Method and apparatus for determining the position of the tibial exit point of the anterior cruciate ligament

• US 20050222574A1
• Filed: 03/21/2005
• Published: 10/06/2005
• Est. Priority Date: 09/27/2002
• Status: Active Grant

• Current Assignee: Aesculap AG (B. Braun Holding GmbH & Co. KG)
• Original Assignee: Aesculap AG (B. Braun Holding GmbH & Co. KG)
• Inventors: Eichhorn, Juergen, Boux De Casson, Francois, Leitner, Francois, Giordano, Nicola
• Granted Patent: US 7,643,868 B2
• Time in Patent Office: Days
• US Class Current: 606/96
• CPC Class Codes: A61B 17/154 for preparing bone for knee prosthesis
• CPC Class Codes: A61B 17/155 Cutting femur
• CPC Class Codes: A61B 17/157 Cutting tibia
• CPC Class Codes: A61B 17/1703 using imaging means, e.g. by X-rays
• CPC Class Codes: A61B 17/1714 for applying tendons or ligaments implements for applying tendons or ligaments A61F2/0805
• CPC Class Codes: A61B 2034/105 Modelling of the patient, e.g. for ligaments or bones
• CPC Class Codes: A61B 2034/2055 Optical tracking systems
• CPC Class Codes: A61B 2034/2068 using pointers, e.g. pointers having reference marks for determining coordinates of body points
• CPC Class Codes: A61B 2034/2072 Reference field transducer attached to an instrument or patient
• CPC Class Codes: A61B 2090/061 for measuring dimensions, e.g. length
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: A61B 5/103 Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes A61B5/08 takes precedence; measuring aids for tailors A41H1/00; measuring instruments specially adapted for dentistry A61C19/04
• CPC Class Codes: A61B 5/4533 Ligaments
• CPC Class Codes: A61B 5/6878 Bone
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves

Abstract

In order to establish an optimum position on the upper side of the tibia for the exit point of an anterior cruciate ligament replacement, it is proposed that, with the leg bent, the position of a number of points along the front edge of the notch is detected and in this way their position and progression on the femur are also determined, that, with the leg straight, the course of this front edge of the notch is projected onto a projection plane which is perpendicular to the longitudinal axis of the tibia in the region of the upper side of the tibia, and that, within the region enclosed by this projected curve, the exit point is selected such that it maintains at least a distance corresponding to the radius of the implant from the projected curve. Furthermore, an apparatus for carrying out such a method is proposed.

Claims

1. Method for determining the position on the upper side of the tibia of the exit point of an implant replacing the anterior cruciate ligament of a knee joint, in which positional data of the tibia and the femur are determined by means of a navigation system, in which geometrical form data of the femur in its region facing the upper side of the tibia are recorded and in which these data are processed together with the positional data of the tibia and the femur in a data-processing system to calculate the positional data for the exit point, with the following individual steps being performed:

with the leg bent, the position of a number of points along the front edge of the notch is detected and in this way their position and progression on the femur are determined,

with the leg straight, the course of this front edge of the notch is projected onto a projection plane which is perpendicular to the longitudinal axis of the tibia in the region of the upper side of the tibia, and

within the region enclosed by this projected curve, the exit point is selected such that it maintains at least a distance corresponding to the radius of the implant from the projected curve.

2. Method according to claim 1, wherein a circular area of a diameter corresponding to the diameter of the implant used is projected into the projection plane, this area is displaced in the area enclosed by the projected curve such that the circular area does not intersect the projected curve, and in that in one of the positions of the circular area achieved in this way its center point is selected as the exit point for the implant.

3. Method according to claim 1, wherein a position of the exit point in which the latter lies as far as possible in the front part of the region enclosed by the projected curve and as close as possible to the projected curve is selected.

4. Method according to claim 1, wherein a navigated sensor is used for recording the positional data for the points located on the front edge of the notch.

5. Method according to claim 1, wherein, during the detection of the position of points on the front edge of the notch, an image of the front edge is shown on an image display of the data-processing system and the points for which the positional data are to be recorded are marked there.

6. Method according to claim 1, wherein the projected curve and the region enclosed by it are presented on an image display, the desired position for the exit point is selected on this image display by means of a displaceable image of a display element and the corresponding positional data are stored in the data-processing system.

7. Method according to claim 6, wherein a circle of a diameter corresponding to that of the implant used is selected as the display element.

8. Apparatus for determining the position on the upper side of the tibia of the exit point of an implant replacing the anterior cruciate ligament of a knee joint, having a navigation system, having marking elements fixedly connected to the femur and the tibia, having a navigated sensor and having a data-processing system which has a memory and a computer unit and to which the positional data for a number of points along the front edge of the notch recorded by the navigation system can be fed and stored in the memory, wherein the computer unit is programmed in such a way that it projects the positional data stored in the memory, and with it the course of the front edge of the notch with the leg straight, onto a projection plane in the region of the upper side of the tibia, which plane is perpendicular to the longitudinal axis of the tibia, and thereby produces a U-shaped projected curve which encloses a region in which the exit point is located.

9. Apparatus according to claim 8, wherein the computer unit is programmed in such a way that it projects a circular area of a diameter corresponding to the diameter of the implant used into the projection plane and displaces it in the area enclosed by the projected curve such that the circular area does not intersect the projected curve, and in that in one of the positions of the circular area achieved in this way the computer unit selects its center point as the exit point for the implant.

10. Apparatus according to claim 9, wherein the computer unit is programmed in such a way that it selects a position for the exit point in which the latter lies as far as possible in the front part of the region enclosed by the projected curve and as close as possible to the projected curve.

11. Apparatus according to claim 8, wherein the computer unit of the data-processing system is programmed in such a way that, during the detection of the position of points on the front edge of the notch, it forms an image of the front edge on an image display of the data-processing system and marks there the points for which the positional data are to be recorded.

12. Apparatus according to claim 8, wherein the computer unit is programmed in such a way that it presents the projected curve and the region enclosed by it on an image display and also presents a displaceable image of a display element for the selected position of the exit point on this image display and stores the corresponding positional data for the selected position in a memory.

13. Apparatus according to claim 12, wherein the display element is a circular area of a diameter corresponding to that of the implant used.