Patent Description:
It is known from <CIT>, an implant for anchoring on a bone has a plurality of anchoring pins which extend away from a fastening side of the implant and are provided for anchoring the implant in the bone. In different areas of the fastening side of the implant, the pin arrangement and/or the geometry of the pins are chosen differently. In particular, in different areas of the fastening side of the implant, the volume of the anchoring pins per unit of surface area of the fastening side of the implant is different, preferably in such a way that the geometry and/or arrangement of the pins is chosen according to the proportion of bone tissue in the total tissue of the bone substance, opposite which the area of the fastening side is provided, in such a way that, in areas where there is a relatively higher proportion of bone tissue as a whole, less tissue is displaced by the anchoring pins than in areas where there is a relatively smaller proportion of bone tissue.

The <CIT> patent demonstrates endoprosthesis for implantation in osteoarticular surgery composed of acetabulum and femoral head, which have sharp protrusions on the limiting surface, whereas the limiting surfaces of the acetabulum and femoral head have the form of a spherical cap, and the sharp protrusions with mutually parallel axes have correspondingly the form of polygonal needles of varying length placed symmetrically, with each needle contacting the adjacent edge needle at its base, whereas the outer polygonal needle protrusions placed respectively next to the supporting edge and the supporting surface have the shortest length, and the total area of the polygonal protrusions and central polygonal needle is advantageously seven times larger than the area of the sphere on which they were placed.

A German patent description <CIT> Al also demonstrates a solution in which the endoprosthesis is more securely fastened through the use of conical irregularities protruding from the limiting surface of the endoprosthesis and pointed towards the connecting surface of the bone. The conical irregularities are separate elements, which have a conical part and a cylindrical part set in the matrix of the acetabulum and in the matrix of the femoral head. For this purpose holes are made in the flat surfaces of the femoral head and on the annular offsets of the external spherical surface of the acetabulum. These holes weaken both the acetabulum and the femoral head of the endoprosthesis in a lateral cross-section, and simultaneously the conical irregularities set in them are at risk of loosening, which leads to unstable embedding of the endoprosthesis in the bone. In a known solution, <CIT> AI the conical irregularities are fully pressed into the spongy bone, which increases the contact area, which facilitates the embedding of the endoprosthesis in the bone material. The flaw of this solution is not using the possible optimum bone-endoprosthesis contact area, due to the fact that the conical irregularities are placed in regular spacing on flat surfaces of the femoral head and on the annular offsets of the external spherical surface of the acetabulum, moreover the flat contact surface by directly contacting the bone at the moment of implantation prevents the later growing in of spongy bone in the form similar to natural, which would ensure good shock absorption of loads on the joint.

The <CIT> invention demonstrates an improved metal acetabulum outer cup with rough lamina for artificial hip join. The improved metal acetabulum outer cup is characterized in that the cup is made by casting or forging, and a rough medical metal lamina is formed on a corresponding surface, contacting with bones of a patient, of the acetabulum outer cup by material increase manufacturing.

The <CIT> invention relates to an acetabulum for a hip prosthesis, comprising an inner cavity and a rear outer surface facing the bone. In order to be able to implant the acetabulum without using cement, at least some areas of the outer surface are porous and osseointegrative, and the acetabulum is made exclusively of a ceramic material.

In the <CIT> invention an artificial hip joint was presented consisting of multi-layer shell core composite structural components, which includes an artificial acetabular bone and an artificial femoral head, which are mutually matched with each other. The artificial acetabular bone has a multi-layer shell core composite structure and is constituted of a ceramic acetabular bone lining, transitional layers, an acetabular bone shell made of a porous metal or a porous alloy or a porous toughened ceramic. The artificial femoral head has a multi-layer shell core composite structure and is constituted of a ceramic spherical shell layer, a transitional layer and a toughened ceramic inner core. The artificial acetabular bone lining and the artificial femoral head spherical shell layer of the hip joint have high rigidity, anti-corrosion and anti-wear performance. In order to improve adhesion and stability the artificial layer of the acetabulum shell and internal layer of the core off the femoral head of the endoprosthesis have high strength and shock resistance. It is a solution which creates micropores.

In the <CIT> invention a hip joint endoprosthesis is presented, provided with a plurality meridional incisions, which define as many segments elastically flexible in the radial direction. The inner surface of the socket is provided with one or more grooves, parallel to the proximal rim, wherein these grooves receive corresponding protrusions of a joint insert. The socket additionally comprises one or more frustoconical portions which form bearing surfaces for corresponding frustoconical portions of the joint insert. The inner surface of the socket bounds a polygonal seat which is adapted to engage with a polygonal portion of the joint insert by means of a form fit.

