Guide assembly
A method for locating the mechanical axis of a long bone involves generating an image of the long bone and determining the angle between the mechanical axis of the bone and a reference axis, which contains at least two reference points towards one end of the bone. A reference arm is positioned relative to the at least two predetermined reference points, and the mechanical axis is located relative to the reference arm with reference to the previously determined angle.
1. A method for locating during a surgical procedure a mechanical axis of an uncut bone having an end with an external surface, comprising the steps of:
(a) generating an image of the uncut bone including the external surface;
(b) defining the mechanical axis of the uncut bone on the image of the uncut bone;
(c) measuring an angle between the mechanical axis of the uncut bone as defined in step (b) and a reference axis on the image of the uncut bone, the reference axis containing at least two reference points located on the image of the external surface of the uncut bone;
(d) during surgery, contacting at least two points on the external surface of the uncut bone with a first plate, the first plate being fastened to an angle indicator, the angle indicator being pivotably fastened to an axis indicator, at least one of the axis indicator and the angle indicator including a scale to indicate an angle between the angle indicator and the axis indicator; and
(e) positioning the axis indicator relative to the angle indicator such that the angle indicated on the scale has a predetermined relationship with the angle measured in step (c).
2. The method of claim 1 , wherein step (e) comprises the step of pivoting the axis indicator relative to the first plate until the angle between the axis indicator and the first plate is substantially the same as the angle measured in step (c).
3. The method of claim 1 , wherein the uncut bone is a femur.
4. The method of claim 3 , wherein the end of the uncut bone includes a medial condyle and a lateral condyle, and one of the at least two reference points is on the medial condyle and one of the at least two reference points is on the lateral condyle.
5. The method of claim 3 , wherein the femur includes a medial condyle and a lateral condyle, the medial condyle has a medial distal facing surface and the lateral condyle has has a lateral distal facing surface, and one of the at least two reference points is on the image of the medial distal facing surface and one of the at least two reference points is on the image of the lateral distal facing surface.
6. The method of claim 3 , further comprising the steps of:
handling a guide assembly comprising the first plate, the angle indicator, the axis indicator and a second plate.
7. The method of claim 1 , wherein the axis indicator has an arm with at least one bore formed therein for guiding a tool that can form a bore in the uncut bone.
8. The method of claim 1 , wherein the axis indicator comprises an axis indicator arm that is detachably fastened to the first plate, and further comprising the step of attaching the axis indicator arm to the first plate.
9. The method of claim 1 , further comprising a locking mechanism for locking the axis indicator against rotation relative to the first plate.
10. The method of claim 1 , wherein the axis indicator rotates about a point that lies on the reference axis.
11. The method of claim 6 , wherein the second plate is pivotably connected to the first plate and is configured to contact a second bone adjacent to the uncut bone such that the guide assembly can be located between the uncut bone and the second bone, and so that the second plate can cause the first plate to be urged against the end of the uncut bone.
12. A method for locating during a surgical procedure a mechanical axis of an uncut bone having an end with an external surface, comprising the steps of:
(a) generating an image of the uncut bone including the external surface;
(b) defining the mechanical axis of the uncut bone on the image of the uncut bone;
(c) measuring an angle between the mechanical axis of the uncut bone as defined in step (b) and a reference axis on the image of the uncut bone, the reference axis containing at least two reference points located on the image of the external surface of the uncut bone;
(d) during surgery, positioning a planar surface of a first plate relative to at least two points on the external surface of the uncut bone, the two points on the external surface of the uncut bone corresponding with the two reference points on the image of the uncut bone, the first plate being fastened to an angle indicator, the angle indicator being pivotably fastened to an axis indicator; and
(e) positioning the axis indicator relative to the first plate on the uncut bone such that the angle between the axis indicator and the planar surface of the first plate is substantially the same as the angle measured in step (c).