Preperation

During the operative procedure, place a guide wire (or the top of an microfracure awl) into the center of the femoral insertion area using your standard operative set up. Alternatively you may advance the the k-wire in the center of the projected bone tunnel forward penetrating the skin on the lateral side of the femur so the the end of the wire is flush with the femoral cortex of the insertion.

Take a picture

Aquire a fluoroscopic image of the knee in a strong lateral plane (both condyles have to overlap perfectly). Start the measuring process in the app and take a picture of the fluoroscopic image from the monitor or a print-out of the image. If you are not happy with the picture you can “redo” the picture. In case that the photo is satisfactory press “use phote”.

1. Blumensaat Line

Touch the screen with two fingers (e.g. index and middle finger) to establish a line. By moving and turning your fingers you can move the line in a way that it perfecty overlies the Blumensaat-line (BS-Line) representing the roof of the interkondylar notch in the femur. (do not use only one finger as no line will be displayed in that case.)

2. Posterior Condyle Line

Now by touching the screen with only one finger, a blue line is displayed being perpendicular (90° angle) to the former BS-line. Move the line to the most posterior aspect of the femoral condyle.

3. Anteriore Condyle Line

Using the tip of your finger, establish and position another line in the same manner as before located at the most anterior aspect of the femoral condyle.

4. Distal Condyle Line

Using the tip of your finger, establish and position another line parallel to Blumensaat line (BS-line) outlining the most distal aspect of the femoral condyle (this line being a tangent to the circle line of the condylar bone).

5. Target point

Using a finger tip, a bullseye is placed over the target point on the femur (e.g. end of the k-wire). The placement is facilitated by an extension of the touchpoint to the bullseye.

Measurement

The app will display the relative ratio of your target point in reference to the outlines of the bone of the femoral condyles. The measurement values relate to the relative distance of the target point of the most posterior and proximal border of the condyles.