In the <CIT> patent presents a fastening shell with a teeth structure arranged in an external side of a semi shell, and a milling tool for forming a shape of teeth flanks. The equator-side oriented flanks of the individual teeth form an angle of less than <NUM> degrees with a component axis such that barbed hook effect is developed in an equator. A path of the tool is curved for forming teeth gaps and formed such that the teeth of a teeth row are consecutively arranged in the teeth gaps and cutting edges of the teeth from the equator towards a pole do not overlap or have a gap of around <NUM>.

The <CIT> patent discusses endoprosthesis which comprises a pivotally connected cotyloid prosthesis and prosthesis of a proximal end of femoral bone having a stem for intraosseous introduction, a neck and a spherical head. On an external surface of the head, there is a cylindrical section in the form of a flat. The endoprosthesis has a spheroidal internal cavity of a depth exceeding a half-radius of the head with an input hole less than the head diameter and equal to its diameter within the cylindrical section to lock and key the head in the cotyloid endoprosthesis. The cylindrical section faces a junction of the head and the neck at an angle approximately <NUM>-<NUM>° to its axis. The head diameter is <NUM>-<NUM>, while the neck diameter is <NUM>-<NUM>. The invention may provide higher reliability and durability of endoprosthesis function after implantation.

The subject of the invention is an endoprosthesis for implantation in bone surgery, especially of the hip joint, better adapted to provide long-term cementless fixation.

The essence of the invention is an endoprosthesis for implantation in bone surgery of ball-and-socket joints, in particular hip joint, the endoprosthesis consisting of a moving connection provided by a contact surface of each of an endoprosthesis femoral head component and an endoprosthesis acetabular component, whereas each of the endoprosthesis head component and the endoprosthesis acetabular component has a bone contacting surface having a shape similar to a sphere, on which pins are placed, each of the pins having an axis principally parallel to the lengthwise axis of the endoprosthesis, characterized in that each on the bone contacting surfaces of the endoprosthesis head component and the endoprosthesis acetabular component has at least two cutting blades with an arc-shaped cross-section outline, wherein each of the blades creates a groove for removal of the products of cutting.

It is advantageous, when the sphere is a convex shell, on which pins are located, forming the endoprosthesis acetabulum, or when the sphere is a concave shell, on which pins are located, forming the endoprosthesis femoral head.

It is also advantageous, when the endoprosthesis has on a spherical surface, in a zone of the lengthwise axis, advantageously rounded and porous supporting surface.

It is also advantageous, when the pins are placed on a spherical surface forming the limiting surface.

Moreover it is advantageous when the cutting blades have an angle of application ß within a range of <NUM>-<NUM>°, advantageously <NUM>°, angle of attack α <NUM>-<NUM>°, advantageously <NUM>°, and a wall thickness H of the cutting blade wall amounting to <NUM>-<NUM>, advantageously <NUM>, and a H1 height of the cutting blade is <NUM>-<NUM> times higher than a H2 height of a opposite wall <NUM> of the groove <NUM>.

It is in particular it is advantageous when the supporting surface has a D2 diameter with a value of <NUM>/<NUM>-<NUM>/<NUM> of the D1 diameter of the femoral head.

It is advantageous when the femoral head endoprosthesis has a cylindrical elongation with an A angle in relation to a centre point within a range of <NUM> to <NUM> degrees and when the end of the grooves is situated in a zone of technological gripping devices, and the distance "z" between the bases of adjacent pins is at least <NUM> micrometers.

It is also advantageous when the pins have a shape of a cone.

It is also advantageous when the pins have shaped side surfaces.

And it is also advantageous when the height of the pins on a surface of the endoprosthesis acetabulum shell decreases from an edge to the supporting surface, the height of the pins on a surface of the convex endoprosthesis femoral head shell decreases from the lengthwise axis of the endoprosthesis to an external direction.

It is advantageous when an insert is introduced on not on an internal spherical surface of the endoprosthesis acetabulum.

The use of the solution presented in the invention is expected to provide the following technical and utility effects:.

