Every listing describes how one segment misaligns relative to the segment below
it. Wedging lives in the disc space between two bodies, which is why a single vertebra can never
demonstrate it. Select a listing and watch L4 move into it.
Assembling
L3 · L4 · L5 — drag to rotate
Oblique
Listing
— — —
No misalignment selected
Select
Decoded
PPosterior. Always first, read from the lateral film.
2Which way the spinous has rotated.
3Wedging, taken on the side of spinous laterality.
-MContact point — mammillary process in the lumbars.
Overlays
Fig. 1
Reading the views. The A–P view carries the wedge and the spinous laterality — it is
where the second and third letters are decided. The lateral view carries posteriority, which is
why the first letter is always taken from it.
The nucleus follows the open wedge. That migration is the reason the contact point
sits where it does — the thrust aims at setting the body back onto it.
CT-derived L4 · body 47.8 × 35.4 mmOne lumbar mesh repeated for L3 and L5Plate I
Gonstead Listings — Pelvis
The Foundation Listing
IIPlate
The pelvis is listed differently. The ilium is read from the PSIS and moves
relative to the sacrum; the sacrum is read from its base, and a dash marks it as a sacral
listing.
Articulating
Sacrum · Innominates · L5–L1 — drag to rotate
Oblique
Listing
— —
Level pelvis
Ilium PSIS reference
Sacrum base reference
Derived
Contact—
Leg—
Signs—
Above—
Overlays
Fig. 2
Watch what happens above. Cycle ASIN against PIEX with the column on. The ASIN ilium
loses lumbar curve; the PIEX ilium increases it — a small change at the foundation producing a
large deviation higher up.
CT-derived sacrum and innominate · left side mirrored at loadCompiled from sources, not seminar notesPlate II
Gonstead Instrumentation
The Nervoscope
IIIPlate
The instrument does not measure temperature. It measures the difference in
skin temperature between the two sides of the spine, one probe either side of the spinous processes.
A level spine reads nothing. Asymmetry deflects the needle — and asymmetry is what the listing has
to explain.
Needle at rest — drift only
Layering tissue
Glide caudad — drag to rotate
Posterior
Reading bilateral differential
0.0
Deflection units — either side of zero
Run example
How it is used
Probes straddle the spinous processes, light even contact, both touching skin.
Glide caudad — down the spine — slowly and at a steady speed. Speed is the
commonest error; too fast and the needle never settles.
Where the needle deflects, stop. That level is a candidate.
Go back over the spot and try to rub the deflection out.
If it rubs out it was surface artifact. If it persists, the reading is real.
What it rules out
PositiveAsymmetry at a level — a subluxation candidate
NegativeCompensations do not give a positive reading. This is how the
instrument separates the two.
Overlays
Fig. 3
Why the rub matters. Both examples deflect the needle on the first pass and look
identical at that moment. Only the second pass separates them: friction heat and surface
irregularity disperse, a genuine neurological asymmetry does not. Run both and watch the first
pass — the point is that you cannot tell yet.
And why this sits beside Plates I and II. The instrument finds the level. The listing
describes what is wrong there. Neither replaces the other, and a compensation will pass the
instrument while still looking misaligned on film.
Instrument drawn as a schematic — mechanism only, no maker's marksDeflection magnitudes are illustrative, not calibratedPlate III