The changing role for neurosurgeons and the treatment of spinal deformity.

Abstract

Spinal deformity has classically and historically been studied by those in the discipline of orthopedic surgery. This may be attributable to the orthopedic interventionalists' experience with osseous fixation for long-bone and other skeletal fractures. Neurosurgeons have maintained a long-standing interest in complex cervical spinal disorders, and their interest in the larger field of complex spinal deformity has been expanding. An understanding of spinal deformity disorders, biomechanics, bone biology, and metallurgy is necessary before clinical, teaching, and research activities can be undertaken within neurosurgery. The authors describe basic and advanced concepts of spinal deformity management with cases to illustrate teaching points.

Full text

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PINAL deformity is a complex subspecialty that in-
volves the management of disorders that affect the
spinal alignment and balance. Neurosurgeons have
traditionally treated various spinal disorders secondary to
traumatic, congenital, neoplastic, and infectious causes in-
volving the spinal column, cord, and nerves as well as a
wide array of degenerative compression syndromes. As
the ability to treat more complex neurosurgical spinal dis-
orders has evolved, spinal instability has often required
the use of modern reconstructive techniques to preserve
neurological function, maintain or correct spinal align-
ment, and achieve structural stabilization. Alternatively,
some complex neurological disorders are associated with
spinal deformity, whereas certain neurological disorders
are indeed caused by deformity of the spinal column (Fig.
1). It is such spinal deformity–related cases, as well as
others with related disorders, that have generated interest
in this discipline and recognition that a fundamental un-
derstanding of spinal deformity is essential for the practice
of neurological surgery.
Types of Spinal Deformity
The practicing neurosurgeon should be familiar with
the two broad classifications of spinal deformity: coronal-
plane (scoliotic) and sagittal-plane (kyphotic and lordotic)
abnormalities; these curvatures can be readily recognized
on physical examination and confirmed on imaging (Fig.
2). Lordosis is also considered a deformity if present in
abnormal locations such as the thoracic spine, a phenom-
enon that never occurs in the normal thoracic spine. Hy-
perlordosis of the cervical and lumbar spine can occur to
compensate for thoracic kyphosis.
Because spinal deformity is a three-dimensional entity,
the compound terms “kyphoscoliosis” and “lordoscolio-
sis” are often used to define further the character of these
complex curves. Often more than one curve exists in cases
in which the primary lesion (that is, structural curve) is the
true pathological curve that is fixed and is defined by its
larger size and rigidity; however, the secondary curves are
often compensatory because of the primary curve.
Causes of Spinal Deformity
The origins of spinal deformity can be classified into two
broad groups: idiopathic or acquired. These classifications
also generally fall into two broad age categories of pedi-
atric and adult, although notable exceptions exist. There are
numerous causes of both adult and pediatric spinal defor-
mities. Tables 1 to 3 provide relatively comprehensive lists
of most causes/origins of spinal deformity.
Clinical Presentation and Decision Making
The practicing neurosurgeon must possess a fundamen-
tal ability to assess various spinal deformities. Additionally
he/she must be able to recognize their clinical presentations
J. Neurosurg Spine / Volume 2 / March, 2005
J Neurosurg Spine 2:233–242, 2005
The changing role for neurosurgeons and the treatment of
spinal deformity
J. PATRICK JOHNSON, M.D., ROBERT S. PASHMAN, M.D., CARL LAURYSSEN, M.D.,
NEEL ANAND, M.D., JOHN J. REGAN, M.D., AND ROBERT S. BRAY, M.D.
Institute for Spinal Disorders, Cedars-Sinai Medical Center, Los Angeles, California
? Spinal deformity has classically and historically been studied by those in the discipline of orthopedic surgery. This
may be attributable to the orthopedic interventionalists’ experience with osseous fixation for long-bone and other
skeletal fractures. Neurosurgeons have maintained a long-standing interest in complex cervical spinal disorders, and
their interest in the larger field of complex spinal deformity has been expanding.
An understanding of spinal deformity disorders, biomechanics, bone biology, and metallurgy is necessary before
clinical, teaching, and research activities can be undertaken within neurosurgery.
The authors describe basic and advanced concepts of spinal deformity management with cases to illustrate teaching
points.
KEY WORDS
•neurosurgery •spinal deformity•scoliosis•kyphosis
233
Abbreviations used in this paper: AP = anteroposterior; MR =
magnetic resonance; PSO = pedicle subtraction osteotomy.
S

