FR2692140A1 - Partial prosthesis for replacement of knee joint - comprises condylar component implanted into lower end of femur, cooperating with shaped tibial plate supported by bone-embedded metal bar - Google Patents

Abstract

The prosthesis includes a femoral condylar component (5) cooperating with a tibial plate (6). A metal bar member (4) is implanted transversely in the upper part of the tibia, with a number of downwardly-projecting spikes (7) to anchor it in the spongy tissue (9) of the bone. The tibial plate of the prosthesis bears against the upper surface of the bar, and is shaped with a slightly concave upper surface (9) to cooperate with the condylar component. The condylar component, which is implanted into the tissue of the lower end of the femur, has a concave lower surface for rotary sliding engagement with the tibial plate. ADVANTAGE - Improved bone anchorage and load-bearing properties.

Description

 The present invention relates to a partial unicompartmental knee prosthesis.

The prostheses currently known are of the pivot type.

Other types of prostheses, with rails, allow the sliding movement of the lower bone on the upper bone.

However, joint necrosis linked to poor alignment of the femur and tibia is often observed.

 The unicompartmental prostheses located between the tibial osteotomies and the total prostheses, give good results. However, the evolution of the prosthesis over time often presents an asymmetrical sinking of the tibial part due to the absence of solid medial support.

 On the contrary, the aim of the present invention is to provide anterior and posterior cortical support near the massif of thorns. It includes a femoral condyle, a convex part of which is rotated on a slightly concave pad of a tibial plateau. The tibial plateau is supported on a spike bar anchored in the tibia.

 The device which is the subject of the present invention is therefore a partial unicompartmental knee prosthesis producing an articulation between a lower bone and an upper bone and comprising a femoral condyle and a tibial plateau characterized in that it comprises a bar placed transversely on a practiced section. in the lower bone of the joint and comprising pins adapted to anchor in the cancellous area of the lower bone, in that the tibial plateau bears on the barette and comprises a concave pad and in that the condyle femoral is anchored to the upper bone and has a convex shape adapted to slide in rotation on the concave pad.

 The following description made with reference to the accompanying drawings for explanatory purposes and in no way limiting it allows a better understanding of the advantages, aims and characteristics of the invention.

- Figure 1 shows a longitudinal section view of the joint and the prosthesis, - Figure 2 shows a bottom view of a bar shown in Figure 1, - Figure 3 shows a sectional view of the bar shown in Figure 2, - Figure 4 shows a view of a section of the lower bone shown in Figure 1.

 In Figure 1 are shown a joint 1, an upper bone 2 carrying an upper groove 10, a lower bone 3 having a cutting section 13 of median axis 14, a cancellous area 9, a hard part 18 and carrying a lower groove 11, a bar 4 carrying pins 7 and an upper surface 15, a femoral condyle 5, a tibial plate 6 comprising a slightly concave pad 8 and a seat 12.

 The joint 1 is formed by all of the elements shown in FIG. 1. The upper bone 2 is a femur. The lower bone 3 is a tibia. The lower bone 3 is cut along a plane perpendicular to the longitudinal axis of the lower bone over half its width, that is to say up to the median axis 14. This cut creates the bone section of the plateau tibial 13. The median axis 16 of the section of the lower bone is oriented perpendicular to the section plane of Figure 1.

 The bar 4 is made of metal. It is presented in Figures 2 and 3.

Rectangular and oriented transversely on a section 13 formed in the lower bone, that is to say perpendicular to the plane of FIG. 1, the bar 4 has on its lower surface rows of pins 7 placed in force in the cancellous region 9 of the lower bone 3. The bar 4 is placed in the lower groove 11 so that the upper surface 15 is level with the section 13 of the lower bone. The bar 4 is offset laterally relative to the median axis 14 of the section of the lower bone.

 The tibial plateau 6 comprises the seat 12 which is metallic and resting and cemented, on the one hand, on the section 13 of the lower bone and on the other hand, on the upper surface 15 of the bar 4.

 The concave pad 8 has a half-sphere shape. It is made of polyethylene.

 The concave pad 8 and the seat 12 are linked together by snap-fastening, for example in such a way that the tibial plateau is in one piece.

 The femoral condyle 5 is anchored to the upper bone 2 and has a convex shape adapted to slide back and forth on the concave pad 8.

 The upper bleed 10 is made in the upper bone. The femoral condyle 5 is anchored in this bleeding.

 It should be noted that the width of the femoral condyle 5 is adapted not to injure the soft parts, the flesh, the muscles or the ligaments which surround the joint 1.

 The convex shape of the femoral condyle 5 reproduces the anatomical curvature of the osteocartilaginous condyle. The width of the femoral condyle is optimized to allow both implantation without risk of sinking of the metal parts and without risk of overflow that could conflict with the soft parts.

 Finally, the femoral condyle 5 is cemented but can be easily removed.

 In FIG. 2 are shown the bar 4 carrying two rows 17 of pins 7 and comprising two longitudinal ends 16.

 In FIG. 3 are shown the bar 4, the pins 7, the longitudinal ends 16 and the upper surface 15 of the bar 4.

 In the two figures 2 and 3, the bar 4 is flat and rectangular. The rows 17 of pins 7 are placed longitudinally on this rectangle. The longitudinal ends 16 do not have pins. This absence of a spike is preferable in order to avoid the hard part 18 of the lower bone breaking during the forceful insertion of the spikes in the cancellous zone 9 and to avoid any contact of a spike with the soft parts which surround the joint 1.

 The length of the bar 4 is less than or equal to the dimension of the lower bone along the median axis 14.

 In Figure 4 is shown a view of a section of the lower bone 3 presented in Figure 1, along the plane of the bone section 13. There is the lower bone 3, the cancellous area 9, the bone section 13 , the lower groove 11, the bar 4, the longitudinal ends 16 of the bar 4, the central axis 14 and the hard zone 18 of the lower bone 3.

 FIG. 4 is easy to understand with reference to FIGS. 1, 2 and 3. The longitudinal ends 16 of the bar 4 come to bear on the hard zone 18.

 The bar 4 incorporated in the prosthesis object of the present invention has the advantage of being easy to position parallel and in contact with the mass of spines and thus provide anterior and posterior cartilage supports.

By means of this bar 4, the tibial plateau has an almost complete peripheral cortical support.

Claims (6)

 1. Unicompartmental partial knee prosthesis providing a joint (1) between a lower bone (3) and an upper bone (2) and comprising a femoral condyle (5) and a tibial plateau (6) characterized in that it comprises a bar (4) placed transversely on a section (15) formed in the lower bone of the joint and comprising pins (7) adapted to be anchored in the cancellous zone (9) of the lower bone in that the tibial plateau rests on the bar and has a concave pad (8) and in that the femoral condyle is anchored to the upper bone and has a convex shape adapted to slide in rotation on the concave pad.  2. Prosthesis according to claim 1 characterized in that the bar is rectangular, metallic and has two rows (17) of parallel pins.  3. Prosthesis according to claim 2 characterized in that the longitudinal ends (16) of the rectangle forming the bar do not have pins.  4. Prosthesis according to any one of the preceding claims, characterized in that the bar is positioned in force and in that its upper surface is level with the section (13) of the lower bone.  5. Prosthesis according to any one of the preceding claims, characterized in that the bar is offset laterally with respect to the median axis (14) of the section of the lower bone.  6. Prosthesis according to any one of the preceding claims, characterized in that the conca ve cushion has the shape of a hemisphere and is made of polyethylene and in that the tibial plateau comprises a metal seat bearing, on the one hand, on the section of the lower bone and on the other hand, on the barette.