Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-11-14
2003-01-21
Pelham, Joseph (Department: 3742)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S425000, C128S920000
Reexamination Certificate
active
06510334
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method of producing an endoprosthesis as a joint substitute for knee joints. The invention further also relates to an operative set for carrying out operations on damaged knee joints utilising an endoprosthesis which is produced in accordance with the method of this invention.
BACKGROUND OF THE INVENTION
A surgical intervention on a knee joint is usually taken into consideration by the attending physician when the patient complains about severe pains in the knee and disabilities as a consequence of, e.g., rheumatoid arthritis or other joint diseases. The surgical intervention conventionally takes place in a plurality of steps for obtaining an adaption to the shape of industrially manufactured joint moldings. Such moldings are presented in different graduated sizes and with different designs for being ultimately fitted to surfaces of the knee joint as prepared, e.g., by using an oscillating sawing blade and mainly provided for the anterior femoral condyle, the distal femur, the proximal tibia and the patella. The surfaces are provided in such a way that a vertical alignment is achieved for the multiple components of the associated endoprosthesis in relation to an axis which is obtained, e.g., by means of a preoperative X-ray image and an intramedullary pin align system for the straight line connecting the center of the hip, the knee and the malleolus. An illustrative representation of such a surgical procedure is described, e.g., in U.S. Pat. No. 4,759,350 (incorporated by referenece) by a reference also to a specific intramedullary pin system.
The implantation of such multiple knee joint endoprostheses is very time consuming and often results only in an approximate toration of the conditions of a healthy knee joint when taking into consideration existing differences in the patient's growth. Complications therefore often occur which must be attributed to the mechanics of the implanted components of the endoprosthesis whereby such complications may lead, e.g., to an anterior knee joint pain syndrome which is caused by an incorrect gliding of the patella with a nonphysiological loading of the femur-patella gliding joint. Irritations also frequently develop, occasionally with considerable hypertrophy of the joint mucosa and pronounced effusions in the knee joint as a consequence of a massive abrasion of the implanted endoprosthesis components, some of which may consist of polyethylene and will then lead to an unfavourable gliding behaviour if such abrasion becomes excessive. Loosening of the bone anchoring of these components may also occur so that it is frequently necessary to implant a new endoprosthesis.
For avoiding such complications as often accompanied by a repeated implantation of a new endoprosthesis with the requirement for a resection of further bone parts there has already been proposed by one of the present inventors a method as described in U.S. Pat. No. 5, 735, 277 (incorporated by reference) according to which still prior to a surgical intervention on a knee joint a preoperative tomographic image of the damaged knee joint is prepared by means either of a computed tomography or by means of a nuclear spin resonance tomography. In accordance with this known method there is further prepared a healthy knee joint tomographic image for which the contours of at least the femoral bone and of the tibia of the damaged knee joint are approximated to those of a healthy knee joint. Afterwards a postoperative tomographic image of the damaged knee joint is prepared for enabling by comparison a determination of the differences between the contours of at least the femoral bone and of the tibia of the healthy knee joint tomographic image and the contours of at least the femoral bone and of the tibia of the postoperative tomographic image of the damaged knee joint. Such a comparison therefore allows a subsequent preparation of a tomographic reference image which accordingly represents those differences. This tomographic reference image finally forms the basis for preparing at least a femoral component and a tibial component of an endoprosthesis which may be used in connection with the factual surgical intervention on the damaged knee joint of which the preoperative tomographic image has been prepared.
Since with this known method a tomographic reference image representing differences between a preoperative tomographic image and a postoperative tomographic image of the damaged knee joint is used as a basis for preparing the components of an endoprosthesis this method could include a multiple error rate in respect to the preparation of such a reference image as caused, e.g., by the preparation of the postoperative tomographic image and further by the determination of the differences that will exist between the postoperative tomographic image and the tomographic image of a healthy knee joint which, e.g., will be prepared by either manually altering the preoperative tomographic image or by preparing a mirror image of a healthy knee joint of the patient. The preparation of such a tomographic reference image of course also raises the computer-oriented assistance for the preparation of an endoprosthesis in accordance with this known method.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to provide a method of producing an endoprosthesis as a joint substitute for knee joints which minimises the error rate in connection with a surgical intervention on a damaged knee joint and which further optimizes the surgical intervention in respect of the possibility to allow a very close adaption at least of the femoral and tibial components of an endoprosthesis to the contours of the bone joints as specifically prepared on respective surfaces during a surgical intervention for snugly fitting thereto the components of the endoprosthesis.
A further object of the present invention relates to the provision of an operative set for carrying out operations on damaged knee joints which will allow a practically ready-made surgical intervention on a damaged knee joint as accompanied with less pain for the patient.
DESCRIPTION OF THE INVENTION
In accordance with a preferred embodiment of the present invention a method of producing an endoprosthesis as a joint substitute for knee joints is started by preparing a preoperative tomographic image of the damaged knee joint. The tomographic image could be prepared either by a computed tomography or by a nuclear spin resonance tomography which allows to define very sharp contours of the damaged knee joint as a correspondingly optimal precondition for all of the subsequent steps of this method.
The tomographic image of the damaged knee joint is then virtually altered for approximating the contours of at least the femoral bone and of the tibia of the damaged knee joint to the contours of a healthy knee joint. This virtual alteration should preferably exemplified with a stretched condition of the knee allowing a precise plotting of the rear and lower joint surface of the femoral bone and of the entire shinbone surface of the tibia to thereby obtain more or less ideal contours for the fitting of the endoprosthesis during the factual surgical intervention as later carried out. This step of virtually altering the preoperative tomographic image may be exemplified manually or may alternatively be exemplified by the preparation of a mirror image of a healthy knee joint of the patient. It may also be prepared by identifying an image of a healthy knee joint having contours of the femoral bone and of the tibia comparable to the contours of the preoperative image of the damaged knee joint.
The altered femoral and tibial components defining therefore respective components of a healthy knee joint are subsequently virtually severed as respectively visual patterns for the endoprosthesis. The severing is carried out on marked severing areas which later serve as thusly predetermined severing areas for severing the associated components of the damaged knee joint from the joint bones during the factual operation
Schuster Christoph
Schuster Luis
LandOfFree
Method of producing an endoprosthesis as a joint substitute... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of producing an endoprosthesis as a joint substitute..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of producing an endoprosthesis as a joint substitute... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3000719