1. State of the Art in Sagittal Balance
X1th International Turkish Spine Congress
State of the Art in Sagittal Balance
Mehmet Bülent Balioğlu
Baltalimanı Metin Sabancı Bone Diseases Training and Research Hospital,
Istanbul, Turkey

2. Introduction
Adult spinal deformity (ASD) resulting in coronal and/or sagittal plane decompensation.
idiopathic scoliosis
de novo or degenerative curves
ASD with a high prevalence among the healthy, elderly population (68%).
Mostly related to the sagittal plane, with little correlation between coronal deformity and self-reported disability.
A common feature of ASD, an increasingly recognized cause of pain, and associated with disability and poor quality of life.
(Savage JW, et al. Global Spine J 2014)
(Schwab F, et al. Spine 2005)
(Lafage V, et al. J Neurosurg Spine 2011)
(Schwab FJ, et al. J Spine 2013)
(Pellise F, et al. E Spine J 2015)
(Joseph SA, et al. J Am Acad Orthop Surg 2009)

3. Introduction
Adults with spinal deformities often experience positive sagittal balance.
These compensatory mechanisms can be a source of major discomfort and disability for patients.
pelvic retroversion
flexion of the knees
restriction of hip motion
Positive sagittal plane imbalance is directly associated with decreased health-related quality-of-life (HRQOL) outcome scores.
Postoperative improvement in sagittal plane alignment significantly improves patient outcomes.
(Glassman SD, et al. Spine 2005)
(Glassman SD, et al. Spine 2005)
(Schwab FJ, et al. Spine 2002)
Recent studies have demonstrated that sagittal balance is the most important and reliable radiographic predictor of clinical health status in the adult with a spinal deformity.
Joseph SA, et al. J Am Acad Orthop Surg 17: , 2009
(Joseph SA, et al. J Am Acad Orthop Surg 2009)
(Pellise F, et al. Eur Spine J 2015)
(Smith JS, et al. Neurosurg Spine 2014)
(Smith JS, et al. Spine 2013)

4. Introduction
Ideal spinal alignment allows a standing posture with minimal muscular energy expenditure.
This is accomplished through a complex relationship between the physiologic curvatures of the spine, the morphology of the pelvis, and the musculature of the axial and appendicular skeleton.
Current radiographic parameters allow us to quantify the degree of malalignment in correlation with patient’s symptoms and health status.
(Schwab F, et al. Spine2010)
(Bhalla A, et al. Seminars in Spine Surgery 2015)

5. Sagittal Balance Cone of Economy
Spinopelvic balance in the sagittal plane is an open linear chain linking the head to the pelvis.
The Dubousset cone of economy concept is important in
maintaining upright posture
minimized energy expenditure with standing and walking
Increasing positive sagittal imbalance causes
a position toward the periphery of the cone
increased muscular effort and energy expenditure
causing pain, fatigue, and disability
If the body is shifted beyond the periphery of the cone, external supports are needed:
a cane, crutch, or walker
(Berthonnaud E, et al. J Spinal Disord Tech 2005)
(Dubousset J. New York, NY: Raven Press; 1994)
(Schwab F, et al. Spine 2010)
Most persons with symptomatic sagittal plane deformity present with alignment at the periphery of this cone.
(Schwab F, et al. Spine 2010)
Cone of Economy

6. Clinical and Radiographic Evaluation
In the radiographic assessment we need
a standard full-length (36-inch) posterior-anterior and lateral spine x-rays
the hips and the knees fully extended
For the lateral radiographs
elbows and wrists should be fully flexed
hands in a fist
the proximal interphalangeal joints placed into the supraclavicular fossa
With no external supports
In Hyperextension films
a bolster placed at the apex of the deformity
prone and supine images
New system radiographs have been developed for postural assessment analysis (EOS Imaging, Paris, France)
(Horton WC, et al. Spine 2005)
A comprehensive neurologic exam must be performed, and any motor or sensory deficits documented.
Savage JW, Patel AA. Global Spine J 4:287–296, 2014

7. Radiographic Evaluation
Regional Parameters
Thoracic Kyphosis
Thoraco-Lumbar
Lumbar Lordosis
Global Alignment
SVA (Sagittal vertical axis)
T1-SPI (T1 & T9 sagittal tilt)
TPA (T1 pelvic angle)
Proximal thoracic slope
Pelvic Parameters
Pelvic Incidence
Sacral Slope
Pelvic Tilt A B C A B C
Regional Parameters
Global Alignment
Pelvic Parameters 7

