WO2009147255A1 - Intramedullar osseointegrated system - Google Patents

Abstract

An intramedullar osseointegrated system, for connecting and fixing a prosthesis in an amputated transfemoral and transhumeral zone, is described, said system being stable in response to longitudinal and torsional forces and being able to withstand early stressing with a reduction in the treatment and adaptation period, whereby a greater stability of the implant is achieved in its location in response to the longitudinal and torsional forces affecting it in its operating condition. The system includes an implant member designed for positioning in the medullar cavity of the bone, a pair of locking screws designed to be screwed into respective radial holes of the implant in a position which is transverse/perpendicular with respect to the bone, a bolt which is connected to the implant member and forms the means for mounting, connecting and supporting the external prosthesis, and a fixing screw which extends through the said bolt and screws a distal end portion thereof into the said implant member.

Description

 "SYSTEM, INTRODUCED OSTEOINTEGRATED"

DESCRIPTION

Object of the Invention

The present invention relates to an intramedullary osteointegrated system, which provides essential novelty characteristics and notable advantages over the means known and used for the same purposes in the current state of the art.

More particularly, the invention proposes the design and development of an intramedullary osteointegrated system conceived in such a way that it provides an important qualitative advantage over previous designs by adding a transcortical double perpendicular block that stabilizes the implant against the longitudinal and torsional stresses that materialize. in an increased capacity to withstand higher and earlier loads than in current systems.

The field of application of the invention is obviously within the industrial sector dedicated to the manufacture of devices with medical application, and more particularly to the manufacture of implants for the adaptation of osteointegrated prostheses in trans-tumor and transhumeral amputees.

Background and Summary of the Invention

It is known by all in general the fact that with a certain frequency, it is necessary to perform amputations in relation to the long bones of the human body, in particular transfemoral amputations (above the knee) and transhumeral amputations (above the elbow) . The subsequent adaptation of prostheses in relation to the amputated limb, so that people affected by this type of interventions can develop a daily activity with the highest level of normality possible, requires the use of an element known as an osteointegrated implant with which it is provided. support and support for the prosthesis, whose implant consists of an artificial element that is placed in the bone for direct union, both functional and structural, between the living bone and the prosthesis under load.

In implants of the type mentioned above, it is desirable that their location be such that they can withstand the longitudinal and torsional stresses resulting from the loads to which they will be subjected during the daily activity of the implant. Likewise, it is also desirable that the implant behavior is such that it can be loaded within reasonable time periods, so that the amputee can overcome the situation associated with the intervention as soon as possible, and return as soon as possible. to a more or less normal degree of activity.

Taking into account these requirements inherent to the osseointegrated modular systems known in the current state of the art, the present invention has as a main objective the development of a novel system with which the previous designs are qualitatively improved by virtue of an improved stabilization of the implant against torsional stress.

This objective has been fully achieved by means of the system that will be described in the following, whose main characteristics are also included in the characterizing portion of the attached claim 1. In essence, the system designed and proposed by the invention has been conceived so that it adds a double transcortical perpendicular block that provides the desired improvement of implant stabilization. For this purpose, the system incorporates an implant element designed to be introduced into the medullary canal of a long bone (for example, the femur or humerus), after milling, and two locking screws that are applied perpendicularly to the implant, transversely to the bone, immobilizing the implant as far as rotation is concerned. A bolt, designed for coupling with the implant, can be threadedly inserted into the implant, while a screw applied through the bolt in the longitudinal direction of the latter, makes the final fixation between the bolt and the implant. In this way, the mentioned bolt constitutes an appropriate support for the fixation of the prosthesis, while the assembly, anchored in its position and fixed against its possible rotation, is perfectly capable of supporting the loads and stresses that βe present during normal use. of the prosthesis.

BRIEF DESCRIPTION OF THE DRAWINGS These and other features and advantages of the invention will become more clearly apparent from the following detailed description of a preferred embodiment, given solely by way of illustrative example and without any limiting character, with reference to the accompanying drawings, in which:

Figure 1 is a schematic perspective view, in which an exploded view appears in the elements that make up the system of the invention, and Figure 2 is also a schematic, partially sectioned perspective view of the elements of the system of the invention assembled and with the system located in its operative position.

Description of a Preferred Embodiment

As mentioned above, the detailed description of the preferred embodiment of the intramedullary osteointegrated system proposed by the invention will be carried out in the following with the help of the attached drawings, through which the same numerical references are used to designate the same or similar parts. Thus, attending first to the representation of Figure 1, you can see a schematic view, in perspective, of a set of elements that make up the proposed system, and among which an implant element indicated by the numerical reference is distinguished 1, transverse locking screws indicated by the numerical references 2, 3, a bolt piece indicated with the numerical reference 4, and a bolt fixing the bolt to the implant which has been indicated with the numerical reference 5.

In accordance with the preferred embodiment, the implant element 1 is sized to be introduced into the medullary canal of the long bone of the amputation stump, after milling, adopts general cylindrical configuration, and has an axial orifice with a larger inlet. diameter and a more internal portion of smaller diameter, stepped, from which a threaded longitudinal hole of smaller diameter extends (not noticeable in the Figure); in relation to the threaded outer surface, the implant has the formation of two transverse holes, directed radially and also internally threaded, of predetermined diameters, and referenced with the numbers Ib, Ic in mutually offset positions according to the longitudinal extension of the implant element 1, and also angularly offset in a predetermined angular magnitude (for example, of the order of 90 °) . The holes Ib, Ic are sized so that they allow the insertion of the locking screws 2, 3, extended perpendicularly with respect to the longitudinal direction of the bone, so that once said screws 2, 3 are coupled in the holes Ib, Ic respectively, the possible rotation of the implant 1 with respect to its accommodation in the medullary canal of the bone is prevented.

