Intramedullary Nail for Transverse Distraction

Abstract

The invention relates to an intramedullary nail (1) for transverse distraction of a tubular bone (2), the intramedullary nail (1) comprising an at least partially hollow tube body (3) extending in an axial direction of the intramedullary nail (1), at least one locking means for locking the tube body (3) in an end portion of the tubular bone (2), a first inner part (5) and a second inner part (7), which are each arranged within the tube body (3) so as to be displaceable in the axial direction toward each other or with each other, a drive within the tube body (3) for axial displacement of the first inner part (5) relative to the second inner part (7), at least one longitudinal recess (11) in the tube body (3), and at least one lever mechanism (20) which comprises at least one lever element (9, 23, 24) which is designed to be extended out of, and to be retracted again into, the tube body (3) in a radial direction, wherein the displacement of the first inner part (5) relative to the second inner part (7) causes the at least one lever element (9) to be moved or extended out of the at least one lateral longitudinal recess (11) in the tube body (3) or causes the at least one lever element (9) to be moved or retracted into the at least one lateral longitudinal recess (11) in the tube body (3).

Claims

1-10. (canceled)

11. An intramedullary nail for transverse distraction of a tubular bone, the intramedullary nail comprising: an at least partially hollow tube body extending in an axial direction of the intramedullary nail; an at least partially hollow tube body extending in an axial direction of the intramedullary nail; at least one insertable anchoring device for locking the tube body in an end portion of the tubular bone; a first inner part and a second inner part each arranged within the tube body to be displaceable in the axial direction counter to or with each other; a drive within the tube body for axial displacement of the first inner part relative to the second inner part; at least one longitudinal recess in the tube body; and at least one lever mechanism which includes at least one lever element which is configured to be extended out of, and to be retracted again into, the tube body in a radial direction, wherein the displacement of the first inner part relative to the second inner part causes the at least one lever element to be moved or extended out of the at least one lateral longitudinal recess in the tube body or causes the at least one lever element to be moved or retracted into the at least one lateral longitudinal recess in the tube body.

12. The intramedullary nail of claim 11 wherein the at least one lever element in a retracted position is aligned axially with the longitudinal axis of the intramedullary nail and in an extended position is aligned by at least 30? with respect to the longitudinal axis of the intramedullary nail.

13. The intramedullary nail of claim 11 wherein the at least one lever element in a retracted position is aligned axially with the longitudinal axis of the intramedullary nail and in an extended position is aligned by at least 45? with respect to the longitudinal axis of the intramedullary nail.

14. The intramedullary nail as in claim 11 wherein the at least one lever element in a retracted position is aligned axially with the longitudinal axis of the intramedullary nail and in an extended position is aligned by at least 60? with respect to the longitudinal axis of the intramedullary nail.

15. The intramedullary nail of claim 11 wherein the at least one lever element in a retracted position is aligned axially with the longitudinal axis of the intramedullary nail and in an extended position is aligned by at least 80? with respect to the longitudinal axis of the intramedullary nail.

16. The intramedullary nail of claim 11 wherein the drive is supported axially on the tube body.

17. The intramedullary nail of claim 11 wherein the at least one lever element is designed to be retracted in the longitudinal direction without actuation of the drive during movement of the intramedullary nail.

18. The intramedullary nail of claim 11 wherein the second inner part is integrally formed with the tube body.

19. The intramedullary nail of claim 11 wherein the drive is configured as a drive selected from the group consisting of electrical, magnetic, electro-magnetic, hydraulic, shape-memory-based, piezoelectric, and pneumatic drives.

20. The intramedullary nail of claim 11 wherein the drive has a motor, a transmission, and a spindle element.

21. The intramedullary nail of claim 11 wherein the first inner part and the second inner part each have a half-cylinder shape.

22. The intramedullary nail of claim 11 wherein (a) the at least one lever element is configured as a rocker arm having an elongate hole and a joint device, (b) in the joint device is rotatably connected on and axially fixed to the first inner part, and (c) the second inner part has a guide element which is guided in the elongate hole in the rocker arm.

