated for patients younger than 5
years and who have development of a structural secondary curve with a fixed
decompensation in which adequate alignment cannot be achieved with other
procedures. This problem usually is due to a hemivertebra at the fourth or fifth
lumbar level because no spine exists below the hemivertebrae to allow
compensation. Hemivertebra excision is safer in this area than in the thoracic
region, as the cauda equina is more tolerant of manipulation than is the spinal
cord.

The hemivertebra is excised in two stages. The spine is approached both
anteriorly and posteriorly in a manner similar to that for a convex growth arrest
procedure. In the first stage, the hemivertebral body and the anterior body of
the pedicle are removed, as well as the adjacent disks and vertebral endplates.
In the second stage of the procedure, the posterior elements of the
hemivertebra are removed, along with the transverse process and posterior
part of the pedicle. This is a technically demanding procedure with a risk of
direct injury to the spinal cord. It also may interfere with the segmental blood
supply to the spinal cord. Some surgeons have advocated that the 2 stages be
separated by 10 days to allow time for the vasculature to recover. Others have
reported successful results when both procedures were performed under the
same anesthetic.

Lazar and Hall have described the simultaneous anterior and posterior
hemivertebra excision technique with posterior instrumentation using
infant-sized Danek hardware. Once the hemivertebra has been excised, the
scoliosis can be corrected by closing the wedge osteotomy. Depending on the
age of the child and the size of the vertebrae, instrumentation is added, usually
a compression system on the convexity of the excised segment, using hooks,
pedicle screws, or both.

When it is not possible to add instrumentation, correction is maintained with a
body cast with a leg extension, and the child usually is nonambulatory for 3-4
months. With the use of internal fixation, the child is placed in a brace with a
leg extension for 4 months with additional immobilization if the fusion is not
solid. Excision of a lumbosacral hemivertebra is contraindicated if a second
hemivertebra is present on the opposite side in the lumbar region. Excision of
either of these hemivertebrae further unbalances the spine and increases the
deformity.

Vertebrectomy

Vertebrectomy is the most radical of all procedures for congenital scoliosis. It
is the removal of two or more vertebrae in their entirety, including pedicles from
both sides, laminae, and bodies. This is performed in order to create mobility
but at the price of instability. This procedure is neurologically risky and must be
accompanied with appropriate spinal cord monitoring and wake-up tests. It
should be reserved for the most severe deformities and performed only by
highly skilled spinal surgeons.

CONGENITAL KYPHOSIS

Natural history

Congenital kyphosis is less common than is congenital scoliosis but can, if left
untreated, cause paraplegia. Two types of congenital kyphosis exist: defects of
segmentation and defects of formation (see Image 11). Defects of
segmentation occur most often in midthoracic or thoracolumbar regions and
may involve 2-8 levels. They tend to produce a round kyphosis rather than a
sharp angular gibbous; therefore, paraplegia rarely is a problem. The main
clinical symptom is low back pain caused by the necessary compensatory
lumbar hyperlordosis. Commonly, the kyphosis caused by the defect of
segmentation starts in the late juvenile years with the progressive ossification
of the disk space anteriorly.

In the early stages, differentiation from Scheuermann disease can be difficult,
but with time, the progressive anterior ossification becomes obvious. The rate
of progression is less than that with a formation failure because the bar forms
in the late juvenile years and the growth discrepancy is not as great.

Defects of formation are more common and may involve only one level, but
multiple defects are possible. The failure of the formation can be purely
anterior, resulting in kyphosis, or can be anterolateral with a posterior corner
hemivertebra, resulting in kyphoscoliosis. The more severe the anterior
defects, the more progressive the deformity. In general, kyphosis caused by
failure of formation is universally progressive and can lead to paraplegia if
untreated. The paraplegia may occur early but is more common during the
adolescent growth spurt, with rapid increase in the untreated kyphosis, and it
may occur following minor trauma. Paraplegia is more common with kyphosis
in the upper thoracic area because this is the part of the spinal cord with the
poorest collateral circulation, the so-called watershed area of the blood supply
of the spinal cord. In North America, congenital kyphosis is the most common
cause of paraplegia due to spinal deformity.

Nonoperative treatment

No role exists for nonoperative treatment of congenital kyphosis. All forms of
nonoperative treatment, including full-time bracing, are useless. The natural
history indicates a universally poor prognosis; therefore, the treatment is
surgical.

Surgical treatment

Defects of formation

The main goal of treatment is prevention of paraplegia. If the defect is detected
early, when the patient is younger than 5 years, and less than 50° of kyphosis
is present, posterior fusion alone will produce a desired outcome.
Postoperatively, the child is placed in a hyperextension cast and is kept
nonambulatory for 3-4 months. In patients younger than 18 months or in those
in whom a pseudoarthrosis is detected, a repeat posterior procedure is
performed to reinforce the fusion or to repair the pseudoarthrosis. To achieve a
good result, it generally is recommended that routine exploration and graft
augmentation be performed at 4-6 months to obtain a thick fusion.

