Hydrogel augmentation for refractory chronic low back pain, does it work?

Hydrogel Augmentation of the Lumbar Intervertebral Disc: An Early Feasibility Study of a Treatment for Discogenic Low Back Pain

Clinical question

Is hydrogel augmentation a safe and effective treatment for chronic low back pain that is refractory to medical management?

Take away point

This early feasibility study with 20 patients experiencing chronic low back pain due to degenerative disc disease refractory to conventional management demonstrated the effectiveness of hydrogel augmentation in pain reduction and function improvement. Two serious adverse events of implant migration required transforaminal endoscopic removal.

Reference

Hydrogel Augmentation of the Lumbar Intervertebral Disc: An Early Feasibility Study of a Treatment for Discogenic Low Back Pain. Beall DP M.D. et al. Journal of Vascular and Interventional Radiology, Volume 35, Issue 1, 51-58.

Click here for abstract

Study design

The study was a prospective, nonrandomized, single-arm, single center study

Funding Source

ReGelTec, Baltimore, Maryland

Setting

Ceduil Medical Center, Barranquilla, Colombia

Figure

Figure 1(a) Lateral fluoroscopic image showing injection of contrast medium (black arrowheads) through 22-gauge needles (white arrowheads) into the L3–4 and L4–5 discs. (b) Lateral fluoroscopic image 2 weeks later showed a pattern of hydrogel after injection into the same discs. Note that the pattern of hydrogel distribution was similar to that of the contrast medium injected during discography 2 weeks earlier.




Figure 2 Box plots demonstrated the numerical rating scale (NRS) pain scores obtained at baseline, 1 month, 3 months, and 6 months for the patient’s (a) back pain and their (b) leg pain. Significance of post hoc Bonferroni-adjusted Wilcoxon signed rank tests were shown between baseline and follow-up visits. Data showed a 5.2-point reduction in back pain and a 3.4-point reduction in leg pain at the 6-month follow-up time point.

Summary

Low back pain is the leading cause of disability worldwide and is most often caused by degenerative disc disease. Originally, this was treated with replacement of the nucleus pulposus tissue to combat lost intradiscal tissue. Hydrogel materials have been investigated due to its similarity to the native nucleus pulposus tissue and its ability to form a continuous implant over time without cracks or fissures. The hydrogel combination of polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, and barium sulfate was developed. The addition of polyethylene glycol allowed the preparation to liquify when heated to 65 °C and be injected through a smaller, 17-gauge needle, providing an ideal minimally invasive treatment approach.

The authors of the study performed a prospective, single arm, single center, clinical trial to evaluate the safety and effectiveness of hydrogel augmentation for refractory chronic low back pain due to degenerative disc disease. 20 patients met the inclusion criteria of clinical and imaging evidence of disc generation at 1 or 2 vertebral levels, disability present for at least 12 weeks, refractory to conventional medical management, and modified Pfirrmann levels II-VI on MR imaging. A complete safety assessment one month after treatment was performed by a safety committee to determine if patient recruitment should continue.

The hydrogel augmentation procedure was successfully performed in 20 patients at 29 total lumbar levels. The hydrogel was placed in the center of the disc with an injected volume ranging from 1.5 to 3.1 mL. Patients were assessed using a numerical rating scale for back and lower limb pain, and an Oswestry disability index for function at their baseline and follow-ups at 1 month, 3 months, and 6 months. There was a statistically significant reduction in back and lower leg pain, along with a statistically significant improvement in function.

18 total adverse events were noted in 12 of the 20 patients. 13 were of mild-moderate severity and not related to the device or procedure. One patient died from a pulmonary thromboembolism attributable to cardiorespiratory factors and unrelated to the study device or procedure. Two patients experienced persistent pain post procedure and were found to have hydrogel extrusion. These were resolved with endoscopic removal and both patients had pain scores of 0 at the 6-month follow-up.

The first limitation of this study is the small study population, with 19 patients who completed the 6 month follow up and 1 patient lost to follow up. This limitation is inherent to an early feasibility study. The next limitation is the lack of comparison arms. Future studies should compare hydrogel with continued non-surgical management, epidural steroid injections, and/or spinal fusion. The last limitation is the involvement of a single treatment site, which limits the generalizability to other interventionalists and locations.

Commentary

This study demonstrated that hydrogel augmentation can successfully treat refractory chronic low back pain caused by degenerative disc disease. Two serious adverse events of hydrogel migration were noted and required endoscopic removal. There were no persistently symptomatic adverse events 6 months post treatment. Determining risk factors associated with hydrogel migration and developing techniques that can minimize this serious adverse event are critical to improve the safety profile of the procedure. Comparisons with current treatment options including medical management, steroid or epidural injections, and spine fusion in blinded, randomized control trials are necessary to delineate the role of hydrogel augmentation in the treatment algorithm of chronic refractory low back pain. Hydrogel augmentation, when validated in larger multi-center trials with comparison arms, may revolutionize degenerative disc disease treatment by providing a minimally invasive intervention early in the disease course.

Post Author

Anthony M. Camargo, BA
MD candidate, Class of 2025
University of Massachusetts Chan Medical School
@anthonymcamargo