The spine is divided into zones. The neck zone (Latin CERVICAL) has seven vertebrae. Numbered from the top they are C1, C2, C3, C4, C5, C6 and C7. Easy, huh? What makes then “neck” or cervical is the location beneath the head and the absence of ribs - USUALLY. There are no absolutely positively anythings in biology. Get used to it. So a cervical vertebra with a rib isn’t called something else, but rather a cervical vertebra with a rib, an abnormality. 

(Vertebra = 1, ver-tih-bruh , and vertebrae = plural, ver-tih-bray)

The chest area is the rib cage (THORAX) and so the twelve vertebrae with right and left ribs are thoracic vertebrae. Numbered from top to bottom they are T1 through T12 (total 24 ribs).

The low back, the LUMBAR spine again usually has no ribs and the 5 vertebrae here are from top to bottom called L1 through L5.

The SACRUM vertebrae are fused into one structure. But look closely and you can see the inherent vertebral pattern. Also the pelvis is essentially made of large fused ribs made quite specialized. Even though the sacrum is one solid hunk we name the divisions S1, S2.. like that .. because the nerve root structure from neck to tail follows this division sequence.

The tailbone, or COCCYX, gets back to the rib free pattern tapering off to a point.
 

First we will talk generalities. Not all scoliosis is idiopathic (a thing unto itself with nothing obvious as the cause). When there is something else, the something else is nearly always important. That said, the spine is a stack of vertebrae which seen from the back is a nearly straight line. Exact precision of every little thing isn’t a matter to worry about. This is biology not machine shop.

Children wiggle and so will have x-rays with the wiggling seen. That is not scoliosis. That is wiggling. We try to concern ourselves with those oddities which can and likely will progress. That is we are concerned about a process, not a shape, per se. If we knew for a fact that the curve seen here would absolutely not change over time, then we would say cool, let it be. So it gets to be a matter of statistics. How much curve makes it how likely to be a progressive process and not just a curve? Beware! The overwhelming bulk of data is about idiopathic scoliosis (ie: almost all teenage girls). You can not, must not, blindly apply those numbers to other kinds of curves.

How much curce? Measured how? Cobb measured the angle between the vertebrae at the ends of the curve (the two which give the maximum angle). Normally parallel, the angle would be zero.

But that curve of say 50 degrees could be between two vertebrae or even 17. We also need to note how many “levels” (vertebrae) are in this curve.

The spine seldom merely side bends in scoliosis. It rotates on a vertical axis bringing ribs on one side backward and ribs on the other side forward. A girl might think her left breast is larger when the left ribs are carried forward by the rotating vertebrae of scoliosis.

So, how many vertebrae are tilted what degree and rotated how much? Oops. One more thing. How stiff is this curve? We could just push and say really nasty stiff or supple... but that is mmmmmm.. it’s OK... but better is the bend measurements. You take the x-ray twice. Once bending to the right and again bending to the left. A very stiff curve will measure nearly the same in both views. A supple curve may straighten or even bend the other way.

<= This is how scoliosis looks on an x-ray. We can count how many levels and mark the Cobb angle in degrees. Rotation can be guessed at by where the spinous processes line up with the vertebral bodies. Stiffness is a wild guess without hands-on or bend films.

Note there are two curves with measurements in this x-ray. To describe which way the curve is directed, we liken the curve to a pointing arrow ) is like > and so points to the right. ( is like < and so points to the left. We put x-rays for spines up the same way we look at people’s backs - left on the left and right on the right. {What do internists know, anyhow?}.

AGE as a KIND:

Remember that we were more interested in the behavior of the curve than that there is curvature. Babies and young children are different in the way they behave in this regard and so their scoliosis has unique names : Infantile Scoliosis and Juvenile Scoliosis. Adult scoliosis that was once idiopathic or adolescent scoliosis has enough peculiarities to advance in name as well as in age... Adult Scoliosis.

When the actual parts of the spine are missing or extra or blue print scrambled we call that Congenital Scoliosis.

When the nervous system is damaged or muscle disease is present and an imbalance of forces supporting the spine or moving the spine lead to curvatures, we call that Paralytic Scoliosis. There is a subset of paralytic scoliosis that stands out by their numbers, and so we have that subset as Spastic Scoliosis, although it is a heavily mixed population of causes within it.

<= Seen from the side, the exaggerated round shoulders condition is NOT scoliosis. That is called Kyphosis and is in another subject. An old term based on wrong understanding USED to call scoliosis “KYPHO-scoliosis”. People still doing that need to go to continuing education meetings or retire. Every once in a blue moon there actually is a kypho-scoliosis, but that is the odd bird.

The “hump” seen in scoliosis is NOT the spine but those ribs we talked about, the ones rotated backward. Scoliosis has a rotatory deformation making ribs prominent as the spine itself typically loses kyphosis and goes flat to lordotic. whereas kyphosis is a true backward bend of the spine itself.

Adult scoliosis poses additional problems. The more mature tissues resist correction more and the tissues are different in vascularity. Blood vessels penetrate the bone surface more in maturity as those surfaces are no longer being reformed on the fly. So things bleed more.

Adult surgeries therefore have to temper expectations against risks even more than in the younger patients (absent other medical issues).