Lots of research doesn't sit well with chiropractic since it is not a lab. It's not something you can just dissect inside a laboratory. And many from the answers are somewhat subjective. The patient feels better. The pain sensation is less. Though you will find x-rays and leg-length checks that can be made.
The Art of Chiropractic
So what is the skill of chiropractic?
To the observer, it is a spinal manipulation procedure. Which basically means you're handling someone's joints, mainly within the spine. Although chiropractors look at other joints too.
Because of the practice philosophy of chiropractic, the spine is much more important because it houses the mind and spinal-cord. All of the nerves flow from the spine. And also the nerves control the organs and muscles.
In defining the art i know of a noticeable difference between manipulation and adjustment. These two terms get interchanged in some circles but they are different.
A manipulation isn't chiropractic!
This may shock you at first, but it's true.
A manipulation infers the practitioner is moving a joint without results of position or direction. This means that the person is trying to mobilise some pot.
So if a drawer is jammed, and also you provide a push and shove, you're actually governing the drawer and its fitting!
It's stuck. You unstick it.
Chiropractors usually have preferred this term. This means that the direction of alignment is taken into account. You are correcting a joint in its relationship with other joints inside a certain plane.
Chiropractors call the misalignment of the spine a "listing." With this we mean, one bone in relationship to another can be posterior to the left, which is how it's rotated. It can be posterior left and tilted down (called posterior left inferior), and so on.
It got much more precise than this following the work of Drs John Grostic and Al Wermsing within the 30's and 40's.
They began to list the skull and atlas (the top spinal bone) when it comes to degrees of displacement as based on x-ray. In this you may have for example, the right 2 degrees on the Left 2 degrees, skull to atlas misalignment.
In the 1980's Dr Don Harrison from Wyoming, dealing with Dr Harry Wong, wanted to find out more about the Grostic style listings in degrees.
They determined that head-to-shoulder postures were the cause of the degree misalignments.
Patterns such as rotations, tilts, and side and forward head carriage produced the various angles that Grostic practitioners have been observing for 40 years.
A Grostic "against the kink" was a rotation and "into the kink" a side bend. Gleam third type in which the head side-tilts on the first vertebra (atlas) only.
The Art of Chiropractic requires the manual procedures, dexterity and skill learnt from chiropractic college. In some colleges they use half-tyres to develop the muscle action required.
There is one more thing called a speeder board, which helps for recoil movement.
In modern days, instruments (for example blocks and activators) are used. These require a comprehension in the practitioner in positioning depth.
These need a sensitivity from the chiropractor, which is why it is an art.
It's okay to have science, but a lot of it's feel. A lot of it is intention, a lot of it is care.