ORTHOPEDIC SCREW FOR MEASURING A PARAMETER OF THE MUSCULARSKELETAL SYSTEM

• US 20100331894A1
• 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: Stein, Marc
• Granted Patent: US 8,690,929 B2
• Time in Patent Office: Days
• US Class Current: 606/301
• 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 dual-mode closed-loop measurement system (100) for capturing a transit time, phase, or frequency of energy waves propagating through a medium (122) is disclosed. A first module comprises an inductor drive circuit (102), an inductor (104), a transducer (106), and a filter (110). A second module housed in a screw (335) comprises an inductor (114) and a transducer (116). The screw (335) is bio-compatible and allows an accurate delivery of the circuit into the muscular-skeletal system. The inductor can be attached and interconnected on a flexible substrate (331) that fits into a cavity in the screw (335). The first and second modules are operatively coupled together. The first module provides energy to power the second module. The second module emits an energy wave into the medium that propagates to the first module. The transit time of energy waves is measured and correlated to the parameter by known relationship.

Claims

1. An orthopedic screw comprising:

a screw including a cavity; and

a passive circuit within the cavity to emit an energy wave in a medium.

2. The orthopedic screw of claim 1 further including:

an inductor; and

a transducer operatively coupled to the inductor.

3. The orthopedic screw of claim 2 further including a flexible substrate where the inductor and transducer are mounted to the substrate and where the substrate includes interconnect for coupling the inductor to the transducer.

4. The orthopedic screw of claim 3 where die of the inductor and transducer is stacked.

5. The orthopedic screw of claim 2 where the flexible substrate is altered from a planar shape to fit in the cavity of the screw.

6. The orthopedic screw of claim 1 further including a module in closed-loop feedback with the inductor and the transducer of the orthopedic screw.

7. The orthopedic screw of claim 6 where the module is coupled in a first path to the inductor of the orthopedic screw electromagnetically.

8. The orthopedic screw of claim 7 where the module is coupled in a second path to the transducer of the orthopedic screw ultrasonically.

9. The orthopedic screw of claim 8 where the closed-loop feedback between the module and the orthopedic screw forms a propagation tuned oscillator for a continued emission, propagation, and detection of energy waves in the medium and where an energy wave transit time, frequency, or phase is monitored over a predetermined distance through the medium.

10. The orthopedic screw of claim 1 where the orthopedic screw is used to measure bone density of a muscular-skeletal system.

11. A method for measuring a parameter of the muscular-skeletal system comprising the steps of:

coupling a first module to a first location of a medium; and

screwing an orthopedic screw in a second location of the medium where the orthopedic screw includes a second module where the first and second modules are in communication.

12. The method of claim 11 further including the steps of:

coupling the first and second modules in a first path electromagnetically; and

coupling the first and second modules in a second path through an energy wave propagating through the medium between the first and second locations.

13. The method of claim 12 further including a step of energizing a transducer in the orthopedic screw to emit an energy wave using electromagnetic energy from the first path coupling,

14. The method of claim 11 further including the steps of:

sending an electromagnetic signal from the first module to the second module;

emitting an energy wave from the orthopedic screw at the second location of the medium where the energy wave propagates in the medium;

detecting the energy wave at the first location in the medium; and

measuring one of transit time, frequency, or phase of the energy wave having propagated from the first location to the second location of the medium.

15. The method of claim 14 further including a step of closing a loop comprising the first path and the second path to sustain an emission, propagation, and detection of energy waves in the medium.

16. A parameter measurement system comprising:

a screw including a cavity;

a circuit within the cavity comprising an inductor operatively coupled to a transducer; and

a module operatively coupled to the circuit in the screw where the module provides energy to the circuit to enable the transducer to emit an energy wave coupled through the screw and into a medium to which a screw is attached.

17. The parameter measurement system of claim 16 where the module is electromagnetically coupled to the inductor of the circuit in a first path and where the module is acoustically coupled to the transducer in a second path.

18. The parameter measurement system of claim 17 where the screw allows a deliver of the circuit in a bio-compatible manner into the muscular-skeletal system.

19. The parameter measurement system of claim 17 where the parameter to be measured is applied to the medium, where the energy wave emitted by the circuit propagates through the medium, where one of a transit time, frequency, or phase of the energy wave over a predetermined distance is measured, and where the parameter is calculated by known relationship to the measured transit time, frequency, or phase.

20. The parameter measurement system of claim 19 where the module and circuit form a closed-loop that continues the emission, propagation, detection, and measurement of energy waves in the medium.