X-Ray & Listing System Terms

  • X-ray Marking/Listing System: The chiropractic subluxation is a structural and functional derangement and fixation between two adjacent anatomical structures that leads to nerve dysfunction and other pathological manifestations. This results in misalignment of one part to the other. Listing system is a shorthand form the directions of misalignment as viewed on the radiographs, and it describes or indicates the directions (vectors) of the corrective adjustment that is three-dimensionally opposite to the misalignment/listing. The Gonstead listing system accounts for all three axes of rotation (θX, θY, and θZ; symbol θ is pronounced theta) and linear translation (X, Y, and Z) of the right hand orthogonal coordinate system – the language of biomechanists. [see the appendix in the back for an explanation of the RHOCS] Dr. Gonstead included the segmental contact point in the listings from C2 to L5, i.e., spinous process (-sp), lamina (-la), transverse process (-T), and mammillary process (-M), although many today leave off –sp.
  • Occiput: The first letter group of the listing denotes the primary direction of misalignment as found on the lateral x-ray (θX and Z-translation): occiput – AS (anterior-superior; +Z, –θX) or PS (posterior superior, –Z, +θX)

    The second letter group is measured on the AP film and indicates laterality with a measure lateral flexion away from the side of laterality. LS (left-superior; +X, +θZ) or RS (right superior; –X, –θZ

    The third letter group, if present, is measured on the AP film and is used to indicate rotation of the occiput (condyle) on C1 (atlanto-occipital articulations) on the side of laterality. LA (anterior on the left; –θY); LP (posterior on the left; +θY); RA (anterior on the right; +θY); or RP (posterior on the right; –θY).

  • Atlas (C1): The first two letters of the listing denotes the primary direction of misalignment as found on the lateral x-ray (θX and Z-translation): AS (anterior-superior; +Z, –θX), AI (anteriorinferior; +Z,+ θX), or A (anterior; +Z).

    The third letter is lateral misalignment as measured on the AP film: L (left & superior; +X, +θZ) or R (right & superior; –X, –θZ). Note: although not indicated in the listing, there is a slight lateral flexion misalignment, probably due to edema in the altanto-axial joint on the side of laterality. The fourth letter, if present, indicates rotation on the Y-axis (θY) of the atlas on axis on the side of laterality as measured on the AP film. If no rotation is measured, no letter is added. If rotation is present, it is either (anterior, i.e., rotation away from the side of laterality) or P (posterior, i.e., rotation towards the side of laterality)Example: ASRA: atlas rotation is +θY.

  • C2 to L5: The first letter denotes posteriority. P (posterior; –Z (usually accompanied by inferior movement; –θX, except in the thoracic spine where it may be accompanied by superior movement, +θX). Anterolisthesis is not listed in the Gonstead listing system.

    From C2 to L5, the second letter denotes left or right spinous laterality. i.e., θY rotation along the long axis of the spine using the spinous process as reference. L (–θY) and R (+θY)

    If a third letter is present, it indicates disc lateral wedging or vertebral lateral flexion (θZ or Z axis rotation) on the side of spinous laterality: S (superior) or I (inferior). If a third letter is present at atlas, it indicates rotation on the side of laterality – A (anterior; θY) and P (posterior; θY).

    If present, a third letter group at the occiput lists angular rotation on the side of laterality – LA (left anterior; +X, –θY); LP (left posterior; +X, +θY); RA (right anterior; –X, +θY); RP (right posterior; +X, –θY).

    If there is significant postero-inferiority (–θX) noted on the lateral film, this is listed as “-inf.” It is commonly used only in the cervical spine.