Following reinforcement, the child is immobilized in a brace or, preferably, a
hyperextension cast for 4-6 months. In their review of 17 cases of congenital
kyphosis fused posteriorly alone in children younger than 5 years, Winter and
Moe found improvement in the kyphosis in 12 patients (71%) with an average
9-year follow-up.

When the deformity is larger than 50° or when the child is older than 5 years, a
combined anterior and posterior arthrodesis is mandatory. The anterior fusion
is performed first, with radical excision of the anterior longitudinal ligament, the
disks, and the related ligaments. If possible, a distractor should be used to
lengthen the anterior column, and structural bone graft from the rib or fibula
should be placed anteriorly to maintain the achieved height.

The anterior procedure is followed (either on the same day or a week after) by
a posterior arthrodesis and compression instrumentation if bones are large
enough to accept hooks and rods. Otherwise, the patient is managed with a
hyperextension cast and bed rest for several months. With the use of
instrumentation and secure fixation, the child is ambulatory without
immobilization. If the fixation is not secured or is in question, cast or brace is
best. Traction has no role in the treatment of congenital kyphosis because
traction in these cases is associated with a high incidence of paraplegia.
A patient who has a neurologic deficit at the time of presentation requires
special consideration. All patients with neurologic deficits should have an MRI
of the spinal canal. In patients who present with minor neurologic deficits
associated with congenital kyphosis (eg, spasticity manifested by hyperactive
reflexes and positive Babinski signs but no loss of motor, bowel, or bladder
function), an anterior decompression of the spinal cord is not necessary. The
anterior and posterior fusion should be carried out as described previously,
and the neurologic deficit will disappear gradually once the spinal canal has
been realigned and the area has been stabilized.

In cases with more marked neurologic loss, the anterior and posterior
arthrodesis must be combined with an anterior decompression of the spinal
cord. The patient is kept nonambulatory for 2-4 weeks to allow maximal cord
recovery and to allow the postoperative edema in and around the cord to
subside.

Defects of segmentation

The choice of treatment depends on the magnitude of the deformity and
whether correction is desired. If discovered early, defects of segmentation can
be treated with a posterior fusion, which should include the entire kyphosis and
one vertebra cephalad and caudad to the lesion. Because the deformity is rigid,
instrumentation is not used unless the congenital kyphosis is part of a longer
kyphosis that requires treatment and fusion.

When the kyphosis presents later with a significant deformity that requires
correction, the combined approach is best, with multiple osteotomies of the
anterior bar of the bone followed by posterior fusion. For larger patients,
compression instrumentation is desirable. If the patient is too small for
instrumentation, hyperextension casting is needed to maintain the correction
until the area of the arthrodesis has fused.

CONGENITAL LORDOSIS

Congenital lordosis is the least common of the 3 major patterns of congenital
spinal deformity. It is caused by a failure of posterior segmentation in the
presence of active growth anteriorly. Asymmetrical defects of segmentation,
like a posterolateral unsegmented bar leading to lordoscoliosis, are more
common. Pure congenital lordosis is rare. Congenital lordosis with failure of
posterior formation is extremely rare. Some authors have not seen any
patients in whom congenital lordosis was caused by a defect of formation.

Congenital lordosis deformity usually is progressive. With an increasing
lordosis deformity in the thoracic spine, the spine-sternal distance (or
anteroposterior diameter of the chest) is reduced and the rib mechanics of
respiration are altered, with resultant respiratory restriction, respiratory failure,
and even early death. When the deformity occurs in the lumbar spine, it results
in hyperlordosis, with the spine approaching the anterior abdominal wall.

Treatment of congenital lordosis is purely operative. Nonoperative treatment
has no role because the condition is progressive. Because the deforming force
in these cases is anterior growth, all cases require an anterior approach.
Because these patients have pulmonary restrictive disease, an anterior
approach has greater risks. If an element of pulmonary failure is present
already, these risks increase. If pulmonary artery hypertension is present
already, surgery probably is contraindicated due to the high mortality rate in
these cases.

Two types of surgery are available, one for anterior fusion and the other for
correction. Anterior fusion can be performed when the surgeon has the
opportunity to see the patient early, before major deformity and loss of
pulmonary function has developed. Anterior fusion is performed with disk
excision, removal of the cartilage endplates, and packing of the disk spaces
with bone chips. The anterior fusion should include the entire involved area
and 1 or 2 vertebrae cephalad and caudad to the lesion. This approach
eliminates the anterior growth potential and provides an anterior fusion
opposite the unsegmented bar.

