Bi-planar expandable cage for spine

An expandable cage for a spine comprising:

• an upper structural body;
• a lower structural body spaced at a predetermined distance below the upper structural body;
• a main frame disposed between the upper and lower structural bodies, and having control mechanism insertion holes defined on two sides thereof in a longitudinal direction for insertion of a control mechanism;
• a sagittal balance control unit coupled to the main frame and coupled to a first side of each of the upper and lower structural bodies, the sagittal balance control unit configured to adjust a sagittal balance of the spine by adjusting a distance between the upper and lower structural bodies using the control mechanism inserted into the control mechanism insertion holes;
• and
• a coronal balance control unit coupled to the main frame and coupled to a second side of the each of the upper and lower structural bodies, the coronal balance control unit configured to adjust a coronal balance of the spine by adjusting an inclination of the upper and lower structural bodies by elevating and lowering the second sides of the upper and lower structural bodies using the control mechanism inserted into the control mechanism insertion holes,
• wherein the sagittal balance control unit comprises:
• a height adjusting screw, disposed in the longitudinal direction of the upper and lower structural bodies, having a screw thread defined on an outer circumferential surface thereof, and configured to rotate according to a rotation of the control mechanism when the control mechanism is inserted therein;
• a height adjusting member, having a screw hole coaxial with the control mechanism insertion hole, and screw-coupled with the height adjusting screw to move according to the rotation of the height adjusting screw;
• and
• a height adjusting link, having an upper end connected to the upper structural body and a lower end connected to the lower structural body, and linked with the height adjusting member to adjust a height between the upper and lower structural bodies according to a movement of the height adjusting member,
• wherein the height adjusting link comprises:
• a fixed shaft coupled to the main frame;
• a moving shaft disposed on the height adjusting member;
• a first height adjusting link frame having one side rotatably coupled to the fixed shaft and another side rotatably coupled to the upper structural body;
• a second height adjusting link frame having one side rotatably coupled to the fixed shaft and another side rotatably coupled to the lower structural body;
• a third height adjusting link frame having one side rotatably coupled to the moving shaft and another side rotatably coupled to the upper structural body;
• and
• a fourth height adjusting link frame having one side rotatably coupled to the moving shaft and another side rotatably coupled to the lower structural body, and
• wherein the height adjusting link has a rhomboidal link structure and the height between the upper and lower structural bodies is adjusted by adjusting a distance between the moving shaft and the fixed shaft.