Motion-assisted thrust techniques are those procedures that incor- porate a component of mechanical assistance in the development of adjustive pretension or the delivery of an adjustive thrust. The assisting mechanical forces are typically provided by non- motorized or motorized articulating adjustive tables. Because the critical force necessary to preload a joint and deliver an HVLA thrust may be difficult to achieve, the use of some form of mechanical assistance may be desirable. In addition, some forms of mechanically assisted technique tend to produce a long-axis tractive force on the articulations being treated. Long-axis dis- tractive movement is a potentially important JP component of all synovial joints. It is not a general focus of most manually applied techniques for the spine, although this movement is a major focus in extremity manipulation. Incorporating it into spinal technique may provide some additional therapeutic effect.
Mechanically assisted techniques have been postulated to augment a practitioner’s physical attributes, allowing for the
4-60 Figure 4-60 adjustment applied in the treatment of a right rota-An example of a resisted side- posture
tion restriction at L4-5. This technique incorporates a segmental contact on the spinous process of the inferior vertebrae of the dysfunction motion segment with a resisted leg contact on the patient’s leg.
Right
Left
4-61 Figure 4-61 hypothenar transverse counterthrust technique Prone thoracic crossed bilateral
applied to induce left rotation at T6-7. Adjustment is applied in the treat- ment of a left rotation restriction or a right rotation malposition at T6-7. Segmental contacts are established over the right T6 transverse process and the left T7 transverse process.
T6 T7 T8
Left Right
4-62 Figure 4-62 applied to induce right rotation at the L3-4 articulation. Side-posture lumbar spinous push-pull
Adjustment is applied in the treatment of a right rotation restriction or a left rotation malposition at L3-L4.
Right
development of forces that would not be otherwise achievable. The use of drop-section table pieces or motorized moving table sections can theoretically provide additional support for produc- ing the needed force. Motion and mechanically assisted proce- dures are relatively new concepts and must be clinically studied. Although they hold promise and are based on sound principles, no clinical data exist to support effectiveness or efficiency. Each of these approaches is discussed here, and specific applications are described where applicable in Chapters 5 and 6.
drop-section Mechanical assistance
The first drop headpiece was introduced in chiropractic in 1952; B.J. Palmer stated that the principle behind the drop head piece constituted one of the greatest advancements in chiropractic.422
Dr. J. Clay Thompson developed adjusting tables with cervical, thoracolumbar, and pelvic drop-piece sections in 1957, with the stated intention of providing a mechanical advantage for producing an HVLA adjustment with minimal discomfort for the patient.
Dr. Thompson believed drop-table procedures used Newton’s laws of motion to develop a certain amount of kinetic energy not seen in other forms of chiropractic technique. He theorized that the mechanical drop mechanism reduced the muscular effort needed by the clinician to produce the adjustive thrust. Therefore, the muscular strength of the clinician is not a limitation in provid- ing manipulative therapy. Moreover, it is thought that when the drop piece releases, the amount of force exerted on the joints is minimal and therefore more comfortable for the patient. Finally, because the patient cannot resist the effects of the drop sections, it is reasoned that joint movements are more easily achieved.
Another theory proposes that the mechanical advantage gained by drop pieces is the shear reactive force that is generated at the termination of the drop. In this model the doctor sets more resistance in the drop mechanism and maintains adjustive force through the termination of the drop. There are, however, no studies to support either of these contentions.423
The Thompson table, and all drop tables, feature mechani- cal drop sections that drop a small distance on the delivery of
a chiropractic thrust. The amount of resistance to pressure can be independently adjusted in each drop section. The patient is positioned on the table with the segment to be adjusted on a drop section with the tension properly set so that the patient’s body weight will not cause the section to drop (Box 4-17). When additional force is applied and the resistance of the drop section is overcome, the section drops and terminates its fall at a preset short distance.
Tables equipped with drop-section mechanisms have levers used to set each drop section in a “cocked-up” position. Some tables use a pneumatic cocking mechanism that is operated by a foot pedal, freeing the clinician’s hands from having to locate the levers. There are, of course, specific considerations for each joint to be adjusted, such as the SCP, vector of thrust, and clinician position. Specific procedures for each joint are described and dem- onstrated in detail in other works.424
Motorized Mechanical assistance (Motion-assisted adjusting)
Motorized mechanical traction is provided by adjusting tables that provide continuous, rhythmic mechanical movement and distrac- tion of the articulations to be mobilized or adjusted. Assisted mechanical distraction of spinal joints began with manually oper- ated tables (McManis table)425 and progressed to include tables
that provide motorized movement and distraction (Cox, Leander, and Hill). The fundamental principle and potential advantage of motion-assisted adjusting is the delivery of an adjustive thrust
1. Select the most efficient and specific technique for the
primary problem.
