A Silicon Implant for Transsacral Prosthetics of a Pulpous Nucleus of an Intervertebral Disc: In-Vitro Study of Its Biomechanics and Stability

G.I. Vilke**, P.V. Zelenkov*, F. Hoer**, S. Midderhof**, K. Verner**

* Burdenko Research Institute of Neurosurgery, Moscow, Russia
** Institute of Orthopedics Researches and Biomechanics, Ulm, Germany


Transsacral prosthetics of a pulpous nucleus with a silicon implant is a prospective method of discogenic pain treatment.

The study goal has been to estimate prosthesis biomechanics and a risk of its migration after conventional microdiscectomy.

Material and Methods. We studied 12 specimens of human spine (L2-L3 segments 6; L4-S1 segments - 6). Standard interlaminar microdiscectomy was used in the L2-L3 group. A silicon implant of a pulpous nucleus was placed via a transsacral approach in all specimens. Both groups were subjected to cyclic load (100-600 H; 100000 cycles). Analysis of segment mobility and X-ray examination were carried out at each stage. Mobility was studied with applying a torque (7.5 Hm) in three planes and a unique load bench. The Vicon MX system was used for analysis of movements. All specimens were studied macroscopically.

Results. Implantation was followed by restoration of segments stability in all planes. The group with microdiscectomy was characterized by a reduced volume of movements in sagittal and frontal planes. It did nor concern the axial plane. Cyclic loads had a destabilizing effect; however, the median of a volume of movements corresponded to initial levels in both groups. The only exclusion was axial rotation in the group with microdiscectomy. We did not reveal silicon implant migration through a dorsal defect of the fibrous ring in this group.

Conclusion. Transsacral prosthetics of a pulpous nucleus with a silicon implant provided restoration of segments biomechanics up to an intact level. The dorsal defect of the fibrous ring led to implant prolapse in the group with microdiscectomy.