Spinal Disorders: Fundamentals of Diagnosis and Treatment Part 71 ppt

and therefore are non-hereditary✔Up to 60 % of patients with congenital scoliosis may have malformations of other organ sys-tems, particularly the genitourinary, cardiovas-cular, and ner

and therefore are non-hereditary

✔Up to 60 % of patients with congenital scoliosis

may have malformations of other organ

sys-tems, particularly the genitourinary,

cardiovas-cular, and nervous systems

✔The classification system is based on either

fail-ure of formation, failfail-ure of segmentation, or

mixed (failure of both formation and

segmenta-tion)

✔Curve progression in congenital scoliosis is

based on both the type and location of

verte-bral anomaly

✔The treatment of congenital scoliosis is

primar-ily surgical

✔The goal of prophylactic surgery is to prevent

curve progression or attempt a slow progres-sive correction over time through fusions in situ and/or hemiepiphysiodeses

✔The principle of corrective surgery focuses on

attempting to correct the spinal deformity at the time of spinal fusion through either osteo-tomies or spinal resections

✔Neurologic monitoring is essential during

cor-rection of congenital curves

Epidemiology

Most cases of congenital scoliosis are sporadic and therefore non-hereditary

The presence of a coronal plane curvature secondary to an anomalous congenital

vertebral defect that is present at birth is known as congenital scoliosis This can be

distinguished from infantile idiopathic scoliosis by the presence of a structural

ver-tebral abnormality If the verver-tebral anomaly results in a sagittal plane deformity it

will result in congenital kyphosis or lordosis Frequently, the resulting deformity is

a combination of both planes, with congenital kyphoscoliosis being more common

than congenital lordoscoliosis The true incidence of congenital scoliosis is

unknown Among the large studies reported there do not appear to be any

signifi-cant ethnic or geographic differences, although there is a greater female to male

ratio (1.4 – 2.5 to 1) Most cases of congenital scoliosis are non-hereditary and pose

little risk to subsequent siblings or offspring [3, 45, 47] In a review of 1 250

congeni-tal deformities at a single institution, Winter found that approximately 1 % of

patients with congenital spinal deformities had a known relative with the problem

[43] In fact, the majority of identical twin studies have shown the congenital defect

to exist in one of the siblings, but not in the other [15, 29, 40] Rare reports of both

twins having congenital spinal anomalies do exist [1] Cases with a syndromic

asso-ciation (Jarcho-Levine, spondylothoracic dysplasia, spondylocostal dysplasia) can

have a hereditary component, and are typically associated with multiple levels of

bilateral failures of segmentation, multiple fused ribs, and missing segments [11, 27,

30] In these cases, where multiple complex anomalies exist, the related risk is up to

10 % for similar lesions in siblings or subsequent generations [22] The incidence of

associated malformation has been reported to be as high as 25 % for urologic

condi-tions [25], 10 % for cardiac condicondi-tions [4], and 28 – 40 % for neuroaxis anomalies

[4, 8, 33, 34, 46]

a b

c

d

e

Case Introduction

Technique for surgical excision of a

hemivertebra through a posterior

only approach A 7-month-old girl

was diagnosed with a congenital

hemivertebra An MRI was obtained

revealing a tethered cord which

was subsequently released She

was otherwise healthy and the

remaining work-up did not reveal

any other associated genitourinary,

cardiac, or neurologic

malforma-tions Radiographs (a) demonstrate

a fully segmented hemivertebra

located at the lumbosacral

junc-tion Due to the magnitude of the

curve, location of the anomaly

resulting in an oblique take-off of

the spine, and associated pelvic

obliquity The patient developed a

substantial clinical deformity (b)

with coronal imbalance These

cases are perhaps the best

indica-tion for early surgical intervenindica-tion.

As a result, at 7 years of age the

patient underwent an excision of

the hemivertebra through a

poste-rior approach only (Fig 4)

Intra-operative images (c) and postoperative radiographs (d) confirm the position of the instrumentation and correction of the deformity Clinically, the patient has immediate improvement in her coronal balance (e).

