PROSTHETIC LIMB MONITORING SYSTEM

• US 20100191153A1
• Filed: 01/27/2010
• Published: 07/29/2010
• Est. Priority Date: 01/27/2009
• Status: Active Grant

• Current Assignee: University of Washington
• Original Assignee: University of Washington
• Inventors: Myers, Timothy, Hafner, Brian, Sanders, Joan
• Granted Patent: US 9,072,463 B2
• Time in Patent Office: Days
• US Class Current: 600/587
• CPC Class Codes: A61B 5/1038 Measuring plantar pressure during gait
• CPC Class Codes: A61B 5/112 Gait analysis
• CPC Class Codes: A61B 5/4585 Evaluating the knee

Abstract

Parameters related to use of a prosthesis by a patient with a limb amputation are monitored using a tool that includes one or more piezoelectric force sensors. The resulting data are processed for use both in short and long term management of amputee patients. The sensor is a small modular unit that fits within or between traditional prosthetic components, e.g., below a prosthesis socket. The data produced by the tool are collected, processed, and stored. Optionally, the data are periodically communicated to a remote site via a network, e.g., over the Internet. The device and associated software used to process the data can be used to characterize activities conducted by a prosthesis user, to determine pistoning or threatening interface stress distributions between the limb and socket, mal-alignment of the socket, use of improper components, and other possibly undesired conditions that the amputee patient using the prosthesis may be experiencing.

Claims

1. Apparatus for collecting and processing data indicative of parameters experienced by a prosthesis while a user fitted with the prosthesis engages in activities, comprising:

(a) one or more piezoelectric sensors that are attached to the prosthesis to monitor forces experienced by the prosthesis as a result of the user wearing the prosthesis while engaging in the activities, each piezoelectric sensor developing a charge in response to a force applied to the sensor;

(b) for each piezoelectric sensor, an impedance transformation device having a relatively high input impedance and a relatively low output impedance, for receiving the charge developed by the piezoelectric sensor and producing a corresponding output signal indicative of the force applied to the piezoelectric sensor;

(c) at least one data device selected from a group of data devices consisting of;

(i) a wireless data transmitter that transmits data comprising the output signals to an external receiver;

(ii) a data storage coupled to receive the output signal from each impedance transformation device and storing the data comprising the output signal; and

(iii) a portable processor that accompanies the user while the user engages in the activities and is coupled to receive the output signal from each impedance transformation device, the processor processing the output signal to produce information indicative of the activities in which the user was engaged, where the information can be used to detect a problem related to the use of the prosthesis by the user; and

(d) a processing system, comprising a memory that stores machine instructions, and a processor that processes the data in accord with the machine instructions that are stored in the memory, wherein the machine instructions cause the processor to carry out a plurality of functions, including;

(i) dividing the data into intervals of time, wherein a duration of the intervals is selected to match features of interest needed to carry out a desired analysis of the data;

(ii) determining at least one type of parameter selected from a group of parameter types consisting of;

(A) force components, wherein each force component is directed along a different one of a plurality of orthogonal axes; and

(B a plurality of moments acting on the prosthesis;

(iii) segmenting the data into groups of segments based on the at least one type of parameter

2. The apparatus of claim 1, wherein the data are transmitted by the wireless data transmitter to the external receiver at the time the data are collected, further comprising a network interface that couples the external receiver to a network, enabling the data to be transmitted and processed in real-time at a desired remote location.

3. The apparatus of claim 1, further comprising a data link for transferring the data from the data storage for processing to characterize the activities performed by the user while wearing the prosthesis.

4. The apparatus of claim 1, wherein the impedance transformation device for at least one piezoelectric sensor is integral within a housing of the piezoelectric sensor.

5. The apparatus of claim 1, wherein the impedance transformation device comprises a charge amplifier.

6. The apparatus of claim 1, further comprising a charge amplifier that amplifies the charge output from the impedance transformation device, to produce the output signal indicative of the force.

7. The apparatus of claim 1, wherein the one or more piezoelectric sensors sense components of the force that is applied, along a plurality of orthogonal axes.

8. The apparatus of claim 1, wherein at least one piezoelectric sensor is disposed in a location selected from a group of locations consisting of:

(a) proximate a base of a socket of the prosthesis;

(b) proximate a base of a pylon of the prosthesis; and

(c) on or within a terminal device portion of the prosthesis.

9. The apparatus of claim 1, wherein at least one piezoelectric sensor produces an output signal indicative of bending of the prosthesis.

10. The apparatus of claim 1, further comprising a plurality of non-piezoelectric sensors that detect a pressure and are disposed on the prosthesis in locations appropriate to determine a center of pressure acting on the prosthesis.

