Apparatus for, and method of, detecting dislocations and material wear in hip replacements
First Claim
1. In combination for determining in a patient'"'"'s hip replacement the positional interrelationship between a ball at the top of a stem in the patient'"'"'s thigh and a socket in the patient'"'"'s pelvis, the socket including a cup and a liner near the bottom of the cup,a coil at the bottom of the liner;
- a member disposed on the patient'"'"'s body near the patient'"'"'s thigh and in magnetizably coupled relationship to the coil for producing a signal having characteristics dependent upon the positioning of the ball in the socket, andfirst means operatively coupled to the member for producing a signal having characteristics dependent at each instant upon the magnetically coupled relationship at that instant between the coil and the member.
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Accused Products
Abstract
In a total hip replacement, a stem of a femoral component is disposed in a patient'"'"'s thigh bone with a ball extending in such femoral component above the stem. The ball is disposed in a hemispherical cup positioned in the patient'"'"'s pelvis and enveloping the ball for frontal movement of the ball relative to the cup. A low-friction liner (e.g., plastic or ceramic) is disposed at the bottom of the cup. To determine whether the ball is properly positioned in the cup, a first member (e.g., a coil) is disposed on the bottom of the liner. A second member (e.g., a patch defining a loop) is disposed on the patient'"'"'s thigh in operatively coupled (e.g. magnetic) relationship to the first member. The operative coupling between the members is variable in accordance with variations in the disposition of the ball in the cup. When the first and second members are respectively a coil and a patch, the coil and a capacitance may be fixed in the patient'"'"'s body in a circuit resonant at a particular frequency. The patch may be included in electrical circuity disposed externally on the patient'"'"'s body and energizable by a source (e.g., a battery) disposed externally on the patient'"'"'s body. This circuity may be resonant at a frequency variable in accordance with variations in the magnetic coupling between the coil and the patch. A sensory indication may be provided when the resonant frequency of the circuity varies outside of particular limits. This indicates that the hip replacement may not be functioning properly in regard to subluxation, dislocation, or excessive material wear.
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Citations
26 Claims
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1. In combination for determining in a patient'"'"'s hip replacement the positional interrelationship between a ball at the top of a stem in the patient'"'"'s thigh and a socket in the patient'"'"'s pelvis, the socket including a cup and a liner near the bottom of the cup,
a coil at the bottom of the liner; -
a member disposed on the patient'"'"'s body near the patient'"'"'s thigh and in magnetizably coupled relationship to the coil for producing a signal having characteristics dependent upon the positioning of the ball in the socket, and first means operatively coupled to the member for producing a signal having characteristics dependent at each instant upon the magnetically coupled relationship at that instant between the coil and the member. - View Dependent Claims (2, 3, 4, 5)
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6. In combination for determining in a patient'"'"'s hip replacement the positional interrelationship between a ball at the top of a stem in the patient'"'"'s thigh and a socket in the patient'"'"'s pelvis, the socket including a cup and a liner near the bottom of the cup,
a first member disposed on the liner in the patient'"'"'s body, a second member disposed externally of the patient'"'"'s body in an operatively coupled relationship with the first member, this operatively coupled relationship being variable in accordance with variations in the positioning of the ball in the socket, and electrical circuitry operatively coupled to the second member for producing a signal having characteristics dependent upon the variations in the operatively coupled relationship between the first and second members.
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11. In combination for determining in a patient'"'"'s hip replacement the positional interrelationship between a ball at the top of a stem in the patient'"'"'s thigh and a socket in the patient'"'"'s pelvis, the socket including a cup and a liner near the bottom of the cup,
a first member disposed in the patient for producing a first signal, a second member disposed on the patient for variable positioning relative to the first member in accordance with displacements of the ball relative to the socket, the second member being in operatively coupled relationship to the first member for producing a second signal having characteristics variable in accordance with variations in the positioning of the second member relative to the first member, and electrical circuitry responsive to the second signal for producing an output dependent upon the characteristics of the second signal.
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17. In a method of determining in a patient'"'"'s hip replacement the positional interrelationship between a ball at the top of a stem in the patient'"'"'s thigh and a socket in the patient'"'"'s pelvis, the socket including a cup and a liner near the bottom of the cup, the steps of:
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providing a first member on the liner in the patient'"'"'s body, providing a second member on the patient'"'"'s thigh in operatively coupled relationship to the first member, the operative coupling between the first and second members being variable in accordance with variations in the disposition of the ball in the socket, energizing the second member to obtain an energizing of the first member a generation by the second member in the first member of a signal having characteristics variable in accordance with variations in the operative coupling between the first and second members, and providing an output in accordance with variations in the characteristics of the output signal beyond particular limits. - View Dependent Claims (18, 19, 20)
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21. In combination,
a socket disposed in a patient'"'"'s pelvis and including a cup and a liner in the cup, a ball at the top of a stem in the patient'"'"'s thigh, the ball being disposed in the socket, a first member disposed in the socket, a second member disposed on the patient'"'"'s thigh externally of the patient'"'"'s body and in operatively coupled relationship with the first member, this operatively coupled relationship being variable in accordance with variations in the positioning of the first member relative to the second member, and means disposed externally of the patient'"'"'s body for producing a signal with characteristics variable in accordance with variations in the operatively coupled relationship between the first and second members.
Specification