Mechanical Traction As Chiropractic Treatment
By Jay Kennedy, DC
Traction therapy (decompression) as a primary treatment for herniated discs is well known in physical therapy and chiropractic.
The distinct benefits of traction are: reduction of intra-discal pressure (IDP) and enhanced circulation; widening of foramina/spinal canal and reduced HNP size; variable body positions adaptable to a directional preference; mechanoreceptor modulation; reproducibility of pull factors and force; and regional mobilization without added segmental pressure.1
The possibility of negative IDP is ultimately determined not by a machine or the specific "pull" but by the condition of the disc(s) and patient position. Gay, et al. concluded, "Distraction appears to predictably reduce nucleus pressure. The effect is dependant on the health of the disc."2 Adams, et al. points out that neither IDP changes nor disc migration can be accurately determined in degenerative discs.3 Normal (hydrostatic) discs will "decompress" when gravity is eliminated in either hyper-flexion or extension recumbent postures (morning flexion stiffness and diurnal height changes prove this). However, when gravity is eliminated and axial tension is applied, the effect is markedly increased. Not coincidently, the FDA requires manufacturers to include the phrase: "Decompression, that is unloading due to distraction and positioning."
The 2008 Spine study also suggests it is distraction (axial) that creates the changes in IDP. The addition of flexion (extension) had no added effect on compressive stresses in the posterior annulus.2 That is, adding flexion had no benefit in terms of disc pressure changes. Practically speaking, having used F/D for some 20 years, I have found that the best results have always followed the least amount of flexion and a greater amount of distraction. The flexion component can become an unwieldy artifact and may account for some F/D reactions. I tend to choose axial traction in the majority of cases where IDP manipulation (decompression) is warranted and a directional preference or radicular symptoms exist.
Some clinicians suggest that the hands-on aspect of F/D is superior to a harness and that it is more "specific," allowing for variable segmental adjustments. However, the notion of chiropractic specificity has been tackled by more illustrious authors than myself, and I'd suggest flushing out that research before finalizing an opinion. It may be better to stretch an entire spinal region since it is often impossible to accurately determine which disc is the site of pain. Some demonstrate no hydrostatic pressure, others seem near normal, some have herniation symptom, while others don't. More concentration to a particular region (upper vs. lower) is plausible in both traction or F/D, but exact levels and pin-point accuracy is doubtful. Also muscle contraction during F/D approaches 5-10 percent of MVC. This may be an untenable artifact in some cases. It's also important to recognize that hyper-mobility of lower lumbar segments may be prevalent in symptomatic individuals. Adding directed pressure may be perturbing.
Cyriax said: "Traction is expedited bed rest without the disuse side effects." If decompression is valuable, axial traction is certainly a reasonable treatment option. However accurate patient classification remains a key ingredient for success. Decompression, therefore, is the potential disc-related outcome achieved during axial traction/distraction. The prime contingency is an intact and hydrostatic disc (unusual with excess dessication/degeneration). Movement of fluid and nutrients can expedite healing in many cases, although the actual mechanism of pain relief is virtually impossible to determine due to the myriad of overlapping effects (stretch receptors, regional mobilization, placebo effect etc.).
It is difficult to get past the intuitive value of axial traction or F/D. If compression is a source of pain shouldn't axial stretch be, at least in part, a viable solution? The answer is yes, it often is a viable part of a successful strategy for compression syndromes...just not always! And just not with the predictability that we demand. However a highly adaptable traction system affords the clinician the best possibility of aligning objective findings and clinical prediction variables to the patient. Ease of use, adaptability and its intuitive value give traction a distinct place in chiropractic practice.
References
- PT Pract 2005 Jan;21(1).
- Gay RE, Ilharreborde B, Zhao KD, et al. Stress in lumbar intervertebral discs during distraction: a cadaveric study. Spine 2008 Nov-Dec;8(6):982-90.
- Adams MA, Burton K, Dolan P, Bogduk N. Biomechanics of Back Pain. Edinburgh: Churchill Livingston, 2006.