Effectiveness of epidural amniotic fluid injection for low back pain.

Background: Epidural corticosteroid injections have long been used to treat pain and inflammation associated with low back conditions including symptoms due to lumbar herniated disc, HNP; spinal stenosis, SS; and degenerative disc disease, DDD. Amniotic fluid, AF, is rich in the proteins and factors that are believed to contribute to healing by minimizing inflammation. AF injections in non-spinal conditions have been shown to be safe and avoid adverse effects related to steroids. Objectives: To investigate the safety and efficacy of a single amniotic fluid injection into the lumbar epidural space for the treatment of low back pain. Specifically, this pilot study was to define indications for future large scale comparative studies. Methods: This IRB approved prospective clinical study of 3 cohorts included 20 patients each with HNP, SS, and DDD with a 1-year follow-up. Patients were enrolled who had LBP ± leg symptoms for >2 months, with clinical and MRI findings for HNP, SS, or DDD. Inclusion criteria necessitated that study patients had not responded to medications, physical therapy, and/or chiropractic. After obtaining consent, 20 patients in each diagnostic group (HNP, SS, and DDD) had 2 cc's transforaminal epidural AF injected at the primary symptomatic level using fluoroscopy. Pre- and post-procedure outcomes measurements were obtained at follow-up periods of 2-3 weeks, 6-8 weeks, 3-4 months, 6-8 months and 1 year. Outcome measures were Visual Analog Scale (VAS) for back and leg pain, Oswestry Disability Scale (ODI), Patient-Reported Outcomes Measurement Information System (PROMIS) scores, and pain medication usage. Using the VAS and ODI measurements, Minimal Clinical Important Difference (MCID) and Success (50 % improvement) rates were derived. Results: The average age (years) of HNP, stenosis, and DDD patients was 46, 60, and 46 respectively. There were no complications or other adverse effects. HNP patients had the greatest reduction in symptoms with average LBP VAS improvement from 6.3 to 2.9, leg VAS from 5.9 to 2.2, ODI from 37 to 19, and PROMIS Physical component 13.1 to 14.7. SS patients had LBP VAS improvement from 6.8 to 5.3, leg VAS from 5.8 to 3.1, ODI from 46 to 33 and PROMIS Physical component 10.9 to 13.0. DDD patients had LBP VAS from 7.0 to 4.8, leg VAS from 3.9 to 2.7, ODI from 41 to 37 and PROMIS Physical component 12.0 to 13.1. HNP patients had a significant reduction in pain medication use. Over the one year follow-up, the HNP group had the greatest rate of attaining MCID (65 %-79 %) and Success (47 %-60 %). SS had a similar rate of Success for leg pain. ODI MCDI and Success rates were significantly greater for HNP vs the other 2 groups. Overall, 15 % of patients had additional injections and 20 % went on to surgery. Conclusions: AF epidural injections are most effective for patients with lumbar HNP and moderately effective for those with SS. AF injections for DDD patients gave inconsistent results. Future prospective studies of AF vs steroid injections are warranted for HNP and stenosis patients, particularly in patients with known adverse reactions to steroids.