INTRODUCTION: A common method to treat herniated discs is to remove the sequester followed by partial or complete removal of the nucleus to avoid a reherniation. Therefore it would be desirable to close the annulus defect in order to preserve as much nucleus material as possible. The aim of this study was to establish an in vitro herniation model and to test a new annulus reconstruction implant.
METHODS: Human lumbar specimens had to prove during intradiscal pressure measurement that the nucleus still features hydrostatic behavior until we found three L2‐3 and three L4‐5 segments (median: 58 years). A rectangular defect (6 x 10 mm) was created at the posterior annulus. Complex cyclic loading was applied until a visible nucleus extrusion occurred. The extruded material was then pushed back into the disc and the annulus defect was treated with the Barricaid (Intrinsic Therapeutics Inc.). The Barricaid consists of a metal anchor that was inserted below the superior endplate of the inferior vertebra connected to a mesh that was placed inside the disc to seal the annulus internally. Disc height and 3D‐flexibility of the intact, defect and implanted specimens were measured in a spine tester. Afterwards re‐herniation was provoked by cyclic loading.
RESULTS: Compared to the intact state, the provoked herniation caused a median reduction of the disc height of 0.6 mm which could be restored up to 0.2 mm with the implant. The increase of the range of motion (ROM), however, could only be improved slightly. In contrast, the fundamental result was that in no case was a reherniation visible in the macroscopic inspection after 100.000 cycles following Barricaid implantation.
DISCUSSION: We were able to establish a herniation model that guaranteed reliable nucleus extrusion during cyclic loading. The Barricaid seems to prevent the nucleus from re‐herniating.