ITPI20090054A1 - SUBACROMIAL SPACER AND INSTRUMENTS FOR ITS PLANT - Google Patents

Description

â € œSUBACROMIAL SPACER AND TOOLS FOR ITS PLANTâ €

DESCRIPTION

Scope of the invention

The present invention relates to a spacer for the joint of a shoulder affected by irreparable lesion of the subacromial cuff. In particular, the spacer is intended to be placed between the head of the humerus and the acromion.

The invention also refers to an instrument set for implanting this spacer in the subacromial site.

Brief notes on the known art

As known, the shoulder joints allow the arm to be articulated with the trunk ensuring a high number of degrees of freedom. The main joint involves the head of the humerus and the glenoid fossa of the scapula.

The stability of the glenohumeral joint is provided by a muscular structure known as the subacromial cuff, formed by portions of the extremities of the subscapularis, supraspinatus, infraspinatus and teres minor muscles; this structure covers the head of the humerus on the anterior, posterior and superior sides, and is dominated by a process of the scapula, called the acromion.

The cuff stabilizes the head of the humerus by opposing the action of the deltoid muscle which, in the initial phase of elevation of the arm, tends to move the head of the humerus in a cranial direction. An unrepairable cuff tear, caused by disease or trauma, causes the head of the humerus to rise, causing a condition known as subacromial impingement, in which the humerus head crawls over the acromion. This complicates abduction movements in particular. In these conditions there is a severe suffering of the cartilage tissue which can develop into arthrosis.

Various devices have been proposed to counteract cranial migration of the humerus in case of irreparable injury to the cuff. They involve the insertion of a spacer or a pad between the lower surface of the acromion, to which they are attached, and the head of the humerus. However, prior art devices have at least one of the limitations set out below: â € “the head of the humerus is replaced with a prosthesis, as described in US 5,944,757, and possibly also the glenoidal joint surface, as in US 4,550,450 : devices of this type are not suitable for treating subjects whose glenohumeral joint is substantially healthy, for example healthy patients in whom the cuff has been damaged in a trauma;

- the natural shoulder joint is assimilated or replaced with a spherical pair, which offers a number of degrees of freedom not sufficient to reproduce the natural movements of the shoulder, in particular the abduction and adduction movements: this is the case , again, of US 4,550,450, and of the device proposed in DE 10164328, which does not however provide for the replacement of the head of the humerus with a prosthesis;

â € “more generally, in the documents cited above, the articular surfaces, one or both artificial, are articulated by sliding one over the other with a substantially spherical coupling, with inevitable deterioration. This is particularly disadvantageous in devices in which the head of the humerus is not replaced by a prosthesis, for example in the devices described in US 6,712,854 and in DE 10164328. In these cases, however, the creation of an articular surface that adapts perfectly to the profile of the humerus head, so as to crawl on it with the least resistance, it is particularly laborious.

Summary of the invention

It is therefore an object of the present invention to provide a spacer intended to be placed in a subacromial site, to maintain a distance between the acromion and the humeral head of a patient affected by a lesion of the subacromial cuff, which does not involve substantial limitations in the natural movements of the shoulder, in particular that does not substantially limit the abduction and adduction movements of the patient's arm.

It is also an object of the invention to provide such a spacer which has a surface, which is easy to manufacture, suitable for engaging without significant interference with the head of the patient's natural humerus or of a humeral head prosthesis.

It is also an object of the invention to provide such a spacer that is suitable for treating patients who have suffered an irreparable injury to a cuff, but who do not require replacement of the humeral head with a prosthesis.

It is another object of the invention to provide such a spacer, which allows to limit wear phenomena on a natural humeral head of the patient with respect to what occurs in devices of the known art, and which therefore reduces the risk of arthrosis.

It is a further aim of the invention to provide such a spacer, and an instrumentation that allows its implantation in this subacromial site by means of a skin access and a minimally invasive technique.

