Lower limb prosthesis and control unit

{
  "publication_number": "US6719806B1",
  "country": "US",
  "kind": "B1",
  "title": "Lower limb prosthesis and control unit",
  "abstract": "A lower limb prosthesis for an above-knee amputee that includes a dynamically adjustable knee movement control unit arranged to control flexion and/or extension of a knee joint of the prosthesis automatically in response to a sensed step-to-step variability of at least one kinetic or kinematic parameter of locomotion in order to reduce the step-to-step variability.",
  "claims": [
    "1. A lower limb prosthesis for an above-knee amputee, the prosthesis including a dynamically adjustable knee movement control unit arranged to control flexion and/or extension of a knee joint of the prosthesis automatically in response to a sensed step-to-step variability of at least one kinetic or kinematic parameter of locomotion in order to reduce the degree of variation between different values of the at least one kinetic or kinematic parameter associated with different respective steps taken by the amputee during locomotion.",
    "2. A prosthesis according to claim 1, wherein the sensed step-to-step variability comprises an electrical signal value representative of the degree of variation of the at least one kinetic or kinematic parameter measured during each of a plurality of steps taken by the amputee during locomotion.",
    "3. A prosthesis according to claim 2, wherein the at least one kinetic or kinematic parameter comprises the magnitude of knee joint flexion during each of said steps taken by the amputee within a predetermined range of locomotion.",
    "4. A prosthesis according to claim 3, wherein the range of locomotion is a speed range.",
    "5. A prosthesis according to claim 3, wherein the control unit comprises a variable damper device coupled to upper and lower limb components which move relative to each other during flexion and extension of the knee joint, a transducer associated with the damper for generating an electrical transducer output signal representative of the relative position of relatively movable parts of the damper, and an electronic control circuit for processing the transducer output signal so as to generate a signal value indicative of the step-to-step variability of the at least one kinetic or kinematic parameter sensed over a plurality of steps taken by the amputee, and to feed an adjusting signal to the damper device to adjust the damping of the knee joint in response to the signal value indicative of the step-to-step variability exceeding at least one preset threshold value.",
    "6. A prosthesis according to claim 1, wherein the control unit is arranged to perform an iterative process of repeated variability sensing and control unit adjusting in order to progressively reduce the variability of the at least one kinetic or kinematic parameter substantially to a minimum.",
    "7. A prosthesis according to claim 1, wherein the control unit is configured to record a value of said at least one kinetic or kinematic parameter during each of a plurality of locomotion cycles, to compare the recorded values to establish a variability measurement, to compare the variability measurement with a reference variability value and, if the variability measurement exceeds the reference value, to initiate a control device adjustment procedure.",
    "8. A prosthesis according to claim 7, wherein the control unit is configured to determine a range of locomotion before recording the at least one kinetic or kinematic parameter values, and to establish the variability measurement in respect of a plurality of the at least one kinetic or kinematic parameter values corresponding to a plurality of consecutive locomotion cycles within the range of locomotion, the control device adjustment procedure being performed during subsequent locomotion cycles within the range of locomotion.",
    "9. A lower limb prosthesis including a dynamically adjustable control device for controlling movement of the prosthesis during locomotion, a transducer for generating a sensing signal related to a kinematic parameter of locomotion, and an electronic control circuit having an input coupled to the transducer and an output coupled to the control device, wherein the transducer and the control circuit are configured to determine the variability of the kinematic parameter and to generate output signals for adjusting the control device thereby to reduce the step-to-step variability of the kinematic parameter so as to obtain an optimum setting of the control device, the step-to-step variability being the degree of variation between different values of the kinematic parameter associated with different respective steps taken by the amputee during locomotion.",
    "10. A prosthesis according to claim 9, wherein the transducer and the control circuit are configured to determine the variability of the kinematic parameter over a predetermined range of locomotion and the output signals are generated to cause the control device to be adjusted to an optimum setting at which the variability of the kinematic parameter when locomotion is within the range is substantially minimized.",
    "11. A prosthesis according to claim 10, wherein the transducer and the control circuit are configured to determine the variability of the kinematic parameter over each of a plurality of predetermined ranges of locomotion, and the output signals are generated to cause the control device to be adjusted to a plurality of respective optimum settings, one for each range, each setting substantially minimizing variability of the kinematic parameter within the respective locomotion range.",
    "12. A prosthesis according to claim 10, wherein the range of locomotion comprises a step period range or a range of kinematic parameter values related to step period values.",
    "13. A prosthesis according to claim 10, wherein the range of locomotion comprises a locomotion category.",
    "14. A prosthesis according to claim 9, wherein the kinematic parameter comprises at least one of a knee flexion angle and a parameter representative of the knee flexion angle.",
    "15. A prosthesis according to claim 9, wherein the kinematic parameter comprises a stride length.",
    "16. A prosthesis according to claim 15, wherein the stride length is used as a second kinematic parameter, the variability of which is determined.",
    "17. A control system for a lower limb prosthesis comprising an input for connection to a transducer on the prosthesis which produces an electrical transducer signal in response to flexion or extension of a joint of the prosthesis, an output for connection to a dynamically adjustable control device associated with the joint for influencing the operation of the joint during locomotion, and a processor circuit arranged to compute, from the transducer signal received at the input, a variability value indicative of the variability of a kinetic or kinematic parameter of locomotion between different steps over a period of time and, automatically in response to the variability value fulfilling a predetermined condition or conditions, to produce an output signal causing the control device to be adjusted in a manner such as to reduce said variability of the kinetic or kinematic parameter.",