23. The intramedullary nail of claim 11 wherein (a) the at least one lever element is configured as a plurality of chain links connected to one another in an articulated manner, (b) one chain link of the plurality of chain links is axially adjacent to the first inner part and another of the plurality of chain links adjoins the second inner part, and (c) the displacement of the first inner part relative to the second inner part causes folding and protrusion of at least two chain links through the lateral longitudinal recess in the tube body.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0023] FIG. 1 is a schematic cross-sectional view of a preferred embodiment of the intramedullary nail according to the invention in a first position.

[0024] FIG. 2 is a schematic cross-sectional view of a further embodiment of the intramedullary nail according to the invention in a first position.

[0025] FIG. 3 is a perspective view of a further embodiment of the intramedullary nail according to the invention in a second position.

[0026] FIG. 4 is a schematic cross-sectional view of the intramedullary nail from FIG. 1 inserted in the first position in a tubular bone.

[0027] FIG. 5 is a schematic cross-sectional view of the intramedullary nail from FIG. 1 inserted in the second position in a tubular bone.

[0028] FIG. 6 is a schematic cross-sectional view of the intramedullary nail from FIG. 1 after leaving the second position.

[0029] FIG. 7 is a schematic cross-sectional view of the intramedullary nail from FIG. 1 in an extended position.

[0030] FIG. 8 is a schematic illustration of a lever mechanism according to another embodiment in a first position.

[0031] FIG. 9 is a schematic illustration of a lever mechanism from FIG. 8 in a second position.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0032] In the description below, exemplary embodiments are explained with reference to the figures, wherein the same reference symbols are used for identical or similar parts. Under some circumstances, identical or similar parts are not explained again in conjunction with each figure.

[0033] The embodiment of the intramedullary nail 1 according to the invention that is described in FIGS. 1-7 comprises a substantially cylindrical hollow tube body 3, in the interior of which a first inner part 5 and a second inner part 7 are accommodated. The first inner part 5 and the second inner part 7 are formed substantially complementarily here as half-cylinders and extend parallel to each other axially, i.e., in the longitudinal direction of the intramedullary nail 1. At its lower end, which is arranged in the lower section in FIG. 1, the intramedullary nail 1 has an end piece 19, which serves for fixing the intramedullary nail 1 to a tubular bone (not shown in FIG. 1). The end piece 19 has a locking means which is attachable to the end portion of a tubular bone, for example with a locking bolt which is guided through corresponding openings in the tube body 3 and through a through hole 21 in the end piece 19. Bolts known from the prior art can be used as locking bolts for fixing intramedullary nails in bones.

[0034] The cross section of the intramedullary nail 1 and thus of the basic body 3 is circular in the preferred embodiment shown here. Thus, the first inner part 5 and the second inner part 7 can be formed correspondingly as complementary half-cylinders. The lower end piece 19 also is substantially in the shape of a cylinder. It should be noted that the intramedullary nail 1 may also have a polygonal cross section, for example a triangular, rectangular, square, pentagonal, hexagonal, or octagonal cross section. An elliptical cross section is also possible. The inner parts 5, 7 can then be suitably designed with a corresponding polygonal cross section.

[0035] A transmission 8 and, adjacent thereto, a motor 10, which together form a drive, are arranged in the upper portion of the intramedullary nail 1. A spindle 12 which is aligned substantially symmetrically to the longitudinal axis 6 of the tube body 3 is driven by the transmission 8. In the embodiment illustrated here, the spindle 12 comprises an external thread which engages in an internal thread in the second inner part 7 such that a rotation of the spindle brings about a movement of the second inner part 7 in the axial direction. It is also conceivable that the operation is carried out in reverse, e.g. via an axially fixed, driven nut in which a spindle is moved. The power supply and control of the drive can be undertaken via an electrical connection, which is not shown in the figures. In this case, the electrical connection can be connected to a receiver which is arranged subcutaneously in order to permit a contactless control and power supply of the intramedullary nail 1 via a control device which is located outside the patient's body. The power source for the drive can preferably be arranged outside the patient's body; in further embodiments also within the intramedullary nail.