8. Regional Sagittal Alignment
Spine must ultimately balance the occiput over the sacropelvic axis in an energy-efficient position.
Regional sagittal alignment is assessed by;
Thoracic kyphosis (T5–T12) (41° ± 12°)
Lumbar lordosis (T12–S1) (60° ± 12°)
Thoracolumbar kyphosis (T10-L1)
Regional deformity is characterized by sagittal malalignment within the cervical, thoracic or lumbosacral regions of the spine.
Hypokyphotic < 20°, Hyperkyphotic > 60°
Hypolordotic < 30°
(Berthonnaud E, et al. J Spinal Disord Tech 2005)
(Dubousset J. New York, NY: Raven Press,1994)
(Schwab F, et al. Spine 2006)
(Schwab F, et al. Spine 2010)
(Joseph S, et al. J Am Acad Orthop Surg 2009)
The spine, which rests on the pelvis (first vertebra), has to adapt its form to stay in balance.
Transition from lumbar lordosis (LL) to thoracic kyphosis (TK) is a point called the inflection point.
Spine segmentation and lumbar lordosis.
Inflection points are the points of change in curvature and do not necessarily correspond to anatomical structures.
Amplitudes of spinal curvature must be measured from these points.
Lumbar lordosis; Measure of the angle measured by Cobb’s method from the sacral end plate to the inferior end plate of the thoracic 12 vertebra.
Thoracic kyphosis: Measure of the angle measured by Cobb’s method between the superior end plate of the most clearly visible uppermost kyphotic thoracic vertebra and the inferior end plate of the thoracic 12 vertebrae or lower most kyphotic vertebra.
(Berthonnaud E, et al. J Spinal Disord Tech 2005)

9. Global Sagittal Alignment
Global spinal alignment is determined by the net interaction of each of the regional alignments.
Assessment is made by a vertical line dropped from the center of the C7 vertebral body.
SVA passes through the posterior superior corner of the S1 vertebral body.
If falls anteriorly or posteriorly, the sagittal balance is positive or negative
Mean in asymptomatic adults 0.5 cm +/- 2.5 cm
Ideal SVA less than +/- 5 cm
Global sagittal deformity occurs when the C7 plumb line, known as the SVA, falls 5 cm or more anterior to the posterior corner of the S1 endplate.
Normal/Neutral C7
Positive SVA C7
Measured as distance between plumb line from mid point of inferior endplate of C7 and supero-posterior corner of S1
In neutral SVA, plumb line from C7 intersects with supero-posterior corner of S1
The C7 plumb line, a vertical line drawn from the center of the C7 vertebral body running parallel to the vertical edge of the radiograph, should pass within a few millimeters of the posterior-superior corner of S1.
(Jackson RP, et al. Spine 1994)
(Schwab, et al. Spine 2010)

10. Global Sagittal Alignment
It is normally kyphotic from T1 to T12 and lordotic from L1 to L5.
The spine, pelvis, hips, and knees are all involved in maintaining the balance.
The following are evaluated
normal and abnormal TK and LL
SVA and the C7 plumb line
SVA increases with age.
(Lafage, V, et al. Spine 2008)

11. Global Sagittal Alignment
T1 spinopelvic inclination (T1-SPI)
T1 or T9 sagittal tilt is the angle subtended by a vertical plumb line from the center of the T1 or T9 vertebral body and a line drawn to the bicoxofemoral axis.
There is a correlation between T1-SPI and patient self reported function
with SRS, ODI, and SF-12 assessments of HRQOL
T1-SPI is superior to the SVA
does not differentiate between compensated offset of the upper thoracic spine and deformity with pelvic retroversion.
T9-SPI can be used, with the added benefit of greater visibility on radiographs as compared to T1
(Schwab F, et al. Spine 2009)
Proximal thoracic tilt (PTT): Angle between the line joining the midpoint of the bicoxo-femoral axis to midpoint of superior end plate of the most visible and most proximal thoracic vertebra and the vertical.
Thoracic apical tilt (TAT): Angle between the line joining the midpoint of the bicoxo-femoral axis to center of thoracic apical vertebra and the vertical.
(Lafage V, et al. Spine 2009)
(Lafage, V, et al. Spine 2008)

