Is a collagen scaffold for a tissue engineered nucleus replacement capable of restoring disc height and stability in an animal model?

Eur Spine J (2006) 15 (Suppl. 3):S433S438DOI 10.1007/s00586-006-0177-xORIGINAL ARTICLEIs a collagen scaffold for a tissue engineered nucleus replacement

capable of restoring disc height and stability in an animal model?Hans-Joachim Wilke Frank Heuer

Cornelia Neidlinger-Wilke Lutz ClaesReceived: 22 May 2006 / Revised: 12 June 2006 / Accepted: 13 June 2006 / Published online: 26 July 2006

Springer-Verlag 2006Abstract The idea of a tissue engineered nucleus

implant is to seed cells in a three-dimensional collagenmatrix. This matrix may serve as a scaffold for a tissueengineered nucleus implant. The aim of this study wasto investigate whether implantation of the collagenmatrix into a spinal segment after nucleotomy is able torestore disc height and flexibility. The implant basicallyconsists of condensed collagen type-I matrix. Forclinical use, this matrix will be used for reinforcing andsupporting the culturing of nucleus cells. In experiments, matrixes were concentrated with barium sulfatefor X-ray purposes and cell seeding was disclaimed inorder to evaluate the biomechanical performance ofthe collagen material. Six bovine lumbar functionalspinal units, aging between 5 and 6 months, were usedfor the biomechanical in-vitro test. In each specimen,an oblique incision was performed, the nucleus wasremoved and replaced by a collagen-type-I matrix.Specimens were mounted in a custom-built spine tester, and subsequently exposed to pure moments of7.5 Nm to move within the three anatomical planes.Each tested stage (intact, nucleotomy and implanted)was evaluated for range of motion, neutral zone andchange in disc height. Removal of the nucleus significantly reduced disc height by 0.84 mm in respect to theintact stage and caused an instability in the segment.Through the implantation of the tissue engineerednucleus it was possible to restore this height and stability loss, and even to increase slightly the disc height

of 0.07 mm compared with the intact stage. There wasno statistical difference between the stability providedby the implant and intact stage. Results of movementsin lateral bending and axial rotation showed the sametrend compared to flexion/extension. However, implant extrusions have been observed in three of sixcases during the flexibility assessment. The results ofthis study directly reflect the efficacy of vital nucleusreplacement to restore disc height and to provide stability to intervertebral discs. However, from a biomechanical point of view, the challenge is to employ anappropriate annulus fibrosus sealing method, which iscapable to keep the nucleus implant in place over along-time...