As stated, the system also includes a bolt element 4, whereby a support and support means for an external prosthesis is provided.

(not represented). This bolt element 4 is generally cylindrical, with a first portion 4c of greater diameter, and with a second portion 4a of smaller diameter and shorter than the first, which constitutes the distal end of the bolt, and which is sized to engage in the hole that of the implant 1, the relative positioning between both elements being ensured against an unwanted rotation of one of them relative to the other, by providing a pair of protuberances 4b extending according to the longitudinal direction of the bolt 4, from the stepped edge formed between both portions 4c and 4a of the bolt 4, in diametrically opposite positions, capable of engaging in respective respective recesses formed in respectively corresponding positions on the outer edge of the implant 1, in diametrically opposite positions with respect to the hole of receiving portion 4a of bolt 4. As can be seen in the representation, the pin 4 also has the formation of a head portion 4d in relation to the proximal end thereof. This head portion is approximately "prismatic, quadrangular, with a lateral dimension substantially larger than the diameter of the cylindrical portion 4c, and provides the base of attachment in the coupling with the outer prosthesis (not shown). The bolt 4 also has a through axial hole, sized to admit the passage and engagement of a fixing screw 5 and solidarity between the implant 1 and the bolt 4, for which purpose, said fixing screw 5 has a length such that, after extending to the entire full length of said bolt 4, can be threaded by its distal end inside the implant element 1.

As those skilled in the art will understand, an osteointegrated system such as the one just described, substantially improves the level of stabilization of the implant, since screws 2 and 3 prevent any unwanted rotation of said implant and of the external parts associated therewith. . The operative condition of the assembly can be seen more clearly in the representation of Figure 2, in which the assembly already assembled is linked to an alleged bone of an amputee, indicated with the numerical reference 6. The implant 1 is housed in the medullary canal βa, threaded in the latter, while the locking screws 2, 3 are directed perpendicularly to said bone 6, passing through inserts made therein to thread into the respective holes Ib, Ic of the implant, while guaranteeing an immobility of the latter regarding possible unwanted rotations. Bolt 4 is already fixed to Implant 1 with the help of the screw 5 (not visible in this Figure), and has the head portion 4a prepared for coupling with the corresponding prosthesis. The set is thus in its operational condition.

The implant system just described has the additional advantage that, by virtue of its positioning and its immobilization capacity, it is much more stable against longitudinal and torsional stresses, which gives it the ability to substantially shorten of the treatment and adaptation period.

Preferably, the implant construction materials will be such that they allow an appropriate osseointegration in the medullary canal of the bone, for which pure or other titanium of a similar nature is preferred; the rest of the elements can be constructed in titanium alloy, so that they provide a structural resistance according to the purposes for which they are intended.

It is not considered necessary to make the content of this description more extensive so that a person skilled in the art can understand its scope and the advantages derived therefrom, as well as to carry out the practical realization of its object.

Notwithstanding the foregoing, and since the description made corresponds only to a preferred embodiment, it will be understood that modifications and variations of detail may be introduced within its essential nature, also protected by the scope of the invention, limited only by the content of the claims that follow.

Claims

1.- Intramedullary osteointegrated system, for the coupling and fixation of a prosthesis in a trans-tumor and transhumeral amputated area, stable against longitudinal and torsional stresses and with the possibility of early loading with a shortening of the treatment and adaptation period, characterized in that the system It is composed of a set of elements such as: an implant element (1), prepared for coupling in the medullary canal (6a) of a long bone (6), generally cylindrical, externally threaded, provided with a hole ( the) axial which is accessed from the proximal end of the implant, and of two holes (Ib, Ic) directed radially in mutually longitudinally and angularly displaced positions, being further provided with a pair of recesses (Id) in correspondence with said end proximal, practiced in diametrically opposite positions with respect to the mentioned hole (the); a pair of locking screws (2, 3), prepared to engage in said holes (Ib, Ic) after crossing the bone (6), in order to prevent unwanted rotation of the implant (1) once lodged in the spinal canal; a bolt (4), constructed so as to have a first cylindrical portion (4c) of a first diameter, and a second cylindrical portion (4a) at the distal end, of a second diameter smaller than the first, forming a stepped transition between both portions, and said second portion (4a) being sized and prepared for engagement in the axial hole (la) of the implant (1), with protuberances (4b) extended according to the longitudinal direction of the bolt (4) towards the portion (4a) of smaller diameter from the stepping between both portions (4c, 4a), also presenting said bolt (4) a head portion (4d) associated with its proximal end, generally quadrangular prismatic and side substantially larger than the diameter of the first portion (4c) of the bolt (4), whose head (4d) constitutes the support base , coupling and support for the external prosthesis associated with the amputated bone portion, and a fixation screw (5), intended to perform the effective fixation between the bolt element (4) and said intramedullary implant (1), sized with a length such that after extending along an axial hole made in the bolt (4), a distal end portion of said screw (5) reaches to, and is screwed into, said implant element (1), in the inside of o axial hole of the latter.