Method and device for evaluating the balance forces of the skeleton

• US 20040228510A1
• Filed: 06/25/2004
• Published: 11/18/2004
• Est. Priority Date: 12/28/2001
• Status: Active Grant

• Current Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Original Assignee: SDGI Holdings Incorporated (Medtronic Plc)
• Inventors: Roussouly, Pierre, Berthonnaud, Eric, Dimnet, Joannes
• Granted Patent: US 7,361,150 B2
• Time in Patent Office: Days
• US Class Current: 382/128
• 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 5/4023 Evaluating sense of balance
• CPC Class Codes: A61B 5/4519 Muscles A61B5/389, A61B5/224 take precedence
• CPC Class Codes: A61B 5/4528 Joints A61B5/4533, A61B5/4538 take precedence
• CPC Class Codes: A61B 5/4561 Evaluating static posture, e.g. undesirable back curvature A61B5/1116 takes precedence

Abstract

The invention concerns a method which consists in producing a radiographic image of the skeleton to be studied, determining the position of the body'"'"'s global axis of gravity (5), selecting on the image segments of the skeleton (S1-S7) to be considered and their articulations (A5), locating the main tensor muscles (M1-M6, M62), and determining by calculation the intensity of the return forces exerted by said tensor muscles to compensate the gravitational force.

Claims

1. A method for evaluating the balance forces of a skeleton within a subject'"'"'s body, comprising:

a) producing a radiographic image of the skeleton, the skeleton having segments articulated to one another, taken in a plane generally perpendicular to the rotation axes of the articulations of the skeleton,

b) simultaneously determining the position of the overall axis of gravity (5) of the subject'"'"'s body on the radiographic image,

c) selecting the skeleton segments articulated to one another on the radiographic image, identifying their positions and those of the articulations, and assigning the weight of the subject'"'"'s body segment corresponding to each skeleton segment,

d) identifying the directions and anchoring points on the radiographic image of the main tensor muscles balancing the subject'"'"'s skeleton, and

e) determining the intensity of a restoring force exerted by the main tensor muscles by calculation, wherein the restoring force compensates for the rotational moment of the force of gravity applied to each skeleton segment about the lower articulation of said skeleton segment.

2. The method as claimed in claim 1, wherein a bearing force of each skeleton segment on its lower articulation is determined by calculation, wherein the bearing force is equal to the resultant of the force of gravity and of the restoring force applied to the skeleton segment.

3. The method as claimed in claim 1, wherein:

the selected skeleton segments comprise at least two segments selected from the group consisting of;

the head (S1), the cervical segment (S2), the dorsal segment (S3), the lumbar segment (S4), the pelvic segment (S5), and the femurs (S6), and

the main balancing tensor muscles comprise the main lateral and median agonist and antagonist muscles.

4. The method as claimed in claim 2, wherein:

the selected skeleton segments comprise at least two segments selected from the group consisting of;

the head (S1), the cervical segment (S2), the dorsal segment (S3), the lumbar segment (S4), the pelvic segment (S5), and the femurs (S6), and

the main balancing tensor muscles comprise the main lateral and median agonist and antagonist muscles.

5. The method as claimed in claim 1, wherein the subject is placed in a stable balance position, the successive positions of the overall axis of gravity (5) for a few seconds are stored with a frequency of several acquisitions per second, wherein the set of stored positions comprise an elliptical cloud of positions, and

wherein the dispersion ellipse which envelopes said cloud of positions is determined, and wherein the radiographic images corresponding to an overall axis of gravity (5) whose position lies in the dispersion ellipse are selected.

6. The method as claimed in claim 2, wherein the subject is placed in a stable balance position, the successive positions of the overall axis of gravity (5) for a few seconds are stored with a frequency of several acquisitions per second, wherein the set of stored positions comprise an elliptical cloud of positions, and

wherein the dispersion ellipse which envelopes said cloud of positions is determined, and wherein the radiographic images corresponding to an overall axis of gravity (5) whose position lies in the dispersion ellipse are selected.

7. The method as claimed in claim 3, wherein the subject is placed in a stable balance position, the successive positions of the overall axis of gravity (5) for a few seconds are stored with a frequency of several acquisitions per second, wherein the set of stored positions comprise an elliptical cloud of positions, and

wherein the dispersion ellipse which envelopes said cloud of positions is determined, and wherein the radiographic images corresponding to an overall axis of gravity (5) whose position lies in the dispersion ellipse are selected.