11. The apparatus of claim 1, further comprising a plurality of non-piezoelectric sensors that detect a bending and which are disposed on the prosthesis in locations selected so that by using the data produced by the piezoelectric sensors, a resultant force location for forces acting on the prosthesis is determined.

12. The apparatus of claim 1, further comprising a source of electrical power that provides energizing electrical power.

13. The apparatus of claim 12, wherein the source of electrical power is selected from a group of sources consisting of:

(a) a kinetic source that responds to movement of the user by producing the electrical power;

(b) a thermal source that produces the electrical power in response to a temperature differential between an environment and the user'"'"'s body; and

(c) a chemical source that produces the electrical power as a result of chemical changes that occur while the user is using the prosthesis.

14. The apparatus of claim 1, wherein at least one piezoelectric sensor includes a housing having parallel plates that are sufficiently stiff to resist bending during use when exposed to a range of force likely to be applied to the prosthesis.

15. The apparatus of claim 1, wherein at least one piezoelectric sensor includes a housing having plates that are substantially parallel, and wherein at least one of the plates has a pyramid adaptor shape on an exterior surface.

16. The apparatus of claim 14, wherein the parallel plates are of a configuration characterized by being stiff and resisting bending, selected from a group of configurations consisting of:

(a) a truss beam;

(b) an I beam; and

(c) a honeycombed plate.

17. The apparatus of claim 1, wherein the machine instructions further cause the processor to characterize the groups of data based on a desired scheme, to represent a plurality of biomechanical events experienced by the prosthesis, in regard to a magnitude or an orientation of at least one parameter selected from a group of parameters consisting of a force, and a moment applied to the prosthesis.

18. The apparatus of claim 17, wherein the machine instructions further cause the processor to characterize the data within the groups of data and create additional subgroups of data based on at least one selected from the group consisting of:

(a) spectral analysis of force and moment magnitudes and orientations;

(b) a force-time integral;

(c) at least one of maximum force, minimum force, mean force, and standard deviation of the force;

(d) a waveform pattern symmetry and consistency;

(e) a dynamic time warping of force;

(f) a wavelet analysis;

(g) a principal component analysis; and

(h) an iterative closest point analysis.

19. The apparatus of claim 17, wherein based on a characterization of the segments as belonging to specific groups of the data, creating a presentation showing a time occurrence for different segments or collections of segments that are members of a common group of the data, relative to other segments or collections of the segments that are members of a different group of the data.

20. The apparatus of claim 17, wherein the machine instructions further cause the processor to further analyze the groups of segments by comparing each segment to a signature waveform representing a biomechanical event of interest, using target or pattern recognition strategies.

21. The apparatus of claim 17, wherein the machine instructions further cause the processor to determine:

(a) a location for a center of pressure on a portion of the prosthesis; and

(b) the plurality of moments acting on the prosthesis, based on the force components and the center of pressure.

22. The apparatus of claim 17, wherein the machine instructions further cause the processor to automatically prepare a report for at least one of the user and a medical practitioner, wherein the report presents results from characterizing the groups of data based on the desired scheme, so as to represent the plurality of biomechanical events.

23. The apparatus of claim 1, wherein each piezoelectric sensor, each impedance transformation device, and each data device are included as integral parts of the prosthesis.

24. A method for collecting, processing, and employing data indicative of kinetic parameters experienced by a prosthesis while a user fitted with the prosthesis engages in activities, comprising the steps of:

(a) attaching one or more piezoelectric sensors to the prosthesis to monitor forces experienced by the prosthesis as a result of the user wearing the prosthesis while engaging in the activities, each piezoelectric sensor developing a charge indicative of a kinetic parameter experienced by prosthesis;

(b) amplifying the charge produced by each piezoelectric sensor, producing a corresponding output signal indicative of the parameter experienced by the prosthesis, the output signal from all piezoelectric sensors being used to produce the data indicating the kinetic parameters; and

(c) processing the data to determine the kinetic parameters experienced by the prosthesis and for evaluating conditions related to use of the prosthesis by the user, wherein the step of processing the data further includes the steps of;

(i) dividing the data into intervals of time, wherein a duration of the intervals is selected to match features of interest needed to carry out a desired analysis of the data;

(ii) determining at least one type of parameter selected from a group of parameter types consisting of;

(A) force components, wherein each force component is directed along a different one of a plurality of orthogonal axes; and

(B) a plurality of moments acting on the prosthesis;

(iii) segmenting the data into groups based on the at least one types of parameter.

25. The method of claim 24, further comprising the step of wirelessly transmitting the data from the prosthesis to one of a local site, and a remote site, where the step of processing the data is carried out.

