1. 2025;28;S203-S213Feasibility and Safety of Treatment of Painful Lumbar Degenerative Disc Disease with an Injectable Hydrogel Implant at One-year Follow-up
   Prospective Study
   Olivier Clerk-Lamalice, MD, Alfonso Spath, MD, Kimberly Carcary, MSc, Kasra Amirdelfan, MD, Pierce D. Nunley, MD, and Douglas P. Beall, MD.

BACKGROUND: Degenerative disc disease (DDD) is the most common cause of chronic low back pain (CLBP). In DDD, proteoglycans within the nucleus pulposus break down and lose their ability to retain water, thereby reducing the volume of intervertebral discs and decreasing their weight-bearing capacity. Mechanical loading shifts to the annulus fibrosus, creating fissures and tears that leak crucial factors in the pain to cascade into the intradiscal space and trigger inflammation. When conventional treatments for CLBP fail, surgical options may be required. These surgeries carry risks and require months to heal. For intervertebral discs requiring augmentation, an implant in the form of an injectable, polymer-based hydrogel was developed for the percutaneous treatment of CLBP secondary to lumbar DDD. We hypothesize that the implant’s hydrophilic properties will increase water retention and hydration, improve biomechanics, distribute axial loading more evenly across the annulus fibrosus, and reduce some mechanical sources of discogenic disc pain.

OBJECTIVE: To evaluate the safety and efficacy of a novel, injectable hydrogel implant for the treatment of CLBP. 

STUDY DESIGN: Prospective, single-arm, multicenter feasibility and safety study.

METHODS: Patients with CLBP lasting for longer than 6 months, DDD (modified Pfirrmann grades 4-8), competent outer annuli, numeric rating scale (NRS) scores >= 4, and Oswestry Disability Index (ODI) scores >= 30 were enrolled in 3 outpatient clinics in Canada and Colombia. The hydrogel implant, melted and equilibrated to 65°C, was injected intradiscally with a 17G needle under local anesthesia, using fluoroscopic guidance. The hydrogel cooled to approximately 42°C as it exited the needle directly into the nucleus. Patients were discharged that day. Clinical assessments included ODI and NRS (taken at one, 3, 6, and 12 months), radiographs, computed tomography, and magnetic resonance imaging (MRI) scans. The primary outcome was the successful insertion  of the implant in a lumbar disc nucleus. 

RESULTS: Sixty patients (36 women, 24 men), 49.0 ± 9.3 years old, received 83 implants (one disc-level: n = 37; 2 disc-levels: n = 23). All patients were implanted successfully without complications during the procedure or at discharge. One patient died (for reasons unrelated to the device/procedure), and one patient was lost to follow-up, for n = 58 at the 12-month follow-up. Five patients (8.6%) experienced increased low back pain (LBP) or leg pain and/or leg paresthesia, due to what radiological procedures confirmed was partial implant migration. Migrated implant portions were removed endoscopically from those patients 2 weeks to 10 months after implantation, constituting a 6% (5/83) failure rate. Mean (standard error [SE]) ODI scores in the patients was 9.6 (1.7) at the final follow-up. In the full cohort, ODI scores improved from the baseline mean (SE) of 57.4 (1.5) to 12.7 (1.8) at one month and 11.2 (2.0) at 12 months (P < 0.001). NRS back pain scores improved from the baseline of 7.3 (0.2) to 2.2 (0.3) at one month and 2.1 (0.3) at 12 months (P < 0.001). NRS leg pain scores improved from the baseline of 5.5 (0.4) to 1.1 (0.2) at one month and 1.4 (0.3) at 12 months (P < 0.001). The number of disc levels treated was not correlated with outcomes.

LIMITATIONS: As was inherent to a feasibility and safety study, limitations included a relatively small patient cohort and lack of a control group. 

CONCLUSION: A novel, injectable, polymer-based hydrogel implant was successfully inserted in 83 of the intervertebral discs of 60 patients for the effective treatment of CLBP secondary to DDD. Clinically significant improvements in function, LBP, and low leg pain were maintained through 12 months.

KEY WORDS: Chronic low back pain, degenerative disc disease, intervertebral disc, lumbar, lumbar disc level L1-S1, disc augmentation, hydrogel, implant, nucleus pulposus, annulus fibrosus, percutaneous treatment, minimally invasive procedure