Patent Description:
The invention relates in particular to a bone plate internal fixator device intended for epiphysiodesis surgery, used to block the natural growth or to correct a limb axis deviation, by limiting the natural growth of the growth plate.

The invention can be usefully applied in the paediatric orthopaedics sector, for epiphysiodesis surgery at the ends of deformed long bones of paediatric patients. Therefore, the following description is made referring to the non-limiting use within the scope of such sector.

Known techniques for epiphysiodesis surgery provide to limit the development of the growth plate, through the insertion into the bone of devices as: screws arranged longitudinally, staples or bone plates.

Among the techniques used for epiphysiodesis, it is widespread to block the growth plate through the use of a bone plate.

Such bone plate is applied to the bone by means of fixing screws which fasten it respectively to the epiphysis and to the metaphysis at the convex area of the bone deformation. Both the metaphysis and epiphysis portions of the bone plate have at least one through hole adapted to receive one of the aforesaid fixing screws.

In the specific sector of the present invention, problems related to the tolerability for the patient of the above described bone plates are known.

In fact, when the fixing screws of the bone plate are positioned above and below the growth plate, they have to adapt to the curve resulting from the constraint of the bone plate and the variations occurring during the growth.

Particular bone plates are thus known, that are constrained to the bone by means of fixing screws which are susceptible to diverge one another, in order to avoid the exceeding compression of the growth plate and to carefully guide the natural growth process of physis and bones.

One solution disclosed in document <CIT> relates to a plate fixator device for the angular correction of bone deformations, comprising a rotatable hinge arranged transversally in the plate, to enable a relative rotation of the plate under the effect of the load of the fixing screws, so as to support the curve variations occurring during growth.

However, the solution known from document <CIT> constitutes a great encumbrance due to the presence of the hinge, which can reduce the tolerability of the bone plate in particular in regions scarcely covered by soft tissues. Furthermore, the solution known from document <CIT> does not further allow to have an adequate centering reference on the growth plate, for the use of a Kirschner wire for temporarily fixing of the bone plate, according to known surgical techniques.

One further solution disclosed in document <CIT> refers to a plate fixator device for controlling the bone growth, in particular for correcting bone deformities; this device comprises two fixing screws which are inserted in suitable holes obtained in the bone plate.

In one example disclosed in <CIT>, the head of each fixing screw has a spherical profile for appropriately rotating in an elongated seat obtained in the plate and thus enabling fixing screws to angulate. In order to enable a rotation of the screws stem, it is required a spherical profile of the head of the screw also containing the engagement through which the screw is operated during the screwing operation; therefore, in this known example, the screw head and generally the bone plate are of great encumbrance as regards the height which may reduce the tolerability of the bone plate especially in regions scarcely covered by soft tissues.

In further examples described in <CIT>, it is provided to make a central connection between the bone plate holes be flexible, so that the fixing screws are capable of moving following the movement of bone sections. Examples of flexible connections known from <CIT> provide: a midsection of the plate made of flexible material, one plate made of fabric with rigid material surrounding the openings, or the use of a flexible band to surround the fixing screws instead of a plate, eventually providing it with a crimping in the middle.

Document <CIT> relates to a bone alignment implant including a first bone fastener with a first bone engager, that is adapted for fixation into the metaphyseal bone and a second bone fastener with a second bone engager, that is adapted for fixation into the diaphyseal bone. A link connecting the two fasteners spans across the physis. This implant acts as a flexible tether between the metaphyseal and the diaphyseal sections of bone during bone growth and is designed to adjust and deform during the bone realignment process.

Document <CIT> relates to an implant for temporary Epiphysiodesis or Hemi-epiphysiodesis, consisting of a plate-shaped, elongated body having at least two openings for receiving bone screws, wherein the plate-shaped body in the region between the openings has a weakening portion and an opening, which lies surgically on the epiphyseal plate. According to the invention, the openings are provided with an at least single-thread, the thread being segmented in such a way that thread-free sections) remain on the inner peripheral side between threaded sections. The weakening portion is formed as a groove which cuts on the top of the plate breakthrough and extends substantially perpendicular to the longitudinal plate axis.

Document <CIT> relates to a mechanical device to hold the osteotomized portion of the vertebra against the vertebral body after the intradiscal device is placed, wherein the device includes a flexible material connecting the plates, so that the screws may converge or diverge to increase pull-out strength.

Document <CIT> relates to a bone plate assembly for fixation of a fractured bone includes a plurality of plate members, a connecting member for retaining the plurality of plate members in a desired configuration and a plurality of locking members for securing the plate members to the connecting member.