These and other purposes are achieved by a spacer adapted to be inserted in a subacromial seat comprised between an acromion and a humeral head of a patient, the spacer comprising:

ï £ § an articulation surface capable of articulating with the humeral head;

ï £ § means of fixing to the acromion,

so that the articulation surface is placed at a predetermined distance from the acromion when the spacer is attached to the acromion,

whose main characteristic is that the articulation surface has a radius of curvature such that the articulation surface engages the humeral head in a substantially point-like contact.

In this way the generalized sliding between the spacer or subacromial pad of known devices and the head of the humerus is eliminated, minimizing friction. For this reason, the spacer according to the invention is practically wear-free. Above all, this does not involve significant wear on the head of the humerus, even when dealing with the patient's natural articular surface. The realization of the spacer according to the invention is also simpler, since it is not necessary to create articular surfaces perfectly conformed to the patient's humerus head. In particular, it is not necessary to subject the head of the humerus to detailed scans and thus obtain a three-dimensional topography to be used in a numerically controlled device for the realization of the articular surface of the spacer.

Advantageously, the radius of curvature is not less than 60 millimeters at each point engaged in the contact. This radius of curvature is, in fact, considerably higher than that of the humeral head of any patient.

Advantageously, the fixing means comprise anchoring blades suitable for making an incision in the acromion, the incision being made by compressing the spacer against the acromion, the anchoring blades being particularly symmetrically arranged with respect to a symmetry plane of the spacer.

This incision can be made by compressing a so-called â € œphantomâ € œ against the acromion.

Preferably, the anchoring blades have transversal through holes, suitable to allow in use a welding between the bone flaps allowing a growth of bone tissue through these transverse through holes. In this way a secondary stabilization, increasing over time, of the spacer in its seat is ensured.

Advantageously, in order to make the anchoring blades penetrate into the acromion, the prosthesis has at least one threaded hole, preferably blind, accessible from the opposite side with respect to the articulation surface and associable with a screw able to engage with this at least one threaded hole through a respective through hole made through the acromion, such at least one threaded hole and the respective through hole being arranged substantially aligned in such a way that by tightening the screw, the prosthesis is tightened against the acromion, favoring the penetration of the anchoring blades into the bone tissue .

Preferably, the spacer has a thickness such that this predetermined distance between the acromion and the head of the humerus is between 4 and 12 millimeters, in particular a thickness chosen between 5, 7, 9 and 11 millimeters, net fixing means to the acromion.

This provides devices suitable for the size of any patient.

Advantageously, the spacer has cross sections that can be inscribed in a rectangle having two opposite sides with a length between 20 and 30 millimeters, in particular between 23 and 27 millimeters and / or two opposite sides with a length between 14 and 20 millimeters, in particular between 15 and 18 millimeters, the sides being connected to each other in particular.

Advantageously, the spacer is made of an alloy of cobalt, copper and molybdenum, which ensure excellent biological compatibility.

Preferably, the articulation surface has a coating in a material selected from:

ï £ § a metal with a specular finish degree, in particular in pure titanium, the coating being made, more particularly, by means of a TiVPS technology of plasma deposition under vacuum;

ï £ § a ceramic material;

ï £ § a material based on PEEK (polyetheretherketone). in order to achieve maximum biological and mechanical compatibility with the surface of the humeral head which articulates with the spacer.

Alternatively, to make the anchoring blades penetrate the acromion, the prosthesis is associated with an instrument set comprising:

ï £ § means for bringing and releasing the spacer into the subacromial site, such means having:

- a gripping portion adapted to tighten the spacer and to be inserted into the patient's shoulder, in particular through an anterior trans deltoid access to bring the spacer to the subacromial site;

ï £ § a maneuvering portion to guide such means to carry and release;

ï £ § means for achieving compression of the spacer against the acromion.

In a particular embodiment, the means for bringing and releasing the spacer in the subacromial seat and the means for carrying out the compression are provided by a gripper, the gripping portion being arranged integral with the resistant arm of a first lever of the gripper, a pressing means having a pressure surface being arranged integral with the resistant arm of a second lever of the gripper, the maneuvering portion and the means for carrying out compression being provided by respective powerful arms of the first lever and of the second lever, the gripping portion being arranged in use in the seat subacromial, the pressure surface being placed in use resting on the patient's shoulder, so that by tightening the forceps the spacer is compressed against the acromion.

