Patent ID: 8388684

Claim:
A two-part prosthetic spinal nucleus device for replacing a nucleus of a spinal disc and being implanted in an intervertebral space within a natural annulus and between natural end plates attached to adjacent axially spaced upper and lower vertebral bones, the device comprising: a rigid upper shell having a one-piece elongate body having a predetermined length between opposite narrow ends and a predetermined width between opposite elongate sides and including a smooth outer surface having a flat configuration extending substantially entirely across the length and width of the shell for facing and non-invasively contacting the natural end plate of the upper vertebra for sliding engagement therewith and sized to fit within the natural annulus of the spinal disc; a rigid lower shell having a one-piece elongate body having a predetermined length between opposite narrow ends and a predetermined width between opposite elongate sides and including a smooth outer surface having a flat configuration extending substantially entirely across the length and width of the shell for facing and non-invasively contacting the natural end plate of the lower vertebra for sliding engagement therewith and sized to fit within the natural annulus of the spinal disc; inner, arcuate bearing surfaces of the one-piece bodies of the upper and lower shells that are in sliding engagement with each other including a dome-shaped inner bearing surface of one of the shell bodies having truncated, diametrically opposite edge portions that extend along the opposite elongate sides of the one shell body such that a diameter of the dome-shaped inner bearing surface is longer than the width of the one shell body and the dome-shaped inner bearing surface extends substantially across the entire width of the one shell body between the opposite edge portions; and the elongate sides of each of the shell bodies extending lengthwise between the narrow ends thereof so that the sides are longer than the width across the narrow ends to allow the shells to be arranged with narrow ends of the shell bodies leading the shells as the shells are inserted through an incision smaller than the elongated sides of the shell bodies so that the natural annulus retains the shells in the intervertebral space with the smooth outer surfaces of the shell bodies extending continuously without interruption across the entire extent of the length and the width thereof between the ends and sides of the respective shell bodies.