Document <CIT> relates to an orthopaedic device for correcting deformities in a bone including first and second end portions to fix to first and second bone regions either side of a growth plate, and a connection portion extending between the first and second end portions. At least the first end portion can protrude relative to the connection portion such that it is at least partly receivable in a first recess formed in the first bone region. The first end portion can be in the form of an end cup and can be fixed to the first bone region by a fixation device such as a screw.

Even though the implants known in the art partly improve the tolerability of the bone plate for the patient, enabling a relative rotation of the plate ends so that the fixing screws can support the variations occurring during the growth, they have however some limits.

First of all, an exceeding flexibility of the bone plate can lead to problems in fixing it in the desired position.

Furthermore, even if they follow the movement of bone sections, flexible bone plates can in any case be of such an encumbrance, especially as regards the height, as to encourage the burst of an inflammatory process in the soft tissue.

In addition, a flexible bone plate can be too delicate, with the risk of breaking when submitted to the stresses caused by the bone growth.

And again, the configurations of the flexible bone plate adopted by the known art can lead to a crushing of the growth plate, thus further reducing the tolerability of the implant.

Aim of the present invention is solving problems of the prior art.

One particular aim of the present invention is providing a bone plate implant that can be optimally fixed to the bone.

One further particular aim of the present invention is providing a bone plate implant that is better tolerated by the patient, even when it is applied in anatomic regions scarcely covered by soft tissues.

One further particular aim of the present invention is providing a bone plate implant that is robust and suitable for epiphysiodesis applications.

One further particular aim of the present invention is presenting a bone plate implant that does not interfere with the growth plate.

One idea of solution underlying the present invention is providing a bone plate internal fixator device for epiphysiodesis, comprising a pair of holding elements, each one respectively comprising a through hole for receiving a respective fixing screw to a bone. The bone plate internal fixator device further comprises a central portion which structurally connects and constrains the holding elements with each other, the central portion being flexible so as to allow flexing of the bone plate.

The invention is a bone plate internal fixator device, as defined by the features of independent claim <NUM>.

Preferably, each one of the through holes comprises a threaded surface that is adapted to couple with a corresponding surface of the respective fixing screw. The holding elements and the central portion are provided as a composite structure.

Advantageously, the threaded surface of the through holes allows to realise an improved coupling with the fixing screws, so that it can be implanted with more precision on the bone and at the same time realise a structurally more stable assembly.

Furthermore, the presence of the threaded surface of the through holes enables to realise a coupling between the head of the fixing screws and the bone plate with less encumbrance as regards the height, and with no projecting portions, thus resulting more tolerable in particular when the implant is applied in anatomic regions scarcely covered with soft tissues.

Also, while the flexible central portions allow for a wide range of angular opening of the bone plate, during evolution of the epiphysiodesis surgery, the fixing screws always remain co-planar to the plane which encompasses the flexing angle, and the axis of each fixing screw remains substantially perpendicular to the respective holding element.

Also, the structure of the internal fixator device with threaded-surface holes generally results to be more robust and therefore suitable for epiphysiodesis applications, wherein the plate is submitted to even relevant stresses.

Furthermore, in order to improve tolerability, the internal fixator device is preferably characterised by a central portion which is raised with respect to the bottom surfaces of the holding elements, so as to limit pressures on the bone physis and avoid the lateral crushing of the growth plate.

Further features and advantages of the bone plate internal fixator device of the present invention will be more apparent from the hereinafter description of exemplary and non-limiting embodiments.

The present description refers to the enclosed drawings, wherein:.

With reference to the example of <FIG>, it is schematically illustrated one first embodiment of a bone plate internal fixator device <NUM>.

The fixator device according to the present invention is particularly adapted to be used in orthopaedics for epiphysiodesis surgery i.e. treatment of long bones malformations, in particular for paediatric and/or adolescent age patients, through the applications of the fixator device across of the physis of such bones.

The internal fixator device <NUM> comprises one first holding element <NUM> and one second holding element <NUM>, which respectively comprise a through hole <NUM> and <NUM>, which are configured to receive one respective fixing screw when the fixator device is implanted to the bone.

Holding elements <NUM> and <NUM> are preferably constituted of a rigid and biocompatible material (e.g. titanium) and have a substantially circular shape, with uniform thickness.

Holding elements <NUM> and <NUM> are structurally interconnected by a central portion <NUM> which constrains holding elements <NUM> and <NUM> with each other, realising a bone plate structure.

