WO1997018769A1

WO1997018769A1 - Intramedullary nail

Info

Publication number: WO1997018769A1
Application number: PCT/FR1996/001842
Authority: WO
Inventors: Pierre Alain Carruzzo; Gérard Saillant; Jean Godefroy
Original assignee: Pierre Alain Carruzzo; Saillant Gerard; Jean Godefroy
Priority date: 1995-11-21
Filing date: 1996-11-21
Publication date: 1997-05-29
Also published as: AU7698396A; FR2741256A1

Abstract

An intramedullary nail (1) including an axial rod (2) supporting tubular spacers (9, 10) and expandable, releasable and interchangeable sleeves (3, 4) slidably mounted on the axial rod (2) between an axial abutment (6) and a control nut (8). Tightening the control nut (8) axially compresses the spacers (9, 10) and the expandable sleeves (3, 4), and thereby causes expansion of the expandable sleeves in order to lock the intramedullary nail (1) in the marrow cavity (11) of a bone (12). The expandable sleeves (3, 4) comprise a substantially continuous, tubular, flexible and expandable circumferential wall made of a biocompatible material and operative to prevent bone rehabitation inside the sleeves.

Description

CENTROMEDULAR NAIL

TECHNICAL FIELD OF THE INVENTION The present invention relates to internal fixation devices for bone fractures of long bones, of the centromedullary nail type comprising an axial rod carrying expansion locking means

Various types of expansion medullary nails are known, including those described in the documents below. In document US-A-4,858,602, the device comprises a hollow tubular body of which a distal end has longitudinal slots. An axial rod is engaged in the axial hole of the hollow body, and comprises a distal head and a threaded proximal end engaged in a corresponding tapping of the tubular body and accessible for its screwing by an external screwdriver through a lateral hole of the tubular body Such a device does not allow a expansion locking only at the distal end of the device, and requires this distal end to be placed in a portion of bone whose medullary canal has a substantially circular section II is therefore not possible to ensure expansion fixation on d other parts of the same channel, and it is not possible to effectively lock the device in portions of channel with flattened section The subsequent extraction of the device is difficult

Document FR-A-2 289 155 describes a similar device in which a hollow tubular body receives an axial rod allowing, by screwing, to move axially a nut carrying deformable oblique tongues which can exit through lateral slots of the tubular body, in the vicinity of one and the other of the ends of the tubular body This device allows a blocking by expansion in the vicinity of the two ends of the tubular body, in fixed positions, it being observed that the locking requires the presence of a medullary canal of substantially circular The subsequent extraction of the device is difficult

Document FR-A-2 653 006 describes another device in which a hollow tubular body receives a threaded axial rod itself carrying a plurality of expandable sockets Each expandable socket is formed from a ring mounted loosely on a smooth portion of the rod axial, and a threaded ring engaged by screwing on a threaded portion of the axial rod, the two rings being connected by flexible uprights adapted to flex radially outward when the rings are brought closer to each other resulting from the screwing of the axial rod. The sockets are blocked in rotation by the fact that the uprights are engaged in lateral slots of the tubular body. This device makes it possible to provide several expansion means distributed along the tubular body, but the position of these expansion means is fixed, and the directions of radial expansion are determined by the position of the slots, and cannot be modified. The subsequent extraction of the device is difficult.

Document GB-A-2 268 068 describes a medullary nail comprising an axial rod with an axial stop and a threaded portion receiving an operating nut. The rod carries two expandable sockets mounted to slide and each comprising two end rings connected by an expandable central part adapted to deform radially outwards under the effect of an axial compression of the expandable socket. The expandable central part is formed of a plurality of uprights connecting the end rings and separated by lights. Each end of the expandable ring receives a hook-shaped end piece, secured to the socket by an axial force engagement of two longitudinal tongues in longitudinal notches. The attachment of the end pieces to the sockets must be mechanically resistant to allow subsequent traction of the device for its extraction from the bone II results that it is not possible to easily modify the length of the socket after attachment of the end pieces It is further noted that it is difficult to extract the nail out of the bone after a usual implantation duration which has allowed bone consolidation EXPOSURE OF THE INVENTION

