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Chiropractic Research / Interpretation of Videofluoroscopic Joint Motion Studies in the Cervical Spine
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By G. Kevin Robinson, DC
2758 Chamblee-Tucker Rd.
Atlanta, GA 30341
ABOUT THE AUTHOR: Dr. Robinson received his DC degree from Life College of Chiropractic in 1980, and has done postgraduate study in Impairment Rating and Orthopedics. A lecturer on the use of videofluorography, he is also the chairman of the recently formed Joint Motion Study Research Society based in Atlanta, GA.
Movement of the vertebrae in the cervical spine from C-2 to C-7 is revealed upon Videofluoroscopic Joint Motion Study Examination. A differentiation between normal and abnormal findings is obtainable. The pattern of motion(15) observed is interpreted diagnostically. The image is obtained by the utilization of a fluoroscopic unit that registered dynamic motion of the cervical spine in various planes of motion. The information is recorded on videotape while simultaneously being viewed on a monitor. The indirect method of obtaining the study is preferred in that an image intensifier is employed to produce an extremely brilliant image with relatively small amounts of radiation.(9)
The procedure is indicated in cases where ligamentous instability is suspected, a condition that may occur following trauma to the cervical spine. Other indications include restricted range of motion, recurrent myelopathic and reticular symptomatology and cases where the patient is considered to be malingering. These indication are basic and can be expanded. The study can be obtained at any point in the patient’s treatment; however, consideration must be given to voluntary limitation of motion that may develop as part of the patient’s pain response(14) and myofacial guarding that may influence the pattern of motion observed.(18) These complicating factors are thus avoided by obtaining the study immediately post traumatically(14) and by careful examination to determine when adequate range of motion is available to evaluate the supporting structures in the spine. For an accurate assessment of the extent of a patient’s injuries when litigation is involved, the study is obtained when the patient reaches maximum medical improvement. Comparative studies may be indicated to reveal progression of degenerative change.
The vertebrae that comprise the cervical spine are arranged in a manner allowing motion to occur while simultaneously protecting the contents of the spinal canal. The shape of the vertebrae and their articulating surfaces are responsible, in part, for the direction of movement that occurs. The muscles and tendons are accountable for the motion that results from their contractions and points of attachment to the vertebrae, respectively. The ligaments and discs allow motion to occur in the joints due to their length, fiber arrangement and elastic qualities while preventing excessive motion that would disrupt the joints’ normal mechanics.(9) The retaining ligaments in the cervical spine common from C-2 to C-7 are: supraspinous, interspinous, ligamentum flavum, posterior longitudinal, anterior longitudinal, the capsular ligaments of the facet joints and the intervertibral discs.(3) The facet joints are considered gliding joints. (8.9) The disc structures, adjacent vertebral bodies and end-plates are considered symphyses.(21) The resiliency maintained by the annulus/nucleus pulposus relationship results in a joint motion consisting of the combined movements of sliding and tilting, (9)(15), which some authors refer to as rocking.(14)
In the lateral view of the cervical spine in the neutral potions the vertebrae are maintained in a symmetrical anterior, curve. The posterior aspect of the vertebral bodies form the anterior curve. The posterior aspect of the vertebral bodies form the anterior wall of the spinal canal while the posterior canal wall is marked by the profiles of the arches at their midpoints. In the absence of trauma the cervical spine maintains its anterior curve even in the presence of advanced disc degeneration.(10)
Upon anterior flexion of the normal neck, the curve is first straightened and then reversed but it always remains symmetrical at all points.(8)(10) In flexion the dorsal borders of the vertebral bodies are arranged like a flight of steps as the result of the anterior sliding of the vertebral bodies.(9)(10)(16)(24) The biomechanical term applied to this motion is translation which occurs coupled with sagittal plane flexion rotation.(23) The intervertebral discs are observed to compress anteriorly and widen posteriorly as the vertebral bodies tile or rock.(2)(9)(13)(15)(24)
Occasionally adults without previous trauma or neck difficulty exhibit during flexion more motion between the fifth and sixth cervical vertebrae than at any other levels.(8)(13) Other authorities state that the greatest amount of motion occurs between the fourth and fifth cervical vertebrae in some normal individuals.(8)(13) If the increased motion at either the C-4/C-5 or C-5/C-6 interspace occurs in flexion without disruption of the overall lsymmetry of the pattern of motion and if all other views of those segments appear normal, then it can be assumed to be within normal limits.