The holding elements <NUM> and <NUM>, and the central portion <NUM> are provided as a composite structure.

A "composite structure" is a structure made of at least two different materials or comprising at least two different material configurations (i.e. solid metal and braided metal), which exhibit different mechanical properties.

In other words, the holding elements and the central portion of the internal fixator device according to the invention, are made at least partially of two materials which are different or differently arranged.

In general, at least part of the holding elements and the central portion are originally provided as independent components of the internal fixator device. Such independent components are connected to form the composite structure during manufacturing of the internal fixator device.

The central portion <NUM> is flexible so as to enable a relative flexing between holding elements <NUM> and <NUM>, i.e. flexing of the bone plate. At the same time, the central portion <NUM> has tensile strength ensuring the structural integrity of the bone plate during the tensile-flexion phase.

The flexing of the bone plate corresponds to a relative rotation of the individual planes of holding elements <NUM> and <NUM>, which result to be adapted to allow the fixing screws to angulate, so as to support the variations of angle occurring during the bone growth, providing an improved tolerability of the implant in epiphysiodesis surgery.

In particular, the flexible central portion <NUM> allows for a wide range of angular opening of the holding elements <NUM> and <NUM> of the internal fixator device <NUM>. In this way, during bone growth in an epiphysiodesis surgery, the variations of angle allowed by the internal fixator device <NUM> can be further improved.

The central portion <NUM> preferably comprises one through hole <NUM>, which is configured to allow insertion of a wire guide (not shown) so as to use a Kirschner wire for centering the bone plate during the implantation, in such a way that the central portion is positioned correctly across of the growth plate.

When considering holding elements <NUM> and <NUM>, each one of them comprises one respective threaded surface <NUM> and <NUM> realised inside the through holes <NUM> and <NUM> respectively.

In particular, preferably, the through holes <NUM> and <NUM> are substantially cylindrical and the threaded surfaces <NUM> and <NUM> are the inner lateral surfaces of the cylindrical holes. In other words, the through holes <NUM> and <NUM> comprise a threaded cylindrical hole, which develops coaxially with inlet and outlet diameters substantially equal to each other.

Such threaded surfaces <NUM> and <NUM>, as will be further described, are adapted to couple with respective correspondingly threaded surfaces of fixing screws, to realise the implant structure.

In particular, the through holes <NUM> and <NUM> the threaded surfaces <NUM> and <NUM> are configured such that the fixing screws always remain co-planar to the plane which encompasses the flexing angle, and the axis of each fixing screw remains substantially perpendicular to the respective holding element <NUM> or <NUM>.

In <FIG> the fixator device <NUM> is visible, in disassembled configuration, so as to appreciate the particular embodiment of the flexible central portion <NUM>.

In this embodiment, the flexible central portion comprises four resilient elements 201a, 201b, 202a, 202b arranged in pairs to constrain holding elements <NUM> and <NUM> between each other. In other possible embodiments, a different number of resilient elements could be provided, for example one single pair.

Resilient elements 201a, 201b, 202a, 202b comprise metallic wires or cables which are constrained with each own end to one respective of the holding elements <NUM> and <NUM>.

The number of metallic wires or cables, their size and structure can be calibrated according to the flexing elasticity and the tension strength desired for the bone plate.

The constraint or blocking of the wires in the holding elements can obtained by welding, plastic deformation (crimping), or other mechanical constraints. In particular, the constraint in the holding elements occurs by means of passing metal wires or cables inside suitable holes <NUM> realised tangentially in holding elements <NUM> and <NUM>.

In general, by the term "wires" it is meant an elongated wire-like element, of any section but preferably circular; such "wires" can be made of uniform and solid material or of material arranged in strand or other composite configurations.

In general, by the term "cables" it is meant an elongated wire-like element, with preferably circular section, made of uniform material or of material arranged as a strand, in particular of metallic or non-metallic material.

Preferably, resilient elements 201a, 201b, 202a, 202b are arranged symmetrically with respect to a longitudinal axis of the fixator device <NUM>, that is to say, a longitudinal axis ideally connecting the centres of holes <NUM> and <NUM>.

Therefore, resilient elements 201a, 201b, 202a, 202b represent one particular embodiment of the already described flexible central portion <NUM>.

<FIG> shows one embodiment of a fixing screw <NUM>, specifically configured for use in a bone plate internal fixator device according to the present invention.

Fixing screw <NUM> is preferably constituted of a rigid and biocompatible material (e.g. titanium).

