ANTI-DISLOCATION BILATERAL HIP PROSTHESIS

Abstract: The present invention relates to an anti-dislocation bilateral hip prosthesis (1) comprising a stem (2), that is introduced within a corresponding vertical hole realised into the femur, a femoral head (4), that is inserted within a corresponding hole realised into the collum femoris, and that couples with said stem (2), said femoral head (4) having a joint spherical end, an acetabular cotyle (7), implanted in the pelvis and an anti friction acetabular cup (8), provided between said acetabular cotyle (7) and said spherical end of the femoral head (4).

Description: ANTI-DISLOCATION BILATERAL HIP PROSTHESYS The present invention relates to an anti-dislocation bilateral hip prosthesis. More particularly, the invention relates to prosthesis of the above kind, realised in such a way to allow a remarkably higher mobility of the lower limbs with respect to what can be obtained by the present prosthesis. Hip prosthesis presently available on the market allows a sufficient gait, but they are characterised y a high dislocation risk. In fact, known hip prosthesis are characterised by remarkable drawbacks. First of all, it must be mentioned the fact that the allow a limited gait mobility for the lower limbs, and particularly limited flexion, adduction and extension. As far as flexion is concerned, i.e. the flexion of the lower limb toward the torso, the maximum reachable angle by the limb is of 90°. During the adduction, i.e. the flexion of the lower limb backward, the maximum reachable angle is of 10°, while in the extension, or flexion of the lower limb along a rear plane, the maximum reachable angle is of 10° with respect to the human body axis when in an erected position. In case the prosthesis is stresses beyond the above-mentioned values, they dislocate, requiring an urgency recovery with the hospital, to reduce the dislocated prosthesis, with the consequent need of being subjected to a general anaesthesia. All the above induces in the patient a high anxiety due to the possibility of the occurrence of a dislocation. In view of the above, the Applicant has realised a hip prosthesis able to solve the above-mentioned drawbacks, mainly allowing a higher gait freedom and remarkably reducing the dislocation risk. By the solution according to the invention, as already said, it is obtained an optimum gait mobility for the lower limbs, with particular reference to the flexion, adduction and extension. Particularly, the solution according to the present invention allows to obtain a limb flexion of about 127°, an adduction angle of 50° and an extension angle of about 42°. Furthermore, by the solution according to the invention, in case the above mentioned values are passed, the prosthesis does not dislocate under standard conditions, i.e. while sleeping, seating, going up and down the stairs, sleeping, etc. with the consequent practical and psychological advantages for the patient. It is therefore specific object of the present invention an anti- dislocation bilateral hip prosthesis comprising a stem, that is introduced within a corresponding vertical hole realised into the femur, a femoral head, that is inserted within a corresponding hole realised into the collum femoris, and that couples with said stem, said femoral head having a joint spherical end, an acetabular cotyle, implanted in the pelvis and an anti friction acetabular cup, provided between said acetabular cotyle and said spherical end of the femoral head. Preferably, according to the invention, said anti friction acetabular cup is kept within the acetabular cotyle by a ring. Particularly, according to the invention, said stem has a truncated cone section, and can be comprised of metallic material, such as titanium alloy, or AISI 316 L stainless steel, or any other anti-rejection material. Still according to the invention, said femoral head can be coupled with said stem by threading, truncated cone coupling, etc. Preferably, said femoral head can be comprised of metallic material, such as titanium alloy, or AISI 316 L stainless steel, or ceramic material, or any other anti-rejection material. Particularly, for the fixing of the femoral head to the stem, a locking screw can be provided, acting along the axis of the stem. Furthermore, according to the invention, said acetabular cotyle can be implanted in the pelvis by screws, or it is cemented, or fixed, or fixed in any other way. Further, said acetabular cotyle can be comprised of metallic material, such as titanium alloy, or AISI 316 L stainless steel, or any other anti-rejection material. Always according to the invention, said anti friction acetabular cup can be comprised of non-toxic polyammidic material according to the F.D.A. rules N° C.F.R. 177.2415 and the UE rules N° 90/128/E.E.C, or of ceramic material or any other anti-rejection material. Still according to the invention, said ring provided between the acetabular cup and the femoral head can be fixed to the acetabular cotyle by screws. Preferably, said ring can be comprised of non-toxic polyammidic material according to the F.D.A. rules N° C.F.R. 177.2415 and the UE rules N° 90/128/E.E.C. The present invention will be now described, for illustrative but not limitative purposes, according to its preferred embodiments, with particular reference to the figures of the enclosed drawings, wherein: figure 1 is a perspective view of an embodiment of a hip prosthesis according to the invention; figure 2 is a vertical section view