An Overview of Vertebral Axial Decompression
Canadian Journal of Clinical Medicine Vol. 5, No. 1, January 1998
Dr. Frank Tilaro, M.D.
(page three of six)

As higher distraction tensions are reached few patients may report an increase in pain of a different quality. Overstretching of the soft tissues in the back likely represents the cause of this pain and the patient should be treated by decreased distraction tensions, so as not to traumatize the soft tissues. The development of a sharp, burning, radiating pain during therapy could represent the stretching of an entrapped nerve. Since the breakdown of scar tissue is an objective, the patient should continue but distraction tensions should be reduced such that any pain elicited does not last more than 15-20 minutes post therapy. Distraction forces are then slowly increased over the ensuing days.

No serious side effects have been reported with VAX-D therapy. A limiting factor affecting the patient's tolerance to therapy is stress to the shoulder girdle and rotator cuff. This may be mitigated by placing a roll under the axilla of the affected side. Should a patient have discomfort from any cause, they may release the handgrips at any time. This adds an important safety factor to the treatment.

MECHANISM OF ACTION

An understanding of spinal biomechanics is necessary to appreciate VAX-D's mechanism of action, to effectively treat and diagnose spinal disorders, and to objectively review old and new therapies. The literature is replete with biomechanical data. Vogel and Stahl have carried out in vitro experiments on intradiscal movements with symmetrical and asymmetrical loading. (21) With symmetrical loading, the nucleus expands and is retained by the annulus. By contrast, if the disc is subjected to an asymmetrical load, the nucleus migrates to the area of least load or resistance.(38) With removal of the load, the nucleus moves from an eccentric to a more concentric position within the disc. Relocation can be accelerated by compression in the opposite direction or by distraction. (21) The annulus of a normal disc can restrain the nuclear movement, but when the elastic properties of the annulus are compromised the structures become susceptible to injury. Fissures and ruptures develop which allow the nucleus to migrate.

Fissures are normally present by 30-35 years of age and increase with advancing age. Fragment sequestra appear as a result of age and trauma. These fragments can move independently and result in protrusions and disc prolapses. Migration of nuclear material and sequestra is influenced by compressive forces, shearing, and increased intradiscal pressure. (24)

Epidemiological data and scientific data have demonstrated that prolonged or repetitive flexion loads stress the posterior annulus resulting in discogenic pain and in some patients disc herniation.(3,25) Adams and Hutton carried out experiments with gradual loading of the disc and concluded that disc prolapses can occur with a sustained flexion load.(2) Hickey and Hukins performed experiments with bending and torsion and demonstrated that the annulus failed posteriorly.(17) Shirtzi-Adl demonstrated that disc fiber layers are most loaded in flexion and least in extension.(40) Nachemson's research on intradiscal pressures showed pressures were highest with flexion.(26) The outer third of the annulus is innervated by the sinuvertebral nerve. Any asymmetrical load associated with elevated intradiscal pressure can result in overstretching and fatigue of the annulus, thereby stimulating the mechanoreceptors in the outer third of the annular wall. Eventually, fissure's will develop in the annulus which can lead to herniation of the central mass of the nucleus. By reducing intradiscal pressure with VAX-D therapy, a therapeutic and prophylactic effect can be realized.

Numerous studies utilizing discography have helped us to understand the role of the disc as a pain generator. Provocational discography is the standard test for discogenic pain.(41) Its reliability has been questioned and opponents generally refer to the work of Holt, but his study has been refuted on methodological grounds.(9,18,41) Recently a pathological marker of symptomatic disc disruption called the high intensity zone (HIZ) was demonstrated on MRI using spin echo gradient heavy T2 imaging.(6,38) An HIZ is evident in the posterolateral view on the sagittal section, which on provocation discography corresponded to a Grade 3 radial tear. The high signal intensity represents fluid within the fissure that may be causing pain either by chemical irritation or mechanical traction of the sinuvertebral nerve. By its cyclic action and ability to reduce intra-negative pressure, VAX-D therapy could displace the fluid to the internal portion of the nucleus thereby ameliorating pain and enhancing healing of the annulus.

Donelson demonstrated it is possible to predict annular competence with the McKenzie mechanical assessment protocol.(12) In his study patients were separated into centralizer's and non centralizer's. Discography was performed in both groups. Centralizer's tended to have an intact annulus or Grade 1-2 tears. Non centralizer's had a disrupted annulus , that is fissures to the outer third of the annular wall or Grade 3 tear. This is very exciting news for those who appreciate the centralization phenomenon because it allows us to clinically assess the competency of the annulus. Patients who centralize on initial evaluation may be treated with specific exercise. Patients who do not centralize on initial examination are excellent candidates for VAX-D therapy. With such an approach, the patients disposition regarding effective therapy is known immediately, which arguably translates to reduced disability and reduced cost.

VAX-D therapy has been shown to convert non centralizer's to centralizer's during or after successful VAX-D therapy. This implies VAX-D is conducive to annular healing.

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