The inner core of this sheep intervertebral disc was surgically removed, after which the outer disc was treated with a collagen patch. The white box (enlarged to the right) offers a close-up view of the alignment and orientation of collagen. The white arrow points to the annulus fibrosus lamellae, sheets of cross-linked collagen fibers on the tough wrapping of the outer intervertebral disc.

Discectomy, a surgical procedure that involves the removal of part or all of an intervertebral disc, is often recommended for people with herniated discs that limit their mobility and cause chronic pain. Research has suggested that 90 percent of Americans will experience intervertebral disc degeneration during their lifetime, and though discectomies may relieve symptoms in some patients, they don’t prevent further disc degeneration and herniation. In a new study published on March 11 in Science Translational Medicine...

Eight sheep underwent partial discectomies in which their nucleus pulposus, the soft inner core of the intervertebral disc, was removed. They then received either a hyaluronic acid injection into the inner intervertebral disc, a collagen patch on the outer intervertebral disc, or both the injection and patch. After six weeks, the researchers found that the combined treatment restored hydration to the disc’s core, repaired injuries to the disc’s outer wrapping, and helped maintain the normal tension and rotation of the lumbar spine.

Although more research is needed before the experimental treatment can be applied to humans, the authors write in the paper’s conclusion that the procedure “has great potential to maintain [intervertebral disc] health and prevent subsequent progressive degeneration in the spine.”

S.R. Sloan Jr. et al., “Combined nucleus pulposus augmentation and annulus fibrosus repair prevents acute intervertebral disc degeneration after discectomy,” Science Translational Medicine, doi:10.1126/scitranslmed.aay2380, 2020.

Amy Schleunes is an intern at The Scientist. Email her at

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