FR2519248A1 - Ball and socket artificial hip joint - uses rugous case in medular cavity to house tail in one piece with pivot locating ball - Google Patents

Abstract

The artificial articulated condyle joint uses male and female ball joint fittings fixed to the respective bones (1,2) being connected. The male (14) is built onto a rigid pivot (15) which houses in to a case (3) with a rugous (7) external surface and rigid but deformable walls. The case is secured in the medullary cavity by freshly bone once the cement has set. The pivot may have a recessed tail (19) with a smooth surface, whilst the case has longitudinal slits (9,10) opening out near the joint. The case also has holes (24) near the slit mouths and its bottom end is plugged (13). The ball (14) may be machined to house onto a tapered stub axle and the case may comprise round (4) and oval (5) sections.

Description

 The absolute rigidity of these monobloc prostheses does not allow to adapt to multiple femoral forms. A large range of prostheses of all sizes is therefore needed, leading to a noticeable increase in their cost price.

 Ablation (because of sepsis for example) of type of prosthesis is generally laborious, if not impossible. In any case it is decadent for the femur.

 The object of the present invention is to avoid the drawbacks by producing a joint bone prosthesis that can accommodate various morfliologies of the same type of bone, without the possibility of cement splitting being possible in the medullary cavity, while finally eradication remains possible when in case of reinter vention the surgeon wishes to replace the prosthesis.

An osteological joint prosthesis according to the invention comprises a socket and a male ball joint each to one of the two bones of the joint, and is characterized in that the male ball joint is integral with a rigid pivot , which is housed for cementing ~ ~ using a cement in an independent sheath rigid walls but deformable, whose outer peripheral face comprises uq large number of asperities and crevices so as to ' constitute a restorative prosthesis after its placement in the medullary cavity of the bone
According to another characteristic of the invention, the pivot has a smooth tail slightly undercut, that is to say whose free end is stamincissant to facilitate its possible subsequent extraction.

 According to another feature of the invention, the sleeve is split longitudinally close to the joint to promote its deformability during installation.

 According to another characteristic of the invention, the end of the sheath farthest from the joint is closed, to prevent any untimely flow of cement to the medullary cavity.

 According to another characteristic of the invention, the edge of the sheath closest to the joint is pierced with openings on either side of each longitudinal slot, to promote a rustling made by the bone itself when it repels, or by the cement after its solidification.

 The method according to the invention for the establishment of a prosthetic joint of the kind specified is characterized in that it comprises the following successive phases a) the empty rehabable sheath is introduced into the medullary cavity where it fits exactly due to its deformability, cement is poured into the sheath; the male swivel pin is in the cement contained within the sheath and the hardening of said cement is awaited.

 The method according to the intention for the extraction of a joint prosthesis of the specified type is characterized in that it comprises the following successive phases: a) the pivot is extracted from its cement sheath, which is facilitated by the smooth forest and stripped of the tail of the pivot; b) the thin layer of hardened cement present in the pile is broken up; c) the empty sleeve being flexible again, it is removed by detaching it from the inside of the bone.

 The accompanying drawing, given by way of example, will provide a better understanding of the advantages of the invention.

 Fig. 1 shows in longitudinal section, a total hip prosthesis according to the invention after its introduction into a femur and into the acetabular cavity of the corresponding pelvic bone.

 Fig. 2 is a perspective view of the rehabable sheath of the prosthesis.

 Fig. 3 is a perspective view of the pivot of the prosthesis.

 Fig. 4 shows in perspective the nail ball joint coni ue of the prosthesis.

 Fig. 5 is a perspective view of the screwed acetabulum of the prosthesis.

Fig. 6 is a schematic perspective of the empty sheath, illus
the shape variation of its cross-section.

There is shown in the drawings a prosthesis according to the invention,
intended to be implanted between a femur 1 and an iliac bone 2 to form the hip joint.

 The prosthesis according to Figure i, comprises a femoral sheath (3) in the general form of a tubular jacket hollow, flared and thin whose section is circular in (4) on a third of its length, then tutelage is oval in ()) in the evacuated area of interest for two-thirds of the length.

 The largest dimension of this oval is increasing on the Sur and as we approach the opening of the femoral sheath.

 The outer wall (6) of the sheath (3) has a surface covered with multiple asperities and crevices (7) likely to be rehabilitated by the neo-formed bone.

 The inner wall (8) of the sheath (3) is completely smooth to allow complete eradication of the cement.

 Two slots (9) and (10) divide longitudinally the sheath (3) over the entire length of the portion (5). They are practiced opposite and perpendicular to the largest dimension of the oval section of the sheath (3).

 They confer an indispensable elasticity of deformation in the thin sheath (3). At the endmost end of the sheath (3), and in the same plane as the slots (9) and (10), a cutaway (11) is practiced, at an angle of about 15a to facilitate the introduct'on the sheath (3) in the femur (1).

 At the lower end of the cylindrical portion (4) of the sleeve (3), an internal thread (12) is provided for receiving a threaded plug (13) made of plastic material.

