• What Is Parallax?

    The Problem: AP pelvis image under C-arm is distorted due to parallax. The following C-arm image shows a straight metal bar laying on top of the pelvis, note the bar is shown bent in the image even though physically it’s perfectly straight. This distortion makes traditional method of determining leg length by drawing a straight line across the pelvis not always reliable.

     

    The Test:

    C-arm parallax

    • Calibrated with the bar at 5mm
    • Surgeon’s Checklist Limb Length feature used to measure to the top of the bar from the Trans ischial Line

  • The Result: 14mm variance from edge to edge