Orthopedic prosthesis, particularly interbody cage for vertebral stabilization

Abstract

Orthopedic prosthesis, particularly an interbody cage for vertebral stabilization, comprising a body (1) made of deformable shape memory material, starting from an expanded configuration corresponding to its condition inserted between two adjacent vertebrae, into a temporarily contracted configuration of oblong shape for its intervertebral insertion. The body (1) has a discontinuous configuration.

Description

[0001] "Orthopedic prosthesis, particularly interbody cage for vertebral stabilization"

[0002] Field of the invention

[0003] The present invention generally relates to orthopedic prostheses such as, non-limiting example, interbody cages for vertebral stabilization, designed to be inserted between two adjacent vertebrae in order to space them apart and thus maintain them at a reciprocal distance sufficient to restore the intervertebral space, achieving decompression of the nerve roots and acceleration of interbody fusion.

[0004] Background art

[0005] Such interbody cages typically comprise a body designed to be inserted between two ad acent vertebrae during the surgical implantation of the interbody cage itself. Examples of such interbody cages are described and illustrated, for example, in EP4231971A1, EP3925577A1, EP3925576A1 in the name of the same Applicant.

[0006] From CN105310803A, CN111096829A, CN111110406A and CN217593157U, interbody cages are known whose body is formed of a shape memory material.

[0007] In interbody arthrodesis procedures, instead of the intervertebral disc that is removed, a cage is inserted to restore the correct distance and angle between the two vertebrae. The cage also serves to provide stability, and the optimal case is represented by devices that occupy a surface corresponding to that left vacant by the removed disc .

[0008] To insert interbody cages, three accesses are possible: posterior access, lateral access, and anterior access.

[0009] Anterior access (surgical technique called ALIF: Anterior Lumbar Interbody Fusion) allows the insertion of larger cages. However, the anterior part of the spine is affected by the passage of the most important blood vessels of the human body and the risk of injury to these vessels makes the operation complicated and requires the presence of a complex medical team, with a consequent increase in costs for the hospital structure.

[0010] Lateral access (called XLIF: Xtreme Lateral Interbody Fusion) provides for the insertion of a medium-sized cage, but also in this case, since a considerable abdominal space must be crossed in order to operate on the spine, the operation is complicated and the patient' s recovery times are longer.

[0011] Posterior access is the simplest from an operative point of view, but the interbody cages that can be inserted are those of the smallest size.

[0012] US2015 / 209152A1 and US2008 / 281346A1 describe interbody cages made of shape memory material similar to that set out in the pre-characterizing portion of claim 1.

[0013] Summary of the invention

[0014] The object of the present invention is to provide an interbody cage for vertebral stabilization that can advantageously be used for insertion with posterior access although having larger dimensions than those currently available and comparable to interbody cages usable for anterior access.

[0015] According to the invention this object is achieved by the feature set out in the characterizing portion of claim 1. The attribute 'discontinuous' is intended to mean that the body of the interbody cage has one or more interruptions, i.e. at least one physical separation zone between its parts .

[0016] Thanks to this feature the shape memory interbody cage according to the invention can advantageously be implanted in its elongated form with posterior access, and thus with an insertion operation that is simpler and less risky for the patient, and then be able to expand to occupy a surface similar to that of a cage of the type insertable with anterior access. The discontinuous configuration of the cage body also makes its insertion easier during its surgical implantation.

[0017] According to embodiments of the invention, the body of the interbody cage has in said expanded configuration a generally quadrangular annular shape with two substantially L-shaped symmetrical portions separated from each other and interconnected by a diagonal element, said contracted configuration having an oblong shape with said two portions partially superimposed (as visible in Figures 3, 4 and 7, 8 of the appended drawings) .

[0018] According to other embodiments of the invention, the body of the interbody cage has in said expanded configuration a generally quadrangular annular shape with a diagonal element divided into two longitudinally adjacent parts, said contracted configuration having an oblong shape with said two parts of the diagonal element longitudinally spaced .

[0019] The cage according to the invention may also have at least one through hole for the introduction within said annular body of material suitable for promoting bone regrowth for the fusion between the vertebrae between which the cage is inserted .

[0020] The shape memory material is conveniently super-elastic, typically Nitinol . The transformation between the initial configuration and the final configuration is carried out through appropriate thermal cycles that allow both the desired elongated shape and the final shape to be impressed once the prosthesis has been returned to room or body temperature .