of the hip prosthesis of figure 1 ; figure 3 is an exploded view of the hip prosthesis of figure 1; figures 4a and 4b show the operation of the prosthesis according to the invention during the flexion, figures 5a and 5b show the operation of the prosthesis according to the invention during the adduction; and figures 6a and 6b show the operation of the prosthesis according to the invention during the extension. Observing first the figures 1 - 3 of the enclosed drawings, it is shown a preferred embodiment of the hip prosthesis according to the invention, which is generically indicated by the reference number 1. The prosthesis according to the invention comprises a plurality of elements, among which a stem 2, that is implanted within the femur 3 (see figure 2). Said stem 2 is realised in such a way to obtain a truncated cone sealing, or cemented, or of a different kind, and it is comprised of metallic material, such as titanium alloy, or AISI 316 L stainless steel, or any other anti-rejection material. By the reference number 4 it is indicated a femoral head, that is coupled with the stem 2 by thread 5 with a truncated cone coupling. Said femoral head 4 is comprised of metallic material, such as titanium alloy, or AISI 316 L stainless steel, or ceramic material, or any other anti-rejection material. When the stem 2 and the femoral 4 are implanted (figure 2), their locking each other occurs by the locking screw 6, preferably comprised of metallic material, such as AISI 316 L stainless steel. BY the reference number 7, it is indicated the acetabular cotyle, that is implanted in the pelvis by screws,, or it is cemented, or fixed, or fixed in any other way. The acetabular cotyle 7 is comprised of metallic material, such as titanium alloy, or AISI 316 L stainless steel, or any other anti-rejection material. Between the femoral head 4 and the acetabular cotyle 7 it is provided the anti friction acetabular cup 8, that is kept into the acetabular cotyle 7 by the ring of the acetabular cup 8. It is comprised of non-toxic polyammidic material according to the F.D.A. rules N° C.F.R. 177.2415 and the UE rules N° 90/128/E.E.C, or of ceramic material or any other anti-rejection material. It is further provided a ring 9 of the anti dislocation sealing acetabular cup 8. Said rig is fixed to the acetabular cotyle 7 by screws 10. The ring 9 is comprised of non-toxic polyammidic material according to the F.D.A. rules N° C.F.R. 177.2415 and the UE rules N° 90/128/E.E.C. Said screws 10 are preferably flared head screws, preferably comprised of metallic material, such as AISI 316 L stainless steel or titanium alloy, or any other anti-rejection material. In figures 4a and 4b it is shown the flexion functionality of the prosthesis 1 according to the invention allowing to reach a flexion angle of 127°. In figures 5a and 5b it is shown the flexion functionality of the prosthesis 1 according to the invention allowing to reach an adduction angle of 50°. In figures 6a and 6b it is shown the flexion functionality of the prosthesis 1 according to the invention allowing to reach an extension angle of 42°. The structure of the prosthesis according to the invention is such that, even the above mentioned gait values are passed, dislocation does not occur in the already mentioned standard conditions. In this way, the person subjected to a surgical intervention obtains a better safety condition. The fact that the dislocation does not occur is due particularly to the presence of the containment rings 9 of the femoral heads 4, opposing a controlled resistance, established before by the orthopaedic surgeon, for example with a value between 500 g and 15 kg, or higher, in function of the patient weight. However, in case the above values and stresses are passed, dislocation occurs, since it is necessary to save the integrity of the osseous tissue on which the prosthesis is implanted. The solution according to the invention allows an easy "closed view" reduction of the prosthesis 1, i.e. without surgical intervention, as occurs in case of dislocation of the known prosthesis, with a general anaesthesia. The reduction of the prosthesis according to the invention only requires a specialistic orthopaedic intervention, that is carried out lengthening the lower limb and its extension according to the adduction direction for about 30°. In this way, prosthesis 1 according to the invention are easily reduced since the femoral heads 4 in that point have the spherical profile comprised of a ring shaped bas-relief having such dimensions to freely allow the reductions in the acetabular cups 8 without any stress. After the reduction of the prosthesis, functionality and stability are not modified with respect to the original condition. Another remarkable advantage obtained by the prosthesis 1 according to the invention concerns the implantology intervention. In fact, by the prosthesis according to the invention (figure 2), in the upper portion of the femur, a vertical truncated cone vertical hole is realised, and a cylindrical hole is realised in the portion of the collum femoris without the necessity of carrying out any excavation and rescission of the upper portion of the femur. The present invention has been described for illustrative but not limitative purposes, according to its preferred embodiments, but it is to be understood that modifications and/or changes can be introduced by those skilled in the art without departing from the relevant scope as defined in the enclosed claims.