Preferably, the gripper also comprises elastic means for returning the opening and locking means in a predetermined relative position of the first lever and of the second lever.

In particular, the means for carrying and releasing the spacer comprise a clamp in which the gripping portion and the maneuvering portion are portions comprising opposite ends of the clamp having a central portion between the gripping portion and the operating portion, the central portion including a curve, such that the subacromial site can be reached through the anterior trans deltoid approach, surrounding the lateral portion of the shoulder not affected by the access. In this way, the same clamp can be used to implant a prosthesis in both a right and a left shoulder, provided that it is rotated 180 ° around its longitudinal axis.

Preferably, the clamp is made of a material chosen from: stainless steel; an aluminum alloy.

In particular, the means for carrying out the compression are provided by a press comprising:

ï £ § a screw with a maneuvering end;

ï £ § a frame comprising:

ï £ § a nut screw that houses and is rotatably engaged by the screw of the press,

ï £ § an extension of the nut screw comprising a transverse portion, substantially perpendicular to the nut screw and a longitudinal portion, which develops according to the direction of the nut,

- a pressure plate arranged in use according to a plane substantially orthogonal to the screw;

the maneuvering portion of the clamp and the pressure plate being adapted to respectively engage an end of the screw opposite the maneuvering end and a seat of the extension of the nut screw, or vice versa, so that the spacer tightened in use in the gripping portion of the clamp and the pressure plate have axes substantially aligned,

so that by operating on the maneuvering end it is possible to vary the relative position of the pressure plate and of the clamp by bringing the press from an open position in which the pressure plate is further away from the clamp to a closed position in which the pressure plate It is closer to the clamp, compressing the spacer against the acromion, and vice versa.

In particular, the pressure plate engages a hollow seat of the transverse portion of the extension of the nut screw by means of a hollow support, and the through hole is made in the acromion when the spacer is positioned in the subacromial seat, by means of a tool of drilling introduced through respective aligned cavities of the seat, of the support and of the pressure plate. In this way it is possible to fix the spacer to the acromion by means of the screw and such at least one threaded hole, avoiding having to center this at least one threaded hole with the respective through hole previously made in the acromion.

Advantageously, the instrumentation also comprises a file, suitable for being inserted through the anterior transdeltoid access, to prepare fixing slots on the lower surface of the acromion, in correspondence with said incision, suitable for engaging with the fixing means of the spacer.

Brief description of the drawings

The invention will be illustrated below with the description of one of its embodiments, given by way of non-limiting example, with reference to the attached drawings in which:

- figure 1 shows two perspective views of a spacer according to the invention;

- figure 2 shows a clamp of an instrument set for implanting the spacer according to the invention;

figure 3 shows the gripping portion of the clamp of figure 2 engaged by a spacer according to an alternative embodiment to that of figure 1;

- figure 4 schematically shows an implantation of a spacer according to the invention in a subacromial site, according to a first implantation modality, which foresees the fixing to the acromion by means of a screw;

- figure 5 shows a forceps for implanting the spacer of figures 1 and 2;

- figure 6 shows a press for implanting the spacer of figures 1 and 2;

- figure 7 shows a press for implanting the spacer of figures 1 and 2, as an alternative to the press of figure 6.

Description of the preferred embodiments

With reference to Figure 1, a subacromial spacer 10 is shown, according to the invention, adapted to be inserted in a subacromial site 1, ie between an acromion 51 and a humeral head 52 of a patient (Figure 4). The spacer 10 has an articulation surface 11 which articulates with the humeral head 52. The thickness S of the spacer 10 is chosen so that, when the spacer 10 is fixed to the acromion 51, the articulation surface 11 is dispose at a predetermined distance from acromion 51, typically this thickness S is between 4 and 12 millimeters, in particular it is chosen in sizes of 5, 7, 9 and 11 millimeters.

The articulation surface 11 has a radius of curvature R preferably greater than 60 millimeters at each point engaged in contact with the head of the humerus 52. This value is greater than the value of the radius of curvature T of the humerus head of any human being, therefore the articulation surface 11 engages the humeral head 52 in a substantially point-like contact, once the spacer 10 has been fixed in the subacromial seat 1. This configuration allows a substantial rolling of the humeral head 52 on the articulation surface 11 of the spacer 10.