12. Global Sagittal Alignment
The interaction between SVA and PT is important to understand the true extent of a patient’s deformity.
T1 pelvic angle (TPA) is a novel parameter showing both trunk inclination and pelvic retroversion.
TPA is the angle between the line from the femoral head axis to the centroid of T1 and the line from the femoral head axis to the middle of the S1 endplate.
Increasing values of TPA have been correlated with worse health outcome measures.
TPA can be measured intraoperatively with the patient in the prone position.
The severe deformity threshold for TPA was determined to be 20° (ODI > 40)
4.1° (ODI change = 15)
(Ryan DJ, et al. Spine 2014)
It is defined as the angle between the line from the femoral head axis to the centroid of T1 and the line from the femoral head axis to the middle of the S1 endplate.
TPA is a direct geometric measure of the magnitude of the thoracolumbar deformity; it combines the information obtained from the SVA and PT values into 1 measurement.

13. (Le Huec JC, et al. International Orthopaedics 2015)
Pelvic Parameters
Position of pelvis plays an important role in upright sitting and standing postures.
Three pelvic parameters have been defined in the literature.
(A) Pelvic incidence (PI)
(B) Pelvic tilt (PT)
(C) Sacral slope (SS)
Pelvic incidence is constant and specific to each individual, and is independent of the spatial orientation of the pelvis.
(PI = PT + SS)
LL = PI +/- 9 °
PT and SS are dynamic pelvic parameters.
PT is correlated with increased pain and disability.
(Lafage V, et al. Spine 2009)
(Le Huec JC, et al. International Orthopaedics 2015)
(PI = 52° ± 10°)
(PT = 15° ± 7°)
(SS = 30° ± 9°)
(Legaye J, et al. Eur Spine J 1998)
Three pelvic parameters have been defined in the literature.
Pelvic incidence (PI) is a constant morphologic parameter, which has been demonstrated to influence lumbar alignment and specifically the degree of lumbar lordosis (LL). In general, LL should approximately match PI (PI = LL ± 9 degrees).
Pelvic tilt (PT) and sacral slope (SS) are dynamic pelvic parameters that measure pelvic version, a compensatory mechanism to help maintain an upright posture in the setting of sagittal malalignment.
(Lafage, V, et al. Spine 2008)
(Labelle H, et al. Spine 2005)
(D. Deinlein et al. Spine Deformity 2013)

14. Pelvic Parameters Compared changes between SVA and PT
Negative SVA (<0); PT = 10°
Neutral SVA (0-5 cm); PT = 16°
Positive SVA (> 5 cm); PT = 21°
SVA increases result in compensatory increase in PT
As PT increases, the SS decreases and PI remains constant.
PI = PT + SS
The degree of pelvic retroversion is essential in understanding the severity of sagittal plane imbalance and plays a key role in determining the amount of surgical correction.
Increasing PT to maintain neutral A B C
Increasing SVA  increase in PT  greater energy expenditure and greater disability
(A) No pelvic retroversion and high sagittal vertical axis (SVA).
(B) Moderate pelvic retroversion and SVA.
(C) High pelvic retroversion and no SVA.

15. SRS-Schwab Classification
A classification system can reliably describe a deformity, and establish a basis for treatment.
The SRS-Schwab ASD classification includes a curve type descriptor, and a three sagittal spinopelvic modifiers:
PI-LL mismatch, SVA, and PT
The most important components are:
PI - LL within 10 degrees (normal)
SVA (quantifies global malalignment)
PT (measures the degree of pelvic retroversion)
Each classified as
Non- pathological (0)
Moderate deformity (+)
Marked deformity (+ +)
SRS-Schwab Classification for ASD
For each modifier, the SRS-Schwab Classification specifies a range of values to classify it in 1 of 3 ways: nonpathological “0,” moderate deformity “+,” or marked deformity “+ +.”
(Schwab F, et al. Spine 2012)

16. SRS-Schwab Classification
These parameters are associated with HRQOL outcomes
They were established on the basis of patient-reported outcome data.
SRS –Schwab classification has
clinical relevance and applicable
surgical goals using the spinopelvic modifiers
SRS-Schwab Classification for ASD
(Schwab F, et al. Spine 2012)
(Schwab F, et al. Spine 2010)
(Terran JS, et al. Neurosurgery 2013)

