AN ORHTOPAEDIC PROSTHETIC DEVICE

Abstract: An orthopaedic prosthetic device (11) applicable to pairs of bone stumps, proximal and distal, of a skeletal segment (12) in which a complete fracture or surgery was followed by a loss of bone material, defining a distance (D) between the respective opposite heads (1a, 2a) of the stumps, the device (11) comprising a tube (3) made of biocompatible, bioresorbable material, may be fitted between the pair of bone segments (1, 2) and has means (4) for fixing the ends, which are also made of biocompatible, bioresorbable material, these means fixing it to the bone segments (1, 2) to define a chamber (C) for protection, guidance and regeneration of the callus between the said two opposite heads (1a, 2a) with which it binds; the tube (3) may also be made of a bone integrating material which can be resorbed and amalgamate with the callus which regenerates within the chamber (C) and into it.

Description: Description An orthopaedic prosthetic device Technical Field The present invention relates to an orthopaedic prosthetic device which may be used in the treatment of comminuted and localised fractures, or when a portion of skeletal segment is removed during surgery, for example, during the removal of a bone tumour. In particular, the present invention relates to an orthopaedic prosthetic device shaped and structured so as to allow, guide and facilitate the repair of the skeletal segment damaged, in those cases in which there is a loss of bone material between the two stumps of the segment which prevents the correct recomposition of the bone segment and the drawing together and contact of the ends of the two stumps. Background Art Many osteosynthesis techniques are currently known in the orthopaedics sector which, through the use of auxiliary synthesis devices called internal or external fixators, tend to allow the repair of fractures and so the regeneration of the callus. As regards external fixators, there are devices which allow more rapid cohesion of the callus forming in the damaged zone, and rapid readjustment to the load upon the bone itself, since they are able to keep the anatomical axis of the damaged skeletal segment aligned as it heals. Moreover, in those cases in which a portion of bone material is missing from the distal and proximal stumps of the damaged skeletal segment, so that they are distanced from one another, internal fixators may be used, normally consisting of metal plates fixed to the bone stumps by suitable fixing means, which can only contain from the structural viewpoint of the connections, or grafts of pieces of bone from the bone bank. If the fracture is not complete, or if there is no loss of bone material, intermedullary pins are normally used, applied along the anatomical axis of the fractured bone. Obviously, these means of synthesis are intended to create structures with mechanical specifications for the support and rigid blocking of the stumps of the damaged skeletal segment, said means being able to guarantee the correct position of the stumps as they heal. In other words, these means of synthesis are mechanical structures, either temporary, which are removed once the skeletal segment has healed, or permanent, which from the bio echanical load-bearing viewpoint, substitute the bone structure of the skeletal segment to which they are applied, as well as making use of the bone induction and bone conduction of the callus during the healing stage. In all cases involving the use of these means of synthesis, the damaged skeletal segment regenerates spontaneously, thus the means of synthesis are only structural mechanical means able to facilitate the mobility of the patient, but do not directly affect the regeneration of the callus of the skeletal segment, and so are distinct from the callus which regenerates spontaneously. Disclosure of the Invention The object of the present invention is to provide an orthopaedic prosthetic device which may be applied at two stumps of a skeletal segment, creating a chamber for the regeneration of the callus which guarantees a more rapid growth of the callus and reduces the time required for repair of the damaged part, which can both bind and directly amalgamate with the callus regeneration process and co-operate, where necessary, with the said internal and external fixators. The present invention relates to an orthopaedic prosthetic device, in particular applicable to at least two bone stumps, proximal and distal, deriving from a fracture of a skeletal segment, whose respective heads are opposite and at a distance deriving from a loss of bone material from the said skeletal segment, such as to prevent correct repositioning of the segment by bringing together and creating a substantial contact between the heads of the relative stumps, characterised in that the device comprises a tube made of biocompatible, bioresorbable material, which may be inserted between the two bone stumps, containing, at the two opposite ends, part of the respective heads of the stumps and having, at its own ends, means made of biocompatible, bioresorbable material for fixing to the heads of the bone stumps, the tube being shaped and structured so as to define, at least over the distance separating the two stumps, a chamber for the protection, guidance and regeneration of the callus of the heads of the stumps of the skeletal segment, designed to bind with the callus and become an integral part of it. The present invention is described below with reference to the accompanying drawings, which illustrate a preferred embodiment, and in which: Figure 1 is a schematic front view of the orthopaedic prosthetic device disclosed, applied to two long bone segments and in combination with a conventional means of synthesis, such as an external fixator; figure 2 is a perspective view of an alternative embodiment of the device shown in figure 1; figures 3 to 5 show alternative embodiments of the device shown in the previous figures. With reference to the accompanying drawings, the orthopaedic prosthetic device which is the subject matter of the present invention is indicated as a whole by the number 11. In figure 1, the prosthetic device 11 is shown applied to a skeletal segment 12 affected by a comminuted complete fracture or which has undergone surgery involving the removal of a portion of the segment 12 itself, for example removal of a tumour, and so has suffered a loss of bone material. The numbers 1 and 2 are used to indicate a pair of bone stumps, proximal 1 and distal 2, positioned at a distance D from one another, deriving from the afore-mentioned loss of bone material, their respective heads la and 2a being opposite one another. Again in figure 1, the device 11 is in combination with a conventional means of synthesis 16, for example, an external fixator The distance D between the bone segments 1 and 2 is a function of the size of the comminuted complete