The spacer 10 has a substantially rectangular cross section, with the vertices suitably joined. The longer side, arranged in use perpendicular to the sagittal plane of the patient, has a length L preferably between 23 and 27 millimeters, in particular it is close to 25 millimeters, while the shorter side has a length l preferably between 15 and 18 millimeters, in particular it is close to 16 millimeters. Alternatively, a spacer 20 (Figures 2 and 3) has substantially elliptical cross sections with sides L and 1 as reported above.

The spacer 10 or 20 is preferably made of an alloy of cobalt, copper and molybdenum, while the articulation surface 11 has a coating in a ceramic material, or in a metal with a specular surface finish grade, such as preferably deposited pure titanium according to a vacuum plasma deposition technique (TiVPS). These materials achieve the maximum compatibility of the spacer 10 or 20 with the destination site, in particular the materials and the structure of the articulation surface 11 minimize the coefficient of friction, substantially rolling, at the point of contact between the articulation surface 11 and the 52 humeral head of the patient.

For fixing to the lower surface 53 of the acromion 51, the spacer 10 or 20 has four anchoring blades 13, symmetrical with respect to the axis of symmetry 12. They are made in such a way that they can be inserted by compressing the spacer 10 or 20 against the acromion 51 making an incision of the acromion 51. In the spacer 10 of the embodiment of figure 1, the fixing means further comprise a threaded hole 14, preferably blind, accessible from the opposite side of the surface of articulation 11, and a screw 15 (Figure 4) suitable for this threaded hole. Several threaded holes and respective screws suitable for these threaded holes can also be provided.

To fix the spacer 10 or 20 to the acromion 51, an instrument set according to the invention can be used, comprising a clamp 30, preferably in stainless steel or aluminum alloy, conventional means for operating the screw 15 , and possibly other general surgical instruments. The clamp 30, shown in Figure 2 and in detail in Figure 3, develops in a plane, between a maneuvering portion 31 and an opposite gripping portion 32 adapted to clamp the spacer 10 or 20 to bring it into the subacromial seat 1 through a € ™ suitable cutaneous opening in the patient's shoulder, in particular a minimally invasive anterior trans deltoid access. The clamp 30 is made up of two halves mutually rotatable around the hinge 36, so as to allow the clamping of the spacer 10 or 20 in correspondence with the grooves 18 (Figure 1), and its subsequent release. The central portion 33 of the clamp 30 has a deviation 34, so that the subacromial site 1 can be reached through an anterior trans deltoid access, surrounding the lateral portion 3 of the shoulder. The clamp 30 can therefore be used to implant the spacer both in a right shoulder and in a left shoulder, provided that it is rotated 180 ° around its longitudinal axis 35.

The implant then requires two minimally invasive skin accesses. A first transdeltoid anterior access is used in a preparatory phase of the implant to move the head of the humerus 52 away from the acromion 51, and possibly to create, using a conventional surgical file, preparation cavities in the lower surface 53 of the Acromion 51, in correspondence with the incisions with made by compressing the anchoring blades 13 of the spacer 10 against the surface 53 of the acromion 51. A second access above the shoulder is used in a subsequent drilling phase of the acromion 51, in which, as shown in figure 4, a through hole 55 is made through the acromion 51, with a diameter sufficient for the passage of the screw 15. This is followed by a phase of introduction and positioning of the spacer 10, in which this the latter is secured in the gripping portion 32 of the clamp 30 (figure 3), which is inserted into the front access, until the spacer 10 reaches the seat subacromial 1, so as to align the blind threaded hole 14 of the spacer with the through hole 55 of the acromion 51. Subsequently, a step of fixing the spacer 10 to the acromion takes place, in which the screw 15 is inserted through the Upper access of the shoulder and the through hole 55 of the acromion 51 until it engages with the blind threaded hole 14 of the spacer 10; by operating on the maneuvering portion 16 of the screw 15, the spacer 10 is forced against the acromion 51 making the incisions in the surface 53 of the acromion 51. The clamp 30 can then release the spacer 10 and be extracted from the patient's shoulder.

