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Principles of Deformity Correction
Josiah N. Orina and Sigurd H. Berven
Introduction
Spinal deformity encompasses a broad spectrum
of malalignments, including sagittal, coronal,
and axial planes. Deformity of the spine may
include segmental malalignments (olisthesis, lateral subluxation, and rotational subluxation),
regional deformities such as scoliosis and kyphosis of the thoracic and lumbar regions, and global
deformities with sagittal vertical axis malalignment and truncal shifts in the coronal plane. The
impact of spinal deformity is determined most
significantly by sagittal plane parameters [1].
Understanding the impact of malalignment on
health status of patients is important in guiding
an evidence-based approach to deformity correction. The purpose of this chapter is to describe
the impact of deformity on health status and to
detail principles and techniques for correction of
spinal deformity.
Deformity of the spine is an important condition affecting the growing spine and a common
condition in the aging spine. The burden of disease on population health is defined by consideration of the prevalence of disease within the
J.N. Orina, MD • S.H. Berven, MD (*)
Department of Orthopaedic Surgery,
University of California, San Francisco,
500 Parnassus Avenue, MU320W, San Francisco,
CA 94143-0728, USA
e-mail: josiah.orina@ucsf.edu; sigurd.berven@ucsf.edu
36
population and the impact of the disease on
health of the individual patient [2]. The Institute
of Medicine has concluded that priorities for
healthcare research and funding should be based
upon the burden of disease. The high prevalence
and impact of adult spinal deformity make an
evidence- based approach to this condition an
important healthcare priority. Deformity of the
spine has a significant and measurable impact on
health-related quality of life. Patients with symptomatic adult deformity report a health status
preference for their condition that is significantly
worse than other common medical conditions [3,
4]. With an aging population, spinal deformity
presents a considerable health and financial challenge to our healthcare economy [5]. Appropriate
management of the condition may encompass a
spectrum of options including nonoperative care,
limited decompression surgeries, limited fusion,
and complex realignment of the spine [6]. The
treatment strategy that is most appropriate for the
individual patient requires consideration of
symptoms, pathoanatomy, comorbidities, and
patient preference. Appropriate care strategies
maximize the expected benefits of care while
limiting the risks and costs of care [7].
Patients seeking care for spinal deformity
characteristically present with symptoms that
may include back pain, radicular symptoms such
as dermatomal pain, neurogenic claudication,
weakness or numbness, functional decline, concern about appearance, and disability. Treatment
is multidisciplinary and comprises nonoperative
© Springer International Publishing AG 2017
L.T. Holly, P.A. Anderson (eds.), Essentials of Spinal Stabilization,
DOI 10.1007/978-3-319-59713-3_36
487
488
J.N. Orina and S.H. Berven
and operative management strategies [8].
Nonoperative care utilizes analgesics, physical
therapy, and injections to improve patient pain
and function. Surgical treatment aims to improve
health status by decompressing the neural elements, correcting the deformity, and stabilizing
the spine. The last decade (2000–2010) has seen
a rapid increase in the operative management of
spinal deformity with a twofold increase in the
number of surgeries performed for this condition
[9]. The rate of rise of surgery in elderly patients
is greater than the rate of rise in younger populations [10, 11]. Understanding the principles of
deformity correction is important to guide an
evidence-based approach to care that applies
across the broad spectrum of clinical presentations, pathoanatomies, and demographics of
patients with spinal deformity.
Goals of Deformity Correction
A fundamental principle in deformity correction
is establishing appropriate goals of care. Goals of
surgical correction of deformity include improvement of pain, function, appearance, and health
status of the patient. Improvement in patientreported health status (pain, function, selfesteem) is an important benchmark in assessing
the effectiveness of surgical management [12–
14]. Patient improvement can be quantified using
a number of health-related quality of life metrics
such as the Oswestry Disability Index (ODI),
EuroQoI five dimensions questionnaire (EQ-5D),
and Short Form (36) Health Survey (SF-36) [
17]. There is a moderate correlation between
radiographic measures of deformity and health
status. Specifically, Glassman et al. identified
global sagittal alignment – the distance of the C7
plumb line from the posterior margin of the
sacrum – to be the radiographic parameter most
highly correlated with clinical health status in
adult deformity [1]. Sagittal plane deformity is
more strongly associated with impaired clinical
health status than coronal plane deformity, but
there are weak to moderate correlations of clinical health status with coronal plane malalignment. Subsequent research extended analysis to
15–
the lumbopelvic region, and Schwab et al. identified the mismatch of lumbar lordosis and pelvic
incidence and pelvic retroversion as significant
radiographic correlates with pain and disability
[18, 19]. The correlation between radiographic
measures of deformity and health status defines
specific goals for surgical correction of deformity. In the young adult, the goal of surgical
reconstruction of the spine is to correct global
balance so that the C7 sagittal vertical axis (SVA)
falls within 4 cm of the posterior aspect of the
sacrum, the lumbar lordosis is within 10º of the
pelvic incidence, and the pelvic tilt is less than
20º [18]. Figure 36.1 demonstrates the method
for calculating SVA, lumbar lordosis, pelvic incidence, and pelvic tilt.
