US-12622711-B2 - Positioning device for implantation of prosthesis in a long bone, in particular for implantation of humeral prosthesis

US12622711B2US 12622711 B2US12622711 B2US 12622711B2US-12622711-B2

Abstract

The present invention relates to a positioning device ( 100 ) for implantation of prosthesis in a long bone, in particular for implantation of humeral prosthesis, comprising: at least one centering element ( 101 ) with a channel ( 102 ) configured to house an intramedullary nail ( 11 ); a support element ( 103 ) configured to hold a reference mask ( 200 ) on a plane ( 12 ) at a resected metaphysis of the long bone; an adjustment element ( 104 ) configured to connect the centering element ( 101 ) and the support element ( 103 ), wherein the adjustment element ( 104 ) further comprises a displacement device ( 105 ) configured to provide a controlled offset to the support element ( 103 ) for displacing the reference mask ( 200 ) over the plane ( 12 ) of the resected metaphysis.

Inventors

Michele Pressacco
ANDREA FATTORI
Antony Pranzetti

Assignees

LIMACORPORATE S.P.A.

Dates

Publication Date: 20260512
Application Date: 20220706
Priority Date: 20210715

Claims (16)

1 . A positioning device for implantation of prosthesis in a long bone, the positioning device comprising: at least one centering element including a channel configured to house an intramedullary nail; a support element configured to hold a reference mask on a plane defined by a resected metaphysis of said long bone; an adjustment element configured to connect said centering element and said support element, wherein said adjustment element further comprises a displacement device configured to provide a controlled offset to said support element, said displacement device including a first slide translating in a first direction parallel to said plane for displacing said reference mask in said first direction parallel to said plane, and said displacement device including a second slide translating in a second direction parallel to said plane for displacing said reference mask in the second direction parallel to said plane, the second direction being different to the first direction.
2 . The positioning device according to claim 1 , wherein said first slide includes a first adjustment system, and said second slide includes a second adjustment system.
3 . The positioning device according to claim 2 , wherein said first slide comprises a first threaded element controlled by the first adjustment system, and said second slide comprises a second threaded element controlled by the second adjustment system.
4 . The positioning device according to claim 2 , wherein said first adjustment system and said second adjustment system comprise predetermined position markings for providing said controlled offset by displacing said reference mask at predetermined increases, both with positive displacement and with negative displacement with respect to an axis of said centering element.
5 . The positioning device according claim 1 , wherein said adjustment element is laterally offset with respect to said centering element and to said support element to allow an unobstructed upper access to said reference mask.
6 . The positioning device according to claim 1 , further comprising a reference mask removably associated with said support element.
7 . The positioning device according to claim 6 , wherein said reference mask comprises a main seat configured to implant a metaphyseal reference on said resected metaphysis.
8 . The positioning device of claim 7 , wherein the metaphyseal reference comprises a Kirschner wire.
9 . The positioning device according to claim 7 , wherein said reference mask further comprises a plurality of auxiliary seats configured to house temporary fastening pins, for holding in position said reference mask once separated from said support element.
10 . The positioning device according to claim 6 , wherein said reference mask comprises a semi-circular portion matching an external dimension of an associated prosthesis component.
11 . The positioning device according to claim 10 , wherein said reference mask further comprises a plurality of references configured externally to said semi-circular reference and indicating a minimum distance of said reference mask with respect to a metaphyseal cortex of said long bone.
12 . The positioning device according to claim 6 , wherein the reference mask is provided in modular sizes corresponding to sizes of prosthesis modular components.
13 . The positioning device according to claim 1 , wherein said adjustment element mechanically connects said centering element and said support element providing a spatial angle with respect to an axis of said centering element so as to allow displacing said reference mask in a tangential manner over said plane, said plane being a resection plane of said metaphysis inclined at the spatial angle with respect to the axis of said centering element.
14 . The positioning device according to claim 13 , wherein said adjustment element provides a L-shaped structure, a first end of said adjustment element defining said spatial angle, a second end of said adjustment element being connected to said support element and being perpendicular to a plane of said reference mask.
