Biomechanical behavior of different artificial lumbar disc implants.

Aim: The aim of this study was to determine the influence of two different artificial nucleus implants for lumbar discs on the biomechanical properties of the spinal motion segment. Methods: From 7 calf spines, the lumbar segments L2/3 and L4/5 were harvested, the lamina and the muscles were removed with care to preserve the anterior and posterior longitudinal ligament. The segments were fixed on a special testing device mounted in an universal testing machine (Zwick, Ulm, Germany). Physiological load with a maximum of 7 Nm was applied in flexion/extension, right and left side bending, and right torsion. Three cycles of measurement were performed in all specimen: a) the intact segment, b) segment after nucleotomy, c) 6 segment with 2 PDN devices (Ray Medical and 8 segments with an autopolymerized polymer. Results: There was a statistically significant (p = 0.0078/p = 0.0313) increase in segmental mobility in all directions after nucleotomy. After introduction of two PDN implants as well as the polymer implant, there was a restoration of segmental mobility for all movement directions with no statistically significant difference (p>0.05) compared to the intact situation before nucleotomy.