Claims: CLAIMS 1. Anti-dislocation bilateral hip prosthesis, characterised in that it comprises a stem, that is introduced within a corresponding vertical hole realised into the femur, a femoral head, that is inserted within a corresponding hole realised into the collum femoris, and that couples with said stem, said femoral head having a joint spherical end, an acetabular cotyle, implanted in the pelvis and an anti friction acetabular cup, provided between said acetabular cotyle and said spherical end of the femoral head. 2. Anti-dislocation bilateral hip prosthesis according to claim 1 , characterised in that said anti friction acetabular cup is kept within the acetabular cotyle by a ring. 3. Anti-dislocation bilateral hip prosthesis according to one of the preceding claims, characterised in that said stem has a truncated cone section. 4. Anti-dislocation bilateral hip prosthesis according to one of the preceding claims, characterised in that said stem is comprised of metallic material, such as titanium alloy, or AISI 316 L stainless steel, or any other anti-rejection material. 5. Anti-dislocation bilateral hip prosthesis according to one of the preceding claims, characterised in that said femoral head is coupled with said stem by threading, truncated cone coupling, etc. 6. Anti-dislocation bilateral hip prosthesis according to one of the preceding claims, characterised in that said femoral head is comprised of metallic material, such as titanium alloy, or AISI 316 L stainless steel, or ceramic material, or any other anti-rejection material. 7. Anti-dislocation bilateral hip prosthesis according to one of the preceding claims, characterised in that for the fixing of the femoral head to the stem, a locking screw is provided, acting along the axis of the stem. 8. Anti-dislocation bilateral hip prosthesis according to one of the preceding claims, characterised in that said acetabular cotyle is implanted in the pelvis by screws, or it is cemented, or fixed, or fixed in any other way. 9. Anti-dislocation bilateral hip prosthesis according to one of the preceding claims, characterised in that said acetabular cotyle is comprised of metallic material, such as titanium alloy, or AISI 316 L stainless steel, or any other anti-rejection material. 10. Anti-dislocation bilateral hip prosthesis according to one of the preceding claims, characterised in that said anti friction acetabular cup is comprised of non-toxic polyammidic material according to the F.D.A. rules N° C.F.R. 177.2415 and the UE rules N° 90/128/E.E.C, or of ceramic material or any other anti-rejection material. 11. Anti-dislocation bilateral hip prosthesis according to one of the preceding claims, characterised in that said ring provided between the acetabular cup and the femoral head is fixed to the acetabular cotyle by screws. 12. Anti-dislocation bilateral hip prosthesis according to one of the preceding claims, characterised in that said ring is comprised of non- toxic polyammidic material according to the F.D.A. rules N° C.F.R. 177.2415 and the UE rules N° 90/128/E.E.C.

Inventors: CALDARONI DONATO, CALDARONI FIORE, CALDARONI, DONATO, CALDARONI, FIORE
Applicants: CALDARONI DONATO, CALDARONI FIORE, TECNOMECCANICA SRL, CALDARONI, DONATO, CALDARONI, FIORE, TECNOMECCANICA S.R.L.
Application year: 2000
Main classification: A61F2
IPC codes: A61B17, A61F2, A61L27