RU2355363C1 - Hip joint endoprosthesis - Google Patents

Abstract

FIELD: medicine; orthopaedics and traumatology.

SUBSTANCE: endoprosthesis comprises a hip component, a head, a neck, a trochanteric portion, a leg with an axial canal, with stepped windows on the lateral surface comprising notches and provided with spring-loaded petals. The latter is covered with grooved faces while being pulled out and provided with a shaft arranged in said canal. Endoprosthesis is equipped with a guide disk with a shaft-hole and latching springs, a support ball and three-flange thrusters with faces to interact with internal surfaces of the petals. The leg has a uniform cross-section. It is provided with a distally dead end and pointed portion, its bottom comprises a partially hemispherical hollow. The stepped windows are perpendicular to the leg axis. Within each step, the windows are inclined at the angle 120 degrees to each other and step-biased at the angle 60 degrees. Internal surfaces of the petals are concave and congruous to external surfaces of said thrusters and variable cross-section: their thickness is decreased at the ends, while thicker bottoms are split lengthwise and forked. The guide disk is attached to internal surface of the leg. The shaft is provided with an axial faceted blind key hole in a proximal end face. Its proximal portion contains a fixed ratchet gear to interact with said for latching springs. Its distal end accommodates a partially hemispherical hollow. The shaft is rotatable in the guide disk of the case. The thrusters are fixed on the shaft between the disk and the distal end of the shaft. External surfaces of the thrusters interact with internal surfaces of the petals. The hollows are opposite and used to mount the support ball. The trochanteric portion of the leg is supplied with a key hole.

EFFECT: improved leg fixation stability ensured by higher contact area between leg fixation elements and bone tissue of femur.

2 cl, 5 dwg

Description

The invention relates to medicine, specifically to traumatology and orthopedics, and is used to replace a pathologically altered hip joint. Over time, the stability of the leg of an artificial joint gradually decreases due to the conflict that occurs in the metal-bone system, bone tissue is resorbed at the point of contact with the metal. To increase the stability of the legs, they are threaded, equipped with annular grooves or windows for bone tissue to grow in them, and cementing is used. However, the above does not provide the necessary stable position of the legs, and during the polymerization of cement, in cases of its use, in addition, there is a danger of burns of bone tissue.

The closest, in its technical solution, is the hip joint endoprosthesis [1], the leg of which is hollow, a spring-loaded rod with the possibility of axial movement is placed in it. In the windows longitudinally located on the lateral surface of the leg, spring-loaded petals are placed, which, interacting with their bevels with conical sections of the stem, are deflected and, resting against the walls of the medullary canal, fix the leg. However, the spring moving the rod does not develop sufficient force to fix the legs with a few petals, and the longitudinally located petals with their distal parts in contact with the bone tissue do not provide sufficient stability for the legs.

The invention consists in a combination of essential features sufficient to achieve the desired technical result, which consists in increasing the stability of the fixation of the legs by increasing the contact area between the elements of the fixation of the legs and bone tissue of the femur.

The essence of the invention lies in the fact that the hip joint implant contains a pelvic component, a head, a neck, a spit, a leg made with an axial channel, on the side surface with tiered windows in the form of slots and with spring-loaded petals placed in the windows, the latter have an outer surface with corrugations and the possibility of extension, and the rod placed in the said channel. The stem has a guide disc with a hole for the stem and spring-loaded dogs, a support ball and three-blade pushers, the latter have outer surfaces for interaction with the inner surfaces of the petals. The leg has a constant cross section, the distal muffled and pointed part, and in the bottom there is a recess in the form of a part of the hemisphere. Tier windows are perpendicular to the axis of the legs, while in each tier the windows are located at an angle of 120 degrees relative to each other with an offset between the tier of 60 degrees. The said petals have concave and congruent inner surfaces of the said pushers and a variable cross section: at the ends, their thickness decreases, and thicker bases are longitudinally split and bifurcated. The guide disc is fixed on the inner surface of the leg, the stem has an axial, blind, faceted hole for the socket key in the proximal end, a fixed ratchet wheel for interaction with the said dogs in the proximal end, and a recess in the form of a hemisphere part in the distal end. The rod is mounted, with the possibility of rotation, in the guide disk of the housing, said pushers are fixed on the rod between the disk and the distal end of the rod, the outer surfaces of the pushers interact with the inner surfaces of the petals. The said recesses are counter-directed and are intended for installation of a support ball; a hole for a socket key is made in the spit part of the leg.

The diameter of the said recesses exceeds the diameter of the support ball, and a gap is provided between the end of the rod and the bottom of the leg.

The implementation of the legs in the form of a tube of constant cross-section provides the ability to place and rotate the rod with pushers in it.

Placing the proximal end of the rod in the hole of the guide disc, and the supporting ball in the opposing hemispherical recesses of the end of the rod and the bottom of the housing, provides centering of the rod, and the gap between the opposing surfaces - its free rotation.

The presence of a faceted blind hole in the proximal end of the stem for the socket wrench and holes made in the spit section, provide the ability to transfer the spring-loaded petals from their original position to the working position.