Fixing screw <NUM> comprises a threaded stem <NUM>, preferably comprising a triangular-profile thread. Fixing screw <NUM> further comprises a tip <NUM>, preferably of the self-tapping type. Fixing screw <NUM> further comprises a head <NUM>, provided with a thread on its own external cylindrical surface. The head <NUM> is provided with proper grasping means <NUM>, for instance a hexagonal recess for screwing the fixing screw <NUM> into the bone.

The head thread <NUM> is adapted to couple with the threaded surfaces <NUM> and <NUM> of the internal fixator device, which are correspondingly threaded, to realise the implant structure.

Preferably, the threaded surfaces <NUM> and <NUM>, and therefore the corresponding head thread <NUM> too, provide a two-starts thread, to simplify the screwing during the implant application and to allow the advancement equal to the pitch of the thread on the stem <NUM>.

Preferably, the thread of stem <NUM> of the fixing screws <NUM> has a thread pitch which is different from the thread pitch of the surfaces <NUM> and <NUM>; this further contributes to simplify the application of the implant. In particular, the thread of stem <NUM> has a pitch which is twice as compared to the thread pitch <NUM>, to enable a suitable advancement and a more accurate application in the terminal screwing part, when the head thread <NUM> engages with the thread <NUM> or <NUM> of the bone plate.

In <FIG> it is shown an implant for epiphysiodesis according to the present invention, that is an assembled kit which comprises a pair of fixing screws <NUM> and a bone plate internal fixator device <NUM>. Fixing screws are applied, through the thread of the head <NUM>, to the respective threads <NUM> and <NUM> in the through holes <NUM> and <NUM> of holding elements <NUM> and <NUM>.

By means of the fixing screws <NUM>, holding elements <NUM> and <NUM> are thus adapted to be fixed, through the assembling screws, respectively to the epiphysis and the metaphysis of a long bone of a paediatric-age patient, for example a bone having an angular deformation to be corrected through the application of the fixator device <NUM>.

The central portion <NUM>, being flexible, allows the stems of the screws <NUM> to angulate, being well tolerated by the patient even in the various phases of the bone growth.

The bone plate internal fixator device <NUM>, as described, is configured such that each one of the fixing screws <NUM> always remain co-planar to the plane to the respective holding element <NUM> or <NUM>, thus avoiding unwanted stresses on the internal fixator device <NUM>, and improving tolerability of the implant.

The threaded surfaces <NUM> and <NUM> of holding elements <NUM> and <NUM> are thus configured to solidly constrain each one of the holding elements <NUM> and <NUM> with the respective fixing screw <NUM>, so as to realise a bone plate assembly that is flexible exclusively in the central portion <NUM>.

The threaded coupling between the head of the fixing screws <NUM> and holding elements <NUM> and <NUM> enables to obtain an improved constraint, so that the internal fixator device <NUM> can be implanted with greater precision and is structurally more stable.

As it can be appreciated in <FIG>, the presence of the threaded surface of the through holes of holding elements <NUM> and <NUM> enables to realise a coupling between the head of the fixing screws <NUM> and the bone plate <NUM> which is less encumbering as regards the height, without projecting portions. In fact, according to the present invention it is not necessary that the fixing screw <NUM> "abuts" with the bottom head surface on the holding elements, but it is sufficient that the respective threads of the screws heads and of the through holes engage with each another, realising a stable assembly.

The internal fixator device according to the present invention is thus more tolerable, in particular when the implant is applied in anatomic regions scarcely covered by soft tissues.

Furthermore, the structure of the internal fixator device <NUM> with threaded surface holes, is in general more robust and adapted to endure stresses in epiphysiodesis applications.

As it can be appreciated in <FIG>, in order to improve tolerability, the internal fixator device comprises a central portion <NUM> which is raised with respect to bottom surfaces <NUM> of the holding elements <NUM> and <NUM>, provided to be placed in contact with the bone surface. Thereby, it is possible to limit pressures on bone physis and thus avoid laterally crushing the bone plate.

In other words, the internal fixator device <NUM> is substantially flat, but the central portion <NUM> is raised with respect to bottom surfaces <NUM> of holding elements <NUM> and <NUM>, which are configured to face towards the stem of the fixing screws <NUM>. Thereby, it is possible to limit pressure on the bone physis.

With reference to the example of <FIG>, it is schematically illustrated one second embodiment of a bone plate internal fixator device <NUM>.

