Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/46—Special tools for implanting artificial joints
  • A61F2/468—Testing instruments for artificial joints
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
  • G01N3/02—Details
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
  • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/38—Joints for elbows or knees
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/46—Special tools for implanting artificial joints
  • A61F2002/4632—Special tools for implanting artificial joints using computer-controlled surgery, e.g. robotic surgery
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
  • G01N2203/0058—Kind of property studied
  • G01N2203/0089—Biorheological properties
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
  • G01N2203/02—Details not specific for a particular testing method
  • G01N2203/022—Environment of the test
  • G01N2203/0244—Tests performed "in situ" or after "in situ" use
  • G01N2203/0246—Special simulation of "in situ" conditions, scale models or dummies

Definitions

• the present invention relates generally to durability testing of test specimens such as but not limited to, artificial orthopedic implants (e.g. hip, knee, spine, etc.) . More specifically, the present invention pertains to a system and method for combining measured signals with virtual signals generated by a model to extend the range of mechanical methods of load testing. Laboratory simulation is a technique that is often used to validate the durability of orthopedic implant designs and to verify manufacturing quality assurance.
• the mechanical interlock and frictional forces may be directly replicated in the specimen, whereas the soft tissue is more difficult to simulate.
• Soft tissue reaction forces have been implemented in orthopedic simulators in the past by use of mechanical springs which have significant disadvantages including limited durability, difficulty in changing values, limited mathematical nature of the reaction forces, difficulty in attaining appropriate configuration and overall complexity of the machine . Therefore, there is a significant need to improve systems that are used to test specimens for durability and other factors. A system that addresses one or more of the shortcomings discussed above would be particularly useful. . SUMMARY OF THE INVENTION The invention provides a system and method to expand capabilities of simulation and durability testing of test specimens such as those exhibiting soft tissue behavior.
• a virtual signal is generated by combining the actual measured signal from a transducer with a supplemental or simulated signal created by a function based on position, load or another known or measurable parameter. This virtual signal may then be inserted into the control loop to adapt the system to this new, calculated or combined signal .
• multiple virtual parameter thresholds can be used in the control loop described above such that when the threshold of one or more functions is met or exceeded, further actions may be enabled and subsequent functions may be implemented to further the testing.
• FIG. 2 is schematic diagram illustrating a means for implementing multiple virtual models with various parameters of a more complex test system than that of FIG. 1.
• DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention replaces the solely mechanical methods commonly used with software and hardware by incorporating a virtual model into the control loop and then controlling to this new, calculated virtual load and/or displacement .
• the virtual load and/or displacement signal is generated by a combination of the actual measured force from a transducer and a supplemental or simulated signal created by a mathematical or other derivable function based on known or measurable parameters (e.g.
• Virtual Load Measured Load + F (n)
• F (n) can take any one or a combination of forms including mathematical, equations, systems of analog, digital or logical operators, systems of linear or non-linear equations, look-up tables, static and dynamic system models, fuzzy logic, etc., while n can be any known or measurable factor (displacement, temperature, load, etc. ) .
• FIG. 1 illustrates schematically the components of a system 100 for implementing aspects of the present invention described above.
• System 100 includes an actuator 110 for imparting loads and/or causing displacement of elements of a test specimen 120 such as an artificial knee.
• Actuator 110 may be a hydraulic, pneumatic, electromechanical device or combination thereof. As appreciated by those skilled in the art, depending on the application, the actuator (s) need support components such as servo- valves, accumulators, power sources, etc. as part of the system 100 but such components are not depicted here since such components are well known.
• a processor/controller 105 provides drive signals to the actuator 110 using load control or displacement control techniques. Processor/controller 105 may consist of analog and/or digital electronic configurations, with or without suitable software routines.
• the load transducer 115 and/or a position or displacement transducer 125 are operatively coupled to the test specimen 120 so as to sense loads and/or displacements in one or more degrees of freedom.
• the processor/controller 105 receives signals indicative of sensed loads or sensed displacements .
• the processor/controller 105 includes a mathematical model or representation 130 of simulated aspects of the test specimen 120 which herein represented as F (n) , as described above.
• the processor/controller 105 receives the actual measured loads and/or displacements from the load transducer 115 and the displacement transducer 125 and combines this information with simulated information in the model F (n) 130.
• the actuator 110 is controlled by the processor/controller 105 as if the virtual (measured + simulated) loading and/or displacement had actually occurred.
• the actuator 110 can be appropriately controlled for repeated cycles wherein after, for example, a durability test, the test specimen 120 can be removed and wear characteristics measured.
• system 100 can be used for testing of an artificial knee or other prosthetic/Orthopedic implant .
• system 100 can be used for testing of an artificial knee or other prosthetic/Orthopedic implant .
• a researcher may know the force input acting on the joint, for example, in a shearing direction, Anterior-Posterior, as well as the displacement of such components, aspects relative to the joint when soft tissues are present can complicate testing.
• Some approaches have included simulating soft tissue by mechanically applying springs between the two components. However, difficulties using this approach include choosing the right spring, locating it correctly, etc. Furthermore, proper modeling of soft tissue may not be accurate using a mechanical spring.
• an aspect of the present invention includes modeling or simulating a mechanical or other system such as the soft tissue as F (n) 130 (e.g. in software), and using this representation as discussed above to control the actuator 110 as a function of the virtual (measured + simulated) loads and/or displacements.
• F (n) can account for widely varying degrees of constraint and thereby widely varying specimen design.
• the test specimen such as an orthopedic or prosthetic implant, may include a microprocessor 135 and internal sensors for measuring force or other parameters, or detecting limits thereof, etc.
• An information signal from the microprocessor 135 can be used to control or change the control loop via the F (n) function.
• FIG. 2 illustrates another exemplary application similar to FIG. 1 in which a system 200 includes multiple- actuators 210 and 212 for imparting loads and/or causing displacement of elements of a test specimen 220 such as an industrial component.
• a processor/controller 205 provides drive signals to multiple actuators, such as actuators 210 and 212, using load control or displacement control techniques.
• Load transducer 215 and 217 and position or displacement transducers 225 and 227 are operatively coupled to the test specimen 220 so as to sense loads or displacements in multiple degrees of freedom.
• the processor/controller 205 receives signals indicative of sensed loads and sensed displacements, while monitoring the result of multiple predetermined models, F ( ⁇ ) 230 and F (____) 232. Signals from multiple load transducers 215 and 217 are combined with multiple displacement transducer-s 225 and 227 along with simulated information in models 230 and 232, until a threshold is either achieved or exceeded, causing one or more of the actuators 210 and 212 to change its- parameter, become activated or disabled from the system 200.
• control logic may implement extended measurement capability on the same sample as its properties change over time or begin to degrade under extreme conditions .
• the test specimen such as a prosthetic implant
• the test specimen may include multiple microprocessors 235 and 237, and internal sensors for measuring force or other parameters, or detecting limits thereof, etc.
• An information signal from the multiple microprocessors 235 and 237 can be used to control or change the control loop via the F (n) and F (_ ⁇ x ) functions .