Indications and Patient Selection
The decision to perform surgical reconstruction
on the patient with spinal deformity is based
upon informed discussion between the patient
and the spine surgeon. Understanding the
expected benefits of surgery, with knowledge of
potential risks and costs, is the basis of informed
choice and appropriate care [20]. Indications for
surgical correction of spinal deformity include
pain and functional limitations that are unresponsive to nonoperative care, progression of deformity, neural deficits, and impairment of health
status related to deformity. In the absence of progressive deformity or neural deficit, a nonoperative approach focused on improving pain and
functionality may be an appropriate initial
approach to care. Nonoperative approaches to
deformity may encompass analgesics, exercise
and physical therapy, physiatry, spinal epidural or
facet injections, and orthotics. Unfortunately,
despite the significant costs of nonoperative care,
there is indeterminate evidence (levels 3 and 4) to
support the efficacy of any specific form of nonoperative care [21, 22]. Studies have shown
poorer outcomes in symptomatic deformity
patients treated conservatively compared to
patients treated surgically [23–25]. While bracing is an effective treatment in preventing
progression in the skeletally immature spine [
26],
36 Principles of Deformity Correction
489
Fig. 36.1 Radiographic parameters important in treatment decisions for adult spinal deformity. (a) Lumbar lordosis is measured from the superior endplate of T12 to the
superior endplate of S1. Pelvic incidence is the angle subtended by a line perpendicular to the midpoint of the superior endplate of S1 and a line from this midpoint to the
center of the femoral heads. Pelvic tilt is the angle between
bracing has not been shown to successfully slow
progression of spinal deformity in the mature
adult skeleton [
27], and the authors do not recom-
mend orthotics for this purpose. Orthotics in the
adult with spinal deformity may be useful intermittently for pain relief and to enable function in
patients with limitations related to pain with
movement.
Patients with progressive deformity, symptomatic neural compromise, and pain and functional
limitations that are unresponsive to nonoperative
care are most appropriate for surgical treatment.
The operative management of deformity in the
adult with spinal deformity is characterized by
significant variability. An appropriate approach to
care requires a multidisciplinary team skilled in
a line from the midpoint of the superior endplate of S1 to
the center of the femoral heads and a vertical line passing
through the center of the femoral heads. (b) Sagittal vertical axis (SVA) is the distance between a plumb line from
the center of C7 and the posterior-superior margin of the
sacrum
preoperative optimization of the patient’s health
status, intraoperative strategies to decompress the
neural elements and restore alignment of the
spine, and postoperative rehabilitation with a
focus on early mobilization and function. Essential
members of the team during preoperative optimization may include primary care providers, cardiologists, pulmonologists, endocrinologists,
physiatrists, and social workers depending on the
patient’s comorbidities, disability, and social
issues. Reversible comorbidities such as poor
nutritional status, poor pulmonary and cardiac
function, osteoporosis, obesity, and nicotine use
should be addressed and treated prior to elective
surgery [
28–30]. Patients with osteoporosis
(T-score of −2.5 or less) must undergo medical
490
J.N. Orina and S.H. Berven
treatment to improve their bone quality prior to
undergoing elective deformity surgery as this can
reduce the risk of postoperative pseudarthrosis
and instrumentation failure. These patients should
be referred to an endocrinologist to consider initiation of teriparatide, an anabolic agent that stimulates osteoblastic activity and significantly
improves bone mineral density [31]. While
bisphosphonates could be considered, these are
less efficacious than teriparatide in improving
bone mineral density [32]. Additionally, animal
studies have suggested that bisphosphonates may
delay bone remodeling after fusion. The impact
they have on fusion rates when used in the perioperative period in humans is unknown [33]. Those
patients with low bone mass or osteopenia
(T-score between −1.0 and −2.5) can be considered for nutritional supplementation with calcium
and vitamin D. Preoperative optimization of the
patient’s health status with treatment of reversible
medical comorbidities such as osteoporosis may
limit complications of care.