17. Sagittal Malalignment
Sagittal imbalance is observed
in degenerative conditions
low back pain
age-related changes
iatrogenic and postrraumatic causes
genetic or metabolic disease processes
Compensation of spinal imbalance in degenerative spinal disorders is seen as
Loss of lumbar lordosis and sagittal imbalance compensated by pelvis retroversion (B)
Neuromuscular control and pelvis insufficient to compensate sagittal imbalance (C)
a. Normal balance;
b. Loss of lumbar lordosis and sagittal imbalance compensated by pelvis retroversion;
c. Neuromuscular control and pelvis retroversion are not sufficient to compensate sagittal imbalance, and the patient bends knees in order to bring back as posteriorly as possible the C7 plumb line. HE hip extension, FOV femur obliquity with vertical
Abnormal parameters of sagittal balance are observed in degenerative conditions, such as LDDD and low back pain.
It is important, however, to differentiate these conditions from age-related changes.
(Le Huec JC, et al. International Orthopaedics 2015)
(Joseph SA Jr, et al. J Am Acad Orthop Surg 2009)
HE hip extension, FOV femur obliquity with vertical

18. Surgical Management
Symptomatic deformity often unresponsive to nonsurgical treatment.
There is an overall long-term success rate of only 27% with conservative treatment.
In symptomatic patients, surgical treatment is superior to conservative care.
Surgical management of patients with ASD may be considered for patients with progression of deformity, neural compromise, and pain and functional limitations.
(Savage JW, Patel AA. Global Spine J 2014), (Ryan DJ, et al. Spine 2014)

19. Surgical Management
Preoperative hip flexion contractures should be corrected prior to spinal reconstruction, as this often significantly contributes to the overall malalignment.
Flexible deformities may be addressed through anterior or posterior spinal decompression/release with instrumentation.
Fixed deformities require corrective osteotomies.
Several computer-based programs may help in preoperative realignment planning.
Spineview Analysis ENSAM, Paris, France)
Surgimap (Surgimap Spine Software, Nemaris Inc, New York, USA)
(Savage JW, et al. Global Spine J 2014)
(Lafage V, et al. Spine 2009)
(Schwab F, et al. Spine 2010)
(Atıcı Y, et al. Eur Spine J 2015)
Atıcı Y, et al. Eur Spine J 2015

20. Type of Osteotomy The choice of osteotomy depends on
goals of the procedure
correction requirements
underlying etiology of the deformity
native bone quality of the patient and the anatomic variations
Posterior column osteotomies (Smith Peterson or Ponte) (Type 1-2)
10° correction per level.
The PSO (type 3-4)
30° correction at a single level.
A vertebral column resection (type 5-6)
up to 40° to 60° from a single level.
A 3CO restores sagittal balance, correlates with HRQOL outcomes.
Spinal Osteotomy Classification, Described by Schwab.
Atıcı Y, et al. Eur Spine J 2015
(Schwab FJ, et al. Spine 2013), (Glassman SD, et al. Spine 2005), (Lafage V, et al. Spine 2009),
(Klineberg E, et al. Neurosurg Clin North Am 2013)

21. (Lafage V, et al. Spine 2009), (Turner JD, et al. Eur Spine J 2015)
Summary
Several radiographic parameters have been shown to correlate with patient quality of life and normative thresholds have been established.
Studies have shown that sagittal balance is the most important and reliable radiographic predictor of clinical health status in adult patients with spinal deformity.
Current radiographic goals include:
SVA within 5 cm
PI and LL mismatch less than 10°
PT less than 20°
T1SPi less than 1°
Restoration of these normal sagittal parameters has become a primary objective in ASD surgery.
Treating surgeons should focus on restoring global spinopelvic alignment, including keeping the SVA within 5 cm, the pelvic tilt to within 25 degrees, and the lumbar lordosis proportional to the pelvic incidence.
(Bhalla A, et al. Seminars in Spine Surgery, 2015), (Schwab FJ, et al. Spine 2013),
(Lafage V, et al. Spine 2009), (Turner JD, et al. Eur Spine J 2015)

22. Thank you for your attention
X1th International Turkish Spine Congress
Thank you for your attention