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symptoms minimal. In cases of adolescent scoliosis, brace
therapy is undertaken to delay or prevent the need for sur-
gical intervention. Surgery, in fact, is often delayed as long
as possible or until maximum possible skeletal maturity
has occurred. Skeletal maturity is determined by the radio-
graphic appearance of the iliac apophysis, more common-
ly known as the Risser sign, where skeletal maturity has
been reached approximately at age 14 years in girls and age
18 years in boys.1,24,29Milder cases of scoliosis often will
not progress significantly after onset of skeletal maturity
and therefore will not require further treatment. If the
deformity progresses to an advanced state, however, surgi-
cal correction becomes necessary; thus, the surgeon re-
quires an understanding of the threshold and decision-mak-
ing process for surgical indications. A general indication
for surgery is the following: deformity exceeding 50˚ with
continued and documented progression or intractable pain
refractory to brace therapy. Severe curvature greater than
70˚ is also likely to be associated with cardiopulmonary or
neurological symptoms even after establishment of skele-
tal maturity; these deficits are more difficult to correct in
J. P. Johnson, et al.
234
J. Neurosurg Spine / Volume 2 / March, 2005
FIG. 1. Magnetic resonance image obtained in a 22-year-old pa-
tient presenting with progressive spastic quadriparesis due to severe
basilar invagination and a large syrinx. He underwent a transoral
approach to decompress the severe deformity and then occipito-
cervical fusion for stabilization.
FIG. 2. Long-cassette 36 ?14–in AP (left)and lateral (right)radio-
graphs obtained to evaluate spinal curvature and sagittal balance.
TABLE 1
Classification and terminology of structural scoliosis
idiopathic
infantile
juvenile
adolescent
neuromuscular
neuropathic
myopathic
congenital
failure of formation
failure of segmentation
neurofibromatosis
mesenchymal disorders
Marfan syndrome
Ehlers–Danlos syndrome
other
rheumatoid disease
trauma
fracture
surgical
irradiation
extraspinal contractures
postempyema
postthoracoplasty
osteochondrodystrophies
diastrophic dwarfism
mucopolysaccharidosis
spondyloepiphysial dysplasia
multiple epiphysial dysplasia
infection of bone
acute
chronic
metabolic disorders
rickets
osteogenesis imperfecta
homocystinuria
others
related to lumbosacral joint
spondylolysis & spondylolisthesis
congenital anomalies of lumbosacral region
tumors
vertebral column
spinal cord
and syndromes to establish appropriate patient care and
surgical or nonsurgical treatment.
Idiopathic scoliosis typically develops in adolescent
girls around the time of menarche and presents with a con-
spicuous chest-wall deformity. Most often the effects are
cosmetic, whereas neurological function is normal and

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advanced stages.2,28,30In general, it is also important to
understand that pediatric deformity is often distinctly dif-
ferent from that in adults because the spinal column in chil-
dren is relatively flexible and mobile in contrast to the stiff
and inflexible column present in adults.
The classification of adult deformity can include cases
involving adolescent patients with scoliosis in whom the
curvature has remained stable into adulthood when it then
becomes symptomatic due to adult degenerative spinal
disease. In such cases the thoracic and lumbar spine are
typically involved and the characteristic rotatory deformi-
ty is present, consistent with adolescent deformity (Fig.
2). Alternatively the de novo adult lumbar degenerative
scoliosis is not related to adolescent scoliosis, and in most
of these cases the scoliotic deformity occurs in women
older than 60 years of age and involves the midlumbar
segments (Fig. 3).
J. Neurosurg Spine / Volume 2 / March, 2005
Changing role for neurosurgeons and spinal deformity
235
TABLE 2
Classification and terminology of nonstructural scoliosis
postural scoliosis
hysterical scoliosis
nerve root irritation
herniation of nucleus pulposus
tumor
inflammatory
related to leg length discrepancy
related to hip contracture
TABLE 3
Classification and terminology of kyphosis
postural (roundback)
Scheurmann disease
neuromuscular
myelomeningocele
developmental (late paralytic)
congenital (present at birth)
congenital
defect of formation (hemivertebra)
defect of segmentation (Klippel–Feil syndrome)
traumatic
due to bone &/or ligament damage w/o cord injury
due to bone &/or ligament damage w/ cord injury
postop
postlaminectomy
after vertebral body removal
postirradiation
metabolic
osteoporosis
osteomalacia
osteogenesis imperfecta
other
skeletal dysplasias
acondroplasia
mucopolysaccharidosis
neurofibromatosis
other
collagen disease
Marie–Strupell disease
other
tumor
benign
malignant
inflammatory & infectious
FIG. 3. Adult patient with degenerative lumbar scoliosis (left
panels) who underwent a multilevel anterior lumbar interbody fu-
sion and posterior instrumentation-assisted fusion (right panels).
Kyphotic deformities are caused by forward sagittal-
plane decompensation and can occur in the cervical, tho-
racic, or lumbar spine. The classic thoracic kyphotic de-
formity is Scheurmann kyphosis (Fig. 4), which occurs in