Children may show striking step formation in segments C-2/C-3 and C-3/C-4, particularly in flexion of the cervical spine.(13)(16) In flexion, the superior facets glide upward and forward in relation to the ones below and the vertebral body shifts forward a corresponding amount.(9) The apophyseal joint spaces do not become deformed as do the intervertebral disc spaces. The planes of the interarticular facets remain parallel during flexion and extension.(2)(20) In full flexion the facets are almost at the point of subluxation.(23) The spinous processes during flexion of the cervical spine separate in a smooth fan-like progression. Flexion motion begins in the upper cervical spine. The occiput separates smoothly from the posterior arch of the atlas, which then separates smoothly from the spine of the axis, and so on down the spine. The interspaces between the spinous process become generally equal in complete flexion. Most important, the spinous processes separate in orderly progression.(12) Duing extension of the patient’s cervical spine, the entire process occurring in flexion is reversed and altered slightly. The curve of the cervical spine in full extension is smoother than the curve when the spine is in flexion. Upon extension, the exaggeration of the lordosis has an accentuated "C" shape while in flexion the reversed lordosis resembles a bow.(13) The normal posterior translation that occurs in the cervical spine with extension results in an arrangements of the dorsal borders of the vertebral bodies that resemble a washboard pattern.(16) This pattern is similar to the stair step phenomenon occurring at these same structures upon flexion, only to a lesser degree. In extension there is a widening of the disc space at its anterior portion and approximation of the posterior portion.(2) The shifting of the facet structures in extension occurs as the inferior surface of the superior facet slides posteriorly and inferiorly upon the superior articulating surface of its subjacent partner. The spinous processes of the cervical vertebrae rhythmically approximate each other upon extension becoming fairly equidistant apart in full extension.(2)
In the oblique view only the apophyseal joints are studied.(2) In flexion they nearly subluxate as previously mentioned. Upon extension, the gliding that occurs between the two opposing facet joint surfaces is considered. The overall approximately occurring between vertebral segments is monitored as to its effects on the intervertebral foramina, their size and shape. Typically the foramina will enlarge upon flexion and narrow slightly upon extension.(3) They should, however, retain much of their oval or rounded appearance.
In the A-P view of the cervical spine, the motions of rotation and lateral flexion are observed.
During rotation that spinous processes will move in the opposite direction that the head is turned.(23) The motion occurs less extensively in the lower C-6 and C-7 segments and is more pronounced in the midcervical region. Normally there is no displacement of the facets upon cervical spine rotation.(2) When the cervical spine is laterally flexed, coupling characteristics are again observed. Axial rotation of the vertebrae turns the spinous processes away from the concavity produced by the lateral tilting of the vertebrae.(23)
In other words, the spinous processes in the cervical spine are displaced laterally, opposite the direction the head is tilted. The inferior articular processes on the concave side glide downward and backward while those on the convex side glide upward and forward. The disc structures narrow on the concave side, widen on the convex side and undergo accommodating torsional strain.(8)
When observing the joint motion from C-2 to C-7 the symmetry(10) of the pattern of motion must always be considered. Below the second cervical vertebra, motion at one intespace generally does not occur without similar motion taking place at other levels. This occurs because the configuration and relationship of the articular processes and discs make independent motion essentially impossible.(8)
Interpretation of a joint motion study is rather complex. Abnormal characteristics include hypermobilities and hypomobilities that are produced by many factors influencing the pattern of motion in the cervical spine. Careful consideration of the patient’s history is mandatory. A distinction between congenital and acquired findings must be established. One must also discern findings that are pre-existing from those that are the result of a specific trauma. In many cases abnormal findings on one view of the study are confirmed on additional views. Flat plate radiographs are often employed to confirm joint motion study findings. Careful orthopedic and neurological examination often verify findings from the joint motion study.
Additionally, the through examiner may obtain clues during the examination that prove helpful in directing his or her attention during the evaluation of the joint motion study. The major injuring vector concept(22)(23) relates the direction of forces which produce a trauma to the actual structural tissue damage that occurs. Through thorough investigation, accuracy in the prediction of joint motion study findings based on the major injuring vector presented can be obtained. Although the degree of accuracy and predictability may vary, it is useful in separating abnormal findings that are traumatically induced from those that are pre-existing in nature.
