This is a common question asked after spinal deformity
surgery.
Parents and caregivers are interested in how close their
child’s spine was able to be returned to a “normal” alignment on x-ray. It is a very reasonable question. I would probably ask a similar question if my
child was having scoliosis surgery. As a
parent, I would want my child’s spine to be as close to “normal” as possible. At first glance it would appear to make sense
that the closer the spine correction was to 100%, the better the person will
look, the less pain they will have in their back and the better they will
function now, and for the long-term.
This however is not often true.
To explain why this is the case, a few important facts/points must be
first presented:
#1 Scoliosis
is a 3-dimensional spine deformity. The
spine twists as it turns, much like a water slide that banks when the slide
turns side-to-side. For a more detailed
explanation of this please go to the blog post on 6-6-2020.
#2 The x-rays
we take of the spine can only easily document 2 of the 3 planes of the
scoliosis (coronal and sagittal plane, see below). The third plane is the axial or transverse
plan, which is the “twisting” of the spine.
Sometimes there is a lot of twist in a scoliosis, and sometimes there is
not much twist. Each child and scoliosis
is different. It is hard to measure the
twisting of the plane on the x-rays.
We can more easily measure the amount of twist or rotation
of the spine in the office using the scoliometer (see below).
#3 When we
talk about how much the scoliosis changes the body, from the patient’s
perspective, we really are trying to assess how much different the right side
is from the left side of the body. How
asymmetric is the body side-to-side.
#4 The
outward changes to each person’s body, by the scoliosis, is unique. For example, two people could have a
60-degree scoliosis, with one person having a lot of changes to their body,
while other person has very little obvious asymmetry.
As a surgeon, we often try to achieve maximal 3-dimensional correction
(see the below radiographs). It is
important to note the x-ray which shows the scoliosis is the view from the
front/back of the patient, and is only in a single plane (coronal plane). However, scoliosis is a 3-dimensional problem,
as I explained in a previous blog post when I talked about the abnormal
rotation of the spine and how we can correct this in surgery. Sometimes the transverse plane or axial
plane, which is what cause the rib prominence and asymmetry, may be the most
aesthetically important part of the deformity.
So when the surgeon answers the parent/caregiver’s question
and says “80%” they are only referring to correction in only one plane of a 3
plane problem (coronal plane). However,
as a surgeon I know that maximally correcting a scoliosis is not always desirable,
or safe. If you make the spine completely straight over the areas you operate,
the spine above and below the surgical area may suffer secondarily and then
cause pain, spinal instability and need further surgery.
The next blog post the reason why we don’t always want 100%,
or even 90% of the spine deformity, will be presented.