Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Patent
1991-05-22
1993-04-13
Isabella, David J.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
623 22, A61F 236, A61F 232
Patent
active
052017710
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates generally to medicine and more specifically to endoprostheses of the hip joint made use of in traumatology and orthopedics, and enables one to effect prosthetic restoration of the femoral head without preliminary enlargement of the medullary canal, as well as to fix the head of the hip joint prosthesis with the aid of additional construction elements made of polymer materials, thus avoiding subsequent resorption of osseous tissue and adding much to the life time of the hip joint endoprosthesis.
BACKGROUND OF THE INVENTION
Known in the art is the prosthetic hip joint Gilibertya P. shaped as a metallic pin inserted into the medullary canal of the femur, a metallic spherical head connected to the pin and introduced into the cotyloid cavity, and a cup-shaped metallic sphere insertable into the cotyloid cavity, i.e., such a sphere that is in contact with the head of the prosthetic hip joint in the course of its functioning (U.S. Pat. No. 3,982,281).
In such an endoprosthesis its pin has a cross-sectional area, which gradually diminishes towards the pin bottom end so that the maximum pin width is less than the diameter of the medullary canal throughout the entire pin length. That is why such a hip joint prosthesis is installed with the aid of additional fixing. Such fixation is carried out with the use of curable osseous cements. To this end after having removed, for a required depth, the spongy layer and the bone marrow, a liquid noncured composition of osseous cement is injected into the thus-formed hollow space, whereupon the pin of an endoprosthesis is inserted into said space.
However, such a construction of the endoprosthesis under consideration fails to provide its reliable fixing in the medullary canal, which is due to low adhesion between the skin surface and the osseous cement, as well as to a wide difference between the elasticity modulus of the material of the endoprosthesis pin and that of the osseous cement and the femoral bone itself.
All the above-stated results, under permanent cyclic load, in loosening of the endoprosthesis and resorption of the bone surfaces. According to recent evidence, 80 percent of such endoprostheses are to be removed after 5 to 7 years of functioning.
Known in the art is the endoprosthesis Niederer (U.S. Pat. No. 4,430,76) which is also shaped as a metallic pin adapted to be introduced into the femoral medullary canal, and a head insertable into the cotyloid cavity. The pin of the prosthesis in question is made as two components arranged at an angle to each other whose plain flat surfaces are provided with a plurality of shallow additional parallel grooves arranged lengthwise of the pin. Such an endoprosthesis is also installed with the use of osseous cements, so that said grooves are filled with the cement. Provision of such grooves adds to the adhesion between the cement and the pin and makes fixation of the prosthesis more reliable. However, even with such construction of the endoprosthesis too great a difference between the elasticity moduli of the cement and pin and permanent cyclic load applied to the hip joint endoprosthesis result in loosening of the latter in the medullary canal, so that the percentage of the prosthesis removed in 5 to 7 years is the same as in the endoprosthesis construction discussed hereinabove.
Known in the present state of the art is an artificial hip joint of the Sivash system, incorporating a metallic cotyloid cavity and an articulated device aimed at substitution of the femoral head. The pin of the endoprosthesis is fashioned as a shaped solid metallic rod, which is tightly inserted into the preliminarily enlarged medullary canal without any additional fixing (cf. `Operative orthopedics` by Movshovich, 1983, Meditsina Publishers, Moscow, pp. 203-207 (in Russian)).
Installation of the aforementioned endoprosthesis should necessarily be preceded by enlargement (by drilling-out) of the medullary canal so as to provide exact correspondence of the latter to the diameter of the rod of th
REFERENCES:
patent: 4153953 (1979-05-01), Grobbelar
patent: 4347234 (1982-08-01), Wahlig et al.
patent: 4718915 (1988-01-01), Epinette
patent: 4990161 (1991-02-01), Kampner
Belykh Sergei I.
Davydov Anatoly B.
Petrulis Algimantas Y.
Prantskyavichus Sigitas V.
Isabella David J.
Nguyen Dinh X.
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