Method for planning positioning of a ball joint prosthesis

Patent metadata

Field	Value
Publication number	US-9713539-B2
Application number	US-201113997388-A
Country	US
Kind code	B2
Filing date	Jan 20, 2011
Priority date	Jan 20, 2011
Publication date	Jul 25, 2017
Grant date	Jul 25, 2017

Abstract

The present invention relates to a method for planning the positioning of a ball joint prosthesis, in particular a hip joint prosthesis, wherein the prosthesis includes a stem and a cup and the method comprises the following steps: —determining the geometric shape of the joint socket, in particular the acetabulum, and the geometric shape of the cup which is to be placed; —defining target areas where the cup has to abut the bony structure of the joint socket, in particular the acetabulum, in order for the cup to be sufficiently fixed; —determining actual areas of the cup which will abut the bony structure of the joint socket, in particular the acetabulum, when the cup is placed; —defining a requirement for the position and/or orientation of the cup on the basis of the position and/or size of the target areas and/or actual areas. The present invention also relates to a method for optimizing the positioning of a ball joint prosthesis, in particular a hip joint prosthesis, wherein the prosthesis includes a stem and a cup and the method comprises the following steps: —defining at least one requirement for the position and/or orientation of the cup; —calculating an optimum position and/or orientation of the cup on the basis of all the defined requirements being fulfilled.

First claim

It is claimed:

1. A computer-implemented medical method for planning an optimized positioning of a hip joint prosthesis, wherein the prosthesis includes a stem and a cup, the method employing a navigation system and a computer and comprising:
acquiring, by the navigation system, a geometric shape of an associated patient's acetabulum;
receiving, at the computer, the geometric shape of the acetabulum, and a geometric shape of the cup which is to be placed;
predefining, by the computer, at least one target area on the surface of the cup where the cup has to abut bony structure of the acetabulum in order for the cup to be sufficiently fixed within the acetabulum;
determining, by the computer based on the geometric shape of the acetabulum and the geometric shape of the cup, at least one actual area of the cup which will abut the bony structure of the acetabulum when the cup is placed;
defining, by the computer, defined requirements comprising at least one requirement for a position and/or an orientation of the cup on the basis of a position and/or a size of the at least one target area and the at least one actual area;
calculating, by the computer, at least one of an optimum position of the cup or an optimum orientation of the cup on the basis of all the defined requirements being fulfilled; and
displaying the optimum position and/or the optimum orientation of the cup to an associated surgeon in a surgical or pre-surgical environment, thereby enabling placement of the cup.

2. The method according to claim 1 , wherein the at least one target area is defined on the basis of the anatomical structure of the patient.

3. The method according to claim 2 , wherein at least one first target region of the at least one target area is defined in an iliac region of the acetabulum, and at least one second target region of the at least one target area is defined in an ischial region of the acetabulum.

4. The method according to claim 3 , wherein at least one third target region of the at least one target area is defined in a pubic region of the acetabulum.

5. The method according to claim 1 , wherein the defined requirements further comprise at least one of the following:
a range of motion (ROM) of the stem within the cup;
a safe zone according to Lewinnek;
a combined anteversion of the cup and the stem.

6. The method according to claim 1 , wherein the defined requirements further comprise:
determining, by the computer, the position of at least two points lying in an anterior region of the acetabular rim;
defining a requirement for the position and/or orientation of the cup on the basis of the determined positions of the at least two points lying in the anterior region of the acetabular rim.

7. The method according to claim 6 , wherein at least one point of the at least two points lying in an anterior region of the acetabular rim lies superior to a point at which the psoas tendon crosses the acetabular rim, and at least one point of the at least two points lying in an anterior region of the acetabular rim lies inferior to the point at which the psoas tendon crosses the acetabular rim.

8. The method according to claim 6 , wherein a threshold value is set for a distance between the rim of the cup and the determined positions of the at least two points lying in an anterior region of the acetabular rim.