Prior to joint motion study evaluation, a number of abnormal characteristics from flat plate radiographs may indicate areas of pathological and/or physiological involvement. These areas are of immediate concern to the examiner. Loss of the normal cervical lordosis may be indicative of muscle spasm resulting from muscular strain (10) or muscle spasm perpetuated by joint pain (3)(11) and instability. Muscle spasm will restrict the pattern of motion.
Cervical hypolordosis is significant when observed in an individual with a seemingly deeper lumbar lordosis and a more horizontally positioned sacrum.(17) If the hypolordosis persists to the point of maximum medical improvement, a 10 percent impairment to the whole person is assigned.(1) The size and angle of the facet joints may influence the cervical lordosis and the degree of motion anticipated. The disc height and A-P width of the vertebral body affect motion potential within the joint as well.(23)
Traumatic kyphotic hyperangulation in the cervical spine occurs following a hyperflexion injury to that region.(16) Tearing of the supraspinous, interspinous, posterior longitudinal, ligamentum flava, the posterior facet joints and the posterior fibers of the intervertebral disc must occur in order for this radiographic evidence to appear, indicating an obvious location of ligamentous instability. An anteriorlisthetic offset(5) is observed as anterior displacement of the segment upon its subjacent partner when measured along the posterior aspect of the vertebral bodies.
When the anterior longitudinal ligament and anterior fibers of the intervertebral disc are injured as in hyperextension, a retrolisthetic offset is common. The offsets are usually exaggerated upon flexion and extension studies revealing a hypermobile joint. If joint degeneration has progressed to the point of bony ankylosis then restriction of motion can be anticipated.(5) Capsular joint adhesions that develop posttraumatically have been associated with hypomobility in the cervical spine as well.(11) If the disc merely thins it will usually be hypermobile.(5)
Spondylitic encroachment from the facet joint structures, uncinate processes of the unco-vertebral joints, vertebral bodies and laminae occurs as part of the degenerative process resulting in stenosis of the intervertebral foramina and spinal canal rendering the neurological components to these structures more vulnerable to injury. If these changes occur in an individual who possesses developmentally smaller foramina and spinal canal then this person’s symptomatic picture is typically worse. (5)(6) The hypermobility accelerating degenerative change(2) in the joints and the resultant intermittent trauma to the neural structures(24) result in a poor prognosis for such individuals.
Another congenital condition affecting a patient’s vulnerability to injury is benign hypermobility syndrome.(12) Although it has not been correlated with increased musculoskeletal complaints it is still regarded by many as a predisposing factor to complex symptomatology posttraumatically. This syndrome results in excessively mobile joints due to a variation in the hystiological components of ligamentous structures.
Other indications of hypermobility observed upon Videofluoroscopic Joint Motion Study are excessive spinous approximation upon extension and increased separation upon flexion indicating disruption of the anterior and posterior elements of the spinal supporting structures previously designated, lack of parallelism by the opposing posterior facet joint surfaces indicating an abnormal rocking motion in a joint that normally glides,(2)(20) revealing damage to the surrounding capsular joint structures,(2) loss of the rocking or sagittal plane rotation with flexion and extension of the cervical spine resulting from disc degeneration and hypermobility occurring upon extension of the cervical spine causing foraminal encroachment by the facet joint structures indicative of capsular joint instability.
It has been my observation that excessive motion does not always occur in segments adjacent to those where bony ankylosis limits or totally prohibits motion. I do, however, consider these joints more vulnerable to injury.
The Videofluoroscopic Joint Motion Study reveals subtle injuries. The examiner providing the results of the study must concern him or herself with the symmetry that occurs within the pattern of motion observed. One must remember that the overall pattern of motion may vary from one person to the next; however, the integrity of motion symmetry must be maintained within the individual. Recently, medical articles have been published that consider these subtle injuries(19) and instability.(7) The further development and clinical application of the Videofluoroscopic Joint Motion Study procedure is justified.(18) As Doctors of Chiropractic, who better to pursue and understand the normal kinematics and biomechanics of the spine that ourselves?
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