An example implementation of the invention is presented in the drawings, where <FIG> presents a view of the acetabulum on the side of the supporting surface, <FIG> presents a detail of <FIG>, <FIG> presents a cross-section of a cutting blade, and <FIG> a cross-section of the acetabulum, <FIG> demonstrates a view of the acetabulum, <FIG> presents a detail of the acetabulum from <FIG>, <FIG> presents a view of the acetabulum on the side of the supporting surface, <FIG> demonstrates a detail of the acetabulum from <FIG>, <FIG> presents a cross-section of the cutting blade, <FIG> presents a view of the acetabulum, <FIG> presents a detail of the acetabulum from <FIG>, <FIG> presents a view of the femoral head, <FIG> presents a detail of the view from <FIG> demonstrates a cross-section of the femoral head, <FIG> presents a view of the femoral head on the side of the limiting surface, <FIG> presents a detail of the view from <FIG>, <FIG> presents a view of the femoral head, and <FIG> a detail of the view of the femoral head from <FIG>, <FIG> presents a view of the femoral head on the side of the limiting surface, <FIG> a detail of the femoral head from <FIG>, <FIG> presents a cross-section of the pins, and <FIG> demonstrates a fragment of the cross-section of the femoral head, <FIG> a cross-section of the pin, <FIG> presents a pin in the form of a cone, <FIG> a pin in the form of a rounded cone, <FIG> a pin in the form of a prism, <FIG> a pin in the form of a cuboid, <FIG> presents a fragment of the cross-section of the acetabulum, <FIG> presents an isometric view of the acetabulum on the side of contact of friction couple, <FIG> presents a cross-section of the endoprosthesis acetabulum and femoral head system embedded on bone surfaces, <FIG> presents a cross-section of the friction couple, and <FIG> presents a cross-section of the femoral head endoprosthesis with a demonstrated angle of elongation of the cylindrical surface.

Hip joint endoprosthesis for implantation in bone surgery of ball-and-socket joints, in particular hip joint, consists of a moving connection provided by the contact surface <NUM> of two modules of the endoprosthesis femoral head <NUM> and acetabulum <NUM>. The surfaces of the endoprosthesis femoral head <NUM> and acetabulum <NUM> which are in contact with the bone next to the joint have a shape similar to a sphere, on which pins <NUM> are placed. The pins <NUM> have an axis in principle parallel to the longitudinal axis of the endoprosthesis and at least two cutting blades <NUM> with an arc-shaped cross-section outline are formed, creating a groove <NUM> for removal of the products of cutting. In the endoprosthesis the sphere is a convex shell, on which pins <NUM> are located, forming the endoprosthesis acetabulum <NUM>. The sphere is a concave shell, on which pins <NUM> are located, forming the endoprosthesis femoral head <NUM>. The endoprosthesis has on its spherical surface, in the zone of the lengthwise axis, advantageously rounded, porous supporting surface <NUM>. The pins <NUM> are placed in the area outside of the supporting surface <NUM>, forming the limiting surface <NUM> and are placed on a spherical surface forming the limiting surface <NUM>. In the endoprosthesis the cutting blades <NUM> have an angle of application g within a range of <NUM>-<NUM>°, advantageously <NUM>°, angle of attack α <NUM>-<NUM>°, advantageously <NUM>% and the wall thickness H of the cutting blade <NUM> wall amounting to <NUM>-<NUM>, advantageously <NUM>, and the H1 height of the cutting blade <NUM> is <NUM>-<NUM> times higher than the H2 height of the opposite wall <NUM> of the groove <NUM>. The supporting surface <NUM> has a D2 diameter with a value of <NUM>/<NUM>-<NUM>/<NUM> of the D1 diameter of the femoral head <NUM>. The femoral head endoprosthesis has a cylindrical elongation with an A angle in relation to the centre point within a range of <NUM> to <NUM> degrees. In the endoprosthesis the end of the grooves <NUM> is situated in the zone of technological gripping devices <NUM>. The distance between the bases of adjacent pins <NUM> is at least <NUM> micrometers. The pins <NUM> have a shape of a cone or a rounded cone or a truncated cone or a regular polyhedron. Moreover the pins <NUM> have smooth side surfaces or shaped side surfaces. The height of pins <NUM> decreases from the edge to the supporting surface <NUM> and from the central axis of the endoprosthesis to the external direction. The height of the highest pin <NUM> is approximately twice the height of the lowest pin <NUM>. The top points of the pins <NUM> create a surface with an outline similar to the surface of the sphere on which they are placed. The pins <NUM> are placed on an external spherical surface of the acetabulum <NUM> and on an internal spherical surface of femoral head <NUM>. Additionally an insert <NUM> is introduced or not on the internal spherical surface of the endoprosthesis acetabulum <NUM>.

The endoprosthesis consists of acetabulum <NUM> and femoral head <NUM>, which on their limit surfaces in the form of spherical shells have polygonal needle protrusions in the form of pins <NUM> with parallel axes and varying length, the total area of which is a multiple of the joint area, whereas the minimum distance "z" between the bases of pins <NUM> is <NUM> micrometers, used in order to enable growth of trabeculae. The bases of pins <NUM> are not tangential. The axes of pins <NUM> are perpendicular to the plane of the supporting surface <NUM> of the femoral head and of the supporting surface <NUM> of the acetabulum <NUM>, respectively. Additionally in order to reduce the abrasive wear of the friction couple of the acetabulum <NUM> and femoral head <NUM> of the hip joint endoprosthesis an insert <NUM> is introduced or not on the internal spherical surface of the endoprosthesis acetabulum <NUM> made of non-metallic material.