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pediatric and adult patients and presents primarily with
thoracic pain. The prototypical lumbar kyphotic deformi-
ty is the iatrogenic flat-back syndrome, usually occurring
if the patient is incorrectly positioned on the operating
table (in a nonlordotic position) due to instrumentation-
induced loss of lordosis (Fig. 5).
Evaluation and Diagnosis of Spinal Deformity
The practicing neurosurgeon is familiar with clinical
evaluation of the spine to determine the presence of signif-
icant medical, musculoskeletal, or neurological abnormali-
ties that may be associated with various spinal disorders;
this evaluation may be expanded to include basic assess-
ment of deformities.19,25Other clinical and radiographic/
neuroimaging abnormalities should be examined in pa-
tients with curvatures to include body habitus and spinal
column alignment that may exhibit a characteristic asym-
metrical hump in the presence of significant scoliotic defor-
mity (Fig. 6). Full-length (36 ? 14–in) standing spinal ra-
diography is performed to assess the overall spinal balance
(Fig. 2). Cobb angles are measured on these radiographs by
using a goniometer in both AP and lateral orientations
(briefly, a perpendicular line is drawn from the endplates of
the most angulated vertebrae involved in the pathological
curve [Fig. 7]). Coronal and sagittal alignment is assessed
using a plumb line in the AP and lateral projections to
determine if decompensation is present (Fig. 8). Dynamic
J. P. Johnson, et al.
236
J. Neurosurg Spine / Volume 2 / March, 2005
FIG. 4. Sagittal MR image revealing Scheuermann kyphosis
with classic multilevel degenerative discs, multiple endplate irreg-
ularities, and wedging of multiple vertebral bodies (arrows).
FIG. 5. Postoperative images of posterior lumbar L2–S1 spinal
fusion (left) and a T11–12 fusion (right) causing severe flat-back
syndrome with a typically stooped position. The patient was treat-
ed with an L-3 posterior PSO to correct the deformity.
FIG. 6. Photograph of a patient with asymmetrical elevation of
the chest wall (that is, rib hump) due to scoliosis causing spine rota-
tion in rib-cage elevation.

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lateral view flexion–extension radiography is performed to
evaluate sagittal-plane instability (that is, spondylolisthe-
sis), and AP lateral bending radiography is conducted to
evaluate the location of a rigid structural curve of a defor-
mity (Fig. 9). Additional data are acquired, as needed, us-
ing MR imaging or computerized tomography myelogra-
phy for routine clinical evaluation. In general there are
fewer indications for MR imaging and computerized to-
mography scanning in idiopathic scoliosis cases, although
most patients with acquired deformity will need to undergo
some form of advanced imaging.
Epidemiology and Classification of Spinal Deformity
The practicing neurosurgeon should also have a basic
understanding of the epidemiology, natural history and cur-
rent classifications of deformity to manage and communi-
cate with patients as well as to confer with other physicians
regarding spinal deformity. Standard terminology estab-
lished in a glossary by the Scoliosis Research Society is
available on their website (www.SRS.org) and serves as a
common language for defining spinal deformity. Although
some familial tendency for adolescent scoliosis is likely,
there is no clear inheritance pattern nor is there an estab-
lished cause of scoliosis.32A minimum curve of 10˚ must
be present to establish a diagnosis of scoliosis (incidence
~ 3% of the population). Curves greater than 20˚ appear in
0.5% and those greater than 40˚ are present only in 0.1% of
the population.
The anatomical classification of spinal deformity is
based on its physical location (thoracic, thoracolumbar, or
lumbar region);7other systems for defining treatment of
adolescent scoliosis were published in 198315(King clas-
sification) and 200116–18(Lenke classification). The clini-
cal presentation of a deformity is somewhat bimodal, with
idiopathic deformity occurring in the adolescent popula-
tion and adult deformity presenting after 50 years of age.
History of Surgical Treatment for Spinal Deformity
The treatment of spinal deformity originated in ancient
times,9,21dating to Hippocrates,14when traumatic spinal
injuries were treated with a “rack system” to straighten the
spine, indicating a long-term recognition of spinal defor-
mity (Fig. 10).
One of the earliest surgical interventions involving an
implant to stabilize the spinal column was described in
1891 by Hadra,10who used wire fixation to correct tuber-
culous deformity. In 1924 Hibbs13established the effec-
tiveness of in situ osseous fusion to stabilize spinal defor-
mity. According to most experts the modern era of spinal
instrumentation was initiated with the development of
hook/rod technology introduced by Harrington12in 1962.
In 1976 Luque20improved on the latter by introducing the
J. Neurosurg Spine / Volume 2 / March, 2005
Changing role for neurosurgeons and spinal deformity
237
FIG. 7. Diagrams showing the use of a goniometer (left) for measurement of Cobb angles from the vertebral endplates
at the distal ends of the curve and measured to determine the maximum curve angle, measurement of the sagittal-plane
angle (center), and measurement of the coronal-plane angle (right).