Spreader tensiometer for measuring tension in an intervertebral disc space

• US 20040059262A1
• Filed: 09/20/2002
• Published: 03/25/2004
• Est. Priority Date: 09/20/2002
• Status: Active Grant

• Current Assignee: Depuy Acromed
• Original Assignee: Depuy Acromed
• Inventors: Grinberg, Alexander
• Granted Patent: US 7,172,561 B2
• Time in Patent Office: Days
• US Class Current: 600/587
• CPC Class Codes: A61B 2017/00261 Discectomy
• CPC Class Codes: A61B 2017/0256 for the spine
• CPC Class Codes: A61B 2090/064 for measuring force, pressure or mechanical tension
• CPC Class Codes: A61B 90/06 Measuring instruments not otherwise provided for
• CPC Class Codes: A61F 2/442 Intervertebral or spinal discs, e.g. resilient non-disc-shaped intervertebral inflatable pockets A61F2/441; non-disc-shaped intervertebral fusion implants A61F2/4455
• CPC Class Codes: A61F 2/4603 for insertion or extraction of endoprosthetic joints or of accessories thereof
• CPC Class Codes: A61F 2002/30616 Sets comprising a plurality of prosthetic parts of different sizes or orientations
• CPC Class Codes: A61F 2002/4667 for measuring torque

Abstract

The present invention relates to a novel spreader tensiometer adapted for use in measuring tension in an intervertebral disc space.

Claims

1. A tensiometer for measuring tension in an intervertebral disc space between opposed vertebral surfaces, comprising:

a) a disc spacer spreader adapted to enter a disc space and distract the disc space upon rotation,

b) a torque gauge adapted to engage the disc space spreader and report a torque required for the rotation of the spreader.

2. The tensiometer of claim 1 wherein the spreader comprises:

i) a distal pedal portion having upper and lower surfaces defining a thickness T therebetween, and lateral surfaces defining a width W therebetween, the upper and lower surfaces being adapted to enter the disc space, the lateral surfaces being adapted for bearing against the opposed vertebral surfaces, the width being greater than the thickness, and

ii) a proximal portion.

3. The tensiometer of claim 2 wherein the width defined by the lateral surfaces of the pedal is between 2 and 4 times the thickness defined by the upper and lower surfaces of the pedal.

4. The tensiometer of claim 3 wherein the width of the pedal is between 6 mm and 20 mm.

5. The tensiometer of claim 2 wherein the lateral surfaces have a convex shape.

6. The tensiometer of claim 5 wherein at least one of the lateral surfaces and the upper surface meet at a junction, wherein the junction has a radius of between 0.5 and 1.5 mm.

7. The tensiometer of claim 2 wherein the pedal further comprises a tapered leading edge.

8. The tensiometer of claim 2 wherein the spreader further comprises an intermediate portion sized to provide a device working length of about 200 mm.

9. The tensiometer of claim 2 wherein the proximal portion of the spreader is adapted to engage the distal portion of the torque gauge.

10. The tensiometer of claim 2 wherein the proximal portion of the pedal comprises a radially-extending stop.

11. The tensiometer of claim 1 wherein the torque gauge comprises:

i) a housing,

ii) a twistable longitudinal beam having a distal end fixedly attached to the housing and a proximal end, and

iii) a means for measuring a deflection of the beam relative to the housing when a torque is applied to the beam.

12. The tensiometer of claim 11 wherein the beam has a shape adapted to twist about the longitudinal axis in relation to the distal end when a torque is applied to the proximal end.

13. The tensiometer of claim 11 wherein the beam has a length and a greatest cross-sectional dimensoin, and the length is at least 10 times greater than the greatest cross-sectional dimension.

14. The tensiometer of claim 11 wherein the distal end of the beam comprises an attachment flange.

15. The tensiometer of claim 11 wherein the housing comprises a body fixedly attached to the distal portion of the beam.

16. The tensiometer of claim 15 wherein the body forms an outer shell around the beam.

17. The tensiometer of claim 15 wherein the body further includes a flange extending outwardly from the body and forming a proximal face.

18. The tensiometer of claim 17 wherein the flange is located on the proximal portion of the outer shell.

19. The tensiometer of claim 14 wherein the housing comprises a body fixedly attached to the spreader.

20. The tensiometer of claim 19 wherein the body is fixedly attached to the proximal portion of the spreader.

21. The tensiometer of claim 20 wherein the body forms an outer shell around the proximal portion of the spreader.

22. The tensiometer of claim 19 wherein the body further includes a flange extending outwardly from the body and forming a proximal face.

23. The tensiometer of claim 22 wherein the flange is located on the proximal portion of the outer shell.

25. The tensiometer of claim 11 wherein the means for measuring the deflection of the beam comprises a stationary member fixedly connected to the housing, and a moveable member fixedly connected to the beam.

26. The tensiometer of claim 25 wherein the stationary member comprises a plate having proximal face having a graduated scale thereon at a radius.

27. The tensiometer of claim 26 wherein the moveable member has a needle shape extending radially to the radius of the graduated scale.

28. The tensiometer of claim 27 wherein the moveable member is attached to the proximal portion of the beam.

29. The tensiometer of claim 25 further comprising:

c) a handle comprising;

i) a distal portion adapted for engaging the proximal portion of the beam, and

ii) a proximal portion adapted for gripping.

30. The tensiometer of claim 29 wherein the moveable member is located on the handle, and extends radially outward from the handle.

31. The tensiometer of claim 25 wherein the moveable member is located at a position proximal to the stationary member.

32. The tensiometer of claim 25 wherein the stationary member comprises a graduated scale, and the moveable member comprises an indicator.

33. The tensiometer of claim 1 wherein the torque gauge comprises:

i) an body portion having;

a distal end portion having an attachment port, and

a proximal end portion having a flange extending radially therefrom forming a proximal face,

ii) an intermediate twistable longitudinal beam having a longitudinal axis, and comprising a distal end portion fixed to the distal end portion of the body portion and a proximal end portion capable of twisting rotation in response to proximally-applied axial torque,

iii) a flat plate attached to the proximal face of the flange, the plate having a proximal face having a graduated scale thereon, and

iv) an indicator extending outwardly from the proximal end portion of the bar and adapted to rotate in correspondence with rotational movement of the longitudinal beam, the indicator being located proximal to the graduated scale.

34. A method of measuring tension in an intervertebral disc space formed from opposed vertebral endplates, comprising:

a) providing a tensiometer for measuring tension in an intervertebral disc space between opposed vertebral endplates, comprising;

a disc spacer spreader comprising a distal pedal having lateral surfaces, the pedal adapted to enter a disc space and distract the disc space upon rotation,

a torque gauge adapted to engage the disc space spreader and report a torque produced by rotation of the spreader,

b) advancing the distal pedal into the disc space,

c) rotating the pedal to bear the lateral surfaces against the opposed endplates, and

d) reading a report of torque on the torque gauge.