Pathogenesis

Up to 60 % of patients

may have malformations

of other organ systems

The etiology in sporadic cases is believed to be related to an insult to the fetus during the 4th–6th week of gestation during spine embryological development [24] It is also during this gestational period that other organ systems are devel-oping in the fetus As a result, up to 60 % of children with congenital scoliosis have malformations in other organ systems, particularly the genitourinary, car-diovascular, and nervous systems [4] Therefore, a careful search for associated anomalies should be conducted in these patients

) non-segmented

Fully segmented hemivertebrae have a normal disc space both superior and

infe-rior to the vertebral anomaly, while a partially segmented hemivertebra has only

one normal disc space and is fused to the adjoining vertebra on the remaining

side A non-segmented hemivertebra has no intervening disc space at all and is

fused to both the superior and inferior vertebrae Furthermore, depending on its

relationship to the spine, a hemivertebra can be further described as:

) incarcerated or

) non-incarcerted

Wedge vertebra and hemi-vertebra are examples of failure of formation

An incarcerated hemivertebra appears to be “tucked into” the spine with its

pedi-cle falling in-line with the adjacent pedipedi-cles, while a non-incarcerated

hemiverte-a

Figure 1 Classification of congenital scoliosis

Congenital anomalies of the spine can be classified either as failure of formation or failure of segmentation.a

Hemiverte-bra and wedge verteHemiverte-bra are two common examples of failure of formation Notice that hemiverteHemiverte-bra can be further

sub-classified as fully segmented, semi- (or partially) segmented, non-segmented, incarcerated and non-incarcerated.

Figure 1 (Cont.)

bBlock vertebra is an example of a bilateral failure of segmentation while unilateral bars are examples of unilateral failure

of segmentation A unilateral bar with a contralateral hemivertebra has the worst prognosis for progression and is an example of a mixed anomaly (both failure of formation and failure of segmentation).

bra protrudes out of the spine with its pedicle lying outside the line of the

adja-cent pedicles [26] In general, a non-incarcerated vertebra has a worse prognosis

for progression when compared to an incarcerated vertebra

Unilateral unsegmented

bars and block vertebra

are examples of failure

of segmentation

A unilateral unsegmented bar is a vertebral bar fusing the discs and facets on

one side of the vertebral column, while a block vertebra is the result of bilateral failure of segmentation with complete fusion of the disc between the involved vertebrae In some cases, fused ribs may also be present, typically on the same side as the unsegmented bar Mixed anomalies are combinations of both failure

of formation and failure of segmentation and can occur in any combination

Clinical Presentation History

Congenital spinal anomaly

may be found incidentally

Patients with congenital scoliosis can present at any time Often the diagnosis

of the spinal deformity is made in utero at the time of the prenatal ultrasound

[5] Although in most cases the exact anomaly cannot be diagnosed at that

time, it is essential that the ultrasonographer also look for other associated conditions such as spina bifida, and cardiovascular, urogenital or other

syn-dromic malformations Prenatal counseling and awareness of the overall prog-Congenital scoliosis is often

associated with other

non-spinal anomalies

nosis of these kinds of deformities is essential to provide appropriate informa-tion to the parents The congenital curve may also be discovered incidentally

on routine radiographs performed for any other reason, such as a chest X-ray for respiratory problems or congenital heart disease, or abdominal films for belly pain The importance of these images should not be overlooked, because later they can provide essential information in assessing progression of the deformity

a b c

d

Figure 2 Physical findings suggestive of congenital spinal anomaly

A careful physical examination of the whole body is mandatory Findings may

be as obvious as a gross coronal imbalance; however, often the signs are more

subtle Evidence ofaspinal asymmetry,ba hairy patch,ccalf ordfoot

asymme-try is suggestive of an underlying congenital malformation.

Otherwise, the child will be referred for the evaluation of a spinal deformity that

was picked up by the family, school nurse, or their physician Findings that

should raise the suspicion of an underlying congenital malformation are:

) a hairy patch

) midline skin hemangioma

) a sacral dimple

) a foot malformation

) leg asymmetry

) urinary symptoms

) an unusual or rigid curve (Fig 2)

Skin stigmata or musculo-skeletal anomalies may indicate congenital anomaly

In extreme cases, congenital scoliosis is only discovered at the time of the surgical

procedure (of what was thought to be an idiopathic scoliosis), as it may not have

been visible on the radiographs due to the rotation of the vertebrae

Physical Findings

The evaluation of the patient follows the same rules as for any spinal deformity

examination An assessment is made of:

) balance of the trunk (plumb line dropped from C7 and the skull)

) balance of the shoulders

) rigidity of the curve ) the rib hump ) associated malformations

The physical examination should include:

) whole spine ) skin ) a complete musculoskeletal status ) a thorough neurologic examination The evaluation must follow

the same rules

as for any spinal deformity

examination

The clinical assessment should also search for:

) craniofacial malformations ) Klippel-Feil web neck ) cardiac malformation ) urinary malformations Serial clinical photographs

are helpful for monitoring

progression

Clinical digitalized photographs should be obtained because they best reflect the

patient’s clinical presentation It is important to note that sometimes, although the Cobb angle does not change, the clinical deformity may worsen and may be picked up as an increased shoulder imbalance, trunk shift or a worsening of the compensatory curve requiring early surgical intervention

Diagnostic Work-up

The high frequency of associated malformations necessitates a thorough diag-nostic work-up of the patient and it is mandatory to not only concentrate on the spinal deformity

Imaging Studies Standard Radiographs Standard radiographs are still the method of choice for an initial screening and

assessment The appropriate initial work-up of patients with congenital scoliosis should include:

) whole spine radiographs ) functional views

) cervical spine radiographs ) spot views of the malformation ) chest radiographs

Whole spine posteroanterior (PA) and lateral radiographs are essential to assess the

deformity comprehensively The best X-rays are usually ones taken at birth, and one should track them down if they are available After 1 year of age, radiographs should be taken as upright standing films, with the legs in extension and the pelvis level, to compensate for any leg length discrepancy The Cobb angle should be

mea-sured from endplate to endplate or, if not feasible, one should use the pedicle lines.