A so-called corrective operation is performed when the patient has a major
deformity and, usually, loss of pulmonary function. The goal is to improve the
spinal alignment and pulmonary function. A combined anterior and posterior
approach is indicated in these cases. Anteriorly, the disks are excised over the
whole area of the deformity, and thin wedges of the adjacent vertebral
endplates are excised, converting the disk excision into an osteotomy that is
wider anteriorly. The disk spaces are not packed with bone chips because the
wedges need to close anteriorly.

The posterior portion of the operation consists of multiple osteotomies of the
laminar synostosis, performed at the same levels from which the disks were
excised anteriorly. The best method for correction is with the passage of
sublaminar wires; when the bones are large enough, these wires are used to
approximate the spine to a kyphotically contoured rod (Harrington, Luque, or
one of the third-generation multiple hook-rod systems). Whenever feasible, a
combined procedure should be performed during the same anesthetic session
in order to gain an immediate increase in lung volume and vital capacity.

SACRAL AND LUMBOSACRAL AGENESIS

Sacral agenesis is the term commonly applied to a group of disorders
characterized by absence of the variable portion of the caudal portion of the
spine. Patients with sacral agenesis lack motor function below the level of the
normal remaining spine, similar to those with myelomeningocele. However,
sensory function is impaired below the level of affected vertebrae. In more
severe cases of sacral agenesis, part or all of the lumbar spine and even the
lower thoracic spine may be absent. Some authors use the term lumbosacral
agenesis in these severe cases.

Hohl first described agenesis of the lower spine in 1852, and Friedel
redescribed it in 1910. Since then, a number of review articles and case
reports have appeared in the literature. Williams appears to have been the first
to use the term sacral agenesis in 1957. As the absence of the coccyx is not
known to cause any problems, mention of its absence seems unnecessary.

Sacral agenesis is an uncommon congenital deformity of the spine occurring in
approximately 1 of 25,000 live births.

Classification

Renshaw classified patients according to the amount of sacrum remaining and
according to characteristics of the articulation between the spine and the pelvis
(see Image 14).

   •   Type I is either partial or total unilateral sacral agenesis.



   •   Type II is partial sacral agenesis with a bilaterally symmetrical defect, a
       normal or hypoplastic sacral vertebra, and a stable articulation between
       the ilia and the first sacral vertebra.



   •   Type III is variable lumbar and total sacral agenesis, with the ilia
       articulating with the sides of the lowest vertebra present.



   •   Type IV is variable lumbar and total sacral agenesis, with the caudal
       endplate of the lowest vertebra resting above either fused ilia or an iliac
       amphiarthrosis.

Etiology

The exact etiology of sacral agenesis is unknown. In the human embryo,
differentiation of the lumbar spine, sacrum, and coccyx occurs between the
fourth and seventh postovulatory weeks. Duraiswami demonstrated that
insulin injected into chick embryos can cause rumplessness, a condition
similar to sacral agenesis. In 1959, Blumel et al first called attention to the
increased incidence of diabetes in mothers of affected children. The incidence
is about 16%. Although maternal diabetes is the risk factor most commonly
associated with sacral agenesis, other less common risk factors also have
been described. Several reports have suggested that exposure to organic
solvents in early pregnancy may increase the incidence of sacral agenesis.

Clinical features

The appearance of the patient depends on the extent of the spinal involvement
and on the degree of neurologic deficit.

   •   Type I: The vertebropelvic articulation is usually stable. The unilateral
       absence of the sacrum results in an oblique lumbosacral joint and
       lumbar scoliosis. The scoliosis generally is not progressive and does
       not require surgical treatment. Hips and knees usually are normal. A
       calcaneovarus deformity of the foot may be present. Sensory loss
       corresponds to the distribution of the involved sacral roots.



   •   Type II: The vertebropelvic junction is stable unless associated
       myelomeningocele is present. Associated congenital anomalies of the
       spine, such as hemivertebrae, may cause progressive congenital
       scoliosis. Motor paralysis is present and corresponds within one level
       with the vertebral defect. Sensation usually is intact. Anesthesia may be
       present at S-4 and distally. In patients with myelomeningocele, the level
       of paralysis may be higher than the level of vertebral deficit, and the
       sensory loss may be more extreme. Hip dislocation occurs in this type
       of sacral agenesis and may be unilateral or bilateral. Foot and knee
       deformities usually are not marked. Most patients with type II
       lumbosacral agenesis are ambulatory.



