Osteosynthesis device

1. An intramedullary osteosynthesis and arthrodesis device for hand or foot bones and formed unitarily with a rigid central zone from opposite ends of which extend anchor zones each formed by a pair of legs extending symmetrically of a longitudinal axis generally bisecting the central zone, the legs each having a base portion fixed to the central zone and a tip forming the respective end, the end of one of the legs of a pair being independent of the other leg of the pair, the legs each further being deformable between a closed position for insertion of each of the pairs of legs into a respective bone and an open position for internally gripping the respective bone, the legs of each pair in the open position diverging away from the central zone and in the closed position converging away from the central zone so as to be more closely spaced at their tips than at their base portions, the base portions of each pair of legs in the closed position being angled inwardly towards one another, wherein an outer surface of each leg is curved at the tip and, in the open position, the outer surface of each leg is adapted to form an anchorage within the respective bones.

2. The intramedullary osteosynthesis and arthrodesis device defined in claim 1 wherein the legs each have a predetermined length measured parallel to the axis and the respective base portions and tips each occupy between one-third and one-half of the length of the respective leg.

3. The intramedullary osteosynthesis and arthrodesis device defined in claim 1 wherein the device is made of an elastic or superelastic memory material.

4. The intramedullary osteosynthesis and arthrodesis device defined in claim 3 wherein the memory material is thermally activatable.

5. The intramedullary osteosynthesis and arthrodesis device defined in claim 1 wherein in the open position the base portions of the legs of each pair form at the outwardly open angle of between 5′ and 25′ and the inside tangent of the tip of said legs make an angle with longitudinal axis close to 0°.

6. The intramedullary osteosynthesis and arthrodesis device defined in claim 1 wherein in the closed position the base portions of the legs of each pair form an outwardly open angle of between 0° and −15° such that an overall width measured transversely of the axis of the device at the tips is smaller than at the base portions.

7. The intramedullary osteosynthesis and arthrodesis device defined in claim 1 wherein in the open position the tips of the legs of each pair define a transverse width measured transversely of the axis that is greater by 50% or 1.5 mm than a transverse width of the legs of each pair where the respective base portions join the central zone.

8. The intramedullary osteosynthesis and arthrodesis device defined in claim 1 wherein, in the closed position, the width of the tips of the anchor zones of each pair is smaller than a transverse width of a respective base portions by 20%.

9. The intramedullary osteosynthesis and arthrodesis device defined in claim 1 wherein the tips are beveled.

10. The intramedullary osteosynthesis and arthrodesis device defined in claim 1 wherein the tips of the legs are formed with outwardly directed notches or are roughened.

11. The intramedullary osteosynthesis and arthrodesis device defined in claim 1 wherein the outer surfaces of the legs are formed with outwardly directed notches set at a sufficiently wide spacing at the base portions to allow gripping by a clamp.

12. The intramedullary osteosynthesis and arthrodesis device defined in claim 11 wherein the central zone has a length measured parallel to the axis generally equal to the wide notch spacing.

13. The intramedullary osteosynthesis and arthrodesis device defined in claim 1 wherein the legs and central zone are generally flat and the central zone is formed with a bend such that the anchor zones extend at an angle Ag comprised between 0° and 30°.

14. The intramedullary osteosynthesis and arthrodesis device defined in claim 1 wherein the device is made of such a material that the force of the expansion of the legs in the blocked introduction position is between 1 kg and 3 kg.

15. The intramedullary osteosynthesis and arthrodesis device defined in claim 1 wherein each leg further comprises a length, the length is adapted to obtain a contact area along the outer surface over the length with the respective bone to form the anchorage.

16. An intramedullary osteosynthesis and arthrodesis device for hand or foot bones and formed unitarily with a rigid central zone from opposite ends of which extend anchor zones each formed by a pair of legs extending symmetrically of a longitudinal axis generally bisecting the central zone, the legs each having a base portion fixed to the central zone and a tip forming the respective end, the legs each further being deformable between a closed position, where the device adopts an H-shape, for insertion of each of the pairs of legs into a respective bone and an open position, where the device adopts an X-shape, for internally gripping the respective bone, the base portions of each pair of legs in the open position diverging away from one another and in the closed position converging towards one another such that the legs of each pair are more closely spaced at their tips than at their base portions when in the closed position wherein an outer surface of each leg is curved at the tip and, in the open position, the outer surface of each leg is adapted to form an anchorage within the respective bones.

17. The intramedullary osteosynthesis and arthrodesis device defined in claim 16 wherein the legs each have a predetermined length measured parallel to the axis and the respective base portions and tips each occupy between one-third and one-half of the length of the respective leg.

18. The intramedullary osteosynthesis and arthrodesis device defined in claim 16 wherein the device is made of an elastic or superelastic memory material.

19. The intramedullary osteosynthesis and arthrodesis device defined in claim 18 wherein the memory material is thermally activatable.

20. The intramedullary osteosynthesis and arthrodesis device defined in claim 16 , wherein in the open position the base portions of the legs of each pair form at the outwardly open angle of between 5° and 25° and the inside tangent of the tip of said legs make an angle with the longitudinal axis close to 0°, and wherein in the closed position the base portions of the legs of each pair form an outwardly open angle of between 0° and −15° such that an overall width measured transversely of the axis of the device at the tips is smaller than at the base portions.