Evaluation of Spinal alignment

1. Evaluation of Spinal
Alignment
Dr Tejasvi Agarwal
Spine Fellow

2. Normal sagittal curves
 Cervical Region: Cervical Lordosis (occiput-C7)
averages 40 deg.
 Thoracic Region: Normal Kyphosis (T1-T12) ranges
from 20 to 50 deg.
 Thoracolumbar Region(T12-L1): its essentially straight
with respect to sagittal plane.
 Lumbar Region: Normal lumbar region(L1-S1) ranges
from 30 to 80 deg.

5. Spinal Balance
 Balance is defined as the ability to maintain center of
gravity of a body within its base of support with minimal
postural away.
 Sagittal balance: Normal sagittal balance is present
when a plumb line dropped from centre of C7 lies
within 2.5cm of posterior superior corner of S1.
 Coronal Balance: Normal coronal balance is present
when a plumb line is dropped from center of C7 body
lies within 1cm of middle of sacrum.

8. Sagittal Vertical Axis
 By convention, If SVA falls behind
L5-S1 disc space- Negative
 If SVA falls through L5-S1 disc
Space– Neutral
 If SVA falls in front of L5-S1 disc
space– Positive.
 In Normal patients, SVA is either
Neutral or Negative.
 In normal patients, SVA passes
anterior to thoracic spine, through
the centre of L1 and posterior to
lumbar spine.

9. Cobb’s Method
 It is most commonly used to quantify curvatures in the
coronal and sagittal planes.

10. Pelvic Incidence
 Three sacral parameters are measured: PI, Sacral
slope(SS), and pelvic tilt(PT).
 Pelvic Incidence: is the angle defined by a line
perpendicular to the sacral end plate at its midpoint and
the line connecting this point to the femoral rotational
axis. It is fixed anatomical parameter unique to a
individual.
 Pelvic Tilt: is defined by a vertical reference line and a
line from the midpoint of the sacral endplate to the
femoral rotational axis.
 Sacral slope: is the angle defined by a line along the
sacral end plate line and a horizontal reference line.

11. PI = PT + SS

12.  The slope of the sacrum sets the stage for the lumbar curve; a
horizontal sacral plate (i.e. small SS) is associated with a small
LL.
 However, SS is positionally dependent and altered in mal-aligned
patients due to pelvic retroversion (increase in PT). Thus SS is
unsuitable to guide planning of surgical mal-alignment correction.
 PI, however, is a morphological parameter that is unique to each
individual and has a strong, positive correlation with LL.
 A new parameter relating PI with LL has emerged to guide
surgical planning and enable a patient-specific approach to
treatment goals.
 This novel parameter, PI minus (−) LL, quantifies the mismatch
between pelvic morphology and the lumbar curve. Using the PI-
LL construct, a PI-LL <100 threshold was identified as a spino-
pelvic sagittal alignment goal.

13. PI - LL

14. Global Sagittal Axis
 The GSA was defined as the angle
formed by a line from the midpoint of
the 2 distal femoral condyles to the
center of C-7, and a line from the
midpoint between the 2 distal femoral
condyles to the posterior superior
corner of the S-1 sacral endplate.

15.  The GSA is sensitive to spine, pelvic, and lower-extremity
compensatory changes in the sagittal plane and holds one of the
strongest correlations with patient-reported clinical scores
reported in the literature (0.6 for EQ-5D).
 The advantage of the GSA is that it reflects different stages of
deformity more accurately than previously defined spinopelvic
parameters.
 Specifically, the GSA becomes a critically important alignment
parameter in assessing 2 types of patients: those whose spine is
severely deformed and subsequently recruit lower-limb
compensations after pelvic retroversion is exhausted; and those
who do not have the ability to compensate by pelvic retroversion.
 The GSA is able to reflect the disability of these 2 populations
because of the involvement of lower limbs in the sagittal profile.

16.  Although the pelvis has been extensively studied in the
spinal literature, the lower limbs are beginning to be
investigated using full-body radiographic images.
 Lower extremity compensation via increased flexion of
the knees and ankles and subsequent pelvic shift plays
a significant role in attempts at sagittal realignment and
is therefore the direct effect of a pathological spinal
deformity.

17. Thank you