Systems and methods for ultrasonic detection of device distraction

1. A method of using ultrasound to measure relative movement between two portions of an implantable medical device, the method comprising:

providing an implantable medical device comprising:

a first elongate member having a first end configured for attachment to a first portion of a skeletal system of a subject, a second end, and a first landmark identifiable by ultrasound; and

a second elongate member having a first end movably coupled to the second end of the first elongate member, a second end configured for attachment to a second portion of the skeletal system, and a second landmark identifiable by ultrasound, wherein movement of the first elongate member in relation to the second elongate member causes a corresponding movement of the first landmark in relation to the second landmark which can be detected using ultrasound; and

implanting the implantable medical device within the subject such that a distance separating the first landmark and the second landmark may be determined at least partially from an image produced by placing an ultrasound probe adjacent the subject's skin near the first landmark and the second landmark.

2. The method of claim 1 , further comprising the step:

placing an ultrasonic probe in a vicinity of one or more of the first landmark and the second landmark.

3. The method of claim 1 , further comprising the step:

obtaining an ultrasound image.

4. The method of claim 1 , further comprising the step:

determining the distance separating the first landmark and the second landmark using the ultrasound image.

5. The method of claim 1 , wherein the first landmark is located on a surface of the first elongate member.

6. The method of claim 1 , wherein the first landmark is located at the second end of the first elongate member.

7. The method of claim 1 , wherein the first landmark comprises a plurality of landmarks spaced along the first elongate member.

8. The method of claim 1 , wherein the second landmark is located on a surface of the second elongate member.

9. The method of claim 1 , wherein the second landmark comprises a plurality of landmarks spaced along the second elongate member.

10. The method of claim 1 , wherein the second landmark comprises at least one pit.

11. The method of claim 1 , wherein the implantable medical device further comprises a magnet configured to be rotated by an external moving magnetic field and configured to move the second elongate member in relation to the first elongate member.

12. The method of claim 1 , wherein one of the first elongate member and the second elongate member comprises a metallic material.

13. A method of using ultrasound to measure relative movement between a first and second elongate member of a medical device implanted in a subject, the method comprising:

placing an ultrasound probe adjacent to at least one of a first landmark and a second landmark of a medical device; and

producing an ultrasound image of the first landmark and the second landmark; determining a distance separating the first landmark and the second landmark at least partially from the image.

14. The method of claim 13 , wherein the ultrasound probe comprises a transducer configured to run at a frequency of 5-10 MHz.

15. The method of claim 14 , wherein the ultrasound probe comprises a linear array transducer.

16. The method of claim 15 , wherein the distance separating the first landmark and the second landmark may be determined at least partially by using an on-screen caliper of an ultrasound console displaying the ultrasound image.

17. The method of claim 15 , wherein the distance separating the first landmark and the second landmark may be determined by performing a scaling operation based on a previously known dimension of the medical device.

18. The method of claim 15 , wherein one of the first elongate member and the second elongate member comprises a metallic material.

19. A device for ultrasonic detection of relative movement between a first member and a second member comprising:

a first member having a first ultrasound scatter pattern;

at least one landmark disposed on a surface of the first member and having a second ultrasound scatter pattern, wherein the second ultrasound scatter pattern can be detected by and distinguished from the first ultrasound scatter pattern using ultrasound;

a second member moveable relative to the first member and having a third ultrasound scatter pattern;

at least one landmark disposed on a surface of the second member and having a fourth ultrasound scatter pattern, wherein the fourth ultrasound scatter pattern can be detected by and distinguished from the third ultrasound scatter pattern using ultrasound, and

wherein using ultrasound detection of the second ultrasound scatter pattern with respect to the first ultrasound scatter pattern and the fourth ultrasound scatter pattern with respect to the third ultrasound scatter pattern allows detection and quantification of relative movement between the first member and the second member.

20. The device of claim 19 , wherein an amount of movement of the first member in relation to the second member is determined by measuring a distance between the at least one landmark disposed on the surface of the first member and the at least one landmark disposed on the surface of the second member on an ultrasonic image.