It is essential that the same landmarks be used during subsequent follow-up mea-surements Several Cobb angles may have to be calculated and recorded, including the Cobb angle measuring the congenital deformity and one of the overall curve The same landmarks

should be used during

each follow-up radiographic

measurement

Functional views (flexion/extension, side bending, or traction views) can be

used to provide information about instability, flexibility, and rigidity of the deformity It is accepted that in congenital scoliosis a worsening of the Cobb angle of at least 10° is sufficiently significant to be termed as progression [23]

classic clinical triad of short neck and low posterior hairline, with a limited neck

range of motion These malformations are often not very well visualized in whole

spine radiographs, and spot views of the malformation and flexion-extension

lat-eral radiographs may also be necessary Recently, studies have noted that the

increased anterior atlantoaxial interval (ADI) frequently seen in these patients

may not necessarily be related to clinical symptoms and that the presence of

occi-pitalization and decreased posterior ADI may provide additional information for

Search for rib synostoses identifying patients at risk for developing subsequent neurologic sequelae [34,

36] In addition, chest cage X-rays will be required in the case of a thoracic curve

to look for rib synostoses, which may behave as a bar if they are close to the spine.

Magnetic Resonance Imaging

When a further assessment is needed or in the process of surgical planning, MRI

can provide valuable anatomic detail MRI with cartilage sequences provides the

best quality pictures of the cartilage endplates, possibly giving the best

informa-tion on growth potential and contact with the intramedullary elements In

addi-tion to better defining the congenital anomaly, MRI has become the modality of

choice for the diagnosis of commonly associated intramedullary disorders such

as syrinx, tethered cord, or Chiari malformations (Fig 3a–c)

Obtaining an MRI scan

to search for associated neurologic malformations

is mandatory

The patient with a tethered cord may be asymptomatic or present with a range

of neurologic symptoms ranging from increased spasticity or gait disturbances,

to progressive loss of motor or bowel and bladder function MRI findings may

include the presence of a low lying conus or thickened filum terminale If present,

surgical untethering is typically warranted to avoid incurring further neurologic

deficits Another association frequently identified on MRI includes the Chiari

malformation Although the clinical presentation in these patients is extremely

variable, the common MRI finding is characterized by caudal displacement of the

cerebellar vermis, tonsils, and cervicomedullary junction into the spinal canal

(Fig 3c)

Computed Tomography

CT can help define the congenital anomaly better

Tomographs are classic for showing a bony bar, but have lost their role in the

diagnostic assessment with the advent of thin-slice high resolution computed

tomography (CT) CT with thin slices and with reconstruction is useful in very

complex deformities and to facilitate surgical planning

a b c

Figure 3 MRI identifies common associated intramedullary disorders

Spinal cord anomalies can occur in up to 40 % of patients with congenital spinal scoliosis Common associated findings includeasyrinx,btethered cord with low lying conus, orcChiari malformation.

Specific Investigations

Renal and bladder ultrasound imaging is recommended for all patients on their

initial presentation and further genitourinary imaging is obtained as indicated

A cardiac assessment is also required by the cardiologist, as congenital scoliosis

has a 12 % incidence of associated cardiac malformation Echocardiography is

therefore often indicated to rule out an underlying cardiac problem

Non-operative Treatment

Bracing usually is ineffective

in congenital scoliosis

Non-operative treatment of congenital scoliosis will consist in either observation

of the curve or bracing Observation should be applied only for non-progressive balanced curves In most instances bracing is ineffective in congenital scoliosis It may be indicated for long flexible curves, controlling compensatory lumbar curves, helping to rebalance the spine, or postoperative use until the fusion is solid

A prerequisite for counseling patients on the choice of treatment is a thorough knowledge of the natural history particularly when surgery is considered In con-genital scoliosis, natural history is predominately influenced by the risk of curve progression

Natural History and Progression

Curve progression in

congenital scoliosis is related

to the type and location

Because of the wide range of deformities that can occur in congenital scoliosis, predicting the risk of curve progression can be difficult As a general rule, the

rate of progression is directly related to:

