Telemetric tibial tray
First Claim
1. In a telemetric knee prosthesis adapted to measure forces transmitted across the knee joint, the knee prosthesis having a femoral component, a tibial bearing member in articulating contact with the femoral component, a tibia engaging member and a tibial tray engaged to the tibial bearing member and the tibia engaging member, the tibial tray comprising:
- an upper plate having a portion configured for engaging the tibial bearing member;
a lower plate having a portion configured for engaging the tibia engaging member, said lower plate spaced apart from said upper plate and defining a plurality of cavities opening away from said upper plate, each of said cavities including a diaphragm adapted to flex when subjected to a load normal to the diaphragm;
a plurality of support posts, each connected between said upper plate and said diaphragm of a corresponding one of said plurality of cavities, wherein said support posts are circular in cross-section and have a diameter that is about ⅓
the diameter of the corresponding one of said plurality of cavities; and
a force sensing element disposed within each of said plurality of cavities and operable to produce an output signal in response to flexing of said diaphragm.
1 Assignment
0 Petitions
Accused Products
Abstract
A telemetric tibial tray includes a lower plate that defines a plurality of cylindrical transducer cavities having circular load diaphragms. An upper plate is attached to the lower plate through support posts projecting from the load diaphragms. The support posts have a circular cross-section and a diameter of about 5.0 mm. The lower plate further defines wiring channels communicating between the transducer cavities and a central cavity housing the circuit board for the telemetric tray. The wiring channels are arranged at a 45 degree angle relative to the sagittal plane of the knee joint in order to reduce the effects of the wiring channel intersection on the strain sensitivity of the tray. Each transducer cavity includes a radial strain gage array with four pairs of radially aligned strain gages, each pair aligned at a 45 degree angle relative to the sagittal plane of the knee joint. Each pair of strain gages includes an inner gage positioned at the point of maximum positive micro-strain across the diaphragm when loaded, and an outer gage positioned at the point of maximum negative micro-strain, to thereby increase the differential strain measured by the gages and increase the strain sensitivity of the tibial tray.
81 Citations
13 Claims
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1. In a telemetric knee prosthesis adapted to measure forces transmitted across the knee joint, the knee prosthesis having a femoral component, a tibial bearing member in articulating contact with the femoral component, a tibia engaging member and a tibial tray engaged to the tibial bearing member and the tibia engaging member, the tibial tray comprising:
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an upper plate having a portion configured for engaging the tibial bearing member; a lower plate having a portion configured for engaging the tibia engaging member, said lower plate spaced apart from said upper plate and defining a plurality of cavities opening away from said upper plate, each of said cavities including a diaphragm adapted to flex when subjected to a load normal to the diaphragm; a plurality of support posts, each connected between said upper plate and said diaphragm of a corresponding one of said plurality of cavities, wherein said support posts are circular in cross-section and have a diameter that is about ⅓
the diameter of the corresponding one of said plurality of cavities; anda force sensing element disposed within each of said plurality of cavities and operable to produce an output signal in response to flexing of said diaphragm. - View Dependent Claims (2)
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3. In a telemetric knee prosthesis adapted to measure forces transmitted across the knee joint, the knee prosthesis having a femoral component, a tibial bearing member in articulating contact with the femoral component, a tibia engaging member and a tibial tray engaged to the tibial bearing member and the tibia engaging member, the tibial tray comprising:
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an upper plate having a portion configured for engaging the tibial bearing member; a lower plate having a portion configured for engaging the tibia engaging member, said lower plate spaced apart from said upper plate and defining a plurality of cylindrical cavities opening away from said upper plate, each of said plurality of cylindrical cavities including a circular diaphragm adapted to flex when subjected to a load normal to the diaphragm and an outer wall; a plurality of support posts, each connected between said upper plate and said diaphragm of a corresponding one of said plurality of cylindrical cavities; and a force sensing element disposed within each of said plurality of cavities and operable to produce an output signal in response to flexing of said diaphragm, said force sensing element including four pairs of radially aligned strain gages, the strain gages of each pair arranged to measure differential strain in a radial direction and includes an inner gage mounted on said diaphragm adjacent the center of said circular diaphragm and an outer gage mounted on said diaphragm immediately adjacent said outer wall of said cylindrical cavity, wherein said circular diaphragm exhibits a micro-strain behavior under load that produces a maximum magnitude at a radial location from the center of said circular diaphragm, and further wherein said inner gage is positioned to span said maximum magnitude radial location.
