FR3100445A1 - ASSEMBLY FORMED BY AT LEAST ONE MEDULAR HUMERAL STEM AND BY THE INSTRUMENTS ALLOWING THE PLACEMENT OF THIS STEM ON THE RESECTED END OF A HUMERUS - Google Patents

Abstract

The invention relates to an assembly formed by at least one humeral medullary rod and by instruments allowing the placement of this rod on the resected end of a humerus, which is characterized: - in that it comprises a second rod medullary (2) having a metaphyseal portion of general shape identical to that of the first medullary rod, so that one or the other of these rods can be placed on a humerus by means of the same instruments; a first medullary rod that the assembly comprises is a so-called "long" medullary rod and the second medullary rod (2) is a so-called "short" rod; one of the instruments that the said assembly comprises is a reamer; and - at least one other instrument is a rasp. Figure for the abstract: figure 9

Description

ASSEMBLY FORMED BY AT LEAST ONE HUMERAL MEDULLARY ROD AND BY THE INSTRUMENTS ALLOWING THE PLACEMENT OF THIS ROD ON THE RESECTED END OF A HUMERUS

The present invention relates to an assembly formed by at least one humeral medullary rod and by the instruments allowing the positioning of this rod on the resected end of a humerus.

It is well known to restore a shoulder prosthesis joint by placing a joint prosthesis, this prosthesis including a humeral implant. This implant includes a medullary rod and an articular piece taking place on the proximal end of the medullary rod. The latter has a tapered shape which allows its fitted insertion into a specially designed cavity in the cancellous bone of the treated humerus; it has a so-called "metaphyseal" proximal portion, which is widened and flared so as to be able to take a large support at the level of the metaphyseal part of the bone, and a so-called "diaphyseal" distal portion, which is tapered so as to be able to take place at the level of the diaphyseal part of the bone. The metaphyseal portion has at its proximal end means for mounting the articular part, and this articular part has means for mounting complementary to those present in the medullary rod; these respective mounting means are in particular in the form of a conical stud with a slight slope and of a corresponding conical cavity capable of receiving the stud with wedging. The articular part in question can be a joint head forming a convex articular surface, for the constitution of a so-called "anatomical" prosthesis, or can be a component forming a concave articular surface intended to cooperate with a conjugate convex articular surface arranged on a scapula implant, for the construction of a so-called "reversed" prosthesis.

The instruments allowing the establishment of such a medullary rod include in particular a rasp capable of cutting the spongy bone according to the shape of the medullary rod to be implanted; frequently, these instruments include a series of such rasps, having sizes which increase homothetically from one rasp to another, so as to allow the cavity to be progressively arranged in the desired shape, by the successive use of rasps with increasingly larger sizes.

A spinal cord stem for a shoulder prosthesis is generally "long", that is to say has a diaphyseal portion of a length greater than the length of the metaphyseal portion of this stem, this diaphyseal portion thus being able to be engaged on a substantial distance inside the diaphyseal part of the humerus. It will be understood that the length of the rod is to be considered along the longitudinal axis of the diaphyseal portion of this rod. It will also be understood that the metaphyseal portion is distinguished from the diaphyseal portion by the fact that it presents the said flared shape and that it has a more or less oval or oblong cross-section; correlatively, the diaphyseal portion is distinguished from the metaphyseal portion by the fact that it has a shape tending to be conical or of constant section and a more or less circular cross section. The cross-section in question is the section of the rod perpendicular to said longitudinal axis.

A long medullary stem is frequently made necessary in a shoulder prosthesis by the fact that this stem is fixed by means of a polymerizable synthetic cement, and that it is therefore necessary that the stem has a substantial contact surface with this cement . However, cement fixation has the disadvantage of being usable only in very specific cases, taking into account in particular the bone necrosis that it generates due to the heating of the cement during the polymerization.

Other long medullary rods are intended to be attached to bone by growth of bone cells through a porous coating they comprise; the length of such a rod is then useful for perfectly positioning the rod relative to the bone, by engagement of the diaphyseal portion of the rod in the diaphyseal part of the bone. Such a long rod anchored by bone growth, however, has the significant drawback of inducing a risk of localized support of the distal end of the rod against the cortical bone, which is painful for the patient and is a source of damage to the bone.

To remedy this drawback, it has been devised to use so-called "short" medullary rods, that is to say having a diaphyseal portion having a length less than that of the metaphyseal portion. The risk of a localized distal support is then eliminated, but such a rod has on the other hand the disadvantage of inducing a significant risk of defective positioning in a humerus given the absence of engagement of the rod at the level of the part bone diaphysis. In addition, such a short rod presents a significant risk of tilting in the metaphyseal part of the bone while anchoring by cell growth takes place, and therefore of the rod losing its original position of implantation. . Such a problem is particularly critical for a shoulder prosthesis given the anatomy of the shoulder joint.

