Patent EA-000400-B1 (EA)
Title: Stem of cement-free hip joint endoprosthesis
Inventor: DOST ANATOLY DMITRIEVICH
IPC: A61L27/00
Filed: 1996-12-31
Abstract: 1. A stem of cement-free hip joint endoprosthesis, comprises a shaped shaft, continuously tapering from its distal extremity upwards, wherein at a proximal extremity a neck with a conic journal is arranged, the axis of the neck forms an obtuse angle with the axis of the stem, and a medial surface in the proximal portion has a smooth curvilinear transition to the neck, characterized in that the cross-section of the stem at least in its distal portion represents an isosceles trapezium the smaller base o f is on the medial surface and the bigger base on the lateral surface, wherein the angle of convergence of the lateral and medial surfaces is greater than the angle of convergence of the dorsal and anterior surfaces, in the proximal portion on the medial surface smooth curvilinear faces to the dorsal and anterior surfaces are made, the dimension of which increases to the neck, on the dorsal and anterior surfaces in the proximal portion recessed areas of a predetermined shape and depth are provided, in which flat plates made of porous bioinactive material are rigidly fixed the thickness of the plates is bigger the depth of the recesses by at least the average pore size and constitutes 20-200 average pore sizes. 2. The stem of hip joint endoprosthesis of Claim 1, characterized in that the angle of inclination of the lateral sides of the trapezoid cross-section is 1-10 degree , preferably 2 degree . 3. The stem of hip joint endoprosthesis of Claim 1, characterized in that the radii of rounding of surfaces of the cross-section at least in the distal portion is not more than 2 mm, preferably 1 mm. 4. The stem of hip joint endoprosthesis of Claim 1, characterized in that the beginning of the faces corresponds to the beginning of the curvilinear portion on the medial surface. 5. The stem of hip joint endoprosthesis of Claim 1, characterized in that the symmetrical curvilinear faces of the increasing size are additionally provided on the neck from the side of trochanter. 6. The stem of hip joint endoprosthesis of Claim 1, characterized in that the angle of convergence of the lateral and medial surfaces is 4-8 degree , preferably 5.5-6.5 degree . 7. The stem of hip joint endoprosthesis of Claim 1, characterized in that the angle of convergence of the dorsal and anterior surfaces is 1-3 degree , preferably 1.5-2 degree . 8. The stem of hip joint endoprosthesis of Claim 1, characterized in that the angle of convergence of the lateral and medial surfaces is greater than the angle of convergence of the dorsal and anterior surfaces by not less than 2-6 degree , preferably by 4.0-4.5 degree . 9. The stem of hip joint endoprosthesis of Claim 1, characterized in that the porous plates are arranged in the zone of crossing the axes of the neck and the stem. 10. The stem of hip joint endoprosthesis of Claim 1, characterized in that the distal edge of the porous plates is arranged higher, than the beginning of the curvilinear portion on the medial surface. 11. The stem of hip joint endoprosthesis of Claim 1, characterized in that the area of the porous plates constitutes not less than half area of the proximal portion of the dorsal or anterior surfaces. 12. The stem of hip joint endoprosthesis of Claim 1, characterized in that the outer surface of the porous plates is made corrugated and the height of ridges is 10-20 of average pore sizes. 13. The stem of hip joint endoprosthesis of Claim 1, characterized in that the clearance in the joint of the recessed area with the porous plate along its contour is less than a half average pore size. 14. The stem of hip joint endoprosthesis of Claim 1 characterized in that the inner surfaces of the porous plates are covered with gel-like or sublimated antimicrobic substance and the pores are filled by at least 60% with said substance. 15. The stem of hip joint endoprosthesis of Claim 14, characterized in that the outer surface of the porous plates is covered with a thin-filmed biocompatible sealed in air and readily soluble in biological fluids non-toxic coating. 16. The stem of hip joint endoprosthesis of Claim 1, characterized in that in the proximal portion on the lateral surface a ridge is provided, the distal edge of which is made with a smooth curvilinear transition, the beginning of which is made on the level of the distal edge of the porous plates. 17. The stem of hip joint endoprosthesis of Claim 1, characterized in that on the proximal portion a face is made at a transition point from the ridge of the lateral surface to the trochanter sde of the stem. 18. The stem of hip joint endoprosthesis of Claim 1, characterized in that the lateral, medial, dorsal and anterior surfaces are made rough, wherein their roughness, expressed via parameter Ra is 0.01-0.2 of the average pore sizes. 19. The stem of hip joint endoprosthesis of Claim 1, characterized in that between the dorsal and anterior surfaces in the proximal portion above the porous plates a through aperture is provided, the axis of which crosses the stem axis and perpendicular to it, and also parallel to the lateral and medial surfaces. 20. The stem of hip joint endoprosthesis of Claim 1, characterized in that the angle of inclination of the neck axis to the stem axis is 131-134 degree , preferably 132 degree . 21. The stem of hip joint endoprosthesis of Claim 1, characterized in that on the trochanter side of the stem a spherical pocket, the axis of which coincides with the stem axis, and radius is bigger or equal to the diameter of the cross hole between the dorsal and anterior sides, wherein the diameter of the pocket section on the trochanter side is not less 2/3 of the stem thickness in this plane. 22. The stem of hip joint endoprosthesis of Claim 1, characterized in that said stem is made of titanium alloys, preferably of forged α + β - alloys. 23. The stem of hip joint endoprosthesis of Claim 1, characterized in that the outer surface in the distal and the proximal portions is covered with a dielectric coating, containing preferably of compounds, comprising components of an alloy with oxygen and carbon and not containing compounds of said components with hydrogen and nitrogen.