2. Position the patient in a balanced, relaxed, and
mechanically efficient position.
3. The doctor should be relaxed and balanced with his or
her center of gravity as close to the contact points as possible.
4. The contacts should be taken correctly and specifically.
5. Articular and soft tissue slack should be removed before
thrusting.
6. Any minor alterations in position or tension should be
made before thrusting.
7. Visualize the structures contacted and the direction of
your adjustive vector.
8. Guard against the loss of established preadjustive joint
tension. Do not noticeably back off before thrusting.
9. The thrust must be delivered with optimum velocity and
appropriate depth.
10. Maintain stability and rigidity through the upper
extremities during the delivery of the adjustive thrust.
11. During the thrust, use additional body weight if
appropriate (body-drop). This is especially important in side-posture pelvic and lumbar adjusting, in which most of the adjustive force is derived from a body-drop thrust.
12. It is just as important to know when not to adjust as to
know when and where to adjust.
13. Primo est non nocere—First, do no harm.
BOX 4-16
basic rules for effective adjustive Technique1. Position the body part over the drop section.
2. Cock the drop section, checking its tension.
3. Establish contacts over the part to receive the thrust.
4. Generate a thrusting action to make the section drop.
5. The thrust may be repeated to patient tolerance.
across a joint that has been mechanically distracted. The pread- justive tension established at the involved joints is established through the movements of the motorized table, freeing the doctor to conserve energy and focus on his or her adjustive contacts, sense of joint tension, and adjustive thrust.
In addition, traction tables are assumed to induce some addi- tional long-axis distraction in the joint to which it is applied. The movement of long-axis distraction (y-axis translation) in spinal segments is not specifically addressed with many manipulative approaches. In the extremity joints, considerable attention and significance are placed on the evaluation and manual treatment for loss of long-axis distraction and its role in producing joint dysfunction.42,426
Using a motorized distraction table may increase the element of long-axis distraction during manipulative treatments. Because motion-assisted palpation and treatment may also be performed with the patient recumbent, many different patient presentations (e.g., acute, chronic, aged, and obese) may be accommodated by this technique.
Most mobilization and adjustive techniques are applicable to motorized distraction tables. Mechanized distraction tables simply provide additional preadjustive tension and joint distraction. This has the potential to decrease the amount of muscular effort and force the doctor must generate to preload a joint before delivering an adjustive thrust. When adjustive procedures are applied, seg- mental contacts and tissue pulls are established in the same fash- ion as they would be for an adjustment delivered on any adjusting table. The adjustive thrust is typically delivered at full excursion of the mechanized table as the doctor senses maximal distraction of the joint.
The fundamental components of motion-assisted adjusting can be illustrated with prone thoracic or lumbar adjustments. In the prone positioning, the adjustive thrust is delivered as the caudal
section stretches. The intermittent distraction opens the involved motion segment, facilitating the adjustment and reducing the required force needed for the thrust. In this tractive state the thrust can also be delivered repeatedly with less force being pro- duced by the clinician. The table is in motion, creating distraction of the patient with the force of the treating hands directed primar- ily headward. A pull-push effect is thus created along the long axis (y-axis) of the body, facilitating the mobilization of the joint and the restoration of long-axis distraction movement (Figure 4-63). In addition, lateral flexion can be induced using a roll for produc- ing prestress and a pulling vector while the table creates long axis distraction (y-axis) movement (Figure 4-63).
The science of chiropractic has made significant strides in the investigation of the art of chiropractic. The profession now has a body of credible research to document some of what it claims. Advocates of manipulative therapy in the healing arts of chiropractic, medicine, osteopathy, and physical therapy have independently concluded that the HVLA thrust is an important clinical intervention for the treatment of dysfunctional condi- tions associated with the NMS system. The acceptance of spi- nal manipulation by other health care professions, industries, and the general population continues to grow despite contro- versies that still exist in clinical practice. The controlled delivery of the adjustive thrust demands much discipline and skill. An adjustive thrust delivered incorrectly carries the risk of patient injury. It takes extensive training and time to perfect adjustive skills and the ability to sense and control the appropriate depth and force of an adjustive thrust. This skill cannot be effectively learned over the course of a few months or by attending weekend courses. The authors hope that this chapter helps advance the development and perfection of adjustive psychomotor knowl- edge and skills necessary for the delivery of safe and effective chiropractic adjustments.
Figure 4-63 a, Diagrammatic representation of the contact point for a left lateral flexion restriction, right lateral flexion malposition, L4-L5.
b, Motion-assisted thrust technique for intersegmental lateral flexion dysfunction (left lateral flexion restriction, right lateral flexion malposition, L4-L5).