The anchoring blades 13 preferably have transverse through holes 17, which allow subsequent welding between the bone flaps, in a secondary stabilization step of the spacer 10 or 20.

Alternatively, implantation of the spacer according to the invention is performed using only the transdeltoid anterior access. To compress the spacer against the lower surface 53 of the acromion 51, an instrument set according to the invention can be used, comprising the forceps 80 shown schematically in figure 5. The forceps comprise a pair of levers 81 and 82, the arms of which resistance 78,79 have at the ends, respectively, the gripping portion 32 to hold and release the spacer 20 in the subacromial seat 1, and a pressure surface 84. The pliers 80 is made in such a way that it is possible to position the portion grip 32 with the spacer 20 in the subacromial seat 1, and the pressure surface 84 resting on the patient's shoulder. By squeezing the powerful arms 85,86 of the two levers 81,82, the compression of the spacer 20 against the acromion 51 is achieved.

The pincer 80 can comprise one or more bending springs 87 for opening return, associated with toothed locking means 88 of a predetermined opening of the pincer 80, to maintain the compression between the spacer 10 and the lower surface 53 of the acromion 51 .

The instruments can, in addition or as an alternative to the pliers 80, comprise a press 60 or 90, respectively shown in figures 6 and 7, in which a screw 61 has a maneuvering end 62; the screw of the press 61 is housed in a nut screw 64 which has an extension 65 with a transverse portion 67 and a longitudinal portion 68 in the order substantially perpendicular and parallel to the nut screw 64.

The preparatory phase of the implant foresees the tightening of the spacer 10 or 20 in the gripping portion 32 of the clamp 30, and the assembly of the clamp 30 on the press 60 or 90. The maneuvering portion 31 of the clamp 30 is able to engage, in an integral connection, with the longitudinal portion 68 of the press 60 and, in the case of the press 90, with the end 63 opposite the operating end 62 of the screw 61 of the latter. The pressure plate 66 is able to engage, in the case of the press 60, with the end 63 opposite the operating end 62 of the screw 61, and in the case of the press 90, with the transverse portion 67 of the extension 65 by means of a cylindrical hollow support 69 which engages in one of the holes 74 of the hollow seats made along the transverse portion 67. In both cases, the pressure plate 66 and the spacer 10 or 20 have their axes substantially aligned, in particular the hole thread 14 of the spacer 10 mounted on the press 90 is aligned with the axis of the hollow cylindrical support 69 of the pressure plate 66.

A phase of introduction and positioning of the spacer 10 or 20 follows, in which the gripping portion 32 of the clamp 30 and the spacer 10 or 20 are brought into the subacromial seat 1 in which the spacer 10 or 20 is to be implanted, through the transdeltoid access. At the end of the introduction and positioning step, the pressure plate 66 is located above the patient's shoulder.

In a subsequent compression step, the distance between the spacer 10 or 20 and the pressure plate 66 is reduced by operating on the operating end 62 of the screw 61 of the press 60 or 90. In the case of the press 60, the nut screw 64 is the extension 65 are fixed with respect to the subacromial seat 1, and the pressure plate 66 integral with the screw 61 is brought closer to the spacer 10. In the case of the press 90 the height of the screw 61 does not vary with respect to the subacromial seat 1, while the nut screw 64 and the extension 65 move towards the patient's shoulder to bring the pressure plate 66 closer to the spacer 10. In both cases, a connection is made between the spacer 10 or 20 and the acromion 51 by means of the anchoring blades 13 (figures 1 and 3), as already described.