26. The method of claim 25, further comprising the step of transmitting the data to a remote site over a network.

27. The method of claim 24, wherein the step of processing comprises the step of characterizing the activities that are carried out by the user while wearing the prosthesis.

28. The method of claim 24, wherein the data comprise two or more parameters selected from a group of parameters consisting of:

(a) a component of force directed along one of a plurality of orthogonal axes;

(b) a moment relative to at least one of the plurality of orthogonal axes;

(c) an indication of the prosthesis bending;

(d) an indication of at least one parameter on a foot portion of the prosthesis, where said at least one parameter is selected from a group of parameters consisting of;

(i) a resultant force position;

(ii) a direction that a force is applied; and

(iii) a center of pressure;

(e) an indication of a position where a shear force is applied to the prosthesis;

(f) a temperature of a portion of the prosthesis;

(g) a velocity of the prosthesis as the user moves about;

(h) an angle of the prosthesis; and

(i) a force inside a socket of the prosthesis.

29. The method of claim 24, further comprising the step of supplying electrical energy to energize the one or more piezoelectric force sensor and other components used for collecting the data by harvesting energy as a result of the activities in which the user engages while wearing the prosthesis.

30. The method of claim 29, wherein the step of supplying electrical energy comprises at least one step selected from the group of steps consisting of:

(a) using a force resulting from the user engaging in activity to provide an input to a piezoelectric generator, producing an electrical output current;

(b) using a temperature differential developed between a portion of a body of the user and an environment to generate the electrical output with a Peltier device; and

(c) using a chemical gradient developed due to a chemical change that occurs as a result of the activity of the user within one of a tissue of the body of the user, and a material of the prosthesis.

31. The method of claim 24, further comprising the steps of:

(a) communicating the data to an automatically adjustable component of the prosthesis; and

,

(b) using the data for automatically adjusting the component to more effectively fit the prosthesis to the user, in regard to the activity of the user.

32. The method of claim 24, further comprising the steps of:

(a) automatically activating collection of the data when the user is at a specific predefined location where the user engages in a training session; and

(b) processing the data that were automatically collected to provide at least one of a medical practitioner and the user with information about a progress of the user in the training session.

33. The method of claim 24, wherein the step of processing the data includes the steps of preparing and presenting a report showing information derived from the data, to provide feedback to the user about a condition related to the use of the prosthesis by the user, wherein the information comprising the report are presented to the user on a device that is readily accessible by the user.

34. The method of claim 24, wherein the step of processing the data includes the steps of automatically:

(a) identifying a pattern for an activity being performed by the user;

(b) detecting whether the activity places the user at risk of injury, and if so, carrying out at least one of the steps of;

(i) warning the user that the activity identified is placing the user at risk of injury; and

(ii) automatically adjusting a component of the prosthesis to reduce a risk of injury to the user as a result of the activity recognized.

35. The method of claim 24, wherein the step of processing the data includes the step of processing the data to provide information for enabling a medical practitioner to determine if the user is either overusing or underusing the prosthesis, or is at a risk of an injury, when engaging in one or more activities.

36. The method of claim 24, wherein the step of processing the data includes the step of processing the data to provide information for enabling a medical practitioner to determine if components used in the prosthesis are appropriate to fit the user properly or should be changed to better fit the user in connection with the activities in which the user has been engaging.

37. The method of claim 24, wherein the step of processing the data further includes the step of characterizing the groups of data based on a desired scheme, to represent a plurality of biomechanical events experienced by the prosthesis, in regard to a magnitude of at least one parameter selected from a group of parameters consisting of a force and a moment applied to the prosthesis.

38. The method of claim 37, wherein the step of processing the data further includes the steps of determining:

(a) a location for a center of pressure on a portion of the prosthesis; and

(b) the plurality of moments acting on the prosthesis, based on the force components and the center of pressure.

39. The method of claim 37, wherein the step of processing the data further includes the step of automatically preparing a report for at least one of the user and a medical practitioner, wherein the report presents results from the step of characterizing the groups of data based on the desired scheme, so as to represent the plurality of biomechanical events.

40. The method of claim 24, further comprising the step of using the data with a model to predict at least one of where and when soft tissue breakdown will occur as a result of use of the prosthesis by the user.

41. The method of claim 24, further comprising the step of using the data with a model to assess an alignment of components of the prosthesis and to determine any change that should be made to correct a problem with the alignment.

42. The method of claim 24, further comprising the step of employing results of the step of processing the data to determine if the activities in which the patient engages are cause for changing the prosthesis or a component of the prosthesis used by the patient.