Intraoperative Strategies
Surgical Techniques for Deformity Correction
Surgical techniques for deformity correction can
be grouped into anterior, posterior, and combined approaches. The choice of surgical technique is influenced by the goals of surgery,
patient comorbidities, and patient and surgeon
preference. The observed variability in surgical
approaches to deformity correction is a reflection of the broad spectrum of goals and preferences that guide care as well as the heterogeneity
in patient presentation.
Anterior Surgery
Indications for Anterior Spine Surgery
The anterior approach to the spine is a powerful
technique for mobilization of the spinal column
and for correction of spinal deformity. Removal
of the intervertebral disc, annulus, and anterior
longitudinal ligament permits excellent mobilization of the motion segment in lateral bending and
rotation. Complete discectomy including endplate preparation creates an excellent environment for bone healing. The advantages of the
anterior approach include mobilization of deformity and interbody healing. Anterior surgery has
several applications in spinal deformity.
Anterior instrumented surgery for treatment
of spinal deformity was first described by
Hodgson and Stock for the management of
kyphosis in Pott’s disease and paraplegia. Allen
Dwyer introduced the anterior approach to the
spine for the management of scoliosis in 1964
and published his experience in 1969 [
original technique involved a two-stage operation. The first stage consisted of a posterior
release with resection of ligaments and facet capsules along the concavity of the deformity. This
was followed by an anterior operation as a second stage in which discectomies were performed
along the deformity followed by placement of
screws into the lateral vertebral bodies along the
convexity. The screws were then compressed
using cables along the convexity to correct the
curve [35, 36]. While arthrodesis rates were high,
the Dwyer approach was associated with late
curve progression, increased thoracic kyphosis,
and inadequate vertebral body derotation [36].
More rigid anterior fixation systems and the use
of interbody implants have improved the ability
to preserve sagittal alignment and maintenance
of correction in anterior spine approaches.
In deformity correction surgery, the anterior
approach to the spine can be useful in the thoracic
and thoracolumbar spine. Anterior surgery may
permit minimization of the number of levels fused,
allowing shorter constructs with preservation of
motion segments [37, 38]. Limitations can include
pseudarthrosis in the thoracic spine and kyphotic
decompensation in the lumbar spine. Deviren and
colleagues reviewed outcomes in 15 adult and 15
adolescent patients with scoliosis treated with anterior instrumentation and reported 67% curve correction in adults and 80% curve correction in
adolescents. All patients achieved solid fusion, and
there were no cases of kyphotic decompensation or
34]. The
36 Principles of Deformity Correction
491
Fig. 36.2 A 32-year-old female with Lenke 5C deformity
and progressive thoracolumbar curvature associated with
pain. Patient underwent T10–L2 single rod anterior
fusion. (a) Preoperative anteroposterior (AP) scoliosis
loss of lumbar lordosis [38]. Figure 36.2 is a single
rod anterior fusion for a Lenke 5C deformity.
Anterior surgery can also be useful in fixed
multiplanar adult deformity for release and mobilization of rigid spinal deformity and improvement of sagittal and coronal balance. The anterior
approach can improve the efficacy of arthrodesis
by involving the large surface of the interbody
space in the fusion area and by capitalizing on a
biomechanical environment of compression
which promotes bone fusion. Indications for
combined anterior and posterior surgery include
planned fusion across the lumbosacral junction
(L5–S1), post-laminectomy deformity, osteoporosis, lumbar pseudarthrosis, and large coronal
deformities/imbalance (structural curves greater
than 60º and coronal imbalance greater than
5 cm). Long posterior-only fusions across the
lumbosacral junction have a high rate of pseudarthrosis, and the addition of anterior supplementation has been shown to improve fusion rates [
39,
40]. Figure 36.3 is an example of a patient with
osteoporosis and progressive post-laminectomy
deformity. A posterior-only revision approach
X-rays. (b) Preoperative lateral scoliosis X-rays. (c)
Postoperative AP scoliosis X-rays. (d) Postoperative lateral scoliosis X-rays
would have been compromised in healing due to
absent posterior elements for interlaminar fusion.
Anterior surgery is a powerful tool for increasing segmental lumbar lordosis, particularly in
patients with lumbar hypolordosis and a high pelvic incidence – lumbar lordosis mismatch.