In addition, the choice to implant a short stem currently implies, for the practitioner, the need to use the corresponding dedicated instruments, which does not allow him, during the intervention, to finally decide to implant a long stem. if the condition of the bone requires it. This results in a certain practical constraint.

The present invention aims to remedy all of these drawbacks.

For this purpose, according to the invention, in addition to a first medullary rod,

- the assembly concerned comprises a second medullary rod having a metaphyseal portion of general shape identical to that of the first medullary rod, so that one or the other of these rods can be put in place on a humerus by means of the same instruments; a first medullary rod that the assembly comprises is a so-called "long" medullary rod, that is to say having a diaphyseal portion of length greater than or equal to the length of the metaphyseal portion of this rod, and the second medullary rod is a so-called "short" stem, that is to say having a diaphyseal portion having a length less than that of the metaphyseal portion of this stem;

- one of the instruments comprising said set is a reamer capable of reaming the spongy bone of the treated humerus at the level of the metaphyseal and diaphyseal parts of this humerus; And

- at least one other instrument is a rasp capable of cutting the spongy bone of this humerus so as to create a cavity for receiving the so-called "long" medullary rod.

The inventors have indeed been able to determine that the drawbacks mentioned above related to the use of a short medullary rod resulted from the use of instrumentation dedicated to such a short rod, influencing in particular one or more short rasps, shape corresponding to that of the short stem; the inventors then designed to provide a set of elements including not only a short rod but also a long rod, these rods having metaphyseal portions of identical general shape, and to provide instruments including a reamer making it possible to ream both the part metaphyseal as well as the diaphyseal part of the humerus to be treated, as well as a rasp allowing to cut a cavity adapted to receive the long rod in an adjusted way. The reamer thus makes it possible to arrange in the spongy bone a bore directed precisely along the longitudinal axis of the diaphyseal part of the bone, this precise orientation of this bore resulting from the engagement, and therefore from the guidance, of the reamer by this diaphyseal part; once this bore has been made, the rasp can be used to carve the cancellous bone from the bore in question, so as to create a cavity adapted to receive the long rod; during this cut, the rasp is precisely guided through the bore in question. Because the two medullary rods have identical metaphyseal portions, the practitioner can decide, during the intervention, to implant either the long rod or the short rod; if he chooses to implant the short rod, he will be assured that this rod will be precisely positioned with respect to the bone by the fact that the cavity receiving this rod will have been arranged from said bore, therefore with a precise positioning with respect to to the bone, resulting from the guiding of the reamer by the diaphyseal part of the bone at the time of the development of this bore.

The invention therefore provides an assembly which makes it possible to ensure the positioning of a short medullary rod on a humerus, with perfect positioning of this rod. This set also allows the practitioner to be able to decide, during the intervention, to implant the other rod than the one he had planned to implant, if this implantation proves to be more favorable to the patient taking into account the conditions encountered. during this intervention.

It will be understood that, by “identical general shape” of the metaphyseal portion of a stem, it is meant that the internal, external, anterior and posterior walls of this metaphyseal portion are identical to the corresponding walls of the metaphyseal portion of the stem. other stem, excluding however any ribs or other reliefs for anchoring in the spongy bone that the metaphyseal portion of one stem might have while the metaphyseal portion of the other stem would lack them. In other words, this identical general shape is that which is capable of being cut by means of the rasp or rasps forming part of the assembly according to the invention.

Preferably, at least one medullary stem has, at its metaphyseal portion, at least one anchoring relief elongated in the proximal-distal direction of the stem, this relief being able to be inserted into the spongy bone of the humerus treated during placement of the rod on this humerus.

This relief allows a perfect grip of the rod in this spongy bone.

According to a preferred embodiment of the invention, in this case, the medullary rod comprises two anchoring reliefs in the form of two fin-shaped ribs, one of which protrudes from the anterior face of the rod and the other protrudes from the posterior surface of the stem.

Each rib advantageously has a height which, from a proximal zone of the rib, decreases progressively in the distal direction.

Each rib thus has a tapered shape which allows progressive penetration of the rib into the spongy bone during the insertion of the medullary rod into the cavity arranged to receive this rod.

The outer edge of each rib may, seen in the sagittal plane, have a main distal part which is rounded according to a first radius of curvature and a proximal marginal part which is rounded according to a second radius of curvature, this second radius of curvature being the order of ten times less than the first radius of curvature.