  • Sacrum: BP (base posterior; –Z, –θX) from viewing of the lateral film of the lumbosacral junction [it is not unusual for a sacral base posterior to be accompanied by hypolordosis or a loss of the normal lumbar anterior curve] Long axis rotation is found on the AP film: P-L (posterior on the left; +Y) or P-R (posterior on the right; –Y). Unfused sacral segments may misalign posteriorward (–Z) According to an article in the journal Spine in February of 1992, previously fused articulations between sacral segments may decalcify and unfuse in later years.
  • Ilium: The “L”-shaped and obliquely oriented sacroiliac joints may move relative to the sacrum and opposite ilium: AS (anterior-superior; +θX, slight θY) or PI (posterior-inferior; –θX, slight θY). It may also misalign In (internal rotation; left +θY, right –θX, slight +θX) or Ex (external rotation; left –θY, right +θY, –θX). If AS or PI is present, it is always listed first. Compound listings combine PI or AS with In or Ex listings. There is also bilateral ilia subluxations with rotation (In and Ex) misalignments. All ilia listings are based on the AP film measurements.
  • Coccyx: Coccyx may pivot in misalignment wherein the apex is misaligned anteriorward. The primary listing is A (anterior –θX). There may be left AL = –θX, –θZ) or right AR = –θX, +θZ) deviation of the apex. Any movable joint may be given a listing based upon and describing it’s direction(s) or vector(s) of misalignment.
  • Posteriority: Misalignment of the vertebra (C2-sacrum) posteriorward (–Z) that is accompanied by inferiorward rotation (–θX). In severe cases, it is a retrolisthesis.
  • Laterality: Rotational misalignment of a vertebra (θY). In the Gonstead System, the lateral position of the spinous process on the AP x-ray film determines laterality, left or right.
  • Rotation: synonymous with laterality and used when there is significant (θY) rotational misalignment.
  • Inferiority: When segments from C2 to L5 misalign, they translate posterior (–Z) and tip inferiorward to the posterior (–θX). When there is significant “inferiority,” it is listed on the listing (usually only done in the cervical spine) at the end of the listing, e.g., PRS-sp-inf. It is usually used only on spinous contact listings.
  • Femur Head Line: It is a line drawn connecting the superiormost points of each femur head. All other ilium measurements are based upon it. It is also compared to the horizontal plane to determine if leg length inequities are present. It is the base line or foundation line in the Gonstead x-ray analysis.
  • “Measured” vs “Actual” Leg Length Deficiencies: The “measured” and “actual” leg length deficiency, if present is analyzed on the A-P xray film. If the femur head line is not parallel to the horizontal plane line, the distance of the superiormost point of the inferior appearing femur head is measured in millimeters to the horizontal plane to acquire the “measured” deficiency. Dr. Gonstead found clinically that the PI, Ex, and PIEx ilium misalignment “lowered” the viewed ipsilateral femur head 2 mm for every 5 millimeters of ilium misalignment while the AS, In, and ASIn “raised” it by the same amount. To get the “actual” deficiency, subtract 2 mm of measured deficiency for every 5 mm of PI and Ex present on that side or add a like amount if the side of leg length deficiency occurs on the side of an AS and In ilium. If the left ilium is PI5In3 with an ipsilateral measured leg length deficiency of 3 mm. Add 2 mm for the PI5 and 1 mm for the In3 to 3 mm measured deficiency for an actual deficiency of 6 mm. An AS5In3 on the side of a 3 mm measured deficiency would have an actual deficiency of 0 mm.
  • Six Stages of Disc Degeneration: Many in chiropractic market a version of “Stages of Subluxation Degeneration.” Earlier, Dr. Gonstead observed stages of disc degeneration on the radiographs. This was broken up into six stages with a rough chronological sequence. D1 is a swollen disc due to acute injury. The entire disc space appears to be thicker (+Y) than is considered normal. (Panjabi and White in their text, Clinical Biomechanics of the Spine, call this fluid ingestion.) D2 is considered to be a normal-height, but due to disc injury, there is a slight loss of height in the posterior as the segment begins to misalign in an inferior (–θX) direction. From D3 to D6, there is a progression of degeneration, initially at the posterior and later involving the entire A-P surface of the disc which results in disc space narrowing. (Herbst RW) The empirically-arrived time sequence from D1 to D6 is thought to average 15+ years. (Cox WA)
  • Split Screen Cassettes: Today, chiropractors are using single-speed or graduated speed xray intensifying screens and primary beamattenuating filters to even out exposure to body segments of different densities in a single exposure. In the past, and not uncommonly today, x-ray screens of different sensitivity speeds were used to compensate for the different body densities.