[0036] As already mentioned above, the intramedullary nail 1 according to the invention may also have other drives than the electromechanical drive with motor 10 and transmission 8 that is illustrated here.

[0037] In principle, the terms radially and axially in this description refer to the longitudinal axis 6 of the tube body 3.

[0038] In the central part, the intramedullary nail 1 of the embodiment shown here has two longitudinal recesses 11, which are aligned substantially parallel to the longitudinal axis 6 and have a width of preferably between 2 mm and 8 mm, even more preferably between 4 mm and 6 mm. Also in the lower section, the tube body 3 has a longitudinal recess 11, which is essentially used for locking and later removal of the intramedullary nail 1 from the tubular bone, as is explained below with reference to FIGS. 6 and 7.

[0039] Also, in the middle region level with the longitudinal recesses or elongate holes 11, the interior of the intramedullary nail 1, in the embodiment shown here, has two rocker arms 9, which, when used as intended, form the lever mechanism which is responsible for the transverse distraction. In other words, the rocker arms 9 rotate about an axis of rotation out of the axial position shown in FIG. 1 in such a way that a radial expansion component provides for the transverse distraction, because the rocker arm 9 moves out of the longitudinal recess 11. For this purpose, said or each rocker arm 9 comprises, on the one side (at the top in FIG. 1), a bore aligned transversely to the longitudinal axis 6 as an axis of rotation, through which bore a rotary bolt 15 is guided. The rotary bolt 15 in turn is fixedly arranged on the rocker arm 9 and pivotably connected to the second inner part 7. In a further embodiment, the diameter of the rotary bolt 15 is slightly smaller than that of a bore through the rocker arm 9.

[0040] An elongate hole 13 in the rocker arm 9 is formed aligned slightly obliquely to the longitudinal axis 6, wherein a guide element or guide bolt 17 is guided through the elongate hole 13 transversely to the longitudinal extent of the elongate hole 13. The guide bolt 17 is fixedly connected to the first inner part 5.

[0041] The lever mechanism with the rocker arm 9 in the embodiment shown here is actuated by the relative displacement of the first inner part 5 relative to the second inner part 7. It is seen in the upper, middle region of FIG. 1 that a cavity is formed between the first inner part 5 and the second inner part 7 in such a way that said cavity is correspondingly reduced in size during an axial movement of the second inner part 7 downward, triggered by the actuation of the motor 10. The second inner part 7 is thus pushed onto the first inner part 5. Since the rotary bolt 15 holds the rocker arm 9 at the foot point on the second inner part 7 and the rocker arm 9 is held in the elongate hole 13 by the forcible guidance of the guide bolt 17, the lower end of the rocker arm 9 in FIG. 1 moves out of the longitudinal recess 11. This tilting movement or pivoting movement about the rotary bolt 15 is limited by the length of the elongate hole 13 and the distance of the second inner part 7 relative to the first inner part 5. The length of the elongate hole 13 and said distance are coordinated with each other such that a maximum pivoting of substantially 90? of the rocker arm 9 with respect to the longitudinal axis 6 is achieved. It is understood that, in the embodiment shown, the dimensions and distances of the two rocker arms 9 and the inner parts 5, 7 are the same, and therefore a synchronous or coordinated movement results. In other embodiments, the lengths of the rocker arms 9 may also differ. Furthermore, it is also possible that the pivot axes of the rotary or guide bolts for each rocker arm 9 deviate slightly from one another. This allows a slightly different tilting direction of different rocker arms 9 to be achieved.

[0042] Owing to the infinitely variable adjustment of the drive having the motor 10, transmission 8 and spindle 12 in both directions, a very fine adjustment of the radial expansion, i.e., the transverse distraction, is possible by means of the rocker arm 9. Thus, a patient themselves can adjust the extent of the transverse distraction by corresponding control of the motor 10 from the outside, without requiring the intervention of medical personnel or even a surgeon.

