SPINE BIOMECHANICS

1. Vertebral
Dysfunctions

2. Vertebral Motion
 Type I: In Type I or neutral group mechanics, the primary and secondary
curves of the spine are present and neither flexion, extension, side
bending, nor rotation has been introduced.
 Upon introducing flexion both facets open, the anterior body translates
forward and the spinous processes moves anteriorly and superiorly.
 Side bending and rotation occur to opposite sides. In right side bending,
the left facet would open, the right facet would remain closed, and the
anterior body would rotate left.

3.  Type II: In Type II or non-neutral group coupling, side bending and rotation
of a vertebral segment usually occur to the same side. However, these
mechanics are not absolute.
 Type II occurs when either flexion, extension, side bending, or rotation
have been introduced, and depending upon which motion was introduced
first, and where it occurs in relationship to the curvature of the spine, the
given mechanics and translation will be determined.
 In the lumbar spine, side bending and rotation will occur to opposite sides
when flexion was previously introduced. In the typical cervical vertebra,
non-neutral coupling is present.

4.  Type III: Mechanics are observed through the restriction of normal motion
when performed secondary to a previous motion.
 For example, the range of side bending that can be achieved when the
posture is erect is far greater than if it were introduced with the trunk in
flexion.
 While this technically appears to be more a property of motion rather than
a definitive mechanical relationship effecting motion, the reader should
note that other writings may allude to type III.

5. Activating Force
 There are essentially two forms of activation forces.
 Intrinsic activation requires the individual to initiate an action after being
positioned by the practitioner, such as a muscle energy technique or
proprioceptive neuromuscular facilitation.
 Extrinsic activation would be a corrective force applied externally, such as a
form of manipulation or the use of gravitational forces, as in sacral
occipital technique.

6. Motion Barrier
 Restrictions to motion may be classified either as
a pathological or anatomical restriction. Pathological barriers are those
barriers to motion, whereby an individual can no longer increase motion
beyond a given point.
 Anatomical barriers, which are also called absolute barriers, are the range
in which tearing of muscle; ligaments, fracture, or dislocation would ensue
if motion were to be continued beyond that restriction. The functional
model attempts to eliminate restriction, thus enhancing motion and
improving the pathological barrier.
 Most manual techniques use one of several direct methods of increasing
motion in the direction of motion lost. However, indirect techniques may
be employed to balance the system, which will increase motion as well.

7. Type I: Neutral Group Dysfunction
 Type I consists of three or more dysfunctional segments which are side
bent and rotated to opposite sides. Upon bending or standing erect, the
dysfunctional segments may slightly improve or worsen, but will never
become symmetrical.
 If numerous segments are involved, the symmetrical configuration appears
to be Scoliotic, with a pronounced fullness of the lamina groove, and the
normally non-palpable Multifidus is distinguishable.

8. Type II: Non-neutral Group
Dysfunction
 This single segment dysfunction usually precedes a Type I dysfunction. It is
named according to the superior segment over the inferior segment of
involvement. For example, a misaligned Type II C7-T1 would be named C7,
and possibly cause a biomechanical peripheral nerve compression of C8.
 This is due to there not being a C8 vertebra, but there is C8 nerve supply
due to the numbering of the spinal nerves. Type II single segment
dysfunctions are side bent and rotated to the same side, and will obtain
symmetry either through flexion or extension.
 If the facet is fixated or locked open, flexion will gain symmetry of
structure, and extension and side bending towards the fixated side will be
diminished.

9.  Conversely, if the facet is fixated or locked closed, extension will have
structural symmetry, but flexion and side bending to the opposite side will
be diminished.
 Due to the translatory relationship of the vertebra, there will be a palpable
fullness on one side of the lamina groove as compared to the other, which
obviously is most marked in a flexion lesion when erect or hyper-extended,
or in an extended lesion when flexed.
 This fullness is created not only by hypertonic muscles, but by a translated
transverse process. If the transverse process is rotated to the right, there
will be a left rotated spinous process, and a right rotated body. Usually, the
somatic pain complaint will be manifest on the side of which the vertebral
body is rotated towards.