   •   Type III: The lumbopelvic junction is relatively stable. Progressive
       kyphosis and scoliosis may develop in these patients, particularly when
       associated myelomeningocele is present. The level of the motor
       paralysis corresponds within one segment level of vertebral deficit.
       Sensation is intact at least down to the fourth sacral nerve root level. In
       total absence of the sacrum, the buttocks are flattened, the cleft is
       shortened, and each buttock is dimpled lateral to the cleft. The normal
       convexity of the sacrococcygeal region is lost. Hip dislocation, knee
       contracture, and foot deformity are common and require treatment.
       Patients with type III sacral agenesis are unable to stand or walk without
       appropriate support.



   •   Type IV: In complete absence of the lumbar spine and sacrum, patients
       are of short stature. The thorax and the pelvis are markedly
       disproportionate. The normal convexity of the sacrococcygeal region is
       lost, and the anus is horizontal. The pelvis is very unstable under the
       spine and tends to roll up under the thorax and drop forward. Almost all
       patients with type IV lumbosacral agenesis develop progressive
       kyphosis and scoliosis. They require surgical treatment for stabilization.
       The hips have severe flexion and abduction contracture and may be
       dislocated. The knees show flexion contracture with large popliteal
       webs. Fixed calcaneus deformities of the feet are present. Complete
       muscle paralysis and atrophy are present at and below the knees.
       Sensation usually is normal down to the knees. These patients have no
       bladder or bowel control. Patients with type IV sacral agenesis require
       spinal-pelvic stabilization or extensive orthotic support to ambulate.

Treatment

High-level sacral agenesis presents the orthopedic surgeon with two unique
problems: spinal-pelvic instability and severe knee flexion contractures with
popliteal webbing. Reconstruction of the lower limb in type IV sacral agenesis
has not been successful due to the absence of muscle fibers and major motor
nerves. Some authors have reported the results of treatment by bilateral
subtrochanteric amputation and fitting with a pelvic-thoracic bucket and
Canadian hip disarticulation prosthesis. These patients could be partially
ambulatory with a swing-to or swing-through gait, as used by persons with
paraplegia.

As long as spinal-pelvic instability remains uncorrected, the patient is neither
able to sit unsupported nor to ambulate without the aid of a pelvic-thoracic
bucket. Many authors have performed spinal-pelvic fusion. Their justifications
for performing spinal-pelvic fusion were to protect the viscera from
unphysiologic compression and angulation and to establish a stable vertebral
pelvic complex about which lower extremity contractures can be stretched or
surgically released. Currently, spinal-pelvic fusion does not seem justified for
asymptomatic spinal-pelvic instability. If the spinal-pelvic fusion is to be
performed, Winter's technique is recommended. Either autogenous tibiae (if
knee disarticulation was performed) or allografts can be used for spinal-pelvic
fusion.
Often, the knee flexion and foot deformities are corrected using surgical
release at an early age. A combination of soft tissue releases, supracondylar
femoral extension osteotomies, and serial casting probably will result in
satisfactory correction of some knee contractures. If amputation is chosen,
disarticulation at the knee is the recommended level of amputation. The
neuromuscular deficit is less in type I and type II sacral agenesis. These
patients have spinal-pelvic stability. They can sit and walk. The foot and knee
deformities should be corrected.

CONGENITAL ANOMALIES OF THE CERVICAL SPINE

Congenital anomalies of the cervical spine, although rare, are worthy of
attention because neurologic compromise from instability or stenosis may be
prevented with early recognition and careful management of those at risk.
Congenital anomalies range in severity from those that are benign and
asymptomatic to those with the potential for fatal instability. Many anomalies
are not discovered until a complication occurs. Anomalies of the
occipitocervical junction often remain undetected until late childhood or
adolescence, and some remain hidden well into adult life. Other anomalies of
the cervical spine, although recognized in early life, may not become clinically
significant until adulthood. Although they are rare, their recognition is important
to prevent catastrophic paralysis due to sport participation or manipulation
during anesthesia.

Basilar impression

Basilar impression (or invagination) is the deformity of the bones of the base of
the skull at the margin of the foramen magnum. The floor of the skull appears
to be indented by the upper cervical spine; therefore, the tip of the odontoid is
more cephalad. This increases the risk of neurologic damage from injury,
circulatory embarrassment, or impairment of cerebrospinal fluid (CSF) flow.
Two types of basilar impression exist: (1) primary, a congenital abnormality
often associated with other anomalies such as atlanto-occipital fusion,
hypoplasia of the atlas, bifid posterior arch of atlas, odontoid abnormalities,
Klippel-Feil syndrome, and Goldenhar syndrome; and (2) secondary, a
developmental condition usually attributed to softening of the bone, in which
the deformity develops later in life.

