Edge-detect receiver for orthopedic parameter sensing

• US 8,490,488 B2
• Filed: 06/29/2010
• Issued: 07/23/2013
• Est. Priority Date: 06/30/2009
• Status: Expired due to Fees

• Current Assignee: OrthoSensor, Inc (Stryker Corporation)
• Original Assignee: OrthoSensor, Inc (Stryker Corporation)
• Inventors: Stein, Marc, Kelly, Andrew
• Primary Examiner(s): Chang, Leonard
• Assistant Examiner(s): HULS, NATALIE F
• Application Number:
  US12/826,085
• Publication Number:
  US 20100326194A1
• Time in Patent Office: 1,120 Days
• Field of Search: 735/84, 736/58
• US Class Current: 73/584
• 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 sensor system uses positive closed-loop feedback to provide energy waves into a medium. A sensor comprises a transducer (604), a propagating structure (602), and a reflecting surface (606). A parameter is applied to the propagating structure that affects the medium. The sensor is coupled to a propagation tuned oscillator (416) that forms the positive closed-loop feedback path with the sensor. The propagation tuned oscillator (416) includes an edge-detect receiver (200) that generates a pulse upon sensing a wave front of an energy wave in propagating structure (602). The edge-detect receiver (100) is in the feedback path that continues emitting energy waves into the propagating structure (602). The edge-detect receiver (200) comprises a preamplifier (212), a differentiator (214), a digital pulse circuit (216), and a deblank circuit (218). The transit time, phase, or frequency is measured of the propagating energy waves and correlated to the parameter being measured.

Claims

1. A sensor for measuring a parameter of the muscular-skeletal system where the parameter being measured affects a medium, where the medium is coupled to or part of the muscular-skeletal system, where the sensor is configured to measure at least one of transit time, phase, or frequency of pulsed energy waves traversing the medium from a first point of the medium to a second point of the medium, where a change in the parameter being measured affects at least one of the transit time, phase, or frequency of the pulsed energy waves and where at least one of transit time, phase, or frequency is converted to the parameter being measured, the sensor comprising:

a transducer coupled to the medium configured to detect a pulsed energy wave; and

an edge-detect receiver coupled to the transducer where the edge-detect receiver is configured to detect an energy wave at the second point of the medium, where the edge-detect receiver detects a wave front of pulsed energy waves and is configured to generate a blanking period where trailing signals of pulsed energy waves are ignored, where the edge-detect receiver is coupled in a positive closed-loop feedback path with the medium and configured to initiate continued generation and propagation of pulsed energy waves through the medium.

2. The sensor of claim 1 where the pulsed energy waves are provided at a first location of the medium, where the edge-detect receiver is coupled to a second location of the medium, where the edge-detect receiver initiates a pulsed energy wave being provided at the first location upon detecting a wave front at the second location, and where the sensor measures one of distance, weight, strain, pressure, wear, vibration, viscosity, and density.

3. The sensor of claim 1 where the edge detect receiver comprises:

a preamplifier operatively coupled to the second location to receive a pulsed energy wave;

a differentiator operatively coupled to the preamplifier to detect a change in slope;

a pulse circuit operatively coupled to the differentiator to generate a pulse on a wave front of a pulsed energy wave; and

a deblank circuit configured to generate a blanking period for a predetermined time period where trailing signals of a pulsed energy wave are not processed.

4. The sensor of claim 1 where the edge-detect receiver is configured to output a single pulse in response to an energy wave.

5. The receiver of claim 3 where a change in slope detected by the differentiator comprises a change in current.

6. The receiver of claim 3 where the pulse circuit generates a pulse on a leading edge of the pulsed energy wave.

7. The receiver of claim 3 where the deblank circuit is operatively coupled to the preamplifier to desensitize the preamplifier from trailing signals of the pulsed energy wave.

8. The receiver of claim 7 where the deblank circuit desensitizes the preamplifier by at least one of reducing gain, decoupling the input of the preamplifier from the transducer, or changing the frequency response.

9. The receiver of claim 3 where the preamplifier is configured to not process an input signal to the preamplifier during a blanking period.