Gluing the Annulus! (Orthopedics this Week)
Repairing the annulus after a micro discectomy is not a new idea. But using glue (specifically fibrin glue) just might be. James Iatridis, Ph.D. and his team have been focusing their efforts on furthering the status of annulus fibrosus repair. They are particularly hoping to find solutions for those who have herniations and who undergo micro discectomy. Dr. Iatridis, director of spine research at the Mt. Sinai School of Medicine, tells OTW, “The goal should be not just to take away the herniated tissue, but to repair the annulus. We have just published two review articles describing the status of annulus fibrosus repair. In the first paper we describe what needs to be repaired biomechanically and strategies for repairing the injured intervertebral disc with different biomaterials. Our concept is that we must restore both annulus fibrosus integrity (detectable with torsional measurements) and nucleus pulposus pressurization (detectable with intradiscal pressure or axial biomechanics measurements).”
“In these articles we describe what an injury to the annulus fibrosus does to the biomechanics and the biological environment, as well as ways to characterize that injury. For example, a puncture in the annulus fibrosus results in a loss of pressurization of the disc. Contrast this with a herniation where there is a greater disruption in the annulus fibrosus. We’re screening different treatments in the lab for degenerative disc disease. Our organizing principle for annulus repair is to achieve three design criteria: the material must mechanically match the native material properties of the annulus fibrosus, support the growth of intervertebral disc cells, and be strongly adherent to seal annulus fibrosus defects under physiological strain levels.”
“At the recent Orthopaedic Research Society (ORS) meeting in San Antonio, we presented two abstracts characterizing our fibrin-based biomaterial which shows promise as an annulus fibrosus sealant. In the first, we enhanced our formulation of a Fibrin-Genipin adhesive with the addition of cell adhesion molecules for improved cell growth. This gel is exciting because it meets our design criteria and it doesn’t degrade as quickly as unmodified fibrin gels. The second abstract described our characterization of this Fibrin-Genipin adhesive in a novel organ culture model, demonstrating biomechanical restoration, strong adhesion with the native tissue, and transport of annulus fibrosus cells from the native tissue into the gel. Given our promising results, we will pursue animal model testing and hope these studies of annular repair will translate to therapies for lumbar microdiscectomy patients that minimize both the likelihood of reherniation as well as further disc degeneration.”