Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Patent
1998-10-21
2000-11-14
Willse, David H.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
A61F 232
Patent
active
061464252
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns an artificial hip joint socket with a special thread, as described in claim 1, which is intended for use as a component of an artificial joint in human beings.
DESCRIPTION OF THE RELATED ART
This type of hip joint socket with threads belongs to the class of so-called screw-in type sockets, since they are designed to be screwed into the bone matrix either after a pre-tapping with a tool or by self-tapping. In this class there are known, with respect to the shape of the outer shell, for example hypo-, hemi-, hyper- or paraspherical, conical, conic-spherical, parabolical, toroidical, elliptical and similar geometries.
With respect to the design of the threads situated upon the outer surface of the shell there exists a certain band width, for example, with regard to the thread profile of the thread ridge and the thread groove as well as to the pitch and the covered extension. In the meantime it has been realized that a subdivision of the thread profile into narrow thread ridges and broad grooves similar to a wood screw thread is advantageous, since it takes into consideration the realationship between the strength of the metallic construction material and the bone material and because the better breadth/height relationship of the bone material remaining between the thread ridges will promote the sustaining of the bone material.
In technical circles the question is still discussed, wether with respect to the shape of the thread tooth a so-called flat (or square) thread with a narrow right-angled cross-section or a slender triangular or, as the case may be, trapezoid shaped thread tooth is the better selection. The corresponding evaluation must take into consideration on the one hand the force requirement during the cutting-in process and on the other hand the short and long term fixation achievable. For both thread types it is the case, that for achieving a screwing-in process at low forces, cutting teeth with a so-called positive cutting angle must be provided along the course of the thread procession of the hip joint socket. Depending upon the number of the cutting-grooves and the therewith formed cutting teeth and the tooth geometry it can be necessary to form, behind the respective cutting tooth, a clearance angle or cut-back in order to prevent the occurrence of too strong of a jamming effect during the screwing-in process. With flat threads it is conventional, for this purpose, to cut back the circumscribing contour in the tooth head area.
The technical research has in the last few years focused above all upon the premature loosening of such hip joint sockets. The understandable goal of a problem-free useful life up to the life expectancy of the patient has been approached stepwise by optimizing the thread profile, sculpturing the thread bottom to better correspond to the contour of the shell outer surface, and coarsely texturing the outer surface. Nevertheless there still remains the need to improve such implants by appropiate fine work or tuning in such a manner that the strived-for goal is achieved. Therefor, besides a much more even transmission of forces from the implant to the acetabulum, there is in particular a demand for a noticeable reduction of the screw-in forces during implantation and a very good tactility of the position at which the outer surface of the hip joint socket comes flush against the bone matrix. With this, the risks of an insufficient deep turning-in or, as the case may be, an overturning of the implant would be easier to keep under control.
The described task is solved according to the invention by a threaded hip joint socket with the properties according to claim 1. Therewith, in a departure from the conventional screw thread having a constant progressing pitch, the pitch of the thread distributed along the outer shell surface measured in the axial direction is varied in dependence upon the curvature of the axial contour, the tooth profile, the helix angle of the cutting groove and the coarseness of the surface, said varia
REFERENCES:
patent: 4834759 (1989-05-01), Spotorno et al.
patent: 4919677 (1990-04-01), Stuhmer et al.
patent: 4963154 (1990-10-01), Anapliotis et al.
patent: 5358533 (1994-10-01), Noiles et al.
patent: 5443520 (1995-08-01), Zweymuller et al.
patent: 5702473 (1997-12-01), Albrektsson et al.
patent: 5755799 (1998-05-01), Oehy et al.
patent: 5997578 (1999-12-01), Hormansdorfer
Jackson Suzette J.
Willse David H.
LandOfFree
Hip joint glenoid cavity with a special thread 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 joint glenoid cavity with a special thread, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hip joint glenoid cavity with a special thread will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2061251