Biomechanical and morphologic evaluation of a three-dimensional fabric sheep artificial intervertebral disc -: In vitro and in vivo analysis

Study Design. We have developed a new artificial intervertebral disc consisting of triaxial three-dimensional fabric for the sheep lumbar spine. To clarify the characteristics of the new implant, a series of biomechanical tests and morphologic evaluations were conducted. Objectives. To investigate the static, viscoelastic, and fatigue properties of the three-dimensional fabric disc in comparison with natural sheep disc and to evaluate their biomechanical and morphologic alteration in vivo. Summary of Background Data. In its human dimensions the three-dimensional fabric disc revealed mechanical properties similar to a natural human disc. Methods. The disc-body units from sheep spine and the sheep three-dimensional fabric discs underwent tensile-compressive (200 N), torsional (5 Nm), and creep-recovery tests (30 minutes-30 minutes, 200 N). After fatigue loading (2 million, compressive 200 N) the biomechanical changes and the debris were investigated. For in vivo evaluation after placing in the sheep psoas muscles for 6 months, the surface of the three-dimensional fabric disc was evaluated using macroscopy and scanning electron microscopy, followed by previous biomechanical tests. Results. The behavior of the sheep three-dimensional fabric disc was similar to that of natural sheep disc in tensile-compressive and creep-recovery tests. In torsional testing the behavior of natural sheep disc was more rigid than that of the sheep three-dimensional fabric disc. After fatigue loading there was no biomechanical change and no debris detected. Six months after surgery no morphologic deterioration was observed nor were there changes in biomechanical parameters. Conclusions. The sheep three-dimensional fabric disc exhibited biomechanical and morphologic biostability, appropriate viscoelasticity, and excellent fatigue properties. The three-dimensional fabric disc has a potential far clinical application of human intervertebral disc-replacement.