Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-09-02
2002-05-07
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C606S130000, C128S920000
Reexamination Certificate
active
06385475
ABSTRACT:
The invention relates to a process for the preoperative determination of the positioning data of endoprosthetic parts of a central joint relative to the bones forming the central joint. Moreover, the invention relates to a device for carrying out this process.
BACKGROUND OF THE INVENTION
In the case of surgical operations, with which joints between two bones have to be replaced by endoprostheses, it is extremely important for the endoprosthetic parts to be positioned exactly relative to the bones; deviations in the order of magnitude of more than 2° already call into question the success of such an operation.
It is known, for the preparation of surgical operations, to determine the position of bones in the body and the relative positioning of the bones bordering on the joint to be replaced by means of various processes in order to be able to plan prior to the operation how the endoprosthetic parts have to be inserted relative to the bones. For example, it is known to determine the outer contour of the bones bordering on the joint to be replaced by means of computer tomography scans; on the basis of the data thus gained sets of data may be compiled which correspond to the outer contours of the bones and which can then be used for planning the orientation of the prosthetic parts (M. Fadda et al “Computer-Assisted Knee Arthoplasty at Rizzoli Institute”; MRCAS 94, Medical Robotics and Computer Assisted Surgery, Pittsburgh, 1994, pages 26 to 31; T. C. Kienzle III et al “A Computer-Assisted Total Knee Replacement Surgical System Using a Calibrated Robot”, MIT Press, Cambridge, Mass., 1996, pages 409 to 416).
This presupposes a complicated examination of the patient prior to beginning the operation which often cannot be carried out at the actual place of operation and therefore, as a rule, also not at the same time as the operation. Moreover, the patient has to be subjected to a high dose of radiation; finally, expensive apparatus and equipment is required for this examination.
It is already known to compare the position of the bones with one another prior to and after the operation in that marking elements are secured to the bones and their position in the space can be determined by suitable camera-like devices (U.S. Pat. No. 5,249,581). The result of the operation can be checked with such a device as the surgeon can compare the orientation of the bones prior to and after the operation. It is not, however, possible with this process to determine the positioning data of the prosthetic parts to be inserted preoperatively; also with this process the position of the prosthetic parts on the bone must be determined preoperatively by, for example, the exact position of the bones in the body and their positioning relative to one another being determined by means of computer tomography scans.
SUMMARY OF THE INVENTION
The object of the invention is to specify a process, with which the position of the prosthetic parts relative to the bone can be determined preoperatively without complicated examination procedures of the patient being necessary for this purpose; in particular, CT scans or similar examination procedures are intended to be made superfluous.
This object is accomplished in accordance with the invention, in a process of the type described at the outset, in that a respective outer articular point is determined by way of movement of the bones about a respective outer joint which is located at the end of the two bones facing away from the central joint, that an articular point is determined for each of the two bones in the area of the central joint, that a direction characteristic for each of these bones is determined by way of a straight-line connection of the two articular points found in this manner for the two bones and that the orientation of the endoprosthetic parts relative to this characteristic direction is determined.
The process described may be used on all body parts, with which the bones determining the joint to be replaced are likewise connected at their other end to additional bones via a joint. In the following, the joint to be replaced is designated as “central joint”, the joints adjoining on the outer sides as “outer joints”. With the process described, the outer joints are used for the purpose of supplying preoperative information concerning the position of the bones adjoining the central joint. The bones coming together at the two outer joints are, namely, moved relative to one another, and as a result of this movement the position of the outer joints is determined, to be more exact articular points of considerable invariance. This becomes clear with the example of the leg although the process described can also be used on all other limbs, for which central and outer joints are present, for example, the arm.
In the case of the leg, the central joint is formed by the knee joint, the two outer joints by the hip joint and by the ankle. The hip joint is a ball joint and so the center point of this ball joint can be determined by way of movement of the thigh in relation to the hip joint, i.e. an articular point of greatest invariance, that is an articular point which is immovable during the movement of the two bones relative to one another.
In a similar manner, such a point of greatest invariance can also be determined for the ankle. In this case, the ankle is essentially a joint which facilitates only a pivoting about a transverse axis but a rotation about the longitudinal axis is also possible to a small extent and so a point can be determined as a result of the superposition of these two pivoting movements which remains essentially unmoved during every movement of the ankle.
In the area of the knee, articular points are determined, in addition, in a similar manner, wherein various methods can be available to the surgeon for this purpose.
When the knee joint is intact and still allows normal movements, the articular points close to the knee can also be determined by way of movement of the two adjoining bones about this joint. The knee joint does perform a relatively complicated rolling and sliding movement; nevertheless, points, with which the movement during the bending of the knee is minimal, may be determined during performance of this complicated, superposed movement and, moreover, during a rotation of the lower leg about the vertical axis; such a point of maximum invariance is defined as articular point.
In accordance with another embodiment of the invention, articular points can also be determined by these being established at the central joint by way of palpation of the joint surfaces. When replacing a central joint, i.e., for example, the knee joint, this area must be opened up in any case, and the surgeon can then establish particular, striking points of the joint surfaces, for example, intercondylar by touch. These are then specified as articular points.
It is also possible in another embodiment of the invention to determine the articular points of the bones at the central joint from a set of data which reproduces the contour of the joint surface at the central joint. This contour of the joint surface can be detected after the opening up of the knee joint, for example, by a scanner which is guided along the joint surface and which in various positions along the joint surface supplies signals corresponding to its position to a data processing system. This may determine the contour of the joint surface in this manner, and on the basis of this determined contour the surgeon can then establish which point will be used as articular point of the central joint.
As a result of this determination of the articular points in the two outer joints and in the central joint, characteristic directions may be determined for each of the two bones forming the central joint in that the two articular points of each bone are connected to one another in a straight line. These characteristic directions are then utilized for the orientation of the prosthetic parts, i.e. on the basis of this characteristic direction the inclination of the prosthetic parts, at which these are intended
Cinquin Philippe
Lavallee Stephane
Leitner Francois
Minfelde Richard
Picard Frederic
Lateef Marvin M.
McAllister Douglas M.
Shaw Shawna J.
LandOfFree
Process and device for the preoperative determination of the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process and device for the preoperative determination of the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and device for the preoperative determination of the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2908613