15 . The positioning device according to claim 1 , wherein a spatial angle between said centering element and said support element corresponds to a spatial angle between a stem of an associated prosthesis component and an upper housing of the associated prosthesis component.
16 . The positioning device according to claim 1 , wherein the first direction and the second direction are perpendicular to each other.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a national phase of PCT/EP2022/068764, filed Jul. 6, 2022, and claims priority to Italian Patent Application No. 102021000018728, filed Jul. 15, 2021, the entire contents of both of which are hereby incorporated by reference. FIELD OF APPLICATION The present invention relates to a positioning device for implantation of prosthesis in a long bone, in particular for implantation of humeral prosthesis. The invention is particularly useful in shoulder prosthesis implantation surgery, in particular of modular shoulder prosthesis both of the anatomical and inverse type; the following description is made with reference to this specific field of application to simplify the exposure thereof. In general, the invention may be used to find an appropriate positioning at a metaphyseal surface of a long bone and to fasten a reference thereat, such as a Kirschner wire, which can be used for further operations during a prosthesis implantation. PRIOR ART In the shoulder prosthesis field, the use of prostheses, typically modular prostheses consisting of a plurality of elements that may be combined together to obtain an anatomical or inverse prosthesis, is now widespread. In the surgical implantation of a prosthesis, it is not always immediate to find a positioning that allows having the prosthesis device well centered in the metaphysis, as well as a prosthesis stem well centered in the bone canal. In fact, in the example of a shoulder prosthesis there are a first Medio-Lateral (M-L) offset, and a second Antero-Posterior (A-P) offset between the prosthesis stem and the humeral head. The most common modular prostheses are made with a symmetrical stem, and not with different stems for right shoulder and left shoulder, therefore a structural correction of the A-P offset is not provided for in the modular prosthesis. Instead, the most common modular prostheses are made with a predetermined correction of M-L offset, which however is selected according to a design corresponding to a literature average value; this predetermined correction is therefore not necessarily the most suitable one for each individual patient in the entire humeral population. In addition, many types of current modular prostheses, especially those with long stems, base the positioning of the stem by referring to the axis of the bone shaft as they are precisely designed for a distal fixation and grip in the shaft itself; to then allow a correct positioning of the prosthetic component of the humeral head (also modular) that is connected to the stem, the latter is generally supplied with different eccentric offsets in order to compensate for the pre-existing anatomical offsets and thus to ensure an optimal positioning. In order to develop ever less invasive and conservative prosthetic components, recently new designs of short stem prostheses are being developed, whose fixation tends to be less and less distal and more proximal (in the metaphyseal area of the bone). However, as a consequence of these new designs of short stem prostheses, if the prosthesis centering occurred based on the metaphysis morphology, it could happen that the stem of the prosthesis collides with the walls of the diaphyseal bone cortex, leading to a non-optimal positioning of the prosthesis implantation. Vice versa, if the prosthesis centering occurred with respect to the bone canal, it could happen that the prosthesis component comes into conflict with the metaphyseal cortices, with the risk of localized bone fracture; furthermore, having these short stem prostheses a much more proximal fixation, inadequate metaphyseal positioning could lead to inadequate fixation. An object of the present invention is to allow the correct positioning of a reference, such as for example a Kirschner wire, which acts as a guide for an implantation of a metaphyseal component of a prosthesis, be it anatomical or inverse, in a long bone. A further object of the present invention is also to allow the correct positioning of a reference on a metaphyseal surface, for a better positioning of a prosthesis component, in particular of a humeral shoulder prosthesis, be it preferably with a short stem or even with a long stem. A further object of the present invention is to provide a positioning device having structural and functional features such as to overcome the drawbacks of the prior art. SUMMARY OF THE INVENTION The solution idea underlying the present invention is to make a mechanical guide that allows a centering in the bone canal and, knowing the diameter thereof specific for the patient starting from radiographs or CT scans, obtaining an indication of how much offset may be applied to the prosthesis stem in order to optimally position the prosthesis on the metaphysis. The positioning tool supplied with the prosthesis, starting from the canal reference, allows determining an initial position of the prosthesis and, if it is not centered on the metaphysis,