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

backgroundPercutaneous 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.