[0021] It is thus possible to make an intervertebral cage adequately designed to be temporarily deformed into its elongated form to be inserted inside a delivery system (a tube, for example) and occupy a sufficiently small space to be insertable posteriorly. Once released, it will regain the original expanded dimension similar to that of interbody cages inserted with anterior access.

[0022] Brief description of the drawings

[0023] The invention will now be described in detail with reference to the appended drawings, provided purely by way of non-limiting example, in which:

[0024] - Figure 1 is a schematic perspective view of a first embodiment of an interbody cage according to the invention, shown in an expanded configuration corresponding to its implanted condition between two adjacent vertebrae,

[0025] - Figure 2 is a plan view of Figure 1,

[0026] - Figure 3 is a schematic perspective view of the first embodiment of the interbody cage according to the invention, shown in an elongated configuration corresponding to the moment of its implantation between two ad acent vertebrae,

[0027] - Figure 4 is a plan view of Figure 3, - Figure 5 is a schematic perspective view of a second embodiment of an interbody cage according to the invention, shown in an expanded configuration corresponding to its implanted condition between two adjacent vertebrae,

[0028] - Figure 6 is a plan view of Figure 5,

[0029] - Figure 7 is a schematic perspective view of the second embodiment of the interbody cage according to the invention, shown in an elongated configuration corresponding to the moment of its implantation between two ad acent vertebrae, and

[0030] - Figure 8 is a plan view of Figure 7.

[0031] Detailed description of the invention

[0032] The embodiments of the invention described here relate to the particular case of an interbody cage for vertebral stabilization. It should be noted that the invention is equally advantageously applicable to orthopedic prostheses for other applications in which the space available for insertion of the prosthesis is limited.

[0033] The concept underlying the invention consists in providing an interbody cage for posterior insertion having a variable configuration from a stable expanded shape of dimensions generally corresponding to those of interbody cages designed for anterior intervertebral insertion, to an unstable shape of different form suitable to allow its posterior insertion, otherwise prevented, and the subsequent return to the expanded shape after its intervertebral insertion.

[0034] With initial reference to Figures 1-4, the interbody cage according to a first embodiment of the invention consists of a monolithic annular body (1) of shape memory material, typically a super-elastic material such as Nitinol (Ni-Ti intermetallic) . In its normal stable configuration at room temperature, shown in Figures 1 and 2, the body (1) has a generally quadrangular expanded shape, substantially regular, with two symmetrical and separate portions (2, 3) generally L-shaped, each having a slightly convex branch (4, 5) and a slightly concave branch (6, 7) . The two portions (2, 3) are interconnected, at the respective inner vertices, by a diagonal element (8) . Branches (5, 6) as well as branches (4, 7) are discontinuous because they present two mutual separation zones, so that the two portions (2, 3) are physically permanently connected only by the diagonal element (8) , which in this case is continuous.

[0035] Branches (4, 5, 6, 7) are conveniently formed with inner and / or outer indentations to facilitate their deformation. For example, and as best visible in Figures 2 and 4, convex branches (4, 6) are formed with outer indentations (23) and concave branches (6, 7) are formed with inner indentations (24) .

[0036] The dimensions of body (1) in its expanded configuration are substantially comparable to those of an interbody cage configured for insertion with anterior or frontal access, and are appreciably greater than those of usual interbody cages configured for posterior insertion.

[0037] Starting from this expanded configuration, body (1) can be temporarily elastically deformed, by suitable thermal treatments, into a contracted and oblong configuration shown in Figures 3 and 4. In this configuration the two portions (2, 3) are symmetrically folded towards the diagonal element (8) and are partially superimposed or interpenetrated, in the sense that branch (5) is arranged partially between branch (6) and diagonal element (8) , and branch (4) is arranged partially between branch (7) and diagonal element (8) . Alternatively, branch (7) could be folded inside branch (4) and branch (5) could be folded outside branch (6) .

[0038] The overall dimensions of body (1) thus contracted correspond to those of body (1) expanded, but the oblong configuration generated as a result of the thermal cycles makes body (1) of reduced bulk for its insertion from behind, i.e. with posterior access, between two vertebrae. Following insertion and return to room or body temperature, body (1) resumes the expanded configuration of Figures 1 and 2 to enable the fusion between the two vertebrae.

[0039] At least one of the branches of body (1) , for example branch (7) of portion (3) , may be formed with a through hole (9) for the insertion inside the cage of material suitable for promoting bone regrowth for the fusion between the vertebrae between which the cage is inserted. Further perforations (10) may also be provided, for example on branches (4, 5) , of polygonal or circular section, serving to improve the integration of the implanted cage.

