Research Review by Dr. Shawn Thistle©


May 2008

Study Title:

Outcomes after a prone lumbar traction protocol for patients with activity-limiting low back pain: A prospective case series study


Beatie PF et al.

Authors’ Affiliations: Departments of Exercise Science and Physical Therapy – University of South Carolina, Virginia Commonwealth University.

Publication Information:

Archives of Physical Medicine and Rehabilitation 2008; 89: 269-274.


Lumbar traction is one of the oldest known treatments for low back pain (LBP). Recent evidence-based practice guidelines1, a narrative literature review2, and even a Cochrane Collaboration Review3 have indicated that mechanical traction for treatment of low back pain (LBP) with or without sciatica cannot be endorsed. This lack of support is based upon clinical trials that compared traction to a sham treatment, placebo, or other treatments using heterogenous samples of LBP patients.

The VAX-D (Vertebral Axial Decompression System) is a newly developed mechanical traction device that is being heavily marketed to chiropractors and other manual therapists. The VAX-D’s manufacturer claims that this table will reduce the patient’s reflex spinal musculature contractions, allowing distraction of the vertebrae and reduction in intradiscal pressure, resulting in symptom reduction. The VAX-D utilizes a pelvic harness while the patient stabilizes him/herself using a hand grip. This prospective case series investigated short and long-term treatment outcomes after administration of a prone lumbar traction protocol using the VAX-D in a group of patients with LBP.

296 subjects participated in this study, all meeting the following inclusion criteria:
  • between the ages of 18-60 with specified medical coverage (not further specified)
  • reported activity-limiting LBP with or without lower extremity pain, with an average intensity of at least 4 on an 11-point Numeric Pain Rating Scale (NPRS) during the month prior to admission
  • score of at least 6/24 on the Roland-Morris Disability Questionnaire (RMDQ)
  • imaging evidence of a degenerative or herniated lumbar disc at a level corresponding to symptoms
  • reported a lack of favourable outcomes with at least 2 previous non-operative interventions (spinal manipulation, TENS, etc.)
Subjects were excluded if they:
  • were currently involved in a worker’s compensation claim or legal action
  • had undergone previous treatment with prone traction
  • had activity-limiting pain in regions other than the low back and legs
  • had previous lumbar/abdominal surgery
  • were currently pregnant, or unable to maintain a prone position
  • were taking any anti-coagulants, corticosteroids, or opiate-based pain medication
Outcome measures included the 11-pt NPRS and the RMDQ – each were administered at baseline, 8 weeks (completion of treatment), and 1 and 3 months post-discharge.

It is worth noting that on intake, all subjects watched a videotape produced by the manufacturer of the VAX-D (see limitations listed below).

Traction treatments on the VAX-D were 30 minutes in length, including 15 cycles of traction/relaxation (60 seconds each) with a working pressure of between 8.9-9.8 Kg/cm2. Treatments were administered on an outpatient basis 5 times per week for 4 weeks, then once per week for 4 weeks, for a total 8 week treatment period.

Pertinent Results:

  • the majority of subjects (79%) reported being symptomatic for at least 6 months
  • the majority of subjects (84.5%) received 16-24 treatments during the 8 week treatment period
  • of the subjects who completed the protocol, 81.4% provided follow-up data at 180 days (3 months) post-discharge
  • highest pain intensity was significantly lower at 3 months post-discharge (p < 0.01)
  • the average decrease in pain intensity ranged from -1.6 to -2.8 on the NPRS
  • RMDQ scores improved significantly at all follow-up times (p < 0.01), including between discharge and 3 month follow-up (p < 0.01)
  • effect sizes based on the RMDQ scores ranges from 2-2.3 at the three follow-up measures

Conclusions & Practical Application:

This case series provides preliminary data regarding treatment outcomes after treatment with the VAX-D system. Patients in this case series generally reported improved pain and disability scores after 16-24 treatments administered over an 8 week period. The authors note however, that there were large variations in the magnitude and meaningfulness of the degree of changes in these measures. They also correctly state that: “Causal relationships between these outcomes and the intervention should not be made until further study performed using randomized comparison groups.”

Several limitations of this project should be kept in mind when interpreting the results:
  • showing subjects a video produced by the manufacturer may have biased them toward successful treatment outcomes
  • the inclusion criterion requiring imaging findings of disc pathology to “confirm” the level of involvement conflicts with current evidence that questions the relevance of such findings in terms of how they correlate to clinical symptoms, or are affected by treatment – the authors mention this in the discussion
  • follow-up data was not available for roughly 20% of patients, and no mention was made of how this was dealt with statistically
  • as a case series, this study had no control group, and hence no causal relationship can be implied between the traction applied with the VAX-D and the observed outcomes
  • the patient sample had relatively chronic pain which had been unsuccessfully treated with other interventions – thus representing a group with an unfavourable prognosis in general
  • further, the authors mention that they did not sub-classify subjects based on the presence or absence of spinal nerve compression – such classification has been previously shown to predict those more likely to respond to this type of intervention4
Practice Implications:
  1. Unfortunately, results of studies such as this are often overstated by device manufacturers, and practitioners who own these devices. The prudent clinician should be critical of such claims based on only one study, and consider these results in combination with previously published reviews that look at the literature as a whole (see references below).
  2. The VAX-D system is quite expensive to purchase – at this time there is no literature comparing this device to those that are less expensive.
  3. Further research is required to determine whether the VAX-D is superior to other mechanical traction devices that utilize different subject positioning (supine versus prone), harnessing techniques, and have different treatment surfaces.

Additional References:

  1. Airaksinen O et al. European guidelines for the management of chronic non-specific low back pain. European Spine Journal 2006; 15(suppl): S192-S300.
  2. Daniel DM. Non-surgical spinal decompression therapy: Does the scientific literature support efficacy claims made in the advertising media? BMC Chiropractic & Osteopathy 2007; 15:7.
  3. Clarke J et al. Traction for low back pain with or without sciatica: An updated systematic review within the framework of the Cochrane Collaboration. Spine 2006; 31(14): 1591-1599.
  4. Fritz JM et al. Is there a subgroup of patients with low back pain likely to benefit from mechanical traction? Results of a randomized clinical trial and subgrouping analysis. Spine 2007; 32(26): E793-E800.