I’m sure you’re referring to these Opalithplättchen, aren’t you?

Impressive that you could remember the name. I’m German and had to look it up since I never heard about Opalith before.

20 years ago, I wanted to jump onto a concrete table tennis table in the school playground from a standing position with both feet at the same time. I didn’t make it and hit my shin up to the bone.

After it was stitched up, it became badly infected weeks later and I had to have another operation while on vacation.

Now I have a 1 inch scar directly on the shin bone which hurts a lot every time I hit it.