fracture suffered, or of the portion of bone affected by a tumour removed. According to the present invention, the device 11 comprises a tube 3 made of biocompatible, bioresorbable material, which is inserted between the said pair of bone stumps 1 and 2. The ends 3a and 3b of the tube 3 are attached to part of the two bone stumps 1 and 2, thus defining a chamber C, for protection, containment, guidance and regeneration, within which a callus can regenerate to rejoin the two bone stumps 1 and 2. The tube 3 may have the shape of a cylinder or truncated cone, depending on the damaged bone zones, that is to say, it attempts to copy the development profile of the bone according to the part concerned. As already indicated above, the tube 3 is used only to define a chamber C for regeneration of the callus, is made of various biocompatible, bioresorbable materials and has new applications in the orthopaedics sector, by which the chamber C binds with the callus which regenerates inside it. In a first embodiment, the tube 3 may be made of biocompatible and bioresorbable material. Therefore, in this case the tube 3 constitutes a chamber C for regeneration of the callus, which is able to guide and correctly contain such growth of the skeletal segment 12, and at the same time be completely resorbed by the human body. More specifically, the tube 3 is made of a material with special chemical and physical properties which render it compatible with the area surrounding bone segments 1 and 2, and also allow a controlled resorption over time, depending on the time required for the generation of the said callus between the two bone segments 1 and 2. In other words, it must be possible for the material used for the tube 3 to be resorbed within the body in a time practically equal to the time necessary for generation of the callus. To obtain these properties, the tube 3 is made in various sizes and preferably of a polymer: for this purpose, in medical fields polylactic materials such as PLA, PLLA or PGA are known, as well as polyhydroxybutyrate or polycaprolactone (all biocompatible materials which are resorbed by the human body) . As shown in figure 2, the tube 3 has end fixing means 4 which fix the tube 3 between the two bone segments 1 and 2 at the respective heads la and 2a this effectively defines the sealed chamber C for bone protection and regeneration between the two opposite heads. These fixing means 4 may be screws 7 which can be inserted in purpose made through-holes 8 made in the ends of the tube 3 (see figure 2) and screwed directly onto the heads la and 2a of the two bone segments 1 and 2 Similarly, small plates 9 may be used (see figure 3), fixed to the tube 3 and the ends of the bone segments 1 and 2, again using screws 10: in both cases, all elements which constitute the fixing means 4 are made of biocompatible and bioresorbable material, like the tube 3 In another embodiment, the tube 3 may be made of a material with bone integrating properties, for example, a ceramic material This type of material, which may be either impermeable or porous, has chemical and physical properties which allow the tube 3 to amalgamate and compact itself with the callus which is generated inside the chamber C between the heads la and 2a of the stumps 1 and 2, forming a single body with the callus itself, which resorbs the tube 3. In other words, in this case the tube 3 constitutes a base with bone conduction and bone induction properties, which can form a single seamless body with the skeletal segment 12 to which it was applied. In the embodiments illustrated m figures 1, 3 and 5, the tube 3 has respective inlet and/or outlet means 5 allowing communication between the chamber C and the outside The means 5 applied to the tube 3, allow probes or suitable surgical apparatus to be inserted in the chamber C so as to check, sample and disinfect the internal zone of the chamber C, or allow the introduction of liquids intended to increase the bone growth factor. These outlet and/or inlet means 5 may consist of a single conduit 6 or catheter (figure 3) made of biocompatible material, one end 6a of which leads into the tube 3, whilst the other end 6b leads directly to the outside of the skeletal segment upon which the tube 3 is fixed; here the catheter 6 may be fitted with safety means (e.g.: a non-return valve, not illustrated here) which prevent the accidental entrance of foreign bodies into the chamber C. The embodiment with at least one pair of conduits 6 and 15 (figure 5) is recommended for disinfecting the inside of the chamber C: one of the catheters is used to introduce sterilising agents, whilst the other allows the "dirty" liquid to be drawn out of the chamber C, so that one of the catheters is always completely "aseptic", for the introduction of any pharmaceuticals subsequently required. In the embodiment illustrated in figure 4, the tube 3 may consist of two complementary longitudinal halves, labelled 17 and 18 respectively, which, using suitable connectors 13, can be assembled to define the chamber C. This embodiment allows the easier, more rapid application of the tube 3 between the two stumps, distal 1 and proximal 2, of the skeletal segment 12. The embodiment illustrated in figure 5 envisages that the internal surface 3c of the tube 3, that is to say, the surface which defines the chamber C, is lined with a layer of biocompatible and bioresorbable material, labelled 14, which can be loaded with slow-release substances which facilitate the reproduction of the callus inside the chamber C. The layer 14 of biocompatible and bioresorbable material may also be used to form sites for cell cultures, such as bone marrow cells and osteoblasts . This embodiment, therefore, has significant advantages, one of which is the method of application, which envisages only one surgical operation, that involving connection of the device, thanks to the bone integration and/or bioresorbable nature of the entire device. Moreover, the idea of isolating the bone regeneration zone within a chamber C, which in some cases is substantially sealed, allows the following to be obtained: greater control and acceleration of the growth of the callus; maintenance of an aseptic environment, with the possibility of introducing both liquid sterilising agents and agents which promote bone growth, thanks to the conduits connected to the chamber C. In some special cases, preferably during application of the tube 3, bone splinters may be inserted in the chamber C, further increasing the bone regeneration process, without these splinters being dispersed. Isolation of the chamber C and all of the agents which it contains allows, on the whole, a considerable increase in the efficiency of the liquids and bone splinters in their bone regenerating role. The present invention may be subject to numerous modifications and variations, all of which are encompassed by the design concept.

