EP0465615A1

EP0465615A1 - Centro-medullary nailing system for immobilizing a bone fracture

Info

Publication number: EP0465615A1
Application number: EP19910901821
Authority: EP
Inventors: Jean-Marie Hardy
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-12-27
Filing date: 1990-12-24
Publication date: 1992-01-15
Also published as: FR2656212A1; JPH04505405A; WO1991009570A1; AU7053391A

Abstract

Le système d'enclouage centro-médullaire pour immobiliser une fracture d'os est remarquable en ce qu'il comprend plusieurs tiges (1), avec capacité de déformation élastique réduite, aptes à être engagées séparément dans le canal médullaire de l'os, de haut en bas, à partir d'un orifice commun (01) formé dans la partie proximale de la tête de l'os, pour être dirigées en bouquet et coopérer avec une zone solide de l'extrémité inférieure dudit os; ledit orifice étant apte à recevoir un manchon d'accouplement (2) conformé pour permettre la réunion de chacune des tiges (1) avec capacité de déplacement en translation limitée desdites tiges, d'une manière séparée.The central medullary nailing system for immobilizing a bone fracture is remarkable in that it comprises several rods (1), with reduced elastic deformation capacity, able to be engaged separately in the medullary canal of the bone, from top to bottom, from a common orifice (01) formed in the proximal part of the head of the bone, to be directed in a bouquet and to cooperate with a solid area of the lower end of said bone; said orifice being adapted to receive a coupling sleeve (2) shaped to allow the meeting of each of the rods (1) with limited translational movement capacity of said rods, in a separate manner.

Description

Central medullary nailing system to immobilize a broken bone.

Numerous nailing systems are known which use an implant slipped into the medullary canal of the bone with the aim of immobilizing a fracture to facilitate its consolidation. In addition, numerous studies have shown that a nailing must meet and meet the following conditions.

- the nailing must be carried out, as far as possible, with a closed hearth and must respect all the vascularization as well as possible.

- the nail must allow support as quickly as possible.

- the nail must have a certain elasticity in flexion and diametrically to best adapt in the medullary canal.

However, it appears that the nailing systems used are not entirely satisfactory and have drawbacks resulting from their design.

Indeed, the introduction of the nail most often requires the prior passage of one or more reamers to calibrate the bone barrel according to the diameter of the nail, which requires some time. In addition, this results in destruction of the intraosseous vascularization which generates callus and a source of significant post-operative bleeding.

It is also necessary to have a large stock of nails of different diameters and length to take account of variations resulting from the morphology. It is understandable that this entails significant costs.

Another drawback results from the fact that the walls of the channel of the bone in contact with the nail are subjected at some pressure. In addition, with certain types of nails, the lower bearing surfaces can be relatively sharp.

Finally, it appears that the reduction of the fracture site is often difficult to obtain, in particular at the level of the femur, since large muscular masses surround the bony barrel, preventing its direct manipulation. Locking the nail is often necessary and difficult to achieve. From patent DE 923085, an expanding nail is known which is formed by several strands of steel which are linked at their distal ends. The proximal part of the nail has a sleeve in which the different steel strands are fixed without any possibility of displacement. Given this design, these types of nails are not self-locking so that they cannot prevent rotation of one bone fragment on the other.

The object of the invention is to remedy these drawbacks.

One of the problems which the invention proposes to solve is, on the one hand, to respect the vascularization by eliminating the need to bore the bone barrel and, on the other hand, to ensure a nailing that is both flexible and rigid .

Such a problem is solved in that the nailing system comprises several rods, with reduced elastic deformation capacity, capable of being engaged separately in the medullary canal of the bone, from top to bottom, from a common orifice formed in the proximal part of the head of the bone, to be directed in a bouquet and to cooperate with a solid area of the lower end of said bone; said orifice being adapted to receive a coupling sleeve shaped to allow the union of each of the rods with limited translational displacement capacity of said rods, in a separate manner.