This shape allows not only a progressive insertion of the rib in the spongy bone but, by the rounding that the said proximal marginal part presents, to arrange, following the growth of the bone cells around the ribs, proximal bone portions allowing longitudinal immobilization of the stem relative to the humerus.

Said first radius of curvature may for example be of the order of 50 mm, said second radius of curvature therefore being of the order of 5 mm.

Advantageously, each rib has, seen in the transverse plane, a rounded free edge.

This rounding avoids any shearing effect at the level of the spongy bone.

The rounding of the free edge of each rib may in particular have a radius of curvature of the order of 2 mm.

Preferably, each rib has a duct which crosses it right through.

This or these ducts are intended to receive suture threads allowing the reinsertion of fractured fragments of the humerus, in particular the reinsertion of the tuberosities.

Preferably, the so-called "long" medullary rod has, on the anterior and posterior sides of its diaphyseal portion, two grooves extending over the entire length of this diaphyseal portion, and the so-called "short" medullary rod has, on the anterior and posterior sides of its diaphyseal portion and on a distal part of its metaphyseal portion, two grooves extending over the entire length of this diaphyseal portion and on this distal part of the metaphyseal portion.

These grooves are intended to be invaded either by a polymerizable cement fixing the medullary stem to the bone, or by the growing bone cells; in this way, they allow perfect wedging of one or the other of the spinal rods in rotation with respect to the bone.

Brief description of figures

The invention will be well understood, and other characteristics and advantages thereof will appear, with reference to the appended diagrammatic drawing, which represents, by way of non-limiting example, a preferred embodiment of the assembly concerned. In this drawing,

Figure 1 is a perspective view of a so-called "long" medullary rod that this assembly comprises;

FIG. 2 is a perspective view of a so-called “short” medullary rod that this assembly comprises;

Figure 3 is a view of the short rod in the sagittal plane;

Figure 4 is a view of the short rod in the frontal plane;

Figure 5 is a view of the short rod in the transverse plane, by its proximal side;

FIG. 6 is a view in longitudinal section of a resected humerus intended to receive one or the other of the aforementioned long and short medullary rods;

Figure 7 is a similar view of the humerus and a reamer for reaming the cancellous bone of this humerus;

FIG. 8 is a similar view of the humerus and of a rasp connected to a manipulation and impaction handle, this rasp making it possible to cut in the spongy bone of the humerus a cavity intended to receive one or the other of the aforementioned long and short medullary rods;

FIG. 9 is a similar view of the humerus and of the long medullary rod connected to an instrument for manipulating and impacting this rod; And

FIG. 10 is a similar view of the humerus and of the short medullary rod connected to the same instrument for manipulating and impacting this rod.

detailed description

The invention relates to an assembly formed by the two humeral medullary rods 1, 2 shown in Figures 1 and 2 and by the reamer 15, the rasp 16 and the handle 17 shown in Figures 7 and 8.

Each medullary rod 1, 2 is intended to constitute, with an articular part mounted on its proximal side, a humeral implant for a shoulder prosthesis, this prosthesis comprising, in addition to this humeral implant, a scapula implant. The articular part forms an articular surface intended to cooperate with the mating articular surface formed by the scapula implant. The articular piece and scapula implant are well known per se so are not particularly described or shown; it will be possible to refer for example to patent application publication No. FR 2 718 954 A1 for the description of an embodiment of an articular part and of a scapula implant as mentioned above.

Each medullary rod 1, 2 has a proximal portion 3 called "metaphysis", which is widened and flared so as to be able to take a large support at the level of the metaphyseal part of the humerus, and a distal portion 4 called "diaphysis", which is tapered so as to be able to take place at the level of the diaphyseal part of this humerus. The metaphyseal portion 3 is distinguished from the diaphyseal portion 4 by the fact that it has a flared shape and that it has a more or less oval or oblong cross-section; correlatively, the diaphyseal portion 4 differs from the metaphyseal portion 3 in that it has a shape tending to be conical and a more or less circular cross-section. The cross section in question is the section of the rod perpendicular to the longitudinal axis of the diaphyseal part 4 of the rod. In FIGS. 1 and 2, it can be considered that line 5 delimits the separation between these respective portions 3 and 4.

It is visible in Figures 1 and 2 that the metaphyseal portions 3 of the rods 1 and 2 are substantially identical from the rod 1 to the rod 2, with the exception of the fact that, with regard to the rod 1, two grooves 6 are present on the anterior and posterior surfaces only of the diaphyseal portion 4, whereas, with regard to the rod 2, two homologous grooves 6 are present not only on the diaphyseal portion 4 but also on a distal part of the metaphyseal portion 3 .

