Hip prosthesis

Details Hip prosthesis Hip prosthesis

1997-02-12

2000-02-29

Willse, David H.

Prosthesis (i.e., artificial body members), parts thereof, or ai

Implantable prosthesis

Bone

A61F 236

Patent

active

060304170

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION

The invention concerns hip prostheses including a rod shaped to be inserted into the medullary canal of a femur, and a neck joined to the upper end of the rod to connect it to a spherical joint head.
Various forms of hip prostheses have been proposed over the years, with rods having various curvatures.
In one prior art a hip prosthesis, for example, has a rod with a single curvature in the anterior-posterior plane with the centre offset to the posterior or anterior side. It seems that a prosthesis of this kind is incorrectly centred in the diaphysis area, which can be a cause of pain.
Prostheses, like that described in document FR-A-2 660 855, have a rod which is substantially straight in the anterior-posterior plane. These prostheses are also subject to incorrect centring which can cause pain and the transmission of mechanical loads to the femur is not well distributed.
Document EP-A-0 038 908 proposes another form of prosthesis in which the rod, in the proximal region, is curved with the centre of curvature displaced towards the anterior end, whereas the curvature of the distal region of the rod has a centre of curvature displaced towards the posterior end. This type of prosthesis is difficult to fit, because of these curvatures, and also difficult to remove. Centring is difficult and often incorrect.
Documents FR-A-2 618 667 and FR-A-2 676 914 describe left femur prostheses in which the rod, in its proximal area has a single righthanded spiral twist.
Document WO-A-91 18560 describes a right femur prosthesis the proximal area of which has a single lefthanded spiral twist.
In these documents the single spiral twist is in the direction of the anteversion of the neck.
On the other hand, documents EP-A-0 128 036 and DE-A-38 29 361 both describe a left femur prosthesis the proximal part of which has a single lefthanded spiral twist. In document EP-A-0 128 036, this single spiral twist is associated with slight posterior curvature of the distal part of the rod, whereas the proximal part of the rod is substantially straight in the anterior-posterior plane.
It appears that the prostheses described in the above documents, with a single spiral twist, are not a sufficiently effective fit in the medullary canal of the femur to achieve the necessary long-term stability and durability of the prosthesis.


SUMMARY OF THE INVENTION

The problem to which the present invention is addressed is that of defining a new prosthesis structure, which, whilst it can be cemented into the femur, can be fitted without cementing in most cases. Despite the lack of cement, the attachment of the prosthesis must be mechanically strong, and the stability of the prosthesis must be improved.
The aim is:
to distribute bending and torsion loads between the prosthesis and the bone optimally in the metaphysis part of the prosthesis,
to immobilise the prosthesis in all planes of the space in the metaphysis area,
to make the gap between the metaphysis part of the prosthesis and the corresponding surface of the bone of substantially constant size,
to centre the rod as a whole in the cavity receiving it in the femur, both in the frontal plane and in the anterior-posterior plane,
to optimise the ratio between the section of the distal part of the rod of the prosthesis and the section of the canal of the diaphysis part of the femur, to prevent points of contact with the rod causing pain,
to eliminate the transmission of loads by the distal part of the rod in the diaphysis part of the femur.
To this end, the prosthesis has a rod with a different shape than prior art rods, some features of the shape of the rod going directly against received wisdom in this art. Accordingly, the invention provides a hip prosthesis including a rod adapted to be inserted and fixed into the medullary canal of a femur, a neck joined to the upper end of the rod to join it to a spherical joint head, the rod having an oblong transverse section proximal area extending from the upper end on either side of an external shoulder to a transition area

Affiliated with

Also associated with

Rating

Hip prosthesis does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Hip prosthesis, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hip prosthesis will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-678728