WE CLAIM:
1. A bi-stage expandable bone fastener, the fastener comprising of:
an expandable outer region (1) comprising of a circular disc (8), a plurality of surfaces (2) conjoined to form a hollow cylindrical structure on the circular disc (8), each of the surface having an external region (2a), the external region (2a) provided with a plurality of ridges having at least two distinct sections of variable thickness, and an internal region (2b), the internal region (2b) having a first expandable ramp (5a) and a second expandable ramp (5b) opposingly positioned with respect to the first expandable ramp; and
a centrally cannulated threaded bolt (3) provide with a first threaded region (11a) proximal to a first end (3a) and a second threaded region (11b) proximal to a second end (3b),
a first conical projection (9a) corresponding to the first expandable ramp (5a) and a second conical projection (9b) corresponding to the second expandable ramp (5b), mounted on the cannulated threaded bolt (3),
wherein the bi-stage expansion of the bone fastener is rendered due to the differential movement of the first conical projection (9a) and the second conical projection (9b) within the first expandable ramp (5a) and the second expandable ramp (5b).
2. The bone fastener as claimed in claim 1, wherein the multiple modes include clockwise mode, anticlockwise mode or a bi-direction movement including both clockwise mode and anticlockwise mode.
3. The bone fastener as claimed in claim 1, wherein the projected end (1b) of the expandable outer region (1) is provided with slotted grooves (10).
4. The bone fastener as claimed in claim 1, wherein the circular disc (8) is provided with an orifice (12) aligning with the cannulated threaded bolt (3) for passage of a guide wire.
5. The bone fastener as claimed in claim 1, wherein a hammering head is provided with a detachable screw driver capable of complimentary fit into the slotted groove (10) of the expandable outer region (1) and the groove (7) of the cannulated threaded bolt (3).
6. The bone fastener as claimed in claim 1, wherein the engaging of the screw driver enables bi-directional movement of the first conical projection (9a) and second conical projection (9b) for bi-stage expansion of the bone fastener.
7. The bone fastener as claimed in claim 1, wherein the first expandable ramp (5a) corresponding to first conical
projection (9a) is bigger than the second expandable ramp (5b) corresponding to the second conical projection (9b) to enable bi-stage expansion of the bone fastener.
8. The bone fastener as claimed in claim 1, wherein the external region is provided with a first ridge (4a) and a plurality of second ridges (4b) having at least two predetermined sections of variable thickness.
9. The bone fastener as claimed in claim 1, wherein the predetermined section for a first ridge (4a) of a particular thickness enables accommodation of the first conical projection (9a) by means of the first expandable ramp (5a).
10. The bone fastener as claimed in claim 1, wherein the predetermined section for a plurality of second ridge (4b) allows adhering of the expandable bone fastener to the bone.
11. The bone fastener as claimed in claim 1, wherein the cannulated threaded bolt (3) is operably coupled to the expandable outer region (1) and is configured to undergo two distinct operations.
12. The bone fastener as claimed in claim 1, wherein the first expandable ramp (5a) acts as a guide rail for movement of the first conical projection (9a) within the first threaded region (11a) of the cannulated threaded bolt (3).
13. The bone fastener as claimed in claim 1, wherein the second expandable ramp (5b) acts as a guide rail for movement of the second conical projection (9b) within the cannulated threaded bolts (3).
14. The bone fastener as claimed in claim 1, wherein the two distinct operations include axial expansion and an asymmetric expansion rendered by the bi-directional movement of the first conical projection (9a) and the second conical projection (9b).
15. The bone fastener as claimed in claim 1, wherein the first conical projection (9a) and the second conical projection (9b) are opposingly threaded, left and right threaded, rendering bi-directional movement of the conical projections, pushing the expandable outer region (1) outwards against a specific section of the bone.
16. The bone fastener as claimed in claim 1, wherein the specific sections of the bone are cortical bone and cancellous bone.