The shapes of the internal, external, anterior and posterior walls of these metaphyseal portions 3 are illustrated by figures 3 to 5, namely the fact that the internal wall 7 of each portion 3 has a concave curvature in the frontal plane (figure 4) and convex in the transverse plane (FIG. 5), that the external wall 8 presents a convex curvature not only in the frontal plane (FIG. 4) but also in the transverse plane (FIG. 5) and that the anterior 9 and posterior 10 walls present curvature in the transverse plane (Figure 5); in the sagittal plane (FIG. 3), these walls 9, 10 diverge from each other in the proximal direction.

Each metaphyseal portion 3 of a stem 1, 2 further has two ribs 11 for anchoring in the spongy bone of the humerus, which are elongated in the proximal-distal direction of the stem, one of these ribs 11 projecting from face 9 and the other projecting from face 10. Each rib 11 is fin-shaped and has, seen in the sagittal plane (FIG. 3), a height which, from a zone proximal to the rib, gradually decreases in the distal direction. In this same sagittal plane, the outer edge of each rib 11 has a main distal part 11d rounded according to a radius of curvature of the order of 50 mm and a proximal marginal part 11p rounded according to a radius of curvature of the order of 5 mm.

The free edge of each rib 11 is also rounded seen in the transverse plane (FIG. 5), according to a radius of curvature of the order of 2 mm.

In addition, each rib 11 is pierced by a duct 12 which crosses it right through and which also extends in the thickness of the walls 9, 10 of the rod, for the possible placement of suture threads allowing to reinsert the tuberosities on the bone when these tuberosities are fractured.

Furthermore, the proximal part of each medullary rod 1, 2 has two conical cavities 13 for receiving a corresponding conical stud secured to the articular part intended to be mounted on the medullary rod, this stud being able to be inserted indifferently into one or the other of these cavities 13. The latter thus allow two different positions of this articular part with respect to the medullary rod. In the example represented, the two cavities 13 are in intersection with each other for a question of lack of space available on the proximal end of the medullary rod 1.

Referring to Figures 1 and 2, it appears that the rod 1 has a diaphyseal portion 4 much longer than the diaphyseal portion 4 of the rod 2, so that this rod 1 is called "long" while the rod 2 is called " short". On stem 1, the diaphyseal portion 4 has a length clearly greater than the length of the metaphyseal portion 3, while, on stem 2, the diaphyseal portion 4 has a length markedly less than that of the metaphyseal portion 3.

The reamer 15 visible in FIG. 7 comprises a tool 20 capable of reaming the spongy bone 101 of the humerus 100 treated along the longitudinal axis of this humerus, both at the level of the metaphyseal part and at the level of the part diaphyseal of the latter. The reamer 15 also comprises a proximal subassembly 21 for handling this tool 20. The latter and this subassembly 21 are of types known per se and are therefore not particularly described.

The rasp 16 shown in Figure 8 has a shape corresponding to the general shape of the rod 1, apart from the ribs 11, so that it allows to cut a cavity allowing to receive, in an adjusted manner, not only the rod 1, as visible in Figure 9, but also the rod 2, as visible in Figure 10. This grater 16 is part of a series of graters whose sizes are progressing from one grater to another in a homothetic way, these different rasps allowing, from the bore arranged by means of the instrument 15, to gradually arrange said cavity.

The handle 17 allows the gripping of the various rasps 16 then the gripping of one or the other of the rods 1 or 2, as visible in FIGS. 8 to 10. It has a proximal anvil 22 allowing the impaction of the rod 1, 2 in cancellous bone 101.

The grater 16 shown, as well as the handle 17, are of known types.

In practice, the native head of the humerus 100 is cut at the appropriate angle as shown in Figure 6 and then the cancellous bone 101 is reamed using the instrument 15 (Figure 7). The engagement of the tool 20 in the diaphyseal part of the bone makes it possible to perfectly position and guide this tool 20, causing the arranged bore to be perfectly centered with respect to this diaphyseal part. The different rasps 16 of the series of rasps are then used to, starting from the bore, progressively carve the bone in order to arrange the said cavity; the larger rasp 16 is shown in FIG. 8. Because the two medullary rods 1, 2 have identical metaphyseal portions 3, the practitioner can decide, during the operation, to implant the long rod 1 indifferently or short stem 2; if he chooses to implant the short rod 2, it will be ensured that this rod will be precisely positioned with respect to the bone 100 by the fact that the cavity receiving this rod 2 will have been arranged from said bore, therefore with a positioning accurate to bone.