9. The method according to claim 6 , wherein the cup is axially symmetrical and a threshold value is set for a distance between a plane which is perpendicular to the symmetry axis of the cup and the determined positions of the at least two points lying in an anterior region of the acetabular rim.

10. The method according to claim 1 , wherein at least one parameter is defined for calculating rotational degrees of freedom for the cup and/or a translational degrees of freedom of the cup,
wherein the rotational degrees of freedom for the cup is in at least one of an anteversion of the cup, an inclination of the cup, and/or a rotation of the cup, and
wherein the translational degrees of freedom of the cup is in at least one of a medial/lateral direction, a caudal/cranial direction, and/or an anterior/posterior direction.

11. The method according to claim 1 , wherein the calculating the at least one optimum position of the cup or the optimum orientation of the cup comprises iterative algorithms and/or algorithms employing brute-force techniques.

12. The method according to claim 10 , wherein a threshold value is set for the at least one parameter, and wherein a value for the at least one parameter below the threshold value is allowed and a value for the at least one parameter above the threshold value is not allowed.

13. The method according to claim 10 , wherein a threshold interval is set for the at least one parameter, and wherein a value for the at least one parameter below the threshold interval is allowed, a value for the at least one parameter above the threshold interval is not allowed, and a value for the at least one parameter within the threshold interval is allowed to a varying extent of allowance which decreases from a lower limit to an upper limit of the threshold interval.

14. The method according to claim 13 , wherein the varying extent of allowance follows a mathematical function, wherein the mathematical function is a sigmoid-like function.

15. The method according to claim 14 , wherein the sigmoid-like functions are combined to an overall error function via a multiplication of single error functions to enforce fulfillment of all single requirements.

16. The method according to claim 15 , wherein the multiplicative combination of sigmoid-like functions are transformed into an additive combination of error functions by taking logarithms.

17. The method according to claim 16 , wherein additional weightings are used to represent the importance of the single error functions within the optimization procedure.

18. The method according to claim 1 , wherein the search space is reduced by analysing the region where bony respectively prosthetic impingements dominate the joint's range-of-motion in specified motion directions.

19. A medical planning system for planning an optimized positioning of a hip joint prosthesis, wherein the prosthesis includes a stem and a cup, comprising:
a medical navigation system, the medical navigation system being configured to acquire a geometric shape of an associated patient's acetabulum;
a display unit; and
a computer operatively associated with the medical navigation system and the display unit, the computer being programmed to:
receive the geometric shape of the associated patient's acetabulum, and a geometric shape of the cup which is to be placed;
predefine at least one target area on the surface of the cup where the cup has to abut bony structure of the acetabulum in order for the cup to be sufficiently fixed within the acetabulum;
determine, based on the geometric shape of the acetabulum and the geometric shape of the cup, at least one actual area of the cup which will abut the bony structure of the acetabulum when the cup is placed;
define defined requirements comprising at least one requirement for a position and/or an orientation of the cup on the basis of a position and/or a size of the at least one target area and the at least one actual area;
calculate at least one of an optimum position of the cup or an optimum orientation of the cup on the basis of all the defined requirements being fulfilled; and
display on the display unit the optimum position and/or the optimum orientation of the cup to an

Assignees

• Haimerl Martin
• Dohmen Lars
• Wegner Melanie
• Gneiting Sabine
• Brainlab Ag

Inventors

• Haimerl Martin
• Dohmen Lars
• Wegner Melanie
• Gneiting Sabine

Classifications

• A61B2034/104

  Modelling the effect of the tool, e.g. the effect of an implanted prosthesis or for predicting the effect of ablation or burring · CPC title

• A61B2034/107

  Visualisation of planned trajectories or target regions · CPC title

• A61B34/10

  Computer-aided planning, simulation or modelling of surgical operations · CPC title

• A61F2/4609 Primary

  of acetabular cups · CPC title

• A61B34/20 Primary

  Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis · CPC title