With basilar impression, the upper cervical spine encroaches on the brainstem
and spinal cord as the base of the skull is displaced toward the cranial vault.
Motor and sensory disturbances are noted in 85% of individuals who are
symptomatic. However, most affected patients remain asymptomatic until the
second or third decade of life, when they may present with headache, neck
ache, and neurologic compromise (prevalence of symptoms, 15%).
Basilar impression is difficult to assess radiographically, and many
measurement schemes have been proposed. Those most commonly referred
to are Chamberlain's (1939), McGregor's (1948), and McRae's (1953) lines on
the lateral radiograph (see Image 15), and the Fischgold-Metzger line on the
anteroposterior projection. Chamberlain's line is drawn from the posterior lip of
the foramen magnum (opisthion) to the dorsal margin of the hard palate.
McGregor's line is drawn from the upper surface of the posterior edge of the
hard palate to the most caudad point of the occipital curve of the skull.
McRae's line defines the opening of the foramen magnum. McGregor's line is
the best method for screening because the bony landmarks can be clearly
defined in persons of all ages on a routine lateral radiograph.

The position of the tip of the odontoid is measured in relation to this base line
and a distance of 4.5 mm above McGregor's line is considered to be on the
extreme edge of reference ranges. More detailed techniques (CT scan and
MRI) generally are reserved for patients in whom the routine examination or
clinical findings may suggest an occipitocervical anomaly.

Treatment depends on the cause of the symptoms and often requires the
combined effort of the orthopedic surgeon and the neurosurgeon. Anterior
impingement from a hypermobile odontoid may require fusion in extension if
the odontoid can be reduced. If the odontoid cannot be reduced, an anterior
excision and stabilization in extension can be considered. Posterior
impingement may require suboccipital craniectomy and decompression of the
posterior ring of C1 and possibly C2 with the release of tight dural bands. This
is followed by fusion of the occiput to C2 or C3.

Occipitocervical synostosis

This malformation is characterized by a partial or complete congenital union
between the atlas and the base of the occiput. It also is known as
occipitalization of the atlas and assimilation of the atlas into the occipital bone.
Occipitocervical synostosis, basilar impression, and odontoid anomalies are
the most common developmental malformations of the occipitocervical
junction. Incidence ranges from 1.4-2.5 per 1000 children, and both sexes are
affected in equal numbers. The age range of patients presenting with this
anomaly is reported at 8-52 years. Some patients develop symptoms following
mild trauma, while others remain entirely asymptomatic throughout life.
Weakness and ataxia in the lower limbs and, occasionally, in the upper limbs
are the primary symptoms.

The following most common signs and symptoms occur in decreasing order of
frequency:

   •   Pain in the occiput and neck
   •   Vertigo



   •   Unsteady gait



   •   Paresis of the limbs



   •   Paresthesias



   •   Speech disturbances



   •   Hoarseness



   •   Double vision



   •   Syncope



   •   Interference with swallowing

Other clinical findings include a short broad neck, a low hairline, torticollis, a
high scapula, and restricted neck movements, like those seen in Klippel-Feil
syndrome. This disorder is commonly associated with C2-C3 fusion.

Other associated anomalies occasionally seen include dwarfism, funnel chest,
pes cavus, syndactylies, jaw anomalies, cleft palate, congenital ear deformities,
hypospadias, and, sometimes, genitourinary tract defects.

Standard radiographs of this area can be difficult to interpret. Tomography, CT
scan, and MRI may be necessary to clarify the pathologic condition. Bony
anomalies that may be visible include a backward tilt of the odontoid process,
an articular facet between the anterior rim of the occiput and the odontoid
process, asymmetrical atlantoaxial joints as seen on the anteroposterior view,
and fusion of the body and lamina of the second to the third cervical vertebrae.

Initially, nonoperative measures in the form of traction and support of the neck
by an orthosis are carried out. If neural impairment is present, consideration
may be given to decompression by laminectomy, craniectomy, and release of
posterior dural bands. The risk of morbidity and death is high.

Odontoid anomalies

Anomalies of the odontoid process (dens) may range from complete absence
(aplasia) to partial absence (hypoplasia) to separate odontoid process, or os
odontoideum (see Image 16). These may lead to atlantoaxial instability and
may cause neurologic deficit and even death. The frequency of these
anomalies is unknown, and, like many anomalies that may be asymptomatic,
they probably are more common than is recognized. Aplasia is extremely rare,
and hypoplasia and os odontoideum are infrequently reported and can be
considered rare. Odontoid anomalies in association with ligamentous laxity
producing atlantoaxial instability are more common in patients with Down
syndrome, Morquio syndrome, Klippel-Feil syndrome, and some skeletal
dysplasias.