During the engagement of the rod 1 or 2 in said cavity, the ribs 11 are gradually inserted into the spongy bone 101 so as to achieve a perfect support grip of the rod in this bone. The fin shape of the ribs 11 allows progressive penetration of these ribs into the spongy bone, and the rounding presented by the free edges of these ribs, both in the frontal plane and in the transverse plane, reduces the risk of shearing of this bone. The roundings presented by the proximal parts 11p of the ribs 11 make it possible to arrange, as a result of the growth of the bone cells around these ribs, proximal bone portions ensuring longitudinal immobilization of the spinal cord 1, 2.

The ducts 12 are used if necessary for passing and/or tying suture threads allowing the reinsertion of fractured fragments of the humerus 100, in particular the reinsertion of the tuberosities if the latter are fractured.

The grooves 6 are for their part intended to be invaded either by a polymerizable cement for fixing the rod 1, 2, or by the growing bone cells; in this way, they allow perfect wedging of one or the other of the rods 1, 2 in rotation with respect to the bone.

The invention thus provides an assembly having, compared to homologous assemblies in accordance with the prior art, the decisive advantages of ensuring the positioning of a short medullary rod 2 on a humerus 100 with perfect positioning of this rod, and to allow the practitioner to be able to decide, during the intervention, to implant the other rod than the one he had planned to implant, if this implantation proves to be more favorable to the patient taking into account the conditions encountered during of this intervention.

Claims (10)

Assembly formed by at least one humeral medullary rod (1) and by the instruments (15, 16, 17) allowing the positioning of this rod on the resected end of a humerus, characterized:
- in that it comprises a second medullary rod (2) having a metaphyseal portion (3) of general shape identical to that of the first medullary rod (1), so that one or the other of these rods ( 1, 2) can be placed on a humerus using the same instruments (15 to 17); a first medullary rod (1) that the assembly comprises is a so-called "long" medullary rod, that is to say having a diaphyseal portion (4) of length greater than or equal to the length of the metaphyseal portion (3) of this stem, and the second medullary stem (2) is a so-called "short" stem, that is to say having a diaphyseal portion (4) having a length less than that of the metaphyseal portion (3) of this stem ;
- one of the instruments comprising said assembly is a reamer (15) capable of reaming the spongy bone of the treated humerus at the level of the metaphyseal and diaphyseal parts of this humerus; And
- At least one other instrument is a rasp (16) capable of cutting the spongy bone of this humerus so as to create a fitted receiving cavity for the so-called "long" medullary rod (1). Assembly according to Claim 1, characterized in that at least one medullary rod (1, 2) has, at the level of its metaphyseal portion (3), at least one anchoring relief (11) elongated in the proximal-distal direction of the rod, this relief (11) being able to be inserted into the spongy bone of the humerus treated during the positioning of the rod (1, 2) on this humerus. Assembly according to Claim 2, characterized in that the medullary rod comprises two anchoring reliefs in the form of two fin-shaped ribs (11), one of which projects from the front face of the rod (1, 2) and the other protrudes from the rear face of the rod (1, 2). Assembly according to Claim 3, characterized in that each rib (11) has a height which, from a proximal zone of the rib, decreases progressively in the distal direction. Assembly according to Claim 3 or Claim 4, characterized in that the outer edge of each rib (11) has, seen in the sagittal plane, a main distal part (11d) which is rounded along a first radius of curvature and a part proximal marginal (11p) which is rounded according to a second radius of curvature, this second radius of curvature being of the order of ten times less than the first radius of curvature. Assembly according to claim 5, characterized in that said first radius of curvature is 50 mm, said second radius of curvature therefore being 5 mm. Assembly according to one of Claims 3 to 6, characterized in that each rib (11) has, seen in the transverse plane, a rounded free edge. Assembly according to claim 7, characterized in that the rounding of the free edge of each rib (11) has a radius of curvature of 2 mm. Assembly according to one of Claims 3 to 8, characterized in that each rib (11) has a duct (12) which passes right through it. Assembly according to one of Claims 1 to 9, characterized in that the so-called "long" medullary rod (1) has, on the anterior and posterior sides of its diaphyseal portion (4), two grooves (6) extending over the entire length of this diaphyseal portion (4), and the so-called "short" medullary rod (2) present, on the anterior and posterior sides of its diaphyseal portion (4) and on a distal part of its metaphyseal portion ( 3), two grooves (6) extending over the entire length of this diaphyseal portion (4) and over this distal part of the metaphyseal portion (3).