Radiologic Manifestations of Spinal Subluxations
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“Basic Chiropractic Procedural Manual”
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Chapter 6: Radiologic Manifestations of Spinal Subluxations
This chapter describes the radiologic signs that may be expected when spinal subluxations are demonstrable by radiography. Through the years, there have been several concepts within the chiropractic profession about what actually constitutes a subluxation. Each has had its rationale (anatomical, neurologic, or kinematic), and each has had certain validity contributing to our understanding of this complex phenomenon.
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Kinetic Intersegmental Subluxations
Segmental hypomobility, also called a “fixation subluxation” by many clinicians, may affect one or several motor units.
It is characterized by reduced motion of the “Spinal Motion Unit” (Please refer to Spinal Anatomy 101), which has been forced to the extreme of a range of motion (eg, flexion, extension, etc). See Figure 6.14. Stress views or videofluoroscopy are necessary to depict this and other kinetic subluxations radiographically, but motion palpation and some orthopedic tests may reveal their presence clinically.
Editor’s Note: In the following picture, the inferior facet of C5 fails to slide forwards and upwards upon the superior facet of C6. Because of that, the IVF cannot open more fully, and the spinous process of C5 fails to move away from the C6 spinous. All together, these are the classic signs of HYPO-mobility.
Hypermobility, called loosening of the vertebral motor unit by Earl Rich and Junghanns, may also be found at one or several levels. It is often found as a compensatory mechanism accompanying hypomobility (fixation) at one or more other levels in the kinematic chain.
Hypermobility (ie, an excessive range of motion) allows excessive range(s) of motion during flexion (Fig. 6.15). Again, this entity can be demonstrated by clinical means as well, but it takes stress radiography to document its presence objectively.
NOTE: If there is excessive translation on flexion/extension films (more than 3 mm), this is a classic sign of instability. (Read Steven Eggleston, DC, Esq’s article as it reviews the methodology for measuring spinal instability.)
Aberrant motion exists when one or several vertebrae move in a way that is not in coordination with neighboring segments during some movement of the spine.
One vertebra, at least, is not in phase with the general movement of neighboring segments (Fig. 6.16). In this view, one segment is extending while the others are in flexion.
White & Panjabi, in their textbook “Clinical Biomechanics of the Spine” refer to this as “paradoxic motion”.
Static Intersegmental Subluxations
Flexion Malposition. In flexion subluxation, there is wedging of the disc space anteriorly as the vertebral bodies somewhat approximate one another anteriorly (Fig. 6.3).
Because of this, the spinous processes separate (open) and the inferior articular processes of the vertebra above glide upward upon the superior articular processes of the vertebra below. This elongates the intervertebral foramen (IVFs) so they appear larger in their vertical dimension.
Extension Malposition. In this type of subluxation, which is one of the most commonly encountered (especially in the low back), the vertebral bodies approximate posteriorly and thus the disc narrows posteriorly (Fig. 6.4).
The posterior articulations show radiographic imbrication as the inferior articular processes of the vertebra above glide downward relative to the superior articular processes of the vertebra below. As the motion unit extends, the IVFs of the unit appear to become smaller in their vertical dimension.
Lateral Flexion Malposition. This subluxation is characterized by lateral wedging of the disc interspace produced by approximation of the vertebral bodies on the side toward which the vertebra above laterally flexes (Figs. 6.5 and 6.6).
This also causes the facet articulation on the side of disc narrowing to imbricate while the contralateral articulation shows separation (opening) of the articular processes as the inferior articular process of the upper vertebra glides upward on the apposing process of the lower segment.
Rotational Malposition. Intervertebral rotation, even in subluxation, is extremely limited at any single intervertebral level except in the upper cervical spine. Thus, there are usually several segments involved in a rotational disrelationship (Fig. 6.7).
The preponderance of the body of a rotated vertebra relative to its spinous process on the side toward which the vertebra has rotated posteriorly is well known to all doctors of chiropractic. A line drawing taken from an actual radiograph will show reverse rotation between the vertebrae that can be portrayed by a dotted line with the top three and the lower two vertebrae rotated in corresponding relationship to one another.
Slippage or “-listhesis”
The next three types of subluxation are those in which the suffix “listhesis” is used. This suffix means “slippage,” and the displacement is usually a gross distortion.
Anterolisthesis or Spondylolisthesis. This malposition is typically produced by interruption of the isthmus (usually congenital) of a displaced vertebra at its pars interarticularis.
This allows separation of the anterior portion of the motion unit to separate from the posterior portion, resulting in anterior slippage of the vertebral body above upon the lower one (Fig. 6.8). In some cases, anterior slipping can occur without pars separation if considerable disc degeneration or facet arthrosis has developed to make the motor unit markedly unstable.
Retrolisthesis. Posterior malpositioning of the upper segment of two vertebrae set (motion unit) is known as retrolisthesis.
The displacement is usually obvious in a radiograph (Fig. 6.9) and often accompanied by some extension of the motor unit and/or approximation of the vertebral bodies due
to intervertebral disc (IVD) narrowing.
Laterolisthesis. The lateral slipping characteristic of this type subluxation is typically accompanied by considerable segmental rotation.
The result is a demonstrable overhang of the lateral margin of the vertebral body
of the upper segment relative to the one below (Fig. 6.10).
Altered Interosseous Spacing
Altered Interosseous Spacing. This form is probably the most common of all subluxations in elderly people. It mainly occurs when IVD degeneration has caused narrowing of disc space, which approximates the vertebral bodies and jams the posterior facets (Fig. 6.11).
Rarely, there may be some swelling or other abnormality of the disc causing increased interosseous spacing (Fig.6.12).
The last type of static subluxation, foraminal occlusion, may be a consequence of one or more of those malpositions previously described (Fig. 6.13).
On the other hand, on rare occasion, there may be no other evidence of disrelationship per se.
Terminology of Radiologic Manifestations of Subluxations
Static Intersegmental Subluxations
A-1. Flexion malposition.
A-2. Extension malposition.
A-3. Lateral flexion malposition (right or left).
A-4. Rotational malposition (right or left).
A-5. Anterolisthesis (spondylolisthesis).
A-8. Altered interosseous spacing (decreased or increased).
A-9. Osseous foraminal encroachments.
Kinetic Intersegmental Subluxations
B-1. Hypomobility (fixation subluxation).
B-2. Hypermobility (loosened vertebral motion unit.
B-3. Aberrant motion.
C-1. Scoliosis and/or alteration of curves secondary to musculature imbalance.
C-2. Scoliosis and/or alteration of curves secondary to structural
C-3. Decompensation of adaptational curvatures.
C-4. Abnormalities of motion.
D-1. Costovertebral and costotransverse disrelationships.
D-2. Sacroiliac subluxations.
Note: The code names (eg, A-1, B-2, C-3, or D-2) listed above are rarely used in professional communications. A descriptive title is used such as “flexion malposition of C5,” rather than “A-1 C5.”