Replacing the Nucleus Pulposus for Degenerative Disc Disease and Disc Herniation: Disc Preservation Following Discectomy

Low back pain is the leading cause of years lived with disability worldwide and thus a significant burden on the economy and healthcare systems. Degenerative changes and/or repetitive abnormal loading in the lumbar spine could lead to structural failures of the intervertebral disc and herniation of the nucleus pulposus, all of which may manifest as chronic back and/or leg pain. Although lumbar discectomy is a clinically beneficial procedure for appropriately selected disc herniation patients, revision discectomy rates range from 2% to 18% within the first decade of the primary discectomy, especially in patients younger than 65 years. Discectomy being a tissue discarding procedure may compromise the biomechanical integrity of the disc and accelerate its degeneration. Nucleus replacement (NR) implants present a promising option to address some of the challenges surrounding lumbar discectomy. An NR implant may be used as an adjunct to discectomy to preserve the biomechanical integrity of the disc and minimize recurrent herniation of the nuclear tissue. Nonetheless, a systematic review of the literature on clinical outcomes for NR implants revealed high rates for endplate remodeling and implant subsidence. A detailed multiscale understanding of the mechanisms of disc herniation and reherniation, closure of the annular defect, and the ability to tailor geometry and material properties for individual patients are needed to develop the next generation of NR implants