Clinical presentation occurs in persons aged, on average, 19 years. Patients
may be asymptomatic or may present with local neck symptoms, transitory
episodes of paresis following trauma, or frank myelopathy secondary to cord
compression. An important factor differentiating os odontoideum from other
anomalies of the occipitovertebral junction is that these patients seldom have
symptoms referable to cranial nerves, as the area of the spinal cord
impingement is below the foramen magnum. In 40% of patients, the clinical
manifestations are limited to neck pain and torticollis without neurologic
involvement, and the prognosis is excellent. A few patients may have
symptoms and signs of cerebral and brainstem ischemia, seizures, and mental
retardation. Sudden death has been reported due to minor trauma.

Recommended radiographic views are open-mouth, anteroposterior, lateral,
flexion-extension, or CT scan reconstructions. Flexion-extension CT scans are
of value because plain films do not always show the anomaly or the extent of
motion. At birth, the normal odontoid can be seen in the lateral view with the
epiphyseal plate. A mistaken impression of hypoplasia may be given by a
lateral extension radiograph.

Partial or complete absence of the dens may be either congenital or acquired.
This extremely rare anomaly may be recognized from birth onward and is best
seen in the open-mouth view. The most common form of hypoplasia presents
with a short stubby peg of odontoid projecting just above the lateral facet
articulations. Tomography is necessary to confirm whether an os odontoideum
is present in addition to the hypoplasia. CT scans are useful in patients with
multiple anomalies when the usual radiographic views are not always reliable
in confirming the presence or absence of an odontoid.

In os odontoideum, there is a jointlike articulation between the odontoid and
the body of the axis, which appears radiologically as a wide radiolucent gap.
This gap may be confused with a normal finding in patients younger than 5
years. Therefore, in children, the diagnosis is confirmed by demonstrating
motion between the odontoid and the body of the axis. Measurements can be
made using a line projected superiorly from the posterior border of the body of
the axis to a line projected inferiorly from the posterior border of the anterior
arch of the atlas. Measurements of more than 3 mm should be considered
pathologic. MRI is helpful for evaluating the space available for the spinal cord.

Surgical stabilization is indicated if neurologic involvement is present with
more than 10 mm of instability on supervised flexion-extension films, if
progressive instability is present, or if persistent neck symptoms are present.
The suggested method of stabilization is posterior cervical fusion of C1-C2,
with wire fixation and an iliac bone graft. This is not without risk, as slight
flexion often is required to pass the wire beneath the posterior ring of the atlas.
Operative reduction should be avoided, and preoperative correction with
traction or positioning is preferred. Prophylactic stabilization is controversial.
However, good outcomes and low morbidity have been achieved with surgery.

Klippel-Feil syndrome

Klippel-Feil syndrome is uncommon. The first case was reported by Maurice
Klippel and Andre Feil in 1912. The term Klippel-Feil syndrome in its present
usage refers to all patients with congenital fusion of the cervical vertebrae,
whether it involves 2 segments, congenital block vertebrae, or the entire
cervical spine. Congenital cervical fusion is the result of failure of normal
segmentation of the cervical somites during the third to eighth weeks of life.
With the exception of a few patients in whom this condition is inherited, the
etiology is undetermined. The frequency is about 1 in 42,000 births, and 65%
of patients are female (see Image 17).

The classic clinical triad of low posterior hairline, short neck, and limitation of
neck motion is seen in 40-50% of patients. The decrease in motion most
commonly is in lateral bending and rotation. Flexion and extension are
relatively well preserved, except in the most massive fusion. A low posterior
hairline seems to reflect the shortening of the neck rather than being a
separate entity.
The age at presentation is extremely variable, extending through the entire life
span. Massive fusions often are noted in infancy or in early childhood due to
the cosmetic deformity. Neurologic problems in infancy usually are related to
craniovertebral junction abnormalities, although cervical vertebral fusions also
may be present in this age group. C1-C2 fusions often present in childhood,
usually with pain. Lower cervical fusions, if they are not massive, often do not
present until the third decade or even later in life, when degenerative changes
or instability of adjacent segments develops.

Patients with Klippel-Feil syndrome present with a wide range of chief
complaints, including cosmesis (either of the neck or due to associated
anomalies such as Sprengel deformity), neck pain alone, radicular pain with or
without weakness, slowly progressive or acute paraparesis or quadriparesis,
and complications caused by associated anomalies. (See the list of associated
anomalies below.)

Diagnosing congenital cervical fusion in infants and young children can be
difficult. Flexion and extension can demonstrate a lack of motion between
fused segments, and flexion and extension laminograms may be necessary to
confirm the diagnosis. CT scans also can be used to define the bony
architecture. Aside from vertebral fusion, flattening (wasp waist) and widening
of the involved vertebral bodies and absent disk spaces are the most common
findings. The sagittal and transverse diameters of the spinal canal usually are
normal. Narrowing of the spinal canal, if it occurs, usually is seen in adults and
is due to degenerative changes or hypermobility. All of these defects may
extend into the upper thoracic spine, particularly in cases in which involvement
is severe. These disturbances may be detected first on routine chest film as a
first clue. With a high thoracic congenital scoliosis, the radiographic evaluation
routinely should include lateral views of the cervical spine.