Claims: Claims 1. An orthopaedic prosthetic device, in particular applicable to at least two bone stumps, proximal (1) and distal (2) , deriving from a fracture of a skeletal segment (12) , said stumps being positioned with the respective heads (la, 2a) opposite one another and at a distance (D) deriving from a loss of bone material from the said skeletal segment (12) which prevents the correct repositioning of the said segment (12) by drawing together and creating a substantial contact between the heads (la, 2a) of the relative stumps (1, 2), characterised in that the device comprises a tube (3) made of biocompatible and bioresorbable material which may be inserted between the said pair of bone stumps (1, 2), containing, at the two opposite ends (3a, 3b) , parts of the heads (la, 2a) of the stumps (1, 2), and having at its ends (3a, 3b), means (4) made of biocompatible and bioresorbable material for fixing to the heads (la, 2a) of the bone stumps (1, 2) ; the tube (3) being shaped and structured so as to define, at least for the entire distance (D) separating the two stumps (1, 2), a chamber (C) for the protection, containment, guidance and regeneration of the callus of the heads (la, 2a) of the said stumps (1, 2) of the skeletal segment (12), designed to bind with the callus and become an integral part of it. 2. The device as described in claim 1, characterised in that the tube (3) is made of a bioresorbable material with physical and chemical properties which guarantee a controlled resorption over time, depending on the time necessary for regeneration of the callus between the two bone stumps (1, 2) . 3. The device as described in claim 1, characterised in that the tube (3) has at least means (5) for connecting the said chamber (C) to the outside environment, for introduction into the chamber of pharmaceuticals and/or biological substances. 4. The device as described in claim 3, characterised in that the said means (5) for connection to the outside environment consist of at least one conduit (6) or catheter, one end (6a) of which leads into the tube (3), and the other end (6b) leading to the outside of the skeletal segment (12) . 5. The device as described in claim 3, characterised in that the means (5) for connecting the chamber (C) to the outside environment include a further outlet conduit (15) , one end (15a) of which leads into the tube (3), the other end (15b) leading to the outside of the skeletal segment (12) . 6. The device as described in claim 1, characterised in that the tube (3) is preferably made of a polymer. 7. The device as described in claim 1, characterised in that the tube (3) is made of a biocompatible material, said material having physical and chemical bone integration properties, and being designed to amalgamate and compact itself with the callus generated between the two heads (la, 2a) of the bone stumps (1, 2) . 8. The device as described in claim 7, characterised in that the said material with bone integration properties is a bioceramic material. 9. The device as described in claim 8, characterised in that the said bioceramic material is a porous and permeable material. 10. The device as described in any of the previous claims, characterised in that the tube (3) consists of at least two longitudinal halves (17, 18), each having connecting means (13), said halves being biocompatible and designed to guarantee stable assembly of the tube (3) . 11. The device as described in any of the previous claims, characterised in that the internal surface (3c) of the tube (3) delimiting the chamber (C) is lined by a layer (14) of biocompatible and bioresorbable material which may be loaded with slow-release substances that facilitate the reproduction of the callus. 12. The device as described in any of the previous claims, characterised in that the internal surface (3c) of the tube (3) delimiting the chamber (C) is lined by a layer (14) of biocompatible and bioresorbable material, said layer being designed to form the site of cell cultures, such as bone marrow cells and osteoblasts which promote the reproduction of the callus . 13. The device as described in any of the previous claims, characterised in that the tube (3) has the shape of a cylinder or truncated cone. 14. The device as described in any of the previous claims, characterised in that the tube (3) defines a chamber (C) , said chamber being substantially sealed.

Inventors: FINI MILENA, GIARDINO ROBERTO, FINI, MILENA, GIARDINO, ROBERTO
Applicants: FINI MILENA, GIARDINO ROBERTO, ISTITUTI ORTOPEDICI RIZZOLI, FINI, MILENA, GIARDINO, ROBERTO
Application year: 1996
Main classification: A61B17
IPC codes: A61B17, A61F2