Phase 1 evaluation of an elastomeric nucleus pulposus device as an option to augment disc at microdiscectomy: Experimental results from biomechanical and biocompatibility testing and first in human

Abstract

Objective: Whilst microdiscectomy is an excellent reliever of pain for recalcitrant lumbar disc herniation (LDH), it has a high failure rate over time due to the ensuing reduction in mechanical stabilization and support of the spine. One option is to clear the disc and replace it with a nonhygroscopic elastomer. Here, we present the evaluation of biomechanical and biological behavior of a novel elastomeric nucleus device (Kunovus disc device [KDD]), consisting of a silicone jacket and a two-part in situ curing silicone polymer filler.Materials and Methods: ISO 10993 and American Society for Testing and Materials (ASTM) standards were used to evaluate the biocompatibility and mechanics of KDD.Sensitization, intracutaneous reactivity, acute systemic toxicity, genotoxicity, muscle implantation study, direct contact matrix toxicity assay, and cell growth inhibition assay were performed. Fatigue test, static compression creep testing, expulsion testing, swell testing, shock testing, and aged fatigue testing were conducted to characterize the mechanical and wear behavior of the device. Cadaveric studies to develop a surgical manual and evaluate feasibility were conducted. Finally, a first-in-human implantation was conducted to complete the proof of principle. Results:The KDD demonstrated exceptional biocompatibility and biodurability.Mechanical tests showed no Barium-containing particles in fatigue test, no fracture of nucleus in static compression creep testing, no extrusion and swelling, and no material failure in shock and aged fatigue testing. Cadaver training sessions showed that KDD was deemed implantable during microdiscectomy procedures in a minimally invasive manner. Following IRB approval, the first implantation in a human showed no intraoperative vascular and neurological complications and demonstrated feasibility. This successfully completed Phase 1 development of the device.