LOAD SENSING PLATFORM FOR MEASURING A PARAMETER OF THE MUSCULAR-SKELETAL SYSTEM

• US 20100326210A1
• Filed: 06/29/2010
• Published: 12/30/2010
• Est. Priority Date: 06/30/2009
• Status: Active Grant

• Current Assignee: Howmedica Osteonics Corp. (Stryker Corporation)
• Original Assignee: OrthoSensor, Inc (Stryker Corporation)
• Inventors: Ellis, Jim, Stein, Marc
• Granted Patent: US 8,516,907 B2
• Time in Patent Office: Days
• US Class Current: 73/862.636
• CPC Class Codes: A61B 5/4509 Bone density determination
• CPC Class Codes: A61B 5/4528 Joints A61B5/4533, A61B5/4538 take precedence
• CPC Class Codes: A61B 5/6846 specially adapted to be brought in contact with an internal body part, i.e. invasive
• CPC Class Codes: A61B 5/6878 Bone
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 8/15 Transmission-tomography

Abstract

A load sensing platform (121) is disclosed for capturing a transit time, phase, or frequency of energy waves propagating through a medium that measures a parameter of the muscular-skeletal system. The load sensing platform (121) comprises a sensing assemblage (1), substrates (702, 704, and 706), springs (315), spring posts (708), and spring retainers (710). The sensing assemblage (1) comprises a stack of a transducer (5), waveguide (3), and transducer (6). A parameter is applied to the contact surfaces (8) of the load sensing platform (121). The sensing assemblage (1) measures changes in dimension due to the parameter. Position of the applied parameter can be measured by using more than one sensing assemblage (1). The springs (315) couple to the substrates (702, 704) providing mechanical support and to prevent cantilevering. The spring posts (708) and spring retainers (710) maintain the springs (315) at predetermined locations in the load sensing platform (121).

Claims

1. A load sensing platform comprising:

a load bearing surface;

a sensing assemblage coupled to the load bearing surface; and

at least one spring coupled to the load bearing surface where the at least one spring provides mechanical support for the load bearing surface and where the sensing assemblage measures a parameter applied to the load bearing surface.

2. The platform of claim 1 where the at least one spring prevents cantilevering of the load bearing surface.

3. The platform of claim 2 further including a spring retainer to retain the at least one spring coupled to a predetermined location of the load bearing surface.

4. The platform of claim 2 where the at least one spring has a linear range of displacement over a measurement range of the sensing assemblage.

5. The platform of claim 2 where the load sensing platform detects position of contact on the load bearing surface.

6. The platform of claim 2 where the at least one spring is coupled to a periphery or center of the load bearing surface.

7. The platform of claim 6 where the at least one spring is a wave spring and where the wave spring couples peripherally to the at least one load bearing surface.

8. The platform of claim 2 where the sensing assemblage comprises:

at least one transducer; and

a compressible waveguide.

9. The platform of claim 8 where the sensing assemblage measures a measures a transit time, frequency, or phase of an acoustic energy wave propagating through the compressible waveguide.

10. The platform of claim 9 where the platform measures a parameter of the muscular-skeletal system.

11. The platform of claim 10 where the platform is coupled between a joint of the muscular-skeletal system.

12. A load sensing platform to measure a parameter of the muscular-skeletal system comprising:

at least one load bearing surface;

at least one spring retainer;

at least one spring; and

a sensing assemblage to measure a parameter and position applied to the at least one load bearing surface where the sensing assemblage is mechanically coupled to the at least one load bearing surface and where the at least one spring retainer maintains a coupling of the at least one spring to a predetermined position on the at least one load bearing surface.

13. The load sensing platform of claim 12, where the at least one spring retainer retains a disc spring coupled to a periphery of the load bearing surface to support and balance the sensing assemblage.

14. The load sensing platform of claim 12 where the sensing assemblage comprises:

a first transducer;

a waveguide; and

a second transducer where the first transducer couples to the waveguide at a first location and the second transducer couples to the waveguide at a second location.

15. The load sensing platform of claim 13 where the waveguide serves as a spring bias.

16. The load sensing platform of claim 12 where the sensing assemblage comprises:

a single transducer to transmit and receive energy waves;

a waveguide where the single transducer is coupled to the waveguide at a first location; and

a reflecting feature at a second location of the waveguide where the single transducer emits an energy wave in the waveguide that is reflected by the reflecting feature to produce a reflected energy wave that is detected by the single transducer.

17. A method of measuring a parameter of the muscular-skeletal system:

applying the parameter to a load bearing surface where a change in the parameter produces a measurable change in one or more dimensions;

measuring the one or more dimensions;

converting a measured dimension to the applied parameter;

applying a spring force to the load bearing surface to reduce hysteresis and return a load bearing surface to a repeatable dimension under quiescent conditions.

18. The method of claim 17 further including the steps of:

coupling a waveguide to the load bearing surface where a waveguide length changes as a force is applied to the load bearing surface;

emitting a energy wave into the waveguide;

measuring one of a transit time, frequency, or phase of the energy wave through the waveguide;

converting a measured transit time, frequency, or phase to a length of the waveguide; and

converting the length of the waveguide to the parameter applied to the load bearing surface.

19. The method of claim 17 further including the steps of:

measuring a change in dimension due to the applied parameter on the load bearing surface at more that one location of the load bearing surface;

comparing a difference in measured parameters at the more than one location; and

determining an applied position of the parameter on the load bearing surface from the difference in measured parameters.

20. The method of claim 17 further including a step of applying the spring force around a periphery of the load bearing surface to prevent cantilevering.