The problem proposed by the present invention is to conceive a new structure of a centromedullary nail allowing an easy extraction out of the bone after an implantation period having allowed satisfactory bone consolidation. In this respect, the idea which is the basis of the invention is to avoid the development of fibrous or bone parts inside the expandable sleeves, said fibrous or bone parts then opposing the contraction of the sleeve expandable for its sliding in the reduced section of the spinal canal

Another problem proposed by the present invention is to allow easy adjustment of the axial position of the expansion locking elements, and adjustment of the directions of radial expansion of the locking elements, so as to be able to adapt the medullary nail according to the geometry of the channel which is to receive it II is in particular important to be able to easily adjust the length separating two expansion locking elements, and this adjustment must be able to be carried out intraoperatively, without requiring special tools

To achieve these and other objects, a medullary nail according to the invention comprises.

an axial rod comprising, at its first end, an axial stop and, at its second end, a threaded portion receiving an operating nut and comprising means for blocking the rotation of the axial rod,

- A plurality of adjacent removable and interchangeable elements, slidably mounted on the axial rod between the axial stop and the operating nut, at least one of said plurality of adjacent elements being a removable and interchangeable expandable sleeve, mounted sliding on the axial rod between the axial stop and the operating nut,

- the expandable sleeve comprising two end rings sliding on the axial rod and connected by an expandable central part adapted to deform radially outward when the end rings are brought together towards one another under the effect axial compression of the expandable sleeve, the expandable sleeve comprising a substantially continuous tubular peripheral wall, flexible and expandable in a biocompatible material It has been observed that the substantially continuous peripheral wall of the expandable sleeve constitutes a barrier preventing any development of tissue fibrous or bone inside the expandable socket This result is obtained although interstices still exist between the space outside the socket and the space inside the socket, interstices formed in particular by the ends of the socket when '' they are in simple support against the adjacent interchangeable elements Thus, it is not necessary try to provide a wall absolutely watertight, nor to provide that this watertight wall occupies the entire length of the intramedullary nail

The biocompatible material may for example be based on polyurethane or silicone, possibly reinforced with fibers increasing its rigidity and / or its elastic stiffness

According to a first embodiment, the substantially continuous tubular peripheral wall can form the external surface of the expandable bushing, either by constituting the central expandable part and the end rings of the bushing, or by enveloping an expandable internal frame. constituted by the end rings connected by flexible uprights which are themselves adapted to flex radially outwards.

According to another embodiment, the expandable sleeve can comprise an expandable frame constituted by the end rings connected by flexible uprights and molded internally with a layer of biocompatible material forming the substantially continuous tubular wall

Preferably, means are provided for locking the end rings in axial rotation on the axial rod, and axial securing means are provided between the corresponding ends of the adjacent elements. In this way, an axial traction on the intramedullary nail, after unscrewing the nut, causing the radial sockets to contract radially, facilitating the extraction of the nail from the bone SUMMARY DESCRIPTION OF THE DRAWINGS

Other objects, characteristics and advantages of the present invention will emerge from the following description of particular embodiments, made in relation to the attached figures, among which - FIG. 1 illustrates the positioning of a centromedullary nail according to an embodiment of the invention in a long bone,

- Figure 2 is an exploded view showing the different parts of a medullary nail according to a second embodiment of the present invention, - Figure 3 is a perspective view of the centromedullary nail of Figure 2 in the retracted assembled position, Figure 4 is a perspective view of a spacer according to the invention;

- Figure 5 is a perspective view of a nut according to the invention, -

- Figure 6 is a perspective view of an expandable socket frame according to an embodiment with three longitudinal uprights according to the invention;

- Figure 7 is a perspective view of an expandable socket frame with two longitudinal uprights according to an embodiment of the present invention; - Figure 8 is a side view of the expandable sleeve frame of Figure 7;