Common associated anomalies with Klippel-Feil syndrome (with percentage of
cases in which they are associated) are as follows:

   •   Scoliosis - 60%



   •   Renal abnormalities - 35%



   •   Sprengel deformity - 30%
   •   Deafness - 30%



   •   Mirror motion (synkinesis) - 20%



   •   Congenital heart disease - 14%

Less common associated anomalies in Klippel-Feil syndrome are as follows:

   •   Ptosis



   •   Duane contracture



   •   Lateral rectus palsy



   •   Facial nerve palsy



   •   Syndactyly



   •   Hypoplastic thumb



   •   Upper extremity hypoplasia



   •   Neurenteric cyst

Three patterns of deformity are at the greatest risk for instability and require
early recognition: (1) fusion of C1 to C3 with occipitocervical synostosis, (2)
long fusion with an abnormal occipitocervical junction, and (3) a single open
interspace between 2 fused segments. Conservative treatment such as activity
modification, bracing, and traction may reduce symptoms. The indication for
and timing of stabilization are not clearly defined. However, if a neurological
lesion is present, if significant pain persists despite conservative measures, or
if instability is documented, spinal fusion must be considered. Similarly, if
neurologic injury is present and stenosis is documented, decompression with
or without fusion is indicated.

Treatment of the cosmetic aspects of this deformity has met with limited
success. Soft tissue procedures, Z-plasty, and muscle resection may achieve
cosmetic improvement in selected patients. All patients with congenital cervical
fusion should avoid contact sports and occupations and recreational activities
that put them at risk for head trauma. The potential for catastrophic outcomes
with this lesion must be kept in mind. Long-term follow-up should be
undertaken and patients and families should be carefully counseled.

SYNDROMES ASSOCIATED WITH CONGENITAL SPINAL DEFORMITY

Several syndromes are associated with congenital spinal deformity. Some of
these are described here.

Down syndrome (trisomy 21 syndrome)

Down syndrome is characterized by hypotonia, flat facies, slanted palpebral
fissure, and small ears. Incomplete fusion of vertebral arches of lower spine
occurred in 37%, atlantoaxial instability in 12%, abnormal odontoid process in
6%, and hypoplastic posterior arch C1 in 26%. Any child with Down syndrome
who develops changes in bowel or bladder function or neck posturing or who
loses ambulatory skills should be evaluated carefully with plain radiographs of
the cervical spine. Most patients develop symptoms when younger than 10
years, when the ligamentous laxity is most severe.

Deletion 5p syndrome (chromosomal number 5 syndrome)

Lejeune et al first described this condition in 1963. The common features are
catlike cries in infancy, microcephaly, and downward slant of the palpebral
fissures. Hemivertebra and scoliosis are frequent occurrences.

Kabuki syndrome

This initially was reported in 1981 by Niikawa et al and by Kuroki et al in Japan.
Skeletal abnormalities include short, in-curved fifth finger secondary to short
fourth and fifth metacarpals, rib anomalies, brachydactyly, sagittal cleft of
vertebral body, hip dislocation, and scoliosis. All cases have occurred
sporadically in otherwise healthy families.
Noonan syndrome (Turnerlike syndrome)

The first case was described by Kobilinsky in 1883. In 1963, Noonan and
Ehmke further delineated the clinical phenotype. This syndrome is
characterized by webbing of the neck, pectus excavatum, cryptorchidism, and
pulmonary stenosis. Skeletal abnormalities include cubitus valgus, spina bifida,
and hemivertebrae.

Aarskog syndrome

Set forth by Aarskog in 1970, Aarskog syndrome has been increasingly
recognized. The common features are hypertelorism, brachydactyly, and
shawl scrotum. Skeletal abnormalities include broad thumbs and great toes,
scoliosis, cubitus valgus, splayed toes with bulbous tips, and metatarsus
adductus.

Cervico-oculo-acoustic syndrome (Wildervanck syndrome)

Wildervanck initially described this syndrome in 1952. This disorder is
characterized by Klippel-Feil anomaly (fusion of 2 or more cervical and
sometimes thoracic vertebrae), abducens paralysis with retracted globs, and
sensorineural deafness, torticollis, and Sprengel deformity.



MURCS association (mülerian duct, renal, and cervical vertebral
defects)

Duncan described the MURCS association in 1979. It consists of a nonrandom
association of mülerian duct aplasia, renal aplasia, and cervicothoracic somite
dysplasia. The incidence of cervicothoracic vertebral defects, especially from
C5-T1, is 80%. Other abnormalities may include Sprengel deformity, upper
limb defects, and moderate frequency of rib anomalies.