The internal fixator device <NUM> comprises one first holding element <NUM> and one second holding element <NUM>, each one comprising a respective through hole <NUM> and <NUM>, similar to the elements already described with reference to the internal fixator device <NUM>.

The central portion <NUM> structurally connecting and constraining holding elements <NUM> and <NUM> between each other, is flexible so as to allow flexing of the bone plate.

The central portion <NUM> preferably comprises one central through hole <NUM>, which is configured to enable the insertion of a wire guide (not shown) so as to use a Kirschner wire.

Through holes <NUM> and <NUM> of holding elements <NUM> and <NUM> each comprise one respective threaded surface <NUM> and <NUM>, respectively.

Such threaded surfaces <NUM> and <NUM> are configured to couple with a corresponding surface of the head of the fixing screw <NUM>, similarly to what described with reference to the internal fixator device <NUM>.

The central portion <NUM> comprises one pair of bridge elements 510a and 510b, made of flexible plastic material, separated between each other by the through hole <NUM>. In one alternative embodiment, the central hole <NUM> may be omitted resulting in one single bridge element.

In general, the pair of bridge elements 510a e 510b is made of flexible plastic material, and is symmetrically arranged with respect to a longitudinal axis of the internal fixator device <NUM>.

In general, a plastic material having suitable resistance and biocompatibility characteristics is polyether-ether-ketone (PEEK).

Also holding elements <NUM> and <NUM> are made of plastic material, being more preferably made in a piece with bridge elements 510a and 510b, in one single mould.

Advantageously, plastic material elements can be more easily obtained through moulding processes, making these embodiments cheaper than embodiments comprising metallic material elements.

Furthermore, plastic materials portions are radiolucent and, in addition to being biocompatible, they also ensure suitable mechanical strength and resilience.

In one alternative embodiment, holding elements <NUM> and <NUM> can be made of metallic material connected to bridge elements by suitable bonding.

The embodiment of the fixing device <NUM> thus envisages different elements for providing the flexible central portion <NUM>, keeping at the same time unchanged the functioning of the bone plate with respect to what already described for the fixator device <NUM>.

<FIG> shows the fixator device <NUM> viewed from below. In this view, it is possible to appreciate that the central portion <NUM> comprises one recess <NUM> on the bottom surface, which enables to further raise the central portion <NUM> and to generate one preferential bending axis of the plate <NUM>. Thereby, the raised central portion <NUM> is further adapted to limit the pressures on the bone physis, when the fixator device <NUM> is implanted.

With reference to the example of <FIG>, it is schematically illustrated one third embodiment of a bone plate internal fixator device <NUM>.

The internal fixator device <NUM> comprises one first holding element <NUM> and one second holding element <NUM>, comprising respective through holes <NUM> and <NUM>. The central portion <NUM> structurally connecting and constraining holding elements <NUM> and <NUM> between each other, is flexible so as to allow flexing of the bone plate. The central portion <NUM> preferably comprises one central through hole <NUM>, which is configured to enable the direct passage of a Kirschner wire, preferably without the aid of a guide wire.

Through holes <NUM> and <NUM> of holding elements <NUM> and <NUM> each comprise one respective threaded surface <NUM> and <NUM>, respectively. Such threaded surfaces <NUM> and <NUM> are configured to couple with a corresponding surface of the head of the fixing screw <NUM>, similarly to what described with reference to the internal fixator device <NUM>.

The central portion <NUM> comprises one pair of bridge elements 710a and 710b, which, among others, realise the geometry of the through hole <NUM>. In general, bridge elements 710a and 710b are arranged symmetrically with respect to a longitudinal axis of the internal fixator device <NUM>.

The embodiment of fixator device <NUM> is therefore distinguished from the fixator device <NUM> or <NUM> due to a different supporting structure.

As visible in <FIG>, the partially disassembled fixator device <NUM> comprises one supporting frame <NUM> made in one piece of plastic material. Thereby, it is realised a perimetric portion <NUM> and <NUM> which is part of the structure of each one of the holding elements; thereby, the perimetric portion <NUM> and <NUM> of the holding elements is made in a piece with bridge elements 710a and 710b.

The supporting frame <NUM> is associated to a pair of annular elements <NUM> and <NUM>, respectively implantable in the perimetric portions <NUM> and <NUM>. Annular elements <NUM> and <NUM> are preferably made of stronger material, such as a metallic material, and include already described threaded surfaces <NUM> and <NUM>.