Landscapes

• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Biochemistry (AREA)
• Physics & Mathematics (AREA)
• Pathology (AREA)
• Immunology (AREA)
• General Physics & Mathematics (AREA)
• Orthopedic Medicine & Surgery (AREA)
• Analytical Chemistry (AREA)
• Transplantation (AREA)
• Chemical & Material Sciences (AREA)
• Vascular Medicine (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Physical Education & Sports Medicine (AREA)
• Animal Behavior & Ethology (AREA)
• Cardiology (AREA)
• Heart & Thoracic Surgery (AREA)
• Biomedical Technology (AREA)
• Engineering & Computer Science (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
• Prostheses (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (5)

Families Citing this family (25)

Citations (4)

Family Cites Families (24)

• 2004
  • 2004-12-03 WO PCT/US2004/040798 patent/WO2005055888A1/en not_active Ceased
  • 2004-12-03 EP EP04813159.3A patent/EP1696838B1/en not_active Expired - Lifetime
  • 2004-12-03 JP JP2006542861A patent/JP4808630B2/ja not_active Expired - Fee Related
  • 2004-12-03 CN CN2004800403651A patent/CN1901856B/zh not_active Expired - Fee Related
  • 2004-12-03 US US11/004,308 patent/US7383738B2/en not_active Expired - Lifetime

Patent Citations (4)

Non-Patent Citations (1)

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