8. The method as claimed in claim 4, wherein the subject is placed in a stable balance position, the successive positions of the overall axis of gravity (5) for a few seconds are stored with a frequency of several acquisitions per second, wherein the set of stored positions comprise an elliptical cloud of positions, and

wherein the dispersion ellipse which envelopes said cloud of positions is determined, and wherein the radiographic images corresponding to an overall axis of gravity (5) whose position lies in the dispersion ellipse are selected.

9. The method as claimed in claim 5, wherein the margin of error in the evaluation of the restoring or bearing forces is determined by calculation as a function of the dispersion ellipse.

10. A device for evaluating the balance forces of the skeleton of a subject, the skeleton having segments articulated to one another and the subject having balancing tensor muscles attached to the skeleton at anchoring points, comprising:

an X-ray source (1) and support means for a target plate (2) sensitive to X-rays,

a subject support plate (3) for supporting the subject (4) in a fixed position between the X-ray source and the support means for the target plate (2) and to generate image position signals of a horizontal position (Og) of the overall axis of gravity (5) of the subject (4),

means (20) for digitizing the radiographic image of the subject on the target plate, so as to generate a digitized radiographic image which is stored in a suitable memory,

means (21) for superimposing the digitized image of a shadow (Hg), cast by the overall axis of gravity (5) on the target plate (2), onto the digitized radiographic image of the subject,

means (22) for selecting, on the digitized radiographic image, the articulated skeleton segments and their articulations, and the anchoring points of the balancing tensor muscles, and

computation means (21) and a program for calculating the intensity of the restoring force exerted by the balancing tensor muscles, wherein the restoring force compensates for the rotational moment of the force of gravity applied to each skeleton segment about the lower articulation of said skeleton segment.

11. The device as claimed in claim 10, further comprising means for evaluating variations in the subject'"'"'s vertical posture by the dimensions of the horizontal-position dispersion ellipse of the subject'"'"'s overall axis of gravity (5), when the subject occupies a stable position.

12. The device as claimed in claim 10, wherein the program further comprises one or more acquisition sequences according to which:

the positions on the radiographic image of the articulations, the segments and the anchoring points of the balancing tensor muscles are selected; and

the means (20) for digitizing the radiographic image of the subject store the selected positions in the memory.

13. The device as claimed in claim 11, wherein the program further comprises one or more acquisition sequences according to which:

the positions on the radiographic image of the articulations, the segments and the anchoring points of the balancing tensor muscles are selected; and

the means (20) for digitizing the radiographic image of the subject store the selected positions in the memory.

14. The device as claimed in claim 10, wherein the program further comprises one or more acquisition sequences according to which:

the digitized radiographic image is displayed on a screen (23),

the positions of the articulations, the segments and the anchoring points of the balancing tensor muscles on said digitized radiographic image are selected by means of an input/output device such as a keyboard (22) or a mouse; and

the program stores the coordinates of the selected points.

15. The device as claimed in claim 11, wherein the program further comprises one or more acquisition sequences according to which:

the digitized radiographic image is displayed on a screen (23),

the positions of the articulations, the segments and the anchoring points of the balancing tensor muscles on said digitized radiographic image are selected by means of an input/output device such as a keyboard (22) or a mouse; and

the program stores the coordinates of the selected points.

16. The device as claimed in claim 12, wherein the program takes into account the dimension of the horizontal-position dispersion ellipse of the overall axis of gravity (5) in order to calculate a margin of error of the calculation of the muscular and contact forces.

17. The device as claimed in claim 13, wherein the program takes into account the dimension of the horizontal-position dispersion ellipse of the overall axis of gravity (5) in order to calculate a margin of error of the calculation of the muscular and contact forces.

18. The device as claimed in claim 14, wherein the program takes into account the dimension of the horizontal-position dispersion ellipse of the overall axis of gravity (5) in order to calculate a margin of error of the calculation of the muscular and contact forces.

19. The device as claimed in claim 15, wherein the program takes into account the dimension of the horizontal-position dispersion ellipse of the overall axis of gravity (5) in order to calculate a margin of error of the calculation of the muscular and contact forces.