- Figure 9 is a side view in longitudinal section of an expandable bushing according to an embodiment of the invention, in the retracted position, - Figure 10 is a side view in longitudinal section of the expandable bushing of Figure 9, in the extended position, and FIG. 11 is a perspective view of an expandable sleeve according to another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment illustrated in FIG. 1, a medullary nail 1 according to the invention comprises an axial rod 2 carrying expansion locking means, for example means 3 and 4

At its first end, the axial rod 2 has an axial stop 6, in the form of a head secured to the rod 2. At its second opposite end, the axial rod 2 has a threaded portion 7 receiving an operating nut 8 The second end of the rod 2 further comprises means for blocking the rotation of the rod, for example a transverse slot on its end face for the engagement of a screwdriver The expansion locking means 3 and 4 are expandable sockets removable and interchangeable slidably mounted on the axial rod 2 between the axial stop 6 and the operating nut 8.

Tubular spacers such as spacers 9 and 10, removable and interchangeable, are also slidably mounted on the axial rod 2 between the axial stop 6 and the operating nut 8 The centromedullary nail 1 thus comprises a plurality of adjacent elements removable and interchangeable, consisting of sockets 3 and 4 and spacers 9 and 10.

The centromedullary nail 1 is engaged in the medullary canal 11 of a long bone 12 such as a humerus. The tightening of the operating nut 8 ensures axial compression of the assembly formed by the spacers 9 and

10 and the expanding sockets 3 and 4 between the operating nut 8 and the axial stop 6, causing the radial expansion of the sockets 3 and 4.

FIG. 2 illustrates the components of a centromedullary nail 1 according to an embodiment with three expandable sockets 3, 4 and 5 in exploded form, while FIG. 3 illustrates the same centromedullary nail in assembled form and radially retracted We thus find the axial rod 2 with its axial stop 6 and its threaded portion 7 The rod 2 can have a circular cross section, allowing free rotation of the elements which are threaded over it The diameter of the rod 2 can for example advantageously be approximately 5 millimeters, the diameter of the head forming the axial stop 6 can be approximately 7.5 millimeters

In addition to the axial rod 2, there is the nut 8, formed of a threaded hollow cylindrical tube, the end 13 of which may have an external hexagon face allowing it to be operated by an appropriate key. A view on a larger scale of the nut 8 is shown in Figure 5, in which there is an axial bore 113 of the nut allowing the passage of the axial rod.

In Figures 2 and 3, there are also two spacers 9 and 10, each formed of a hollow cylindrical tube, and shown on a larger scale in Figure 4

In Figures 2 and 3, there are finally three expandable sockets 3, 4 and 5

An embodiment for the sockets 3 and 4, for example for the socket 3, is illustrated on a larger scale in FIG. 6 In this figure, an expandable socket frame 3 is shown, comprising two end rings 14 and 15 shaped to slide on the axial rod 2 and connected by three flexible longitudinal uprights 16, 17 and 18 adapted to flex radially outward when the end rings 14 and 15 are brought together under the effect of an axial compression of the expandable sleeve 3. According to an embodiment providing suitable results, the end rings 14 and 15 may have an outside diameter of approximately 7 millimeters, with a central hole whose diameter is slightly greater than 5 millimeters for the passage of the axial rod 2 of diameter equal to 5 millimeters. The flexible uprights 16, 17 and 18 can have a thickness of approximately 1 millimeter in the radial direction, and a width of approximately 2 millimeters. In the rest position, the flexible uprights 16, 17 and 18 can be slightly curved, with convexity facing outwards, so as to obligatorily bend outwards during an axial compression bringing the end rings 14 and 15 closer together. one towards the other.

In the embodiment illustrated in Figure 7, the frame of the expandable sleeve 5 is also formed from two end rings 14 and 15, but the end rings 14 and 15 are connected by only two longitudinal uprights 16 and 17 diametrically opposite As in the embodiment of FIG. 6, the longitudinal uprights 16 and 17 are, at rest, advantageously bent with convexity facing outwards.