[0043] FIG. 2 shows essentially the same intramedullary nail 1 from FIG. 1 in an alternative embodiment, in which only the lower end differs, as follows. Instead of a separate end piece 19 as in the embodiment shown in FIG. 1, the end piece is integrally formed with the first inner part 5 in FIG. 2. This in turn means that the lower end of the intramedullary nail 1 is fastened to the tubular bone by the corresponding locking means through the first inner part 5.

[0044] FIG. 3 shows, in a perspective illustration, the preferred embodiment of the intramedullary nail 1 according to the invention in a second position in which the rocker arms 9 are extended. It can be clearly seen that the amount of radial protrusion of the rocker arms 9 is considerably greater than the diameter of the intramedullary nail 1. This amount can be optimized by suitable selection of the dimensions of the longitudinal recesses 11 and of the rocker arms 9. In addition, it is seen in FIG. 3 that the rocker arm or rocker arms 9 do not have to be fully unfolded or deployed. In principle, any adjustment angle is possible between the angle 0?, i.e., the folded state, and the angle 90?, i.e., the fully unfolded state. This results in a very flexible use of the intramedullary nail for transverse distraction.

[0045] FIGS. 4 and 5 show a schematic cross-sectional view of the intramedullary nail 1 from FIG. 1 inserted in the first and second position in a tubular bone 2, here a lower leg bone. The tubular bone 2 is shown here in dashed lines and is expressly not part of the present invention. The intramedullary nail 1 is fixed axially and in a torsion-proof manner in the lower and upper portion of the tubular bone 2 via corresponding locking means through openings 21. This type of fixation by means of minimally invasive intervention is known in the prior art. To prepare the transverse distraction, an elongate portion 4 in the central region of the tubular bone 2 is removed, i.e., for example, sawed out at its circumference with a fine bone saw. The intramedullary nail 1 lies against the elongate portion 4 of the tubular bone 2 over the entire length thereof in the position of FIG. 4. This represents the starting position before the transverse distraction, i.e., the drive within the intramedullary nail 1 has not yet been actuated. The first inner part 5 has not yet been displaced with respect to the second inner part 7, and instead there is still the original axial offset in between.

[0046] FIG. 5 shows the state after actuation of the drive and thus after or during the transverse distraction. The first inner part 5 and the second inner part 7 are displaced closer into each other by the drive (not shown in FIGS. 4 and 5), wherein the rocker arms 9 have moved from their starting position aligned in the axial direction (FIG. 4) into the unfolded or extended distraction position. In the embodiment illustrated here, the rocker arms 9 have each moved radially outward by the same amount through the longitudinal recesses 11. In this case, they have come into abutment laterally against the elongate portion 4 of the tubular bone 2 and have moved said portion transversely outward by a distraction distance such that a distraction space 14 results between the outer surface of the tube body 3 and the inner surface of the elongate portion 4. At this point it should be noted that the illustration selected here is schematic.

[0047] FIG. 6 shows a third position of the intramedullary nail 1 of the embodiment from FIG. 1 in the tubular bone 2, which is a particular position: the intramedullary nail 1 is removed in this position from the tubular bone 2, namely axially substantially along the longitudinal axis 6. Before the intramedullary nail 1 can be removed, the corresponding locking means at the upper or lower end of the tubular bone has to be loosened and removed so that no further axial fixation is available. If the intramedullary nail 1 is now pulled further upward, e.g., by a surgeon, the rocker arms 9 are initially still extended, i.e., in their distraction position. However, as soon as the upper rocker arm 9 lies against the upper portion of the tubular bone 2, that is, at the end of the elongate portion 4, a further movement of the intramedullary nail 1 upward causes the rocker arm 9 to fold in. This is possible because of the guidance in the elongate hole 13. At the same time, the forcible guidance in the elongate hole 13 also causes the first inner part 5 to move apart relative to the second inner part 7, because the rocker arm 9 is fixed at its foot on the second inner part 7 via the rotary bolt 15. Consequently, the first inner part 5 moves downward relative to the second inner part 7 and also to the tube body 3. This in turn causes displacement of the end piece 19 within the tube body 3 through the first inner part 5.