A precondition for the operation of the system is the fitting of the shape and size of the endoprosthesis femoral head <NUM> to the size and shape of the endoprosthesis acetabulum <NUM> in order to ensure the correct operation of the friction couple.

The endoprosthesis femoral head <NUM> is placed in the grips of an external device providing rotational movement, not shown on the drawing. This device moves the endoprosthesis around its angle of symmetry with a specific speed adapted to the machined material. The endoprosthesis, in the form of femoral head <NUM> is rotated, using the cutting blades <NUM> to remove bone tissue <NUM>, which falls into the groove <NUM> between the wall of the cutting blade <NUM>, and the wall <NUM> of the groove <NUM> or between the wall of the cutting blade <NUM> and the pins <NUM>. The bone tissue <NUM> is moved by the pressure exerted by the newly cut bone tissue <NUM> between the wall of the cutting blade <NUM> and the wall <NUM> of the groove <NUM> or between the wall of the cutting blade <NUM> and the pins <NUM> out of the endoprosthesis, through the direct surface of the contact of the endoprosthesis with the bone tissue <NUM> surface. This process lasts until an optimum position of the endoprosthesis is obtained. The endoprosthesis causes a slight filling of the space between the pins <NUM> with small fragments of bone, which will feed the process of bone reconstruction and stabilization of the endoprosthesis. After removing the diseased tissue of the joint connection and using the cutting blades <NUM> to obtain a shape similar to the outline created by the tips of the pins <NUM>, the endoprosthesis is disconnected from the device providing rotational movement, not shown of the drawing, and then is placed on the previously prepared surface and gradually inserted into the spongy bone space, in parallel to the axis of symmetry of a femoral head <NUM> of the joint. The supporting surface <NUM> does not contact the periosteum, the cortical substance and the spongy substance, into which the pins <NUM> at a distance longer than the plane of the supporting surface <NUM> are simultaneously inserted. The pins do not penetrate the spongy bone fully, to enable releasing of excessive intraosseous fluid pressure. The space between the pins <NUM> which is not filled with bone tissue <NUM> in this process will be filled with osteoblasts in the process of tissue regeneration, which will grow during the convalescence period.

The implantation method for acetabulum endoprosthesis is similar to the implantation of the femoral head, whereas the acetabulum endoprosthesis is implanted in such a manner that the supporting surface <NUM> of the truncated limiting surface adheres to the bone in a plane perpendicular to the axis of the central acetabulum <NUM> of the bone and be placed in a manner symmetric to this axis, and polygonal pins <NUM> in the area of the spherical belt on the limiting surface <NUM> of the endoprosthesis acetabulum <NUM> are partially sunk into the spongy structure of the bone. The remaining space between the polygonal needle protrusions <NUM> not sunk into the spongy bone, up to the limiting surface <NUM> are filled with osteoblasts which grow during the convalescence period as a result of lack of movement between the endoprosthesis acetabulum and the bone <NUM>. The supporting surface <NUM> with a slight rounding protects the implanting process against possible trauma to blood vessels present in the direct vicinity of the cut tissue.

Additionally in order to reduce the abrasive wear of the friction couple of the acetabulum <NUM> and femoral head <NUM> of the hip joint endoprosthesis an insert <NUM> is introduced or not on the internal spherical surface of the endoprosthesis acetabulum <NUM> made of non-metallic material.

Claim 1:
An endoprosthesis for implantation in bone surgery of ball-and-socket joints, in particular hip joint, the endoprosthesis consisting of a moving connection provided by a contact surface (<NUM>) of each of an endoprosthesis head component (<NUM>) and an endoprosthesis acetabular component (<NUM>), whereas each of the endoprosthesis head component (<NUM>) and the endoprosthesis acetabular component (<NUM>) has a bone contacting surface having a substantially spherical shape, on which a plurality of pins (<NUM>) are located, each of the pins (<NUM>) having an axis principally parallel to a lengthwise axis of the endoprosthesis, characterized in that the bone contacting surface of each of the endoprosthesis head component (<NUM>) and the endoprosthesis acetabular component (<NUM>) has at least two cutting blades (<NUM>) with each of the blades (<NUM>) having an arc-shaped cross-section outline,
wherein each of the blades (<NUM>) creates a groove (<NUM>) for removal of products of cutting.