Interspinous spacer devices for dynamic stabilization of degraded spinal segments

An interspinous spacer device for the stabilization of a degraded spinal segment, the device comprising:

• a base comprising:
• a body containing a curved internal track bounded at opposite ends by a lower track wall and an upper track wall, and bounded laterally by a curved anterior track wall, a curved posterior track wall, and two side track walls, wherein the curved internal track opens upward into an aperture contained within the track upper wall and extending through an upper surface of the body, wherein the aperture has an aperture cross-sectional area that is smaller than a corresponding track cross-sectional area of the curved internal track;
• and
• a caudal attachment fitting comprising a first caudal attachment plate and a second caudal attachment plate projecting perpendicularly downward from opposite edges of the body of the base;
• and
• a sliding rod comprising:
• a retaining plate situated within the curved internal track comprising an upper surface, a lower surface, an anterior face, a posterior face, and two side faces, wherein the retaining plate has a non-circular cross-sectional shape and a plate cross-sectional area that is larger than the aperture cross-sectional area and smaller than the track cross-sectional area;
• a column comprising a lower column end attached to the upper surface of the retaining plate and an upper column end situated opposite to the lower column end and protruding upward from the upper surface of the body through the aperture of the body;
• and
• a cranial attachment fitting comprising a lower plate attached to the upper column end of the sliding rod, and a first cranial attachment plate and a second cranial attachment plate attached to opposite edges of the lower plate, wherein the first and second cranial attachment plates extend perpendicularly upwards from the lower plate;
• wherein the non-circular cross-sectional shape of the retaining plate is essentially matched with a cross-sectional shape of the curved internal track such that the retaining plate of the sliding rod slides freely within the curved internal track without significant resistance force to actuate an arcuate movement of the sliding rod along a range of movement limited by the track, and with a center of rotation of the arcuate movement situated at a perpendicular distance from the anterior track wall that is equal to a radius of curvature along the length of the curved internal track;
• and
• wherein the base is attachable to a caudal spinous process of a vertebra situated caudal to the degraded spinal segment and the sliding rod is attachable to a cranial spinous process of a vertebra situated cranial to the degraded spinal segment.