Studies demonstrate that approximately 70% of
the total segmental lumbar lordosis comes from
L4 to S1 vertebral segments, and nearly 50% of
total segmental lumbar lordosis comes from the
L5 to S1 segment [
41, 42]. Total segmental lum-
bar lordosis also correlates strongly with spinal
sagittal balance [
41]. In patients with hypolor-
dotic deformity and significant sagittal plane
imbalance, sagittal alignment can be improved
by restoring lumbar lordosis via L4–S1 anterior
lumbar interbody fusion (ALIF). Hsieh and colleagues reviewed a series of 32 patients treated
with ALIF and 26 patients treated with transforaminal lumbar interbody fusion (TLIF) and
found that ALIF was superior to TLIF in improving lumbar lordosis [43]. ALIF resulted in a 6º
improvement in lumbar lordosis whereas TLIF
actually led to a 2º decrease in lumbar lordosis.
492
J.N. Orina and S.H. Berven
Fig. 36.3 A 68-year-old female with osteoporosis
(T-score = −2.8) and three prior laminectomies for neurogenic claudication. Patient developed post-laminectomy
deformity with progressive sagittal and coronal plane
malalignment. The surgical approach was a combined
anterior fusion with structural allograft at L3–S1 and a
Patients with major thoracolumbar or lumbar
coronal curves often have a compensatory fractional curve at the lumbosacral junction. This
compensatory curve can be quite rigid in the
region of L4–5 and L5–S1 and may have a significant impact on coronal and sagittal alignment
of the spine. Additionally, the proximal end vertebra of this lumbosacral fractional curve can be
significantly tilted. Attempting to correct the
major thoracolumbar/lumbar scoliotic curve
without also addressing the fractional curve can
result in suboptimal coronal correction or even
worsening of coronal balance postoperatively. A
balanced correction of the major thoracolumbar
deformity and the fractional curve is an important goal in adult deformity correction. Correcting
the stiff fractional curve can be accomplished by
horizontalizing the tilted proximal end vertebra
via ALIFs at L4–S1. Because the ALIF procedure
posterior instrumented fusion at T10–S1. A posterior-only
revision approach would have been compromised in bony
healing due to absent posterior elements for interlaminar
fusion. (a) Preoperative AP scoliosis X-rays. (b)
Preoperative lateral scoliosis X-rays. (c) Postoperative AP
scoliosis X-rays. (d) Postoperative lateral scoliosis X-rays
involves removing the anterior longitudinal ligament and the concave annulus, the surgeon may
apply distractive forces across the disc space to
horizontalize and derotate the tilted proximal end
vertebrate. In contrast, TLIFs do not involve sectioning of the anterior longitudinal ligament
which can result in less correction of a stiff fractional curve than can be achieved with the
ALIF. Figure 36.4 is an example of a 52-year-old
female with progressive lumbar kyphosis and
severe lumbosacral pain. Her trunk shift is
ipsilateral to the concavity of the fractional lumbosacral curve. Inadequate correction of L4–S1
compared with the major curve from T11 to L4
may have resulted in exacerbation of coronal
plane deformity. An anterior approach to the
spine at L3–S1 facilitated correction of lumbar
lordosis and permitted correction of the deformity from T11 to L4 from a posterior approach.
36 Principles of Deformity Correction
493
Fig. 36.4 52-year-old female with lumbar hypolordosis
and a T11–L4 levoscoliotic major curve. She presented
with progressive deformity and a rigid fractional lumbosacral compensatory curve from L4 to S1. Her trunk shift
is ipsilateral to the concavity of the fractional curve.
Correction of the major curve from T11 to L4 without
adequate correction of the fractional curve from L4 to S1
may have resulted in exacerbation of the coronal plane
deformity. An anterior approach to the spine at L3–S1
Limitations of Anterior Surgery
While anterior surgery – especially when combined with posterior surgery – has been shown
to have good clinical outcomes in spinal deformity cases, it has been associated with significant perioperative morbidity. Any anterior
approach through the chest wall and into the
pleural space can lead to decline in pulmonary
function. Graham and colleagues reported the
pulmonary function tests of 51 patients with
scoliosis treated with an anterior procedure
(thoracotomy, thoracoplasty, and minimally
invasive thoracoplasty). The authors found a
significant decline in postoperative pulmonary
function test values at the 3-month mark compared to preoperative values [44]. Vascular
facilitated both restoration of the lumbar lordosis and
reduction of the fractional curve. This permitted correction of the deformity from T11 to L4 from a posterior
approach without precipitating further coronal imbalance.
