Ernest Eckford Tucker
Etiology of Lesions and Principles of Technique
With the description of the sacroiliac lesion before
us for illustration, it is possible for us to consider the etiology of
lesions and the principles of technic. To some extent the conditions
of the sacro-iliac lesion are true of all lesions, that is of all primary,
direct or traumatic lesions as distinguished from warp or habit lesions.
The contrast between these two and a more detailed description of individual
lesions will be given later; the general principles only will occupy us
Primary lesions are due to a sudden straining of
an articulation beyond its normal range of motion so that it is unable
to return spontaneously. There is then found to be a double deviation,
a deviation in two directions, from mid position, as though having reached
the limit of normal motion, and being strained farther, it turned in some
abnormal way. In such position the articular surfaces are no longer
parallel but assume an angle to each other. Some part of one side
then engages against the opposite surface, and makes a dent, so that when
released it does not slide back normally, but under the tension of the
stretched ligaments assumes even a sharper angle, restrained by the
dent it has made. The ligaments, radially disposed, permit this abnormal
motion and even provide for the secondary deviation. In the resulting
position the fibres of this ligament are not necessarily all stretched,
but possibly only a few of the fibres are stretched, the rest relaxed.
The factors in lesion then are: motion beyond
normal under high tension; assuming of an angle; indentation of a surface
by a projecting portion; high tension of part or all of restraining ligament;
in partially returning toward normal, the assuming of position still farther
The principles of technic here described apply to
all such lesions. They are necessarily mechanical principles, and
are exceedingly obvious as principles, though not so easy of application
as they are of understanding.
First, it is necessary to have tension or pressure
or fixation on both of the bones involved in lesion; as on both sacrum
Since, however, it is rarely possible to take hold
of the two bones, and in most cases is impossible to get effective hold
of either of them, as in the dorsal and lumbar spine, it is therefore necessary
to use other factors—positions in which there is ligamentous drag on the
one, through the weight of the body; and motions in which all of the joints
are at the limit of their motion, between the lesion and the point that
can be taken hold of. This principle—that joints must be at the
limit of their possible normal motion before corrective force can be transmitted
through them or made effective on them is the point that seems to me
most neglected, and to be responsible for most of the failures in technic.
As for instance it is necessary to have all of the joints of the spine
and of the shoulder at the limit of their motion before tension can be
transmitted through them to the sacrum.
Third, it is necessary to so direct this tension
or pressure that it comes to a focus at the point desired. As
in breaking a stick held in the two hands it is possible to break it in
the middle or near either end by differently adjusting the force of the
two hands, so is it in directing the force of correction.
For instance in the first ethnic described for correction
of anterior sacral lesion, if the pressure of the left arm is over the
middle of the crest instead of over the anterior superior spine, the effect
is not to cause gapping of the lesion, but to cause increased pressure
over the point in lesion. The technic then takes effect at the last
lumbar joint. So also if the spine be flexed, the effect of rotation
of the shoulder backward is to cause strain at the apex of the posterior
curve rather than at the point desired.
Fourth, it is necessary so to direct the force
that it serves to release the engaged part from its indentation against
the opposite surface; as in pressing down on the anterior superior spine
the articulation is gapped open in the back, the front edge being the fulcrum
therefor. To do this it is usually necessary to use one part of
the articulation as the fulcrum for the other part. In a rotated
dorsal vertebra, for instance, the engaged side is the side toward which
rotation has occurred; as in a spine rotated to the right, the articular
surface on the right is caught in flexion, the left side extends alone,
producing secondary rotation to the right. To release this it is
necessary to carry the left side to the limit of its motion and with that
limitation as a fulcrum, to gap open and release the engaged part.
Fifth, with all articulations at their limit and
the leverage adjusted, a quick spring is much more effective than steady
force; it needs only a fraction of the force, with less danger of injury
to soft parts, and gives a cleaner and more perfect correction. This
because the parts engaged are elastic. The quickness of the spring
should be in proportion to the elasticity. It is also easier to apply
just the right degree of force, calculated beforehand, in the quick spring
than in the steady pressure. A quick and shallow springing motion
does not go so far beyond the instant of actual correction as a steady
force, because in the latter it is impossible to calculate the moment of
release, and so to check the corrective force.
MEANING OF THE “POP”
The instant of correction of a lesion is usually
indicated by a “pop.” This is not always the case. Also the
pop may signify the making as well as the correction of a lesion.
Let us examine the mechanical factors in the “pop.”
In the lesion we have articular surfaces at an angle
with each other, and some edge of one surface engaged against the other
surface, making an indentation or a wrinkle of the tissue, by which it
is held as a lesion. But this means that whereas at one point there
is compression, at another there is separation, with a vacuum, or at best
negative pressure, suction as we would call it, a potential vacuum.
What fills this potential vacuum? The tissue of the joint we will
remember is elastic; it is compressible, but it is also expansible.
Gas or fluid may collect there under the differential pressure, but also
the tissue may expand to fill the negative space. All of the bony
tissue involved is under high pressure from the stretched ligament, whose
elastic tension holds them in their false position. As Dr. McConnell
discovered, if all of the ligaments of a joint be cut, the lesion will
correct itself. (See also A. T. Still Research Institute Bulletin
When, therefore, under the sudden spring of the corrective
force the engaged point is released, the readjustment takes place under
all of these elastic forces. The “pop” is in proportion to the suddenness
of the release and t he degree of elastic tension of the ligaments and
of the elasticity of the tissues compressed.
These principles of correction may be thus summarized:
To transmit force, articulations must be at the limit
of their motion.
Effort must be properly focused on lesion.
It must be so directed as to release the engaged
One side of a joint used as fulcrum for the other.
Elastic spring to overcome elasticity of parts.
Many operators carefully avoid the “spring” technic, finding
it painful and giving a shock to the patient. They use a technic that
involves so stretching the ligaments that release comes spontaneously.
If cutting of all of the ligaments allows a lesion to correct itself, so will
sufficient stretching of them bring the same result. Meanwhile the patient
profits by the stimulation that comes from the stretching. The choice
here is between the radical technic with positive results and the gentle technic
with much greater expenditure of labor but less pain to the patient, and less
immediate results, with greater danger of recurrence. Probably a combination
of the two is best. Our purpose at present is to build a mental picture
of the mechanics of lesions and their correction, for which purpose the radical
technic is described. Different description of the gentle technic is not
necessary; it consists in a gentler modification of the radical technic.
The principle of this gentler technic is like that of moving a heavy barrel,
by very slightly tilting one side and then rolling it. With a clear picture
of all the leverages, with a practiced control of all tension, and with persevering
practice, this gentler and more ideal technic may be mastered.