If PI correction is applied, what is the approximate magnitude of femur height change based on the data?

• A. 2 mm
• B. 4 mm
• C. 6 mm
• D. 8 mm

Answer: (B)

Correcting pelvic tilt (PI) changes how the pelvis and legs align, so the measured femur height shifts as the pelvis is realigned. The data show that applying the PI correction produces a femur height change of about four millimeters. This represents a moderate, clinically meaningful adjustment in functional leg length without implying only a tiny change or a dramatic one. A much smaller change would not reflect a substantial realignment, while a larger shift would exceed what the data support. So the approximate magnitude is four millimeters.