ERC Display mm vs X-Ray mm

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For those who have done LL or currently going through it. Has your lengthened mm amount that your ERC is displaying match your measured distracted gap shown on your x-ray?

If not, which do you think is more accurate? The x-ray measurement or ERC display?

I am not sure which one to believe. X-rays can be effected by angles, x-ray tech, knee flexion, etc
The ERC can be effected by gear skipping, both sides being lengthened accidentally etc.

I currently have a 5mm difference between the ERC display and x-ray measurement and I am not sure which one to believe.

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Quote from: Body Builder on July 21, 2023, 02:17:17 PMI used X rays with a ruler next to my feet and it was a very precise way to measure the bone gap, much better than the programs my doctor used (although the difference was ay max 2-3 mm). And the height I gained was exactly the same after my last x ray with the ruler

So I would essentially place a metal ruler next to my femur as my x-ray is being taken?

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Quote from: Maison on July 21, 2023, 03:45:12 PMThe ERC Display generally corresponds well with the actual nail lengthening amount, but it isn't flawless. If there's an issue with the equipment or a patient's operational error, the actual lengthening might vary slightly.

X-ray images are magnified more than the real object.
To correct this, we can use tools like a calibration ball or a ruler, or measure a nail diameter.
If an x-ray shows a nail's diameter as 11 mm, but it's really 10 mm, the image is 10% larger.

So if x-ray calibrated properly and the nail diameter is 11mm and the distraction gap says 70mm, the gap should be accurate technically?