A memory coiling spiral as nucleus pulposus prosthesis: concept, specifications, bench testing, and first clinical results.

The intradiscal cavity left after a discectomy can be filled by a new nucleus prosthesis made of polycarbonate urethane in the form of a "memory coiling spiral." Biomechanical tests have demonstrated that this device compensates for the loss of disc height, decreases the compression of the facet joints, and restores the kinematics of the spinal segment, without deformation of the vertebral endplates or migration. The device is currently under clinical investigation. Inclusion and exclusion criteria of the pilot study are presented, and preliminary results of the first five patients supplied with the spiral are reported after an average follow-up time of 24 months. No migration of the device has been observed so far. With its easy application due to the standardized approach and the memory coiling mechanism, this device represents an advance within the nonfusion techniques.

A spiral implant as nucleus prosthesis in the lumbar spine.

Microdiscectomy represents the gold standard in disc surgery on the lumbar spine. The remaining defect in the intervertebral disc space can be filled with a newly developed nucleus prosthesis presented in this paper. This prosthesis consists of polycarbonate urethane (Sulene PCU), and takes the form of a memory coiling spiral. It can be easily implanted using the standard microdiscectomy approach with no further tissue damage. Biomechanical tests have shown that anatomical distances can be restored by the spiral for both the facet joints and the endplates. Endplate deformations are not statistically different when compared to intact conditions. Inclusion and exclusion criteria of an in vivo pilot study are presented. The paper describes the insertion setup for the spiral and the technique of implantation. Five patients have been supplied with the implant to date. The first results on postoperative magnetic resonance images are presented.