Researchers describe technique to “re-inflate” herniated disc

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Lawrence Bonassar (Picture: John Munson/Cornell University)

A research collaboration led by Cornell University (Ithaca, USA) professor Lawrence Bonassar has led to the development of a new technique for the treatment of a herniated disc, repairing the disc “like a flat tyre”.

The team’s paper describing the technique, Combined nucleus pulposus augmentation and annulus fibrosus repair prevents acute intervertebral disc degeneration after discectomy, was published this month in Science Translational Medicine.

The study team found that injecting hyaluronic acid into the inner region of a herniated disc (nucleus pulposus) and applying a photo-crosslinked collagen patch to the outer annulus fibrosus healed disc defects and maintained biomechanical support in the lumbar spines of sheep for six weeks after discectomy.

“This is really a new avenue and a whole new approach to treating people who have herniated discs,” Bonassar says. “We now have potentially a new option for them, other than walking around with a big hole in their intervertebral disc and hoping that it doesn’t re-herniate or continue to degenerate. And we can fully restore the mechanical competence of the disc.”

Bonassar’s research group seeks engineering-based solutions for degenerative disc disease. The group has developed a collagen gel that incorporates riboflavin, a photoactive vitamin B derivative. Instead of sewing up a ruptured disc, the researchers can patch it by applying their gel and shining light on it to activate the riboflavin, they add. The resulting chemical reaction causes fibres in the collagen to bond together, and the thick gel stiffens into a solid. The gel provides a more fertile ground for cells to grow new tissue, sealing the defect better than any suture could.

“The idea is, if you have a herniation and you’ve lost some material from the nucleus, now we can re-inflate the disc with this hyaluronic acid gel and put the collagen cross-linking seal on the outside. Now we’ve refilled the tire and sealed it,” Bonassar says. “What the paper shows is that both of those things are critical.”

Bonassar’s other collaborator, Roger Härtl, a neurosurgeon at New York-Presbyterian Hospital (New York, USA), used the two-part technique to repair lumbar discs in sheep. The team found the technique successfully healed the damage to the annulus fibrosus, restored disc height and maintained mechanical performance of the spine, up to six weeks after injury.

The technique only takes five or 10 minutes and can be applied in conjuction with a discectomy. The technique could be used to address other types of disc degeneration, or integrated into other spinal procedures and therapies, the researchers claim.

“The beauty of this is it’s a relatively simple application of the technology,” Bonassar points out. “We hand the surgeon a needle, they inject it. Here is this other needle and they inject it. Then shine a light; OK, you’re done.”

The research was supported by the Clinical and Translational Science Center, which is supported by the National Institutes of Health and National Center for Advancing Translational Sciences; and the Colin MacDonald Fund.


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