Thereby, it is realised a threaded coupling between screws <NUM> and threaded surfaces <NUM> and <NUM> of the annular elements <NUM> and <NUM> which is structurally more robust, leaving the frame <NUM> the task to contribute to the flexibility of the central portion <NUM>.

The fixator device <NUM> thus obtained enables to improve size tolerance and implementation quality, leaving unchanged the above described optimal functionalities.

The engraftment of annular elements <NUM> and <NUM> in the respective seats obtained in the perimetric portions <NUM> and <NUM> preferably occurs through appropriately knurled surfaces, to avoid the undesired rotation of annular elements subject to the tightening torque of fixing screws <NUM>.

<FIG> shows the fixator device <NUM> viewed from below. In this view, it is possible to appreciate that the central portion <NUM> comprises one recess <NUM> on the bottom surface, which enables to further raise the central portion <NUM>. Thereby, as already described, the raised central portion <NUM> limits pressures on the bone physis.

In general, it is possible to appreciate how in all embodiments, the internal fixator device advantageously has lower and upper perimetric edges which are rounded for a higher tolerability.

In particular, generally, embodiments provide bone plate internal fixator devices that are substantially flat, with an oblong shape without narrowing. In this sense, herein described embodiments differ from typical "eight plates" known in the art.

Flexible central portions of internal fixator devices according to the present invention provide members, such as resilient elements or bridge elements, which are arranged tangentially with respect to the perimeter of holding elements. Thereby, though ensuring a proper flexibility of the bone plate, it is provided an improvement of mechanical stability. Furthermore, the portions of the oblong shape without narrowing enable an improved manipulation by the surgeon during the application of the implant.

In conclusion, it is synthetically described a use of the bone plate internal fixator device of the present invention, referring to <FIG>.

Once having made a relatively non-invasive incision in the skin and in the flesh of the patient to be submitted to the implantation, the fixator device <NUM> is placed across of the physis, so that the two holding elements <NUM> and <NUM> are in contact respectively with the epiphysis and metaphysis of the bone to be treated.

A fixing wire inserted into the physis cartilage through the central through hole in the flexible central portion <NUM> allows to keep in position, though temporarily, the fixator device <NUM>.

Fixing screws <NUM> are at first inserted into the through holes, so as to penetrate in the corresponding portions of epiphysis and metaphysis of the bone until the head <NUM> reaches and engages with the threaded surface of through holes.

During the growth of the physis tissue, fixing screws <NUM> undergo a dragging action which determines an angular opening over the whole treatment, that is tension and flexing of the bone plate of the internal fixator device <NUM>.

By enabling flexing of the bone plate <NUM>, an angular opening of fixing screws <NUM> is also enabled, following the bone growth for the whole duration of treatment.

Advantageously, the bone plate internal fixator device according to the present invention, has a flat conformation and uniform thickness without projections so as to avoid friction areas with soft tissue surrounding the implant.

At the same time, advantageously, the bone plate internal fixator device according to the present invention, has an increased structural stability thanks to the constraint between the threaded surfaces of the through holes and the screws heads, resulting in a better performing implant and able to follow curve variations due to the growth of the bones.

Still advantageously, the fixator device conformation has a rational structure and adapted to be manufactured with qualitatively good tolerances.

Claim 1:
Bone plate internal fixator device (<NUM>; <NUM>; <NUM>) for epiphysiodesis, comprising a pair of holding elements (<NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>), each one of said holding elements (<NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>) respectively comprising a through hole (<NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>) configured for receiving a respective fixing screw (<NUM>) to a bone; said bone plate internal fixator device (<NUM>; <NUM>; <NUM>) further comprising a central portion (<NUM>; <NUM>; <NUM>) which structurally connects and constrains said holding elements (<NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>) with each other,
said central portion (<NUM>; <NUM>; <NUM>) being flexible so as to allow flexing of said bone plate (<NUM>; <NUM>; <NUM>) and angular opening of said bone plate (<NUM>; <NUM>; <NUM>) during evolution of the epiphysiodesis surgery,
wherein said flexing of said bone plate further allows a relative flexing between said holding elements (<NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>),
characterized in that said central portion (<NUM>; <NUM>) comprises at least one bridge element (510a, 510b; <NUM>, 710b) made of flexible plastic material,
in that said holding elements (<NUM>, <NUM>) are made of said flexible plastic material in a piece with said at least one bridge element (510a, 510b),
and in that the fixing screws (<NUM>) always remain co-planar to a plane which encompasses a flexing angle, the axis of each fixing screw (<NUM>) remaining substantially perpendicular to the respective holding element (<NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>).