Claims
- 1. A hip prosthesis comprising a femoral shank, a neck and a head, characterized in that head (2) forms with the neck (1) a one-piece assembly (A) having at its base a housing (b) that extends in the same direction as the longitudinal axis of the neck and is directed according to the length of the neck, and limited to said neck so that the strength of said head is not effected by the presence of said housing, said housing being provided for receiving a Morse cone (5) forming an integral part of the upper pole (a) of the femoral shank (4) in such a way that continuous circumferential clearance (e) is present between the base (7) of the neck (1) and the upper plane (8) of the shank (4).
- 2. A hip prosthesis according to claim 1, characterized in that said assembly (A) is selected from a set of assemblies (A) having different lengths (L), and the shank (4) is selected from a set of shanks of different sizes, related to a function of morphological criteria.
- 3. Prosthesis according to one of claims 1 or 2, characterized in that the dimensioning of the neck (1) is such that its diameter is maximum at its base (7) and minimum at the level of its connection zone (6) with the head (2).
- 4. Prosthesis according to claim 3, characterized in that the rod (4) and the assembly (A) are made from steel.
- 5. Prosthesis according to claim 3, characterized in that the shank (4) is made from titanium and the assembly (A) from steel.
- 6. Prosthesis according to claim 3, characterized in that the shank (4) is made from titanium and the assembly (A) from nitrided titanium.
- 7. Prosthesis according to claim 3, characterized in that the shank is made from titanium and that in the assembly (A), the neck is made from titanium and the head is made from ceramics.
- 8. Prosthesis according to claim 1, wherein said assembly is selected from a plurality of different size assemblies.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 87 11096 |
Aug 1987 |
FRX |
|
Parent Case Info
This application is a continuation of application Ser. No. 178,263, filed on Apr. 6, 1988, now abandoned.
The invention relates to a hip prosthesis with interchangeable epiphysis.
Femoral prostheses are at present widely used. They are implanted in the upper end of the femur when the femoral head needs to be replaced, in the case more particularly of traumatism or arthritis.
Two types of techniques are used. In one, recourse is had to total hip prosthesis, in which the shank, the neck and the head form a one piece assembly. This technique has numerous drawbacks among which for example the following may be cited:
the impossibility of adjusting the length of the neck after sealing the femural piece, which requires a considerable stock of test prostheses and final prostheses;
the absence of alternative solution if, during the operation, the head is scored, as if often the case when soft material such as steel is used;
the need to revise the whole femoral shank at the time of renewing the prosthesis for isolated acetabular loosening.
To limit these drawbacks, interchangeable heads have been used fitted to the tapered portion provided therein by means of a Morse cone integral with the shank/neck assembly, which has the further advantage of allowing variable lengths of the neck/head assembly to be obtained through relative penetration of the two parts.
This solution proves relatively satisfactory for heads of large diameter which still make it possible to have necks of sufficient dimensions. On the other hand, it is no longer the case when it is a question of small diameter heads (and so of necks) however, these heads are characterized, at least for the metal/polyethylene pair, by a lifespan considerably longer than that of large diameter heads. It is then advantageous to keep a small diameter head. Unfortunately, in the case of heads 22.2 mm in diameter, more particularly, the solution of the conventional Morse cone can no longer be applied. The taper must in fact be very fine, so as to avoid impingement against the edges of the coloidal cupula, which risks making it abnormally fragile in a zone of maximum stress. In addition, this fineness is incompatible, considering the usual angles of Morse cones, with substantial variations in the lengths of the neck/head assembly.
The purpose of the present invention is to overcome these drawbacks and relates to a new combination of any diameter, for example anatomic size but moreover head of small diameter, to cooperate with a fine prosthetic neck, avoiding impingement with the edges of the acetabular cup, this neck/head assembly mounted on the shank being interchangeable and allowing variations of length.
US Referenced Citations (7)
Foreign Referenced Citations (2)
| Number |
Date |
Country |
| 0011665 |
Nov 1978 |
EPX |
| 2580171 |
Oct 1986 |
FRX |
Continuations (1)
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Number |
Date |
Country |
| Parent |
178263 |
Apr 1988 |
|
Patent Grant
4950300