 The ball joint (14) of the joint is carried by a rigid pivot (15).

 According to Figure 3, the pivot (15) has at its upper part a base (16) extended by a neck (17), itself ending in a truncated cone (18). At its lower part the pivot (15) ends with a tail (19) which is both smooth and thinned towards its end in a contoured profile.

 Figure 4 shows a sphere constituting the male ball (14).

It comprises a conical orifice (20) embossing on the trunk of cane (18) of the pivot (15) as shown in Figure 1.

 Figure 5 shows the prosthetic acetabulum (21) preferably with screw thread (22). A plastic interposition (23) having a half + Pher shaped recess is fitted into the prosthetic acetabulum (21). It constitutes the female ball joint and serves as a seat for rotation to the sphere (14).

 The openings (24) are pierced in the sleeve (3) on either side of the slots (9), (10).

Operation is as follows
For the placement of the prosthesis, the surgeon begins by introducing the sheath (3) in the medullary cavity of the femur where it rests very accurately with many points of support, because of its deformability. This is due both to the presence of the slots (9), (10) and the fact that the walls of the sheath (3) are thin.

 Then, the surgeon injects the pasty cement (25) into the sheath (3), then engages the tail (19) of the pivot (15). The sheath (3) and its plug (13) prevent any contact of the cement with the organic tissues. After its solidification, the cement (25) is in the openings (24) locking pins which prevent any opening of the slots (9), (10) under the weight of the body and the thrust of the pivot (I-).

 The whole is a rigid block, well tolerated by the organization.

 In addition, the fixation of the sheath (3) in the femur by bone proliferation in the anfractuosities (7) takes place both quickly and firmly due to the quality of the contact between the bone and the sheath (3).

 The system relating to the invention makes it possible to design a total hip prosthesis called "rehabitable" non-traumatic for the bone since flexible in its implementation phase, and rigid and dimensionally stable in its functional phase.

 It eliminates cardiac and other accidents due to the transport of chemical substances in the body. It preserves intact the biomechanical qualities of the bone given the absence of contact oscillation.

When against the surgeon wants to extract a prosthesis implanted in a femur, it protic in three times
1 time: remove the pivot from its cement sheath, which is relatively easy since its tail is smooth and slightly undercut.

 2 times: breaking up the thin layer of cement with the "chisel struck" eradication can be total and without difficulty.

 3 times: remove by taking off the sheath flexible once again due to the absence of pivot and the destruction of the rigid structure that gives the cement.

 The cost price of the pivots can be decreased substantially because of their constant size.

 It should be noted that the devices of the invention are made of a biologically compatible material, preferably for the present invention, a titanium alloy for the sheath, the pivot and the acetabulum screwed, and ceramic for the spherical ball.

 It should further be understood that the foregoing description has been given by way of example only and that it in no way limits the scope of the invention which would not be overcome by replacing the materials and the details of execution. described by any other equivalent.

 It goes without saying that the system according to the invention may be stetched to all other implanted articular prostheses.

With regard to the method of setting up, the surgeon can stretch calibrated the femoral canal to the reamer, before introducing the sleeve 3rd
Finally, it will be noted that the inner walls of the sheath 3 are smooth and flared upwards, which, in the case of ablation of the prosthesis, makes it possible to easily extract the sheath 3, the cement core 25 which is solidified therein. For that, it is enough to break the small cement pions housed in the openings 240

Claims (8)

4EVENDIC4TIONS  1 - osteological articulation prosthesis comprising a female retula and a rotatable socket each to fix on one of the two bones of the articulation X characterized in that the patella tle (14) is integral with a rigid pivot (15) , which is housed in an independent sheath (3) with rigid walls, but deformable, whose outer peripheral face has a large number of gaps and crevices (7) so as to constitute a rehabitable prosthesis after its establishment in the medullary cavity of the bone and hardening of the cement.  2 - prosthesis according to claim 1, characterized in that the pivot (15) has a tail (19) smooth and light undercut.  3 - prosthesis according to claim 1, characterized in that the sheath (3) is interrupted laterally by two longitudinal slots (9), (10) open near the joint.  4 - Prosthesis according to any one of the preceding claims, characterized in that the end of the sheath (3) farthest from the ball (14) is closed by a plug (13).  5 - prosthesis according to claim 3 g characterized in that the sheath (3) has its wall closest to the ball (15) pierced with openings (24) located on either side of each of the slots (9), ( 10).  6 - Prosthesis according to any one of the preceding claims, characterized in that the sphere of the male ball (14) is removable 2 pierced with a conical orifice (20) which allows its adaptation to a truncated tip (18 ) integral with a neck (17) of the pivot (3) 0  7 - prosthesis according to any one of the preceding claims d characterized in that the shape of the sheath (3) is substantially cylindrical of revolution in (4) over 1/3 of the length to give at this location a circular cross section k then that it is oval in (5) in the flared zone interesting the other two thirds of its length.  8 - prosthesis according to any one of claims 1 to 7, characterized in that the inner wall of the sleeve (3) is both smooth and flared upwardly.