This embodiment of FIG. 7 is advantageous for producing expansion in a diametrical plane, so that this embodiment may be particularly suitable for expansion locking in a portion of medullary canal of oblong cross section, the uprights 16 and 17 coming to engage in the tops of the oblong shape For this, it is necessary to be able to control the angular orientation of the expanding socket 5 with two uprights 16 and 17, to orient the uprights 16 and 17 facing the tops of the oblong shape before tightening the nut 8 This can be obtained for example by providing, on the axial rod 2, a flat and, on the end rings 14 and 15, a corresponding flat 19 or 20 engaging on the flat of the rod axial 2 to prevent the relative rotation of the expandable sleeve 5 around the axial rod 2

Such a dish 19 or 20 can also be provided on the end rings 14 and 15 of the expandable sleeve 3 in the embodiment of FIG. 6 However, in this case, the expandable sleeve 3 produces an expansion in three radial directions regularly distributed around the longitudinal axis, so that such an expandable socket is more particularly adapted to an expansion in a portion of the medullary canal having a circular cross section or round, and the control of the angular orientation of the expandable sleeve is then not useful.

As indicated above, the outward radial bending of the uprights 16, 17 and 18 can be ensured by the fact that, in the rest position, the uprights are curved with convexity facing outwards

Alternatively, it is possible to provide uprights 16, 17 and possibly 18 having a coaxial helical shape. If the propellers rotate in the same direction, it is then necessary to provide means for blocking the end rings 14 and 15 in rotation, by example by the flats 19 and 20 engaging on the flat of the axial rod 2

On the other hand, by providing for example two helical uprights 16 and 17 with inverted pitch, it is possible to dispense with the means for blocking the end rings 14 and 15 in rotation.

In Figure 8, there is shown, in side view, the frame of the expandable sleeve 5 of Figure 7

In Figure 9, there is shown in longitudinal section a preferred embodiment of the entire expandable sleeve 5 We find the end rings 14 and 15, and the flexible longitudinal uprights 16 and 17 The frame of the expandable sleeve 5 is overmolded internally with a tubular layer 23 of biocompatible elastic material such as a polyurethane or a silicone The layer 23 of elastic material constitutes a substantially continuous tubular peripheral wall and prevents bone rehabitation inside the expandable sleeve 5 after implantation of the centromedullary nail 1 in a bone As illustrated in FIG. 10, during axial compression bringing the end rings 14 and 15 close to each other, the flexible uprights 16 and 17 bend while bending towards the exterior, and the layer 23 of flexible material follows this deformation while remaining attached to the uprights 16 and 17 It should be noted that, in this mode of r realization, the layer 23 of elastic material does not cover the external face of the uprights 16 and 17, so that contact is made directly between the uprights 16 and 17 and the bone

In FIG. 11, there is shown in perspective another preferred embodiment of the entire expandable sleeve 5. There are also the end rings 14 and 15 and the flexible longitudinal uprights 16 and 17 of the frame. In this embodiment , Wall substantially continuous tubular device 23 forms the external surface of the expandable sleeve 5, and envelops the expandable internal frame constituted by the end rings 14 and 15 connected by the flexible uprights 16 and 17 which are themselves adapted to flex radially towards outside In this embodiment, it is possible to prefer a continuous wall 23 made of a more resistant material such as a reinforced polyurethane, favoring a pressure distribution over a larger area of the bone.

In the embodiments described above, the expandable sockets comprise a frame with an end ring and flexible connecting uprights. It is however possible to design, without departing from the scope of the present invention, a homogeneous expandable socket in which the same material constitutes the times the end rings and the tubular expandable central part By axial bringing together of the end rings, the central part forms an annular protrusion in a bead

It may be advantageous to further provide axial securing means between the corresponding ends of the adjacent elements such as the spacers and the expandable sleeves In this way, after unscrewing the nut 8, an axial pull of the elements hooked together following the others causes the axial spacing of the end rings 14 and 15 and therefore the radial contraction of the expandable sockets, facilitating the extraction of the centromedullary nail

