In 1997, a study was reported of 39 patients (19 with ruptured discs and sciatica, 6 with facet joint pain, 4 with ruptured discs without sciatica, and 10 with other low back pain) who were randomized to decompression reduction stabilization or 20 conventional traction sessions (Shealy, 1997). More patients randomized to DRS achieved pain relief than those who were randomized to standard traction. Neither the patients nor the observing physicians were randomized to the treatment, and there was no long-term follow-up.
Gose and colleagues reported on an uncontrolled retrospective case series of 778 cases which showed improvements in pain, mobility, and activity in the majority of patients, but the study did not detail methods of patient identification or collection of data and did not indicate the duration of treatment success (Gose, 1998)
A randomized trial comparing vertebral axial decompression (using the VAX-D device) with transcutaneous electrical nerve stimulation (TENS) in 44 patients with a confirmed disc protrusion or herniation was published in 2001from Australia (Sherry, 2001). While a 68% success rate was associated with VAX-D compared to a 0% success rate associated with TENS therapy, there was no true placebo control. Neither patients nor interpreting physicians were blinded to the therapy (a sham intradiscal pressure reduction was not attempted). Many studies regarding low back pain have demonstrated that the placebo effect is rather high (40% - 50%), and without a true placebo control, the results are difficult to interpret scientifically.
The only report of an adverse event was published in 2003, which described a patient with a large lumbar disk protrusion who experienced sudden, severe exacerbation of radicular pain during a VAX-D session. Follow-up MRI of the lumbar region showed marked enlargement of the disk protrusion, and urgent microdiscectomy was required (Deen, 2003).
Ramos reported a nonrandomized comparison of patients receiving 10 sessions versus 20 sessions of vertebral axial decompression treatment (Ramos, 2004). Patients receiving 20 sessions had a response rate of 76% versus a 43% response in those receiving 10 sessions. The study has several limitations and deficiencies: it is not randomized, the follow-up time is not stated, and it does not use a validated outcome measure. None of the studies described mentions the duration of treatment benefit
A review of the literature concerning distraction manipulation of the lumbar spine, particularly regarding physiological effects, clinical efficacy, and safety was published by a group from the Mayo Clinic (Gay, 2005). They identified 30 articles: 3 were uncontrolled or pilot studies, 3 were basic science studies, and 6 were case series. Most were case reports. The authors concluded, “Little data are available describing the in vivo effect of distraction when used in combination with flexion ore other motions. Despite widespread use, the efficacy of distraction manipulation is not well established. Further research is needed to establish the efficacy and safety of distraction manipulation and to explore biomechanical, neurological, and biochemical effects that may be altered by this treatment.”
A systematic literature review of spinal decompression via motorized traction for chronic discogenic low back pain from the Department of Anesthesia, Stanford University School of Medicine was published in 2006 (Macario, 2006). The authors concluded, “These data suggest that the efficacy of spinal decompression achieved with motorized traction for chronic discogenic low back pain remains unproved. This may be, in part, due to heterogeneous patient groups and the difficulties involved in properly blinding patients to the mechanical pulling mechanism. Scientifically more rigorous studies with better randomization, control groups, and standardized outcome measures are needed to overcome the limitations of past studies.”
A review of non-surgical decompression therapy from the Parker College of Chiropractic was published in 2007 (Daniel, 2007). The author concluded, “There is very limited evidence in the scientific literature to support the effectiveness of non-surgical spinal decompression therapy. This intervention has never been compared to exercise, spinal manipulation, standard medical care or other less expensive conservative treatment options which have an ample body of research demonstrating efficacy. Considering the cost-benefit relationship, many better researched and less expensive treatment options are available to the clinician.”
The Agency for Healthcare Research and Quality evidence based assessment on vertebral decompressive therapy for treatment of lumbosacral pain was released in August 2007. The authors concluded, “Currently available evidence is too limited in quality and quantity to allow for the formulation of evidence-based conclusions regarding the efficacy of decompression therapy as a therapy for chronic back pain when compared with other non-surgical treatment options.” This article is one of the few to address frequency of adverse events. It noted, from survey data, that approximately 10% of patients could not tolerate the procedure.
A prospective, longitudinal case series of 296 patients with low back pain and evidence of a degenerative and/or herniated intervertebral disk at one or more levels of the lumbar spine were studied (Beattie, 2008). An 8-week course of prone lumbar traction, using vertebral axial decompression, consisting of five 30-minute sessions a week for 4 weeks, followed by one 30 minute session a week for 4 additional weeks was performed. A numeric pain rating scale and the Roland-Morris Disability Questionnaire were completed at pre-intervention, discharge, and at 30 days and 180 days after discharge. 83.4% and 81.4% of the subjects were available for evaluation at 30 and 180 days, respectively. Significant improvement for all post-intervention outcome scores as compared to pre-intervention was noted. The authors concluded, “Causal relationships between these outcomes and the intervention should not be made until further study is performed using randomized comparison groups.”
A retrospective review of 94 patients with chronic discogenic low back pain with the DRX9000 was also published in 2008 (Macario, 2008). Patients received 30-minute DRX9000 sessions daily for the first 2 weeks tapering to 1 session/week. Treatment protocol included lumbar stretching, myofascial release, or heat prior to treatment, with ice and/or muscle stimulation afterwards. Primary outcome was verbal numerical pain intensity rating before and after the 8-week treatment. The 94 patients had diagnoses of herniated disc, degenerative disc disease, or both. The retrospective chart audit provided preliminary data that chronic low back pain may improve with DRX9000 spinal decompression. The authors concluded, “Randomized double-blind trials are needed to measure the efficacy of such systems” [motorized spinal decompression devices].
The Medical Letter on Drugs and Therapeutics published an analysis of spinal decompression machines in June 2008 (the Beattie, 2008 article, but not the Macario, 2008 article, was included in the review). The authors concluded, “There is no acceptable evidence that non-surgical spinal decompression machines can correct degenerated or herniated discs or that they relieve pain in patients with these conditions. There is also no convincing evidence that the physiological responses of lumbar tissue to power traction equipment are superior to those with standard mechanical traction.”
There continues to be a lack of rigorous clinical evidence supporting the efficacy of vertebral spinal decompression. The policy statement is unchanged. Specifically, a placebo effect may be expected with any treatment that has pain relief as the principal outcome. All systematic reviews to date have noted that randomized trials with validated outcome measures are required to determine if there is an independent effect of this treatment. No such trials have been identified.