Delayed percutaneous intradiscal hydrogel herniation causing neurological injury after minor trauma: illustrative case

Abstract

Background: Percutaneous intradiscal hydrogel injection has been used to treat low-back pain (LBP) due to degenerative disc disease with or without mild radicular pain. Complications from these procedures are underreported. In this case lesson, the authors present a rare case of a patient with herniated intradiscal hydrogel following a minor trauma leading to neurological injury.

Observations: A 36-year-old female who had been previously treated with L4-5 and L5-S1 intradiscal hydrogel injections for LBP presented with painful, progressive right-sided lower-extremity weakness after experiencing a twisting trauma. Cross-sectional imaging results revealed a herniated hydrogel-based disc implant in the spinal canal. She underwent an urgent L4-5 laminectomy for decompression and removal of the herniated implant. A large annular defect was noted. Postoperatively, she had resolution of her right leg pain but experienced persistent right foot drop requiring an ankle-foot orthosis.

Lessons: Herniated intradiscal hydrogel implants can lead to permanent neurological injury. While the risk factors for hydrogel herniation have not been elucidated, they can be related to pre-existing disruptions to the annulus and/or posterior longitudinal ligament, excess volume of hydrogel injection, and insufficient fixation time. Further research is needed to determine the safety and efficacy of this technology. https://thejns.org/doi/10.3171/CASE24394.

Keywords: case report; degenerative disc disease; interventional pain procedure; intradiscal hydrogel; neurological injury; spine surgery.

FIG. 1.

Lumbar T2-weighted MRI before hydrogel injection. A: Sagittal MR image showed evidence of DDD and loss of disc height at L4–5 and L5–S1. B: Axial L4–5 MR image showed a central annular tear. C: Axial L5–S1 MR image demonstrated a right-sided paracentral disc herniation causing impingement of the S1 nerve root.

FIG. 2.

Sagittal (A) and axial L4–5 (B) and axial L5–S1 (C) lumbar CT after hydrogel injection. Hyperdense hydrogel material is noted within the L4–5 disc and extending to the outer annulus. A minimal amount of hyperdense material is noted within the L5–S1 disc. Extruded L5–S1 hydrogel material courses along the right S1 nerve root.

FIG. 3.

Posttrauma sagittal (A) and axial (B) lumbar CT. The hyperdense hydrogel was observed in the spinal canal at the L4–5 level, slightly eccentric to the right, causing spinal stenosis.

FIG. 4.

Posttrauma sagittal T1-weighted (A) and T2-weighted (B) MR images of the lumbar spine and axial T1-weighted (C) and T2-weighted (D) MR images of the L4–5 intervertebral disc space. The herniated hydrogel caused compression of the right lateral recess and central canal. The hydrogel implant was iso- to hypointense on T2-weighted imaging and hyperintense on T1-weighted imaging.

FIG. 5.

Resected hydrogel implant.