For this, for example, the spacers such as the spacer g in FIG. 4 may include, near their ends, a thread. Likewise, the expandable sockets such as the socket 3 in FIG. 6 may have, on their rings end 14 and 15, a respective tubular extension 21 or 22 threaded and shaped to be screwed into the threaded ends of the spacers such as the spacer 9

In the embodiment of Figure 8, the expandable sleeve 5 has a ring 15 with a tubular extension 22 threaded, while the ring 14 does not have such an extension, for example to come only to bear against the head forming the axial stop 6 of the axial rod 2

It will be understood that, with such a structure of a centromedullary nail, it is easy to reverse the position of the elements along the rod, increase the number of tubular spacers and decrease the number of expandable sockets, or vice versa, and choose the type of expandable socket according to the geometry of the channel in which the centromedullary nail 1 is intended to lock.

The present invention is not limited to the embodiments which have been explicitly described, but it includes the various variants and generalizations thereof contained in the field of claims below.

Claims

CLAIMS 1 - Centromedullary nail (1) comprising:

- an axial rod (2) comprising, at its first end, an axial stop (6) and, at its second end, a threaded portion (7) receiving an operating nut (8) and comprising means for locking in rotation of the axial rod (2), a plurality of adjacent elements (9, 10, 3, 4, 5) removable and interchangeable, slidably mounted on the axial rod (2) between the axial stop (bj and the operating nut (8), at least one of said plurality of adjacent elements being an expandable and interchangeable expanding sleeve (3, 4, 5), slidably mounted on the axial rod (2) between the axial stop (6) and the '' operating nut (8),

- the expandable sleeve (3, 4, 5) comprising two end rings (14, 15) sliding on the axial rod (2) and connected by an expandable central part (16, 17, 18) adapted to deform radially towards the outside when the end rings (14, 15) are brought towards each other under the effect of an axial compression of the expandable sleeve (3, 4, 5), characterized in that the sleeve expandable (3, 4, 5) comprises a substantially continuous, flexible and expandable tubular peripheral wall (23), made of a biocompatible material.

2 - centromedullary nail according to claim 1, characterized in that said biocompatible material is based on polyurethane or silicone 3 - centromedullary nail according to one of claims 1 or 2, characterized in that said tubular peripheral wall (23) substantially continuous forms the external surface of the expandable sleeve (3, 4, 5), and envelops an expandable internal frame constituted by the end rings (14, 15) connected by flexible uprights (16, 17, 18) adapted to bend radially outward

4 - Centromedullary nail according to one of claims 1 or 2, characterized in that the expandable socket (3, 4, 5) comprises an expandable frame constituted by the end rings (14, 15) connected by flexible uprights ( 16, 17, 18) and molded internally with a layer (23) of said biocompatible material forming said substantially continuous tubular peripheral wall 5 - Centromedullary nail according to any one of claims 1 to 4, characterized in that said biocompatible material is armed.

6 - Centromedullary nail according to any one of claims 1 to 5, characterized by:

- means (19, 20) capable of locking the end rings (14, 15) in axial rotation on the axial rod (2),

- Means (21, 22) for axial securing between the corresponding ends of adjacent elements (s, lυ, 3, 4, b), so that an axial pull on the medullary nail, after unscrewing the nut (8 ), causes radial contraction of the expandable sleeve (s) (3, 4, 5).

7 - Centromedullary nail according to any one of claims 1 to 6, characterized in that: - at least one removable and interchangeable tubular spacer (9) is slidably mounted on the axial rod (2) between the axial stop ( 6) and the operating nut (8).

8 - Centromedullary nail according to claim 7, characterized in that it comprises at least two expandable sockets (3, 4) and a spacer (9)

9 - Centromedullary nail according to any one of claims 1 to 8, characterized in that the end rings (14, 15) are connected by longitudinal uprights (16, 17, 18) regularly distributed around the axial rod ( 2). 10 - Centromedullary nail according to claim 6, characterized in that the end rings (14, 15) are connected by helical uprights