[0040] The variant of the cage shown in Figures 5-8 is generally and conceptually similar to that described above with reference to Figures 1-4, and only the differences will now be described in detail using the same reference numerals for identical or similar parts.

[0041] Also in this variant the cage consists of a monolithic annular body (11) of super-elastic shape memory material, e . g . Ni tinol .

[0042] In its stable configuration at room temperature shown in Figures 5 and 6, body (11) has a generally quadrangular expanded shape analogous to the embodiment of Figures 1 and 2 with two symmetrical and separate portions (12, 13) generally L-shaped, each having a slightly convex branch (14, 15) and a slightly concave branch (16, 17) . In this case the two portions (12, 13) are interconnected directly at the ends of respective branches (15, 16) and (14, 17) , so that in practice body (11) consists of a continuous ring rather than discontinuous as in the previous embodiment. A diagonal element (18) extends between the inner vertices of portions (12, 13) and is in this case discontinuous, i.e. formed of two separate and longitudinally aligned parts (19, 20) , of which part (19) is joined to the inner vertex of portion (12) and part (20) is joined to the inner vertex of portion (13) .

[0043] The dimensions of body (11) in its expanded configuration are substantially comparable to those of an interbody cage configured for insertion with anterior or frontal access, and significantly greater than those of current interbody cages configured for posterior insertion.

[0044] In this expanded configuration, the two parts (19, 20) of diagonal element (18) are longitudinally adjacent, i.e. directly facing each other.

[0045] Starting from this expanded configuration, body (11) can be temporarily elastically deformed, by generally known thermal treatments, into a contracted configuration of oblong shape shown in Figures 7 and 8. In this configuration, branches (15, 16) and (14, 17) of the two portions (12, 13) are extended and the two parts (19, 20) of diagonal element (18) are longitudinally spaced from each other. Also in this case the overall dimensions of body (11) thus contracted correspond to those of body (11) expanded, but the oblong configuration generated makes body (11) easily insertable from behind, i.e. with posterior access, between two vertebrae. Following insertion and return to room or body temperature, body (11) resumes the expanded configuration of Figures 5 and 6 to generate the fusion between the two vertebrae.

[0046] At least one of the branches of body (11) , for example branch (17) of portion (13) , may be formed with a through hole (22) for the insertion inside the cage of material suitable for promoting bone regrowth for the fusion between the vertebrae between which the cage is inserted. Further perforations (21) may also be provided, for example on branches (14, 15) , of polygonal or circular section, to improve the integration of the implanted cage.

[0047] Naturally, the construction details and embodiments may be widely varied from what has been described and illustrated without thereby departing from the scope of the invention as defined in the following claims.

Claims

CLAIMS1. Orthopedic prosthesis, particularly an interbody cage for vertebral stabilization, comprising a body (1;11) made of shape memory material deformable, starting from an expanded configuration corresponding to its condition inserted between two ad acent vertebrae, into a temporarily contracted configuration of elongated shape for its intervertebral insertion, characterized in that the body (1; 11) has a discontinuous configuration.

2. Orthopedic prosthesis according to claim 1, characterized in that in said expanded configuration the body (1) has a generally quadrangular annular shape with two substantially L-shaped symmetrical portions (2, 3) separated from each other and interconnected by a diagonal element (8) , said contracted configuration having an oblong shape with said two portions (2, 3) partially superimposed.

3. Orthopedic prosthesis according to claim 1, characterized in that in said expanded configuration the body (11) has a generally quadrangular annular shape with a diagonal element (18) divided into two parts (19, 20) longitudinally adjacent to each other, said contracted configuration having an oblong shape with said two parts (19, 20) of the diagonal element (18) longitudinally spaced from each other.

4. Orthopedic prosthesis according to any of the preceding claims, characterized in that it has atleast one through hole (9; 19) for the introduction into said body (1; 11) of material suitable for promoting bone regrowth for the fusion between the vertebrae between which the cage is inserted.

5. Orthopedic prosthesis according to any of the preceding claims, characterized in that it has a plurality of through perforations (10; 21) .

6. Orthopedic prosthesis according to any of the preceding claims, characterized in that the shape memory material is super-elastic, preferably Nitinol.

7. Orthopedic prosthesis according to claim 2, characterized in that the annular-shaped body (1) comprises branches (4, 5, 6, 7) formed with inner or outer indentations (23, 24) .

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