    "18. A control system to claim 17, wherein the processor circuit is arranged to optimize the adjustment of the control device by alternately deriving the variability value and adjusting the control device in an iterative manner.",
    "19. A method of controlling a lower limb prosthesis for an above-knee amputee comprising: sensing a step-to-step variability of at least one kinetic or kinematic parameter of locomotion; and controlling flexion and/or extension of a knee joint of the prosthesis automatically in response to the sensing step in a manner such that said step-to-step variability is reduced, the variability being the degree of variation between different values of said at least one kinetic or kinematic parameter associated with different respective steps taken by the amputee during locomotion.",
    "20. A method according to claim 19, wherein the sensing step comprises measuring said at least one kinetic or kinematic parameter during each of a plurality of steps taken by the amputee and computing a variability value indicative of the variability of said at least one kinetic or kinematic parameter of locomotion between different steps over a period of time, and wherein the controlling step comprises automatically adjusting a control device associated with the knee joint for variably resisting flexion and/or extension of the knee joint.",
    "21. A method of controlling a lower limb prosthesis for an above-knee amputee comprising: generating a signal indicative of a step-to-step variability of at least one kinetic or kinematic parameter of locomotion sensed over a plurality of steps taken by the amputee, the variability being the degree of variation between different values of the at least one kinetic or kinematic parameter associated with different respective steps taken by the amputee during locomotion; adjusting a control device which controls flexion and/or extension of a knee joint of the prosthesis automatically in response to the signal indicative of a step-to-step variability obtained in the generating step; and repeating the generating and adjusting steps in an iterative process so as to progressively reduce said step-to-step variability substantially to a minimum.",
    "22. A self-teaching method for a lower limb prosthesis for an above-knee amputee, the prosthesis including a dynamically adjustable knee movement control device, a transducer for producing a signal representative of a kinetic or kinematic parameter of locomotion, and a processing circuit coupled to the transducer and the control device, wherein the method comprises: producing a transducer output signal representative of values of said kinetic or kinematic parameter during locomotion; processing the transducer output signal in the processing circuit to generate a signal representative of a level of the step-to-step variability of said kinetic or kinematic parameter over a plurality of steps taken by the amputee; generating an adjusting signal and feeding it to the knee movement control device to dynamically adjust the control device thereby altering the degree to which the control device affects knee joint flexion and/or extension in subsequent steps, the adjusting signal being generated in response to said signal representative of a level of the step-to-step variability such that the adjustment causes said variability to be reduced substantially to a minimum as locomotion proceeds.",
    "23. A self-teaching lower limb prosthesis for an above-knee amputee comprising upper and lower leg components, a knee joint mechanism which interconnects the upper and lower leg components and which includes a knee movement control device, and an electronic control system comprising a transducer producing a transducer output signal representative of values of a kinetic or kinematic parameter of locomotion and a processing circuit coupled to the transducer, the processing circuit receiving the transducer output signal and, in response thereto, generating a signal representative of variability of said kinetic or kinematic parameter from step to step, wherein the knee movement control device includes an adjusting element for varying the degree to which it affects flexion and/or extension of the knee joint mechanism and wherein the processing circuit has an output connected to the adjusting element to set the control device for subsequent steps and provides to the output in response to the signal representative of variability an adjusting signal which dynamically adjusts the adjusting element so as to cause variability of said kinetic or kinematic parameter to be reduced substantially to a minimum."
  ],
  "description_excerpt": "This invention relates to a lower limb prosthesis including a dynamically adjustable joint movement control unit arranged to control either or both of flexion and extension of the joint automatically.\n\nThe control circuit includes a radio receiver for receiving command signals from a remote control transmitter operated by a prosthetist, a processor for processing the command signals and the transducer signals, and a memory for storing a map of valve settings against locomotion speed ranges. The processor has a teaching mode whereby the amputee is asked to walk at a particular speed and the system is “taught” by the prosthetist inasmuch as the prosthetist causes the valve to be adjusted under remote control in real time while the amputee is walking until the best gait is obtained. The same process is performed at different walking speeds and the prosthetist selects a valve setting for each speed which, in his or her opinion, appears to produce the best walking gait. These valve settings are stored at the end of a teaching session. In a playback mode of the processor, signals corresponding to the stored valve settings are fed to the motor-driven valve automatically according to the speed at which the amputee walks.\n\nThe above system has yielded notable improvements in gait for above-knee amputees due to its adaptation of resistance to knee joint movement to different settings suiting different walking speeds rather than relying on a fixed resistance setting for all walking speeds. These improvements have been achieved without requiring excessively lengthy sessions with the prosthetist.",
  "cpc": [
    "A61F 2/70",
    "A61F 2/64",
    "A61F 2/74",
    "A61F 2/80",
    "A61F 2002/5003",
    "A61F 2002/607",
    "A61F 2002/704",
    "A61F 2002/705"
  ],
  "ipc": [
    "A61F 2/68"
  ],
  "assignees": [
    "Chas A Blatchford and Sons Ltd"
  ],
  "inventors": [
    "Mir Saeed Zahedi",
    "Andrew John Sykes"
  ],
  "filing_date": "1999-03-03",
  "publication_date": "2004-04-13",
  "grant_date": "2004-04-13",
  "priority_date": "1998-03-04",
  "application_number": "US-62379000-A",
  "family_id": "10827979",
  "cited_by_count": 119,
  "citations": [
    "US5133774A",
    "EP0549855A2",
    "US5571205A",
    "GB2280609A",
    "US5893891A",
    "WO1996041599A1",
    "US6113642A"
  ]
}