) the potential for asymmetric growth, and therefore related to the presence

or absence of an intervening disc(s) ) the location of the vertebral anomaly (Case Introduction)

one fully segmented hemivertebra (1 – 3 degrees/year)

wedge vertebra (minimal to no growth potential)

block vertebra (stable)

Lowest risk of progression

While these examples are fairly straightforward, the anatomy in many mixed

anomalies can be unclear, with a prognosis that is unknown In these instances,

the patient must be followed closely for evidence of curve progression In

gen-eral, the overall average progression per patient is 5 degrees per year [44]

Early surgical intervention may be required to address curves that result in significant shoulder, pelvic, or trunk imbalance

Location of the congenital anomaly can affect both curve progression and

overall appearance of the patient Upper thoracic curves tend to progress less

than thoracolumbar and lumbar curves However, although these upper thoracic

curves seldom reach 30°, they can cause significant shoulder imbalance that may

require early surgical intervention Similarly, low lumbar curves can induce an

oblique take-off from the spine resulting in pelvic obliquity and truncal

imbal-ance Mid-thoracic curves, with the apex centered at T5–T7, can induce a

pro-gressive compensatory low thoracic or lumbar curve that may need to be

included in the fusion if they become bigger and structural In these instances it

may be important to consider early surgical intervention before these changes

occur [3]

Operative Treatment

General Principles

The treatment of congenital scoliosis is primarily surgical

The treatment of congenital scoliosis is primarily surgical [14, 46] The goal is to

achieve a solid fusion and prevent further progression, and if possible decrease

the deformity to achieve as straight a spine as possible at the end of growth

How-ever, the curves are often rigid and correction difficult to achieve; therefore the

best approach is early recognition and careful monitoring [22] In this manner,

early “prophylactic” surgery is possible by anticipating and halting progression

before significant deformity occurs [3] It is even possible in some cases to

achieve partial correction over time However, in many cases some degree of

immediate correction is desired In these cases, the surgical procedures are

designed to correct the curve through the use of spinal instrumentation,

osteoto-mies, and spinal column and vertebral resections

Surgical Techniques

“Prophylactic” Surgical Procedures These procedures are predominantly referred to as “in situ fusions and hemiepi-physiodesis.” The general principle is to balance the growth by slowing or

stop-ping the convex side growth while allowing the remaining concave growth poten-tial to catch up

In situ fusion can be done with a single posterior fusion with or without instrumentation, or with an anterior fusion, or as an anterior-posterior fusion These operations can be performed if the three-dimensional aspects of the defor-mity have been fully understood However, the compensatory curve above or below the fused segment may still progress after such procedures Some correc-tion of the so-called fusions can be achieved if one uses a corrective cast postop-eratively

Asymmetric growth

is balanced by arresting

growth on the convex side

Hemiepiphysiodesis tends to achieve progressive correction over time, taking

advantage of the intact growth plates on the concave side of the deformity (Case Study 1) In most cases it requires an anterior and posterior approach to the spine Anteriorly, one-third of the disc space and corresponding endplates on the convexity of the curve are removed and fused The hemiepiphysiodesis can be performed through a mini-thoracotomy, thoracoscopically, or even transpedicu-larly [17, 31] Posteriorly only the convex side is approached and fused The patient is then immobilized in a cast in the position of maximum correction to take advantage of the flexibility of the curve The results are, however, somewhat

unpredictable [13, 18, 42], and these procedures are typically limited to young

The outcome of hemiepiphysiodesis

is not easily predictable

patients (under 5 years of age) and to curves of less than 50° They should not be carried out if there is a kyphosis component to the deformity A very careful fol-low-up is necessary, as progression of the deformity can still occur during the adolescent growth spurt

Corrective Surgery Procedures Posterior Curve Corrections

Neurologic monitoring

is essential during

correc-tion of congenital curves

Posterior spine fusion without instrumentation and correction with a cast is an option in young children, but the lack of anterior fusion exposes the spine to the crankshaft phenomenon if the anterior growth plates overcome the posterior fusion Posterior spine fusion with instrumentation is indicated in older patients, where there is no risk of crankshafting [46] Anterior and posterior spine fusion with discectomies and instrumentation can achieve a significant correction in the mobile segments of the spine The danger with all corrective procedures is overcorrection and distraction of the curve with subsequent neurologic compli-cations In such cases the distraction should not be done first The compression rod should be inserted first and then only minimal distraction applied on the concave rod The use of spinal cord monitoring and/or a wake-up test after cor-rection is mandatory Neurologic monitoring can never be emphasized enough during such corrections (Case Study 2) Anterior stabilization of the spine with a strut graft done through a convex, or for biomechanical reasons from a concave, approach should be considered if there is a significant kyphotic component to the deformity