VACTERL association

This association consists of vertebral defects, anal atresia, cardiac anomalies,
tracheoesophageal fistula with esophageal atresia, radial and renal dysplasia,
and limb bud anomalies. Vertebral anomalies occurred in 70% of cases. Other
less frequent defects are defects of the lower limb and spinal dysraphia with
tethered cord.

Jarcho-Levin syndrome (spondylothoracic dysplasia)

Jarcho and Levin described this disorder in 1938. It is inherited as an
autosomal recessive condition, although autosomal dominant inheritance has
been reported. Abnormalities included are short trunk, dwarfism of prenatal
onset, short thorax with a crablike rib cage associated with multiple vertebral
and rib defects, posterior fusion and absence of ribs, lordosis, and
kyphoscoliosis. Although most affected individuals die in early infancy as a
result of recurrent pulmonary infection, a small number have lived beyond age
1 year.

Proteus syndrome

This syndrome most commonly is characterized by hemihypertrophy,
subcutaneous tumors, and macrodactyly. Skeletal abnormalities include bony
prominences over the skull, angulation defects of the knees, scoliosis,
kyphosis, hip dislocation, dysplastic vertebrae, and clinodactyly.

Other

Other examples of syndromes associated with congenital spinal deformity are
arteriohepatic dysplasia, Gorlin syndrome, fibrodysplasia ossificans
progressiva syndrome, Morquio syndrome, spondylo-carpo-tarsal synostosis
syndrome, multiple synostosis syndrome, and Coffin-Lowry syndrome.

PICTURES




Picture Type: X-RAY

Caption: Picture 1. Congenital spinal
deformity. Minor malformations of the
spine are seldom apparent and often are
identified only on routine chest films.




Picture Type: Photo

Caption: Picture 2. Congenital spinal
deformity. Clinical results of an untreated
unilateral unsegmented bar.
Picture Type: Photo

Caption: Picture 3. Congenital spinal
deformity. Patient with severe congenital
hyperlordosis.




Picture Type: X-RAY

Caption: Picture 4. Congenital spinal
deformity. Congenital kyphosis from a
posterior unbalanced hemivertebra.




Picture Type: Image

Caption: Picture 5. Congenital spinal
deformity. Ventromedial cells of the
sclerotome migrate toward the midline of
the embryo to surround the neural tube
and the notochord, forming the
precursors of the vertebral arch and
vertebral body.



Picture Type: Image

Caption: Picture 6. Congenital spinal
deformity. Vertebral morphogenesis;
each vertebral sclerotome splits into a
cranial and caudal portion, which
recombine with the superior and inferior
sclerotome, permitting the segmental
spinal nerves to grow out and innervate
the myotome derivatives.


Picture Type: Image

Caption: Picture 7. Congenital spinal
deformity. The cervical spine has 8
nerves as a result of the resegmentation
of the sclerotome. The cranial portion of
the first cervical sclerotome combines
with the fourth occipital sclerotome to
contribute to the base of the skull,
whereas the eighth cranial somite
contributes to C7 and to T1.



Picture Type: Image

Caption: Picture 8. Congenital spinal
deformity. Failure of formation. Top left:
anterior central defect. Top right:
incarcerated hemivertebra. Bottom from
left to right: free hemivertebra, wedge
vertebra, and multiple hemivertebrae.




Picture Type: Image

Caption: Picture 9. Congenital spinal
deformity. Failure of segmentation. Left:
block vertebra. Right: unilateral
unsegmented bar.
Picture Type: X-RAY

Caption: Picture 10. Congenital spinal
deformity. Mixed vertebral deformity
involving the thoracolumbar spine.




Picture Type: X-RAY

Caption: Picture 11. Congenital spinal
deformity. Anterior unsegmented bar
leads to congenital kyphosis.




Picture Type: Image

Caption: Picture 12. Congenital spinal
deformity. Lateral unsegmented bar leads
to scoliosis.




Picture Type: Image

Caption: Picture 13. Congenital spinal
deformity. Hemivertebra. A: fully
segmented hemivertebra. B:
unsegmented hemivertebra. C:
incarcerated hemivertebra.
Picture Type: Image

Caption: Picture 14. Congenital spinal
deformity. Sacral agenesis classification.
A: type I. B: type II. C: type III. D: type IV.




Picture Type: Image

Caption: Picture 15. Congenital spinal
deformity. Lateral craniotomy. The
drawing indicates the 3 lines used to
determine basilar impressions.




Picture Type: Image

Caption: Picture 16. Congenital spinal
deformity. Gradation of odontoid
appearance.




Picture Type: X-RAY

Caption: Picture 17. Congenital spinal
deformity. Klippel-Feil syndrome with
congenital fusion of entire cervical spine.



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