Arthroscopic indenter

Claim 2

A computer controlled indenter to measure stress relaxation of cartilage overlying bone comprising: a loading shaft having a distal end for placement proximate to the cartilage; a system for aligning the loading shaft comprising: a frame which can be fixed in relationship to the bone; a protective sheath for said loading shaft movably attached to said frame; and means for detecting reflected light for determining alignment of said sheath; and means for aligning said sheath substantially perpendicular to said cartilage; an electromechanical actuator comprising a motor and adapted to axially move said loading shaft; a force transducer adapted to measure a force applied to the cartilage by said loading shaft; and a computer, operatively connected to said actuator and transducer, to calculate stress relaxation of the cartilage as a function over time of measured force required to maintain said distal end at a set displacement upon the cartilage.

Claim 3

The indenter of claim 1 further comprising: (a) a needle thickness probe affixed to the distal end of the shaft; and (b) a computer adapted to calculate thickness of the cartilage during use as a function of displacement of the shaft between the point at which the measured force indicates the needle has encountered the cartilage and the point at which the measured force indicates the needle has encountered underlying bone.

Claim 4

The indenter of claim 1 wherein the force transducer comprises: (a) a surface placed in pressure communication with one end of the shaft; and (b) an electrical circuit attached to the surface, the circuit adapted to measure changes in electrical resistance in linear response to the force placed on the surface during use.

Claim 5

The indenter of claim 1 wherein: (a) said computer is adapted to establish and maintain a desired position for the shaft during a data-acquisition period; and (b) during the data-acquisition period, said computer is adapted to collect force versus time measurement data.

Claim 6

The indenter of claim 1 wherein: (a) said computer is adapted to establish a desired position of the shaft during a pre-data acquisition period; and (b) during the pre-data acquisition period, said computer is adapted to collect force versus time measurement data for determining the point for beginning the data acquisition period.

Claim 7

The indenter of claim 1 adapted to measure cartilage in vivo.

Claim 8

A computer controlled indenter to measure the creep deformation of cartilage overlying bone comprising: a loading shaft having a distal end for placement proximate to the cartilage; a system for aligning the loading shaft comprising: a frame which can be fixed in relationship to the bone; a protective sheath movably attached to said frame; and means for detecting reflected light for determining alignment of said sheath; and means for aligning said sheath substantially perpendicular to said cartilage; an electromechanical actuator comprising a motor and adapted to axially move said loading shaft while maintaining constant force upon the cartilage; a positional detector adapted to measure the displacement of said shaft; and a computer, operatively coupled to said actuator and said positional detector, to calculate creep deformation of the cartilage as a function over time of measured displacement of said shaft at a constant force applied to said loading shaft.

Claim 9

A computer controlled indenter to measure the creep deformation of cartilage overlying bone comprising: a loading shaft having a distal end for placement proximate to the cartilage; a system for aligning the loading shaft comprising: a frame which can be fixed in relationship to the bone; a protective sheath movably attached to said frame; and means for detecting reflected light for determining alignment of said sheath; and means for aligning said sheath substantially perpendicular to said cartilage; an electromechanical actuator comprising a motor and adapted to axially move said loading shaft while maintaining constant force upon the cartilage; a positional detector adapted to measure the displacement of said shaft; and a computer, operatively coupled to said actuator and said positional detector, to calculate creep deformation of the cartilage as a function over time of measured displacement of said shaft at a constant force applied to said loading shaft.

Claim 10

The indenter of claim 7 further comprising: (a) a needle thickness probe affixed to the distal end of the shaft; and (b) a computer adapted to calculate thickness of the cartilage during use as a function of displacement of the shaft between the point at which the measured force indicates the needle has encountered the cartilage and the point at which the measured force indicates the needle has encountered underlying bone.

Claim 11

The indenter of claim 7 wherein the position detector comprises a linear variable differential transformer having a displacement resolution.

Claim 12

The indenter of claim 7 wherein: (a) said computer is adapted to determine a zero position for the shaft at the cartilage tissue surface; (b) said computer is adapted to establish and control the actuator to maintain a predetermined force against the cartilage by the shaft during a data-acquisition period; and (c) during the data acquisition period, said computer is adapted to collect cartilage displacement versus time measurement data.

Claim 13

The indenter of claim 7 adapted to measure cartilage in vivo.