Another problem which the invention proposes to solve is to ensure self-locking of the system. For this purpose, each of the rods is preformed so as to delimit a straight part cooperating with the sleeve and at least one curved part cooperating with the medullary canal.

Each of the rods is made of a material capable of being deformed at the time of its introduction, while having the capacity to return, after their introduction, to its initial state.

To solve the problem of having a system that is both flexible and rigid, the sleeve has over its entire height a series of vertical through and parallel holes, for the passage and assembly of the rods.

It appears that the sleeve ensures a concentration of the forces collected by each rod, while each of them, taking into account its own elasticity, undergoes the stresses of the fracture center.

To solve the problem of avoiding any risk of upward migration of the rods, the upper part of the sleeve has arrangements for fixing a member acting as a plug to ensure the translational locking of the rods.

Another problem which the invention proposes to solve is to take account of the losses of bone substances. In this regard, after fixing the plug on the sleeve, said plug leaves a free space constituting a reserve chamber for the possible overflow of the rods depending on the loss of bone substance. In some cases, the cap has a collar to be fixed in the corresponding part of the bone.

Likewise, the sleeve has arrangements for fixing it in the corresponding part of the bone.

Another problem which the invention proposes to solve is to be able to direct each rod to implant it exactly where it is necessary, in particular at the level of the external condyle, the internal condyle, the posterior notch and the trochlea to achieve, in these conditions, a real anti-rotary tripod.

Such a problem is solved in that the curved part is terminated by a more accentuated curvilinear part and of reduced length, to direct the rod as a function of its point of implantation in the lower part of the bone.

Similarly, the sleeve has locating means for its angular orientation.

Another important problem that the invention proposes to solve is to achieve universal nailing taking into account the different morphologies and all types of fractures.

To solve this problem, the length of each rod is identical and determined to be greater than the greatest length of bone considered.

The invention is explained below in more detail with the aid of the accompanying drawings, in which:

Figure 1 is a sectional view showing a fracture immobilized by means of a nailing system according to the invention.

Figure 2 shows a preferred embodiment of each of the rods forming part of the system. Figure 3 is on a larger scale, a view taken along line 3.3 of Figure 1.

Figure 4 is on a larger scale, a bottom view corresponding to Figure 1. Figures 5, 6 and 7 are partial views in longitudinal section, showing different embodiments of the coupling sleeve.

Figures 8 and 9 are partial views showing different embodiments of the end of the rods.

Figure 10 is a front view of another embodiment of the sleeve.

FIG. 11 is a partial view in section showing the nailing of a bone with the sleeve illustrated in FIG. 10.

FIG. 12 is on a larger scale, a plan view taken along line 12. 12 of FIG. 11.

Figures 13, 14, 15 and 16 are partial perspective views showing the main impaction faces of the nailing system according to the invention.

We see in Figure 1, a bone (O) whose fracture center has been immobilized by the nailing system executed according to the invention. For this purpose, the system essentially comprises several rods (1) and a coupling sleeve

(2).

Each of the rods (1) is determined to be engaged in the bone marrow canal (O), from top to bottom, from a common orifice (01) formed in the proximal part of the head of the bone (O). The rods are engaged separately by the orifice (01), being directed precisely, in a bouquet, to cooperate with a solid area of the lower end of the bone considered. The orifice (01) is suitable for receiving the sleeve coupling (2) shaped, as will be indicated in the following description, to allow the meeting of each of the rods (1), while allowing their relative displacement in translation in a limited manner.