(a) Preoperative AP scoliosis X-rays. (b) Preoperative lateral scoliosis X-rays. (c) Postoperative AP scoliosis
X-rays. Patient underwent L3–S1 anterior lumbar interbody fusion followed by T10 to pelvis posterior instrumented fusion. (d) Postoperative lateral scoliosis X-rays
complications can also occur, and control of the
great vessels, segmental vessels, and recurrent
iliolumbar vein is vital to the safety of the anterior approach. Avulsions of great vessels or
venous injury can be life threatening.
Neural injury can result from compromise of
the segmental vascular supply to the spinal cord
secondary to vessel ligation. Direct nerve trauma
can also result from retraction and cauterization at
the neural foramen and within the psoas muscle.
The surgeon should be keenly aware of risk factors for neural injury and paraplegia during the
anterior approach for spinal deformity correction
such as intraoperative hypotension, kyphosis, preoperative neural deficits, prior ligation of contralateral vessels, and congenital deformity.
494
J.N. Orina and S.H. Berven
Intraoperative neuromonitoring is a valuable
adjunct as motor evoked potentials and somatosensory evoked potentials can signal early changes
in spinal cord function. Electromyography and
motor evoked potentials are also useful in detecting injury to peripheral nerves.
Anterior surgery may also result in complications related to genitourinary injury. Identification
of the ureter and retraction of the ureter with the
peritoneum can minimize risk of ureteral injury
during anterior approach to the lumbar spine.
Preoperative ureteral stent placement may be
useful in revision surgery. Retrograde ejaculation
is a well-reported complication of anterior lumbar surgery in men and is due to thermal injury or
direct injury to the autonomic fibers of the superior hypogastric plexus supplying the internal
vesicular sphincter [45].
In addition to the complications of the
approach, anterior surgery often requires staged
procedures. This increases the cost of care, recovery time, and length of hospitalization, all of
which consume more healthcare resources.
Therefore, the use of anterior surgery should
offer an incremental benefit over a posterior-only
approach to add value as a strategy for care.
Specific Surgical Approaches
to the Anterior Spine
The anterior spine can be accessed via different
approaches depending on the location of the spinal pathology. The transthoracic approach provides an anterolateral corridor that allows spine
access from T5 to L2. Access above T5 is limited
by the scapula and is more effective using a transsternal approach. Access between T12 and L2
requires a thoracolumbar approach with release
of the diaphragm from the chest wall. The patient
is placed in the lateral position, and careful attention is given to protecting the axillary region,
eyes, and arms. The incision is made along the
axis of a rib 1–2 segments above the level of the
uppermost disc to be excised. In kyphosis, the
incision may be placed at the level of the upper
disc to be excised. In the setting of coronal deformity, access to the spine is more direct when
approaching from the convex side of the deformity. Ligation of segmental vessels may compro-
mise segmental vascular supply to the spinal
cord. This is an important consideration in the
setting of kyphotic deformity, previous anterior
surgery, and at the watershed levels (T8–L1).
The thoracoabdominal approach permits
access to the spine from T8 to the sacrum. The
thoracolumbar approach requires release of the
diaphragm from the chest wall and permits continuity in the exposure of the thoracic and lumbar
spine. The incision of the diaphragm may begin
at the costochondral junction anteriorly or from
the costovertebral junction posteriorly.
Instrumentation using vertebral body screws is
difficult below the level of L4 due to the position
of the iliac crest. However, interbody instrumentation can be extended to the pelvis. It is important to identify and mobilize the ipsilateral ureter
during this approach. Placement of a ureteral
stent preoperatively may be useful in revision
surgeries. Vascular considerations include identification and control of the recurrent iliolumbar
vein and the L5 segmental vessel. Preoperative
assessment of aortic calcification is also useful to
avoid plaque rupture and embolization.
Abdominal wall pseudohernia after surgery is
common and can be minimized by direct visualization of abdominal muscle innervation during
exposure. A direct hernia is prevented by meticulous closure of the transversus abdominis and
internal oblique, followed by separate closure of
the external oblique layer and by limiting the distal extent of the incision.
The paramedian approach gives the spine surgeon access from the L2–3 interspace to S1. A
transverse incision permits access to one or two
motion segments, whereas a longitudinal incision
may be used for access from L2 to the sacrum.
The patient is positioned supine, and a lumbosacral roll is useful in increasing lordosis. The L5–
S1 level is accessed between the common iliac
arteries as they bifurcate from the aorta. L4–5 is
commonly exposed lateral to the common iliac
vessels.
The direct lateral approach to the anterior column permits access to all disc spaces above L5–
S1. In the lumbar spine, the approach may be
transpsoas or antepsoas. The direct lateral
approach significantly reduces the length of the