[0048] This makes it possible for both rocker arms 9 to fully move back into the tube body 3 and fold in. In particular, the end piece 19 is pushed out of the tube body 3 downward. This can be done by the fact that, after release of the locking means through the through opening 21 in the end piece 19, there is no longer any axial fixation on the bone and, by pulling of the entire intramedullary nail 1 upward, the end piece 19 can move into the space which has become free in the tubular bone 2. For medical use or for the patient, this means that, even without actuation of the drive or in the event of failure or a malfunction of the drive, a residue-free, substantially problem-free removal of the intramedullary nail 1 can be undertaken with minimal surgical intervention. FIG. 7 shows schematically the removed intramedullary nail 1, in which the rocker arms 9 are folded in and the end piece 19 protrudes downward out of the tube body 3.

[0049] FIGS. 8 and 9 schematically illustrate an alternative embodiment for the lever mechanism of the intramedullary nail 1 according to the invention. FIG. 8 shows the lever mechanism 20 in the retracted position, i.e. the manner in which it is axially aligned within the tube body 3 (not shown). A first lever element 23 is coupled to the second inner part 7 via a first pivot axis 26, the first pivot axis 26 being aligned transversely to the longitudinal axis 6 of the tube body 3. A second lever element 24 is coupled on the distal side of the second inner part 7 of the first lever element 23 via a second pivot axis 27, the second pivot axis 27 being aligned parallel to the first pivot axis 26. The second lever element 24 is in turn connected in an articulated manner to the first inner part 5 via a third pivot axis 28, wherein the third pivot axis 28 is also aligned parallel to the first pivot axis 26. The lever mechanism shown in FIGS. 8 and 9 is a link chain or rigid chain here. Such mechanisms can also be implemented with segmented belts, which also function in tension and not only with thrust. Owing to the relative displacement of the two inner parts, a function in tension can also be realized in addition to the thrust principle shown in the figures.

[0050] If the drive of the intramedullary nail 1, as described above for example, then moves the second inner part 7 in the direction of the first inner part 5, which is axially fixed with respect to the tube body 3, the first lever element 23 and the second lever element 24, as shown in FIG. 9, move out of the axial alignment along the longitudinal axis 6 into a tilting position. In this case, the two lever elements 23, 24 move out through the longitudinal recess 11 in the tube body 3 and the lever mechanism 20 transversely to the longitudinal axis 6 such that said lever mechanism contributes to the transverse distraction. The principle of the lever mechanism 20 shown in FIGS. 8 and 9 corresponds to a chain link arrangement, wherein the number of lever elements is not limited to two as shown in the illustration. There is a multiplicity of possible designs for such a lever mechanism 20. For example, the lever elements do not necessarily have to be rectilinear. The decisive factor is that the relative displacement of the first inner part 5 with respect to the second inner part 7 results in folding of the lever elements, which then move out of the longitudinal recess in the tube body in the axial direction. In addition, a movement of the inner parts 5, 7 in the opposite direction is intended to bring about folding or retraction of the lever mechanism 20.

[0051] Similar to the principle shown in FIGS. 8 and 9, a toggle lever mechanism is also conceivable, in which one end of a first lever element is fastened in an articulated manner in the central region of a second lever element.

[0052] For convenience in interpreting the figures, the following list of reference numbers is provided:

TABLE-US-00001 1 - intramedullary nail 2 - tubular bone 3 - tube body 4 - bone segment/elongate portion 5 - first inner part 6 - longitudinal axis 7 - second inner part 8 - transmission 9 - rocker arm 10 - motor 11 - longitudinal recess 12 - spindle 13 - elongate hole 14 - distraction space 15 - rotary bolt 17 - guide element 19 - end piece 20 - lever mechanism 21 - through opening 23 - first lever element 24 - second lever element 26 - first pivot axis 27 - second pivot axis 28 - third pivot axis