As shown in FIG. 2, each of the rods (1) is preformed so as to delimit a rectilinear part (1a) extended by a curvilinear part (1b) itself formed by a curved part (1b1) with a large radius of curvature and an end portion (1b2) of more accentuated curvature. The curvilinear part (1b1-1b2) of each rod makes it possible to direct it to implant it very exactly at the point considered, namely, for example, the external condyle, the internal condyle, the posterior notch and the trochlea, of so as to make a real anti-rotary tripod (Figure 4). Note that the end part (1b2) has a spherical shape at the end

(Figure 9) or spatula (Figure 8). The rectilinear part (la) of each rod is intended to cooperate with the arrangements of the sleeve (2). In addition, each rod (1) is made of a material capable of being deformed by elasticity at the time of its introduction through the orifice (01), while having the capacity to return, after its introduction, to its initial state.

Advantageously, the rods are made of steel with limited elastic deformation capacity of the type Z 2 CND 17-13 hardened at 1440 MPa of elasticity. Obviously, this example is given â. indicative, not limiting.

Importantly; the total length (L) of each rod is identical and determined to be greater than the greatest length of bone considered. As an indication, this length (L) is of the order of 60 cm. We will see in the following description, that the straight part of the rod may appear in overflow from the sleeve. In this case, it will suffice to cut off the projecting part of the rods, relative to the terminal end of the sleeve (2). So we get custom nailing.

The sleeve (2) has over its entire height, a series of vertical and parallel through holes (2a), for the passage and assembly of the rods (1). The diameter of the holes (2a) is determined to allow free sliding of each of the rods (Figures 1 and 3). Advantageously, the holes are regularly distributed over a circumference while being located near the circular edge of the sleeve. The holes (2a) are preferably, but not limited to, four in number.

It therefore appears that the sleeve (2) has the effect of ensuring a concentration of the forces collected by each rod, while each of them, taking into account its own elasticity, is able to undergo the stresses of the fracture center. The sheath assembly (2) - rod (1) therefore behaves like a real dynamic system adapting to the different situations imposed by stresses at the fracture site.

Note, as shown in particular in Figures 10, 11 and 12, that the sleeve (2) can itself be fixed to the bone, after its introduction into the orifice (01). Under these conditions, the assembly produced is perfectly stable, no longitudinal displacement of the bone relative to the nailing system is possible, preventing any rotation at the fracture site. For example, the sleeve (2) may have lateral ears (2b) for the introduction of fixing members of the screw type (3) (Figure 11). In this case, the rod insertion hole (01) intended to receive the sleeve (2) is machined to allow the passage of the fixing lugs (Figure 12).

As an indication, the sleeve (2) can be made of metal such as stainless steel 316, or titanium TA 6V ELI. Likewise, its exterior surface may be smooth or grooved. Note that the sleeve (2) has arrangements, such as notches (2c) adapted to allow the location of the angular orientation of said sleeve. The length of the sleeve may vary, to. indicative, from 40 to 100 mm.

As shown in particular in FIGS. 5, 6 and 7, provision is made to equip the upper part of the sleeve with a member capable of ensuring the locking in translation of the rods (1) by prohibiting or limiting, under these conditions, the 'possible upward displacement, outside the sleeve, of said rods. In the example of Figure 5, the shutter member is constituted by a washer (4) fixed by screws in particular, in the central part of the sleeve (2). In Figures 6 and 7, the shutter member is constituted by a plug (5), which can be screwed. the upper end of the sleeve (2). The plug (5) may have an overflowing flange (5a) for the engagement of fixing screws, so as to make the assembly of the sleeve and the cap integral with the corresponding part of the bone, at the level of the greater trochanter. We also plan to adapt the shutter member

(4) or (5) on the sleeve, so as to leave a free space (e), constituting a reserve chamber for housing the projecting part of the rods, as and when the loss of bone substance. Note that the shutter member, whatever its embodiment, can allow the extraction of the sleeve.

Reference is now made to FIGS. 13, 14, 15 and 16, showing diagrammatically, a technique for installing the nailing system according to the invention:

- We proceed in a known manner, the incision of the bone at the level of the greater trochanter.

- we realize at this level, the hole (01) for the introduction of the rods (1) and the housing of the sheath (2) (figure 13).

