INTRAMEDULLARY NAIL FOR THE REDUCTION OF BONE FRACTURES OF THE ANKLE, FOOT AND FOR ARTHRODESIS OF THE ANKLE, TARSUS AND

METATARSUS

The present invention relates to an intramedullary nail for the reduction of bone fractures or for arthrodesis of the ankle, tarsus and metatarsus.

The bones of the tarsus together with those of the metatarsus and phalanges, form the skeleton of the foot. The tarsus is a group consisting of seven short bones, divided into two rows: the proximal row is formed by the talus or astragalus and by the calcaneus and the distal row by the navicular bone, the three cuneiforms and the cuboid. The talus articulates with the tibia and fibula, the heel forms the support for the rear part of the foot arch, the cuneiforms and the cuboid articulate with the metatarsal bones and the navicular bone is interposed between the talus and the cuneiforms.

As is known, for the reduction of ankle and tarsus bone fractures and the effects and pathologies that these have upon the articulation of these areas, a particular type of intramedullary nail is used that is inserted from the plantar aspect of the heel into the medullary part of the tibia.

Intramedullary nails are hollow cylindrical bars made of suitable metal material, sometimes angled at one end and featuring transverse holes that allow for the passage of the screws necessary for stabilizing bone stumps in the correct manner.

The above mentioned type of intramedullary nail presents some difficulties however: in particular, during surgery, the surgeon must have a range of intramedullary nails available featuring different axial angles and seats for the passage of variously orientated screws. It is the task of the surgeon to choose the intramedullary nail that is suitable for the case in hand, so as to be able to perform the best possible linking of the portions of bone to be stabilized.

Furthermore, known nails do not allow the surgeon to modify the orientation of the ankle and foot after their insertion and locking in place.

The device object of the following patent, therefore offers a series of solutions to obviate the aforesaid drawbacks.

The main object of the following invention is to provide a universal intramedullary nail to be employed according to the contingent requirements of the surgeon in all the various cases and to allow any inclination of the ankle and foot, even after the intraosseus insertion of the nail and this without necessarily having a wide selection of nails on hand.

Another object of the present invention is to provide an intramedullary nail consisting of a pair of elements connected by a mechanical joint which allows for a certain posture to be conferred to the ankle with the foot in flexion or extension, in pronation or supination and in any other attitude relative to the leg.

A further object of the following invention is given by the possibility, using only one component of the intramedullary nail, to exclusively fuse the talus to the calcaneus.

Another object of the present invention is given by the possibility of fusing only the tibia- astragalus-calcaneus, with screws of suitable length, and binding also the navicular and cuboid to the aforementioned arthrodesis.

Another object is given by the possibility of performing a static and/or dynamic compaction of these joints.

A further object is that of being able to use the nail for both right and left limbs to compress the calcaneus against the astragalus and then both of these against the tibia, thanks to the progression of a threaded dowel screwed into the hollow of one of the two components.

Another object of the present invention is to provide an intramedullary nail that, thanks to its particular constructive characteristics, is able to offer greatest assurances of reliability and safety during use with a reduction in surgical maneuvers. ·

A final object of the present invention is that of rendering it readily available by constructing it from elements and materials commonly commercially available and making it competitive from an economic point of view.

These and other objectives are achieved by the intramedullary nail for the reduction of bone fractures and for arthrodesis of the foot and ankle which is herein described in a non-limiting preferred embodiment of further developments within the context of the invention itself with the aid of six tables of drawings illustrating the following figures:

- Fig. 1 : exploded front view of the intramedullary nail according to the present invention;

- Fig. 2: front view of the intramedullary nail component to be inserted into the tibial medullary channel;

- Fig. 3: plan view, section A- A, of the head of the component of the nail in Figure 2;

- Fig. 4: plan view, section B-B, of the head of the component of the nail in Figure 2;

- Fig. 5: plan view, section C-C, of the stem of the component of the nail in Figure 2;

- Fig. 6: plan view, section D-D, of the stem of the component of the nail in Figure 2; - Fig. 7: front view of the component of the intramedullary nail to be inserted into the body of the astragalus and into the front portion of the calcaneus;

- Fig. 8: plan view, section E-E, of the component of the nail in Figure 7;

- Fig. 9: plan view, section F-F, of the component of the nail in Figure 7;

- Fig. 10: front view, section G-G, of the component of the nail in Figure 7;

- Fig. 11 : front view, section J- J, of the component of the nail in Figure 7;

Fig. 12: side view of the intramedullary nail being applied to bone segments;

- Fig. 13: side view of the intramedullary nail applied to bone segments;

- Fig. 14: a side view in section of the intramedullary nail mechanical joint.

