Rotational position determination

Patent metadata

Field	Value
Publication number	US-10039606-B2
Application number	US-201214431848-A
Country	US
Kind code	B2
Filing date	Sep 27, 2012
Priority date	Sep 27, 2012
Publication date	Aug 7, 2018
Grant date	Aug 7, 2018

Abstract

A method and a device is provided for determining a rotational position of a first feature of a first bone section relative to a second feature of a second bone section, the method comprises the steps of determining a longitudinal axis of a bone and determining a plane extending perpendicular to the longitudinal axis of the bone, determining a first projected vector representing a first direction defined by a feature of the first bone section, determining a second projected vector representing a second direction defined by a feature of the second bone section, and determining an angle between the first projected vector and the second projected vector.

First claim

The invention claimed is:

1. A method for determining a rotational position of a first feature of a first bone section of a fractured bone relative to a second feature of a second bone section of the fractured bone for connecting any misalignment between the first and second bone sections caused by the bone fracture, the method comprising the steps of:
determining a longitudinal axis (X) of a bone and determining a transverse plane (P) extending perpendicular to the longitudinal axis of the bone;
determining a first projected vector (V 1 p ) in the plane (P), based on a first direction defined by a feature of the first bone section of the fractured bone;
determining a second projected vector (V 2 p ) in the plane (P), based on a second direction defined by a feature of the second bone section of the fractured bone;
determining an angle A between the first projected vector (V 1 p ) and the second projected vector (V 2 p ) to determine any anatomical misalignment between the first and second bone sections of the fractured bone;
determining from a database of non-fractured bones an angle B between the first projected vector (V 1 p ) and the second projected vector (V 2 p ) of a non-fracture bone; and
rotating the first bone section relative to the second bone section through an angle C being the difference between angle A and angle B.

2. The method of claim 1 , wherein determining at least one of the first and second projected vectors (V 1 p , V 2 p ) comprises the steps of identifying at least two points at the feature of the corresponding bone section, and projecting the at least two points onto the plane (P), the two projected points (TP 1 , TP 2 ) defining the projected vector (V 1 p , V 2 p ).

3. The method of claim 1 , wherein at least one of the longitudinal axis (X) of the bone, the feature of the first bone section and the feature of the second bone section is determined on the basis of a 3D image of at least a section of the bone.

4. The method of claim 1 , wherein at least one of the longitudinal axis (X) of the bone, the feature of the first bone section and the feature of the second bone section is determined on the basis of a 2D image of at least a section of the bone, wherein the 2D image further includes a visualization of a reference body.

5. The method of claim 4 , wherein the reference body comprises a structure forming a characteristic 2D projection image for determining a 3D orientation of the reference body.

6. The method of claim 4 , wherein the reference body is adapted to be fixedly connected to the bone.

7. The method of claim 4 , wherein the reference body is at least a part of an implant.

8. The method of claim 7 , wherein the implant comprises an axis and the axis of the implant represents one of the longitudinal axis (X) of the bone, the feature of the first bone section and the feature of the second bone section.

9. The method of claim 4 , wherein the reference body is adapted to be fixedly connected to the first bone section while being visible in an image showing the second bone section.

10. The method of claim 9 , wherein the reference body is at least a part of an aiming device.

11. A device for determining a rotational position of a first feature of a first bone section relative to a second feature of a second bone section of a fractured bone, the device comprising a processing unit adapted for:
determining a longitudinal axis (X) of a bone based on received image data, and determining a transverse plane (P) extending perpendicular to the longitudinal axis of the bone;
determining, based on received image data, a first projected vector (V 1 p ) in the plane (P), based on a first direction defined by a feature of the first bone section of a fractured bone;
determining, based on received image data, a second projected vector (V 2 p ) in the plane (P), based on a second direction defined by a feature of the second bone section of a fractured bone;
determining an angle A between the first projected vector (V 1 p ) and the second projected vector (V 2 p );
determining whether the angle A represents a correct alignment between the first and second sections of the fractured bone by comparing angle A to angle B of a non-fractured bone;
determining from a database of non-fractured bones an angle B between the first projected vector (VIP) and the second projected vector (V 2 p ) of a non-fractured bone; and
calculating an angle C being the difference between angles A and B for rotationally aligning the first and second bone sections.

12. The device of claim 11 , further comprising an imaging unit for providing 2D projection image data of at least a section of the bone.

13. The device of claim 12 , wherein the processing unit is further adapted for identifying a projection of a reference body and for determining a 3D orientation of the reference body.

14. The device of claim 11 , wherein the imaging unit is adapted to provide 3D image data of at least a section of the bone.

15. A computer software which when executed on the processing unit of the device of claim 11 causes the device to perform the steps of the method of claim 1 .

16. A method for determining and correcting any rotational misalignment between a proximal portion and a distal portion of a fractured femur caused by the fracture comprising:
inserting a bone nail into the fractured femur along a longitudinal axis of the fractured femur;
inserting a screw through the bone nail in an axis transverse to the longitudinal axis;
taking a digital fluoroscopic image of the bone nail, screw and fractured femur including the proximal portion and distal portion of the long bone along a viewing direction (VD);
displaying the digital image on a monitor;
defining a transverse plane perpendicular to the longitudinal axis in the displayed digital image;
projecting a first vector defined by the transverse axis of the bone screw onto the displayed transverse plane;
projecting a second vector onto the displayed transverse plane, the second vector tangent to points on the posterior medial and lateral condyles on the distal portion of the fractured femur;
using a computer to determine an angle A between the first and second vectors to determine any misalignment between the proximal and distal portions of the fractured femur by comparing the angle A between the first and second vectors of the fractured femur to an angle B between the same first and second vectors of a healthy counterpart of the fractured femur contained in a database of healthy femurs; and
rotating the proximal portion of the fractured bone about the bone nail axis with respect to the distal portion about an angle C being the difference between angle A and angle B to correct the determined misalignment.

17. The method as set forth in claim 16 wherein the healthy counterpart femur is chosen from the database of healthy femurs based on the width of the shaft or the diameter of the femoral head relative to the distance between the femoral condyles (DC) of the fractured femur.

18. The method of claim 17 further comprising measuring the distance Dm between the condyles tangent points of the second vector along the viewing direction (VD);
calculating with the computer the angle B between the viewing direction and the second vector by calculating the arc sinus of Dm/Dc, calculating the angle C between the viewing direction (VD) and the first vector;
calculating the angle between the first and second vector (angle A) by subtracting angle C from angle B;
comparing the calculated angl

Assignees

• Stryker European Holdings I Llc

Inventors

• Blau Arno
• Simon Bernd

Classifications

• G06T7/73

  using feature-based methods · CPC title

• A61B17/1725

  for applying transverse screws or pins through intramedullary nails or pins · CPC title

• A61B17/1703 Primary

  using imaging means, e.g. by X-rays · CPC title

• G06T2207/30008

  Bone · CPC title

• A61B19/50 Primary

  Human Necessities · mapped topic