FEMORAL COMPONENT

COMPOSANT FEMORAL

English Abstract

A femoral component of a replacement hip joint having a tapered
collarless stem for fixing in a medullary canal by cement and in which,
at the proximal end of the stem, there is a pronounced laterally
projecting heel adapted to extend into the greater trochanter of the
femur into which it is to be fitted.

Claims

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CLAIMS
1. A femoral component of a replacement hip joint having a tapered
collarless stem for fixing in a medullary canal by cement and in which,
at the proximal end of the stem, there is a pronounced laterally
projecting heel adapted to extend into the greater trochanter of the
femur into which it is to be fitted.
2. A femoral component as claimed in claim 1 in which the distal
surface of said heel is substantially concave.
3. A femoral component as claimed in claim 1 in which the distal
surface of said heel is substantially convex.
4. A femoral component as claimed in claim 1 in which the distal
surface of said heel is substantially straight.

Description

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FEMORAL COMPONENT:
This invention relates to a femoral component of a replacement
hip joint of the "Exeter" type which has a tapered collarless stem for
fixing in a medullary canal by cement.
The "Exeter" type femoral component of the kind shown in
British Patent No 1 409 054 is well known and comprises a neck which
carries a bail head for cooperation with an acetabular socket. The
neck is connected to a tapered collarless stem. Thus there is no
collar for resting either on the bone or the cement in the area where
the stem joins the neck of the implant. This type of stem has evolved
so that the stem can be given a polished finish to help it slide down
inside the bone cement and the present invention relates to this type
of femoral component.
It has been found that it is preferable to provide anchorage
for the stem to resist as much as possible rotation of the stem after
implantation.
The present invention is intended to provide a femoral
component which takes advantage of this facility.
In known constructions of femoral components of this type, for
example as shown in British Patent No 1 409 054, the lateral side of
the component is usually straight or tapered in relation to its
longitudinal axis and leads directly to a shoulder at the proximal end
which curves around to meet the neck which carries the ball head. Such
components are fitted by reaming out the medullary canal
appropriately. There is, however, space in bone within the greater
trochanter and the femoral component according to the present invention
is intended to take advantage of this to provide greater resistance to
stem rotation after implantation.
According to the present invention a femoral component of a
replacement hip joint which has a tapered collarless stem for fixing in
a medullary canal by cement and in which, at the proximal end of the

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stem, there is a pronounced laterally projecting heel adapted to extend
into the greater trochanter of the femur into which it is to be fitted.
Thus, the distal facing part of the heel can provide a lateral
portion which is greater than that of known collarless stems and which
is particularly adapted to resist torque.
It will be appreciated that, in order to fit the femoral
component according to the invention, it is necessary to broach the
medullary canal so that there is a cavity within the greater
trochanter.
The invention can be performed in various ways, but one
embodiment will now be described by way of example and with reference
to the accompanying drawing, in which:
Figure 1 is a side view a femoral component according to the
invention shown in position in a femur; and
Figure 2 is an end view of the device shown in Figure 1.
As shown in Figure 1, a cross-sectioned femur is indicated by
reference numeral 1. The intramedullary canal 2 of the femur has been
broached to accept a femoral component, and it will be seen that, at
the greater trochanter indicated by reference numeral 3, the canal 2
has been opened out in a lateral direction which causes an exposed
portion of the canal 4 to extend as a slot within the greater
trochanter 3.
The proximal part of the prepared canal has a pronounced angled
portion 5.
The especially adapted femoral component for use in such a
canal is indicated by reference numeral 10 and comprises a stem 11, a
proximal portion 12 and a neck 13 on which is located a spigot 14 to
accept a ball head (not shown).

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The proximal end of the stem, where it leads into the proximal
portion 12, has a pronounced laterally projecting heel 15 which extends
into the greater trochanter 3 when it is fitted. As will be seen from
Figure 1, the particular widely-splayed shape of the proximal portion
12 provides a distal surface 16 to the heel, which can be concave,
convex or straight, but increases the lateral width of the component to
provide not only a greater area of contact to absorb loads and resist
torsional displacement, but to absorb loads in general.
The invention has great advantages over components of standard
shape, and can be fitted in most patients, provided there is sufficient
healthy bone.

Representative Drawing