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4. In a telemetric knee prosthesis adapted to measure forces transmitted across the knee joint, the knee prosthesis having a femoral component, a tibial bearing member in articulating contact with the femoral component, a tibia engaging member and a tibial tray engaged to the tibial bearing member and the tibia engaging member, the tibial tray comprising:
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an upper plate having a portion configured for engaging the tibial bearing member; a lower plate having a portion configured for engaging the tibia engaging member, said lower plate spaced apart from said upper plate and defining a plurality of cylindrical cavities opening away from said upper plate, each of said plurality of cylindrical cavities including a circular diaphragm adapted to flex when subjected to a load normal to the diaphragm and an outer wall; a plurality of support posts, each connected between said upper plate and said diaphragm of a corresponding one of said plurality of cylindrical cavities; and a force sensing element disposed within each of said plurality of cavities and operable to produce an output signal in response to flexing of said diaphragm, said force sensing element including four pairs of radially aligned strain gages, the strain gages of each pair arranged to measure differential strain in a radial direction and includes an inner gage mounted on said diaphragm adjacent the center of said circular diaphragm and an outer gage mounted on said diaphragm immediately adjacent said outer wall of said cylindrical cavity, wherein said circular diaphragm exhibits a micro-strain behavior under load that produces a zero-crossing point between the center of said circular diaphragm and said outer wall of said cylindrical cavity, and further wherein said outer gage is positioned between said zero-crossing point and said outer wall. - View Dependent Claims (5, 6)
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7. In a telemetric knee prosthesis adapted to measure forces transmitted across the knee joint, the knee prosthesis having a femoral component, a tibial bearing member in articulating contact with the femoral component, a tibia engaging member and a tibial tray engaged to the tibial bearing member and the tibia engaging member, the tibial tray comprising:
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an upper plate having a portion configured for engaging the tibial bearing member; a lower plate having a portion configured for engaging the tibia engaging member, said lower plate spaced apart from said upper plate and defining a plurality of cavities opening away from said upper plate, each of said plurality of cavities including a diaphragm adapted to flex when subjected to a load normal to the diaphragm, said lower plate further defining a central cavity disposed between said plurality of cavities and a plurality of wiring channels, each communicating between a corresponding one of said plurality of cavities and said central cavity; a plurality of support posts, each connected between said upper plate and said diaphragm of a corresponding one of said plurality of cavities; a force sensing element disposed within each of said plurality of cavities and operable to produce an output signal in response to flexing of said diaphragm said force sensing element including four pairs of radially aligned strain gages, the strain gages of each pair arranged to measure differential strain in a radial direction; a circuit element disposed in said central cavity for processing said output signal from said force sensing element in each of said plurality of cavities; and wiring electrically connecting each force sensing element in said plurality of cavities to said circuit element to transmit said output signal, said wiring disposed in a corresponding one of said plurality of wiring channels, wherein said lower plate defines a plane perpendicular to the sagittal plane of the knee joint when the knee prosthesis is implanted therein, wherein each of said four pairs of strain gages is aligned in a one of two radial planes that are at about 45 degrees relative to said sagittal plane, and wherein none of said four pairs of radially aligned strain gages is aligned with said wiring channel communicating with said corresponding one of said plurality of cavities. - View Dependent Claims (8)
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9. A telemetric knee prosthesis comprising:
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an upper tibial tray plate having a portion configured for coupling with a tibial bearing member; a lower tibial tray plate spaced apart from the upper tibial tray plate and defining a plurality of cavities opening away from the upper tibial tray plate, each of the plurality of cavities including an outer wall and a diaphragm adapted to flex when subjected to a load on the diaphragm; a plurality of support posts, each of the plurality of support posts extending between the upper tibial tray plate and the diaphragm of a corresponding one of the plurality of cavities; and a plurality of force sensing elements, each of the plurality of force sensing elements disposed within one of the plurality of cavities and operable to produce an output signal in response to flexing of the diaphragm in the respective one of the plurality of cavities, each of the plurality of force sensing elements including an inner gage positioned such that at least a portion of the inner gauge is mounted at a location on one side of the diaphragm directly opposite to where a portion of the corresponding one of the plurality of support posts contacts the other side of the diaphragm. - View Dependent Claims (10, 11, 12, 13)
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Specification