The press 90 also allows a step of making the through hole 55 through the acromion 51 (figure 4) by means of a drilling tool, for example a drill bit 70, not shown, which is introduced into an upper cutaneous access of the shoulder of the patient through the hole 74, the hollow support 69 of the pressure plate 66 and a hole made through the pressure plate 66; the tip 70 and is centered with respect to the threaded hole 14 of the spacer 10 (figure 1) by means of centering means, not shown, inside the cable support 69. Making the hole 55 during implantation, instead of before introduction of the spacer in the subacromial seat, the use of the spacer 10 in which the threaded hole 14 is made is favored: it is not in fact necessary to align the threaded hole 14 with the previously made through hole 55 on site. In this case, a fixing step follows by screwing the screw 15 which passes through the through hole 55 and engages the threaded hole 14 so as to force the spacer 10 against the surface 53 of the acromion 51, stabilizing the connection.

Then follows a phase of secondary stabilization of the spacer 10 or 20 in which a real welding takes place between the bone flaps through the transverse holes 17 made in the blades 13 inserted in the acromion 51.

By means of the press 60 it is possible to implant the spacer 20, represented in figure 3, according to an embodiment thereof in which the hole 14 of figure 1 is not provided, and the anchoring blades 13 are without interruptions and can for example be arranged as in Figure 3, ie arranged in a cross along the planes of symmetry of the spacer. In the case of the press 90, on the other hand, the spacer 10 having at least one blind threaded hole 14 is preferably implanted.

The extension 65 has in the transverse portion 67 engagement seats 74 for the engagement of the screw 61 of the press or of the support 69 of the pressure plate 66; the longitudinal portion 68 has in the case of the press 60 engagement seats 75 for the interlocking of the clamp 30, and in the case of the press 90, a longitudinal groove 76 for the passage of the clamp 30 in its movement along the transverse portion 67. Engagement sites 74 and 75 are chosen according to the size of the shoulder in which the implant is made.

The above description of a specific embodiment of the spacer according to the invention, of an instrument set for the implantation of this spacer, and of the methods of use of such instrument set, is able to show the invention from conceptual point of view so that others, using the known technique, will be able to modify and / or adapt this specific embodiment in various applications without further research and without departing from the inventive concept, and, therefore, it is understood that such adaptations and modifications will be considered as equivalents of the specific embodiment. The means and materials for carrying out the various functions described may be of various nature without thereby departing from the scope of the invention. It is understood that the expressions or terminology used have a purely descriptive purpose and therefore not limitative.

Claims (6)

CLAIMS 1. A spacer (10,20) able to be inserted in a subacromial site (1) between an acromion (51) and a humeral head (52) of a patient, called humeral head (52) having a radius of curvature ( 5), said spacer (10,20) comprising: - an articulation surface (11) adapted to articulate with said humeral head (52); - fixing means to said acromion (51), so that said articulation surface (11) is arranged at a predetermined distance from said acromion (51) when said spacer (10,20) is fixed to said acromion (51) , characterized in that said articulation surface (11) has a radius of curvature (R), said radius of curvature (R) being greater than the radius of curvature (T) of said humeral head (52), such that said articulation surface (11) engages said humeral head (52) in substantially point-like contact. A spacer (10,20) according to claim 1, wherein said radius of curvature (R) is not less than 60 millimeters at each point engaged in said contact. A spacer (10,20) according to claim 1, wherein said fixing means comprise anchoring blades (13) suitable for making an incision in said acromion (51), said incision being made by compressing said spacer (10,20) against said acromion (51), said anchoring blades (13) being in particular arranged symmetrically with respect to a plane of symmetry of said spacer (10,20). A spacer (10,20) according to claim 3, in which said anchoring blades (13) have transversal through holes (17), suitable to allow growth of bone tissue through said transverse through holes (17). 5. A spacer (10) according to claim 3, having at least one threaded hole (14), preferably blind, accessible from the opposite side with respect to said articulation surface (11) and associable with a screw (15) adapted to engage with said at least one threaded hole (14) through a respective through hole (55) made through said acromion (51), said at least one threaded hole (14) and said respective through hole (55) being arranged substantially aligned so that by tightening said screw (15), the spacer is tightened against said acromion (51) favoring the penetration of the anchoring blades (13) into said bone tissue. 6. A spacer (10, 20) according to claim 1, having a thickness (S) such that said predetermined distance is between 4 and 12 millimeters, in particular a thickness (S) selected between 5, 7, 9 and 11 millimeters, net of said fixing means to said acromion (51).