The presence on the rod of a ratchet wheel interacting with spring-loaded dogs located on the guide disk provides a metered translation and holds the spring-loaded petals in the working position.

A variable cross-section of the petals ensures their location flush in the device in its original position.

When longitudinally split and bifurcated bases of the petals, when the device is in the working position, they are closed under the pressure of the projections of the pushers, and create pressure on the wall of the medullary canal. During bone resorption, pressure on it is maintained due to the opening of the tense (spring-loaded), bifurcated bases of the petals.

The multi-tiered arrangement of windows with petals on the surface of the leg, at an angle of 120 degrees relative to each other in each tier, in combination with their offset between the tiers by 60 degrees, in the presence of corrugation on the outer surfaces of the petals, ensures a stable position of the endoprosthesis leg in the bone marrow canal.

The endoprosthesis is shown in the attached drawings. Figure 1 presents its General view with breakouts; figure 2 is a cross-section of the legs along the pushers in the initial position; figure 3 is the same in the working position; figure 4 - the relative position of the protrusions of the pushers in one tier with respect to the protrusions of adjacent tiers; figure 5 is a fragment of a rod with pushers.

The device comprises a pelvic component 1, a head 2, a neck 3, a trochanteric section 4 and a leg 5, which is a tube that is muffled and pointed in the distal section. In the leg, perpendicular to its axis, windows 6 are made in which spring-loaded petals 7 are arranged in many tiers. In each tier the windows are arranged at an angle of 120 degrees relative to each other, the offset between the tiers is 60 degrees. In the channel of the leg 5 is mounted, rotatably, a rod 8, the proximal end of which is installed in the hole of the guide disc 9, mounted on the inner surface of the legs 5. The distal end of the rod 8, having a hemispherical indentation in the end, is mounted on a support ball 10, which in turn, it is installed in the hemispherical recess of the bottom 11 of the leg 5. In the proximal end of the rod 8, a faceted recess 12 is made for a socket key (not shown) for the introduction of which a hole 13 is made in the spit section 4. On the rod 8, oksimalnom its section, is fixed a ratchet wheel 14 which interacts with spring-loaded pawls 15 arranged on the disk 9. The spring 7 have variable pitch cross section, are flat springs, thinner at the ends and thicker, longitudinally split and bifurcated, - at the bottom. The inner surface of the petals is made concave and congruent to the convex surfaces 16 of the pushers 17. The pushers are secured to the stem 8 in tiers, at the levels of the petals on the surface of the legs, like the petals 7, at an angle of 120 degrees relative to each other, with an offset between tiers, making up 60 degrees.

The device is used as follows.

One of the well-known surgical approaches, excising the scarred tissue and joint capsule, exposes the area of the hip joint. The proximal femur and acetabulum are resected. A scan corresponding to the diameter of the leg of the prosthesis processes the bone marrow canal of the thigh. The leg, in the initial position of the petals, is inserted into the medullary canal, and physiological neck antetorsion is established. The acetabular component is fixed in the treated acetabulum. The socket wrench, through the hole in the trochanteric part of the leg, is inserted into the faceted groove of the stem and rotate it, creating pressure with three-blade pushers on the petals, pushing them out of the slots. This ensures the fixation of the legs in the medullary canal with renewable compression.

Information sources

1. RF patent No. 2066153, A61F 2/32, 1996, BI No. 25.

Claims (2)

1. An endoprosthesis of the hip joint containing the pelvic component, head, neck, spit, leg made with an axial channel on the lateral surface with tiered windows in the form of slots and with spring-loaded petals placed in the windows, the latter have outer surfaces with corrugations and the possibility of extension , and a rod located in the said channel, characterized in that it has a guide disc with a hole for the rod and spring-loaded dogs, a support ball and three-blade pushers, the latter have outer surfaces for interaction with the inner surfaces of the petals, the leg has a constant section, the distal muffled and pointed part, and in the bottom there is a recess in the form of a part of the hemisphere, tiered windows are perpendicular to the axis of the legs, while in each tier the windows are located at an angle of 120 ° relative to each other with with an offset between the tier of 60 °, the said petals have concave and congruent inner surfaces of the said pushers and a variable cross section: at the ends, their thickness decreases, and thicker bases are longitudinally split and bifurcated, the guide disc is fixed on the inner surface of the leg, the stem has an axial, blind, faceted hole for the socket wrench in the proximal end, a fixed ratchet wheel for interaction with the said dogs in the proximal end, and in the distal end a recess in the form of a part of the hemisphere and mounted for rotation in the guide disk of the housing, said pushers are fixed on the rod between the disk and the distal end of the rod, the outer surfaces of the pusher s cooperate with internal surfaces of the lobes, said recesses oppositely directed and are intended to set the reference bead section legs in trochanteric an opening for the socket wrench. 2. The endoprosthesis according to claim 1, characterized in that the diameter of the said recesses exceeds the diameter of the support ball, and a gap is provided between the end of the stem and the bottom of the leg.

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