- Is introduced through the hole (01), a reducing pin of any known and appropriate type, so as to reduce the fracture to align the two fragments of the bone considered, resulting from said fracture. Note that one can use a reduction lever, shaped to fit on the reduction pin and lock in the upper shaft of the medullary canal, so as to manipulate and adjust it relative to the lower shaft, allowing in these conditions, the easier passage of the reducing pin at the fracture site. Such ancillary equipment is not described in detail, since it is perfectly known to a person skilled in the art.

- Then, each rod (1) is introduced separately, through the orifice (01), so as to direct them as indicated above, that is to say, with a view to their implantation in particular at the level of the external condyle , internal condyle, posterior notch and trochlea, using an anti-rotational tripod (Figure 14). For orientation of the rods, an image intensifier can be used in a known manner.

- Introducing and positioning the sleeve (2) in the orifice (01) (Figure 15).

- Is cut by any known and appropriate means, such as cutting pliers, the projecting part of the rods (1) (Figure 16).

- the sleeve C2) is fitted with the shutter member

(4) or (5).

- possibly securing the sleeve by means of screws engaged in the ears (2c), for example.

- the skin is closed.

The advantages clearly come from the description, in particular it is emphasized and recalled:

# the sleeve allows the concentration of the forces of each of the rods, which continue to act separately, so that the assembly constitutes a nailing system that is both rigid and elastic.

# the lower self-locking by constituting an anti-rotator tripod.

# respect for the vascularization inside the bone. # creation of a tailor-made nailing set, taking into account the adaptation of the rods to the length of the bone considered.

# possibility of constituting a reserve chamber between the upper end of the sleeve and the obturator member to allow possible migration up the rods, taking into account the loss of bone substance.

Claims

R E V E H D I C A T I O NS

-1- Central medullary nailing system characterized in that it comprises several rods (1), with reduced elastic deformation capacity, capable of being engaged separately in the medullary canal of the bone, from top to bottom, from a common orifice (01) formed in the proximal part of the head of the bone, to be directed in a bouquet and to cooperate with a solid area of the lower end of said bone; said orifice being adapted to receive a coupling sleeve (2) shaped to allow the meeting of each of the rods (1) with limited translational movement capacity of said rods, in a separate manner.

-2- System according to claim 1, characterized in that each of the rods (1) is preformed so as to define a straight part (1a) cooperating with the sleeve and at least one curved part (1b) cooperating with the medullary canal.

-3- The system of claim 2, characterized in that each of the rods (1) is executed in a material capable of being deformed at the time of its introduction, while having the ability to return, after its introduction, its initial state.

-4- The system of claim 1, characterized in that the sleeve (2) has over its entire height a series of vertical through and parallel holes (2a), for the passage and a meeting of the rods (1).

-5- The system of claim 4, characterized in that the upper part of the sleeve (2) has arrangements for fixing a member (4) - (5) acting as a plug to ensure the locking in translation of the rods (1). -6- The system of claim 5, characterized in that the plug (5) has a flange (5a) to be fixed in the part of the corresponding bone.

-7- System according to any one of claims 5 and 6, characterized in that after fixing the plug (5) on the sleeve (2), said plug leaves a free space (e) constituting a reserve chamber for possible overflow of the rods (1) depending on the loss of bone substance.

-8- The system of claim 4, characterized in that the holes (2a) of the sleeve are regularly distributed over a circumference.

-9- The system of claim 1, characterized in that the sleeve (2) has locating means (2c) for its angular orientation.

-10- The system of claim 1, characterized in that the sleeve (2) has arrangements (2b) for fixing in the corresponding part of the bone.

-11- The system of claim 2, characterized in that the curved part (1b) is terminated by a more accentuated curvilinear part and of reduced length, for directing the rod as a function of its point of implantation in the lower part of the 'bone.

-12- The system of claim 1, characterized in that the length of each rod (1) is identical and determined to be greater than the greatest length of bone considered.