Gerhard Fuhrmann, Ulrich Gross, Bertram Kaden, Herman Josef Schmitz, Thomas Fritz, Curt Kranz: Intervertebral disk endoprosthesis. Mecron Medizinische Produkte, Spencer & Frank, March 26, 1991: US05002576 (468 worldwide citation)

An intervertebral disk endoprosthesis is filled with an elastic material and provided with cover plates at its end faces, and has a circular or elliptical corrugated tube surrounding the viscoelastic material, the tube being terminated by cover plates.

Ulrich Gross, Herman Josef Schmitz, Bertram Kaden, Gerhard Fuhrmann: Intervertebral implant. Spencer Frank & Schneider, April 26, 1994: US05306308 (458 worldwide citation)

An intervertebral implant consisting of a disc-shaped spacer made of rigid material and insertable between opposed and adjacent vertebrae in which the opposing sides (1, 2) of the implant bordering the vertebrae are circular discs and have a central raised dome (3 or 4) and roof-shaped projections t ...