BONE CUTTING METHOD FOR ALIGNMENT RELATIVE TO A MECHANICAL AXIS

1 . A method of bone preparation for a prosthetic joint comprising the steps of:

coupling a first bone cutting jig to a first bone;

coupling a sensored insert to the first bone cutting jig where the sensored insert is configured to measure load and position of load and where the sensored insert includes a three-axis accelerometer;

positioning a joint to a target flexion value as measured by the three-axis accelerometer of the sensored insert;

rotating the joint between a first point and a second point where the first and second points are on opposing sides of the joint;

monitoring the joint on a remote system as it is rotated between the first and second points where the sensored insert transmits at least one of position, rotation, or tilt data from the three-axis accelerometer data to the remote system;

calculating alignment of the first bone relative to the mechanical axis; and

positioning the first bone cutting jig such that the first bone is cut at a predetermined angle relative to the mechanical axis.

2 . The method of claim 1 further including a step of pivoting the joint between the first and second points from a first pivot point.

3 . The method of claim 2 further including a step of rotating the joint within a predetermined range where a maximum of an arc occurs between the first and second points.

4 . The method of claim 3 further including the steps of:

rotating the joint between the first and second points at least two times;

measuring a plurality of data points over an arc between the first and second points; and

determining where a maximum of the arc occurs along the arc.

5 . The method of claim 4 further including the steps of:

measuring each data point with a 15 bit or great precision; and

calculating alignment relative to the mechanical axis using the location data from the three-axis accelerometer.

6 . The method of claim 5 further including the steps of:

referencing the three-axis accelerometer to a first reference plane; and

referencing the three-axis accelerometer to a second reference plane where the second reference plane is perpendicular to the first reference plane.

7 . The method of claim 6 further including the steps of:

coupling a second bone cutting jig to a second bone;

coupling the sensored insert to the second bone cutting jig;

positioning the joint to a target flexion value as measured by the three-axis accelerometer of the sensored insert;

rotating the joint between a third point and a fourth point where the third and fourth points are on opposing sides of the joint;

monitoring rotation of the joint on a remote system where the sensored insert transmits three-axis accelerometer data to the remote system;

calculating alignment of the second bone relative to the mechanical axis; and

positioning the second bone cutting jig such that the second bone is cut at a predetermined angle relative to the mechanical axis.

8 . The method of claim 7 further including the steps of:

pivoting the joint between the third and fourth points from a second pivot point; and

rotating the joint within a predetermined range where a maximum of an arc occurs between the third and fourth points.

9 . The method of claim 8 further including a step of positioning the joint where the sensored insert is at approximately a 45 degree angle when pivoting on the first or second pivot point.

10 . The method of claim 1 further including a step of using the sensored insert as a trial insert to measure load and position of load when installed in the prosthetic joint.

11 . A method of bone preparation for a prosthetic joint comprising the steps of:

coupling a bone cutting jig to a bone;

coupling a shim to a sensored insert;

coupling a tab of the shim into a slot of the bone cutting jig where the sensored insert is configured to measure alignment relative to a mechanical axis and where the sensored insert includes a three-axis accelerometer;

positioning a joint to a target flexion value as measured by the three-axis accelerometer of the sensored insert;

rotating the joint between a first point and a second point where the first and second points are on opposing sides of the joint;

monitoring rotation of the joint on a remote system where the sensored insert transmits three-axis accelerometer data to the remote system;

calculating alignment of the first bone relative to the mechanical axis from quantitative measurement data from the three-axis accelerometer; and

positioning the bone cutting jig such that the bone is cut at a predetermined angle relative to the mechanical axis.

12 . The method of claim 11 further including a step of pivoting the bone from a predetermined location.

13 . The method of claim 12 further including a step of rotating the joint within a predetermined range where a maximum of an arc occurs between the first and second points.

14 . The method of claim 13 further including the steps of:

rotating the joint between the first and second points at least two times;

measuring a plurality of data points over an arc between the first and second points; and

calculating an offset of the bone from the mechanical axis using at least one of position, rotation, or tilt data from the three-axis accelerometer.

15 . The method of claim 14 further including the steps of:

referencing the three-axis accelerometer to a first reference plane; and

referencing the three-axis accelerometer to a second reference plane where the second reference plane is perpendicular to the first reference plane; and

measuring each data point with a 15 bit or great precision.

16 . A method of bone preparation for a prosthetic knee joint comprising the steps of:

coupling a first bone cutting jig to a tibia;

coupling a sensored insert to the first bone cutting jig where the sensored insert is configured to measure load and position of load and where the sensored insert includes a three-axis accelerometer;

positioning a knee joint to a target flexion value as measured by the three-axis accelerometer of the sensored insert;

rotating the knee joint between a first point and a second point where the first and second points are on opposing sides of the knee joint;

monitoring rotation of the knee joint on a remote system where the sensored insert transmits three-axis accelerometer data to the remote system;

calculating alignment of the tibia relative to the mechanical axis using at least one of position, rotation, and tilt data from the three-axis accelerometer; and

positioning the first bone cutting jig such that the tibia is cut at a predetermined angle relative to the mechanical axis.

17 . The method of claim 16 further including the steps of:

placing a heel of a leg in an approximately fixed location;

positioning the knee joint where the sensored insert is at approximately a 45 degree angle;

rotating the knee joint between a first point and a second point, where the first and second points are respectively on a medial and lateral side of the knee joint, and where rotating the knee is pivoting on the heel of the leg; and

saving an alignment value of the tibia.

18 . The method of claim 17 further including the steps of:

coupling a second bone cutting jig to a femur;

coupling the sensored insert to the second bone cutting jig;

positioning the joint to a target flexion value as measured three-axis accelerometer of the sensored insert;

rotating the joint between a third point and a fourth point where the third and fourth points are on opposing sides of the joint;

monitoring rotation of the joint on a remote system where the sensored insert transmits three-axis accelerometer data to the remote system;

calculating alignment of the femur relative to the mechanical axis using at least one of position, rotation, or tilt data from the three-axis accelerometer; and

positioning the second bone cutting jig such that the second bone is cut at a predetermined angle relative to the mechanical axis.

19 . The method of claim 18 further including the steps of:

positioning the knee joint where the sensored insert is at approximately a 45 degree angle;

rotating the knee joint between a third point and a fourth point, where the third and fourth points are respectively on a medial and lateral side of the knee joint, and where the rotating the knee is pivoting on a femoral head of the femur; and

saving an alignment value of the femur.

20 . The method of claim 19 further including the steps of:

referencing the three-axis accelerometer to a first reference plane; and

referencing the three-axis accelerometer to a second reference plane where the second reference plane is perpendicular to the first reference plane;

rotating the joint within a predetermined range where a maximum of an arc occurs between the first and second points or the third and fourth points;

determining a maximum of the arc;

measuring each data point with a 15 bit or greater precision; and

calculating total alignment relative to the mechanical axis by subtracting the alignment value of the femur from the alignment value of the tibia.