As illustrated in Figure 1 , the intramedullary nail 1 referred to in the present invention consists of two hollow cylindrical elements 2 and 3, both of which are characterized by the presence of suitable through holes that allow for the passage of screws V, which are required to secure the nail to the various bone segments.

With reference to Figures 2 to 6, the hollow cylindrical element 2 of the intramedullary nail 1 to be inserted into the medullary canal of the tibia T up to the articular surface in contact with the astragalus A, has at its distal end 22 and in the corresponding slot 23 the housing for a wing nut 4.

At the ends 21 and 22 of the hollow cylindrical component 2 of the intramedullary nail 1, pairs of transverse elliptical holes are shown that are necessary for clamping, by means of suitable screws V, the hollow cylindrical element 2 of the intramedullary nail 1 to the bone component of the tibia T. In particular, at end 21 of the hollow cylindrical element 2 there are elliptical holes 211 and 212 and at end 22 there are elliptical holes 221 and 222.

With reference to Figures 12 and 13, the clamping phase of the hollow cylindrical element 2 to the bone component of the tibia T involves the use of a single pair of elliptical holes, 211 and

221 for applications of the nail involving the tibia belonging to the left lower limb and 212 and

222 in the case of fastening the nail to the tibia of the right lower limb.

With reference to Figures 7 to 13, the hollow cylindrical element 3, having a length less than the hollow cylindrical element 2, is connected to it by means of a mechanical joint comprising an Allen screw 5 and a wing nut 4, in particular, with reference to Figure 14, the Allen screw 5 is inserted into the cavity 31 of the hollow cylindrical element 3 until contact is made between head protrusion of the threaded rod 52 of the Allen screw 5 through hole 34 of the cylindrical element 3 is achieved.

With reference to Figures 12 and 14, between the Allen screw 5 and the bottom 33 of the cylindrical element 3 a safety washer 6 is interposed in order to ensure stability of the mechanical link. Following the passage of the Allen screw 5 through the hollow cylindrical element 3, said Allen screw 5 is screwed to the wing nut 4 which was previously inserted within the slot 23 of the hollow cylindrical element 2; in particular, the wing nut 4 is bound within the slot 23, and therefore with the cylindrical element 2, by means of fins 41, which are engaged within holes 231 and 232 in a transverse sense with respect to slot 23.

Screwing Allen screw 5 into the wing nut 4 allows the hollow cylindrical element 2 to be attached to the cylindrical element 3, which, having only three degrees of movement, will be constrained to perform only rotational movements around the infinite axes passing through the center of the link; the movements allowed by this constraint, which is equivalent to a spherical hinge, are permitted also by means of beveled edge 24 of the cylindrical element 2, whose corresponding seat within the cylindrical element 3 is formed of a radiused concavity 35. The hollow cylindrical element 3, being inserted into the body of the astragalus A and into the anterior portion of the calcaneus C, will, when fully inserted, allow intramedullary nail 1, to regulate, as far as possible, the degree of plantar or dorsal flexion given to the foot with respect to any possible medial (supination) or lateral (pronation) inclination or any other intermediate posture, before tightening the Allen screw 5 to the wing nut 4 thereby locking the two mirrored and embossed surfaces - concave with respect to the cylindrical element 2 and convex with respect to the cylindrical element 3 - in the desired position.

Finally, within the hollow cylindrical element 3 there are three elliptical through holes 301, 302 and 303, with different axial directions such that the nail can be used in both right and left limbs, for the passage of the two screws V, an upper rear transtalar screw that may, if it is longer, be extended until it reaches the navicular and beyond, and the lower rear transcalcaneal screw, which can reach as far as the cuboid and beyond in hole 303 in the case of the right foot and in hole 302 in the case of the left foot.

The possibility of being able to rotate the hollow cylindrical element 3 in an axial direction with respect to the hollow cylindrical component 2 before tightening the locking grub screw 7 within the threaded hole 32, allows for the insertion of the talar and calcaneal screws V in a latero- medial direction. The talar and calcaneal screws V are inserted after tightening the articulation; they can be pushed from the bottom upwards entering into holes 301, 302 and 303, thus leading to the compaction of the calcaneus C against the astragalus A and, in turn, of these two against the tibia T.