I would love to hear from sambo guys on this in regards to safety .eg prevelence of injuries from lower extremity locks. I personally would rather be in a knee bar than most guillotine chokes. wrecked cervical vertebre are just as hard to get over as wrecked knees.
I get to see more injuried arms from armbars and shoulders from throws than injuries due to kneebars or achilles locks.
In fact, i've never seen someone get injuried from a kneebar or an achilles lock, not even in very large competitions. I've seen a lot of people being hurt and sore because of them but not properly injuried. Some ice and two day's rest and they're back to training.
Then again, in sport sambo, special care is taken that it's a proper straight kneebar and a proper straight achilles lock. With twisting holds, sometimes all it takes is for someone to accidentally fall down to cause injury, even if it wasn't the intent of the person applying the hold.
As for bicep/calf slicers/crushers... i've only seen one person get injuried from it, and it wasn't a break or anything. He had some minor damage to arm muscles, but it was because he tried to turn away from the move making my weight fall down on his arm during the submission. I've heard stories of people having stress fractures from these, but, well, i guess they were being stubborn about not tapping, or just had bad luck (or lack of calcium).
IMO, all of these submissions come from positions where the attacker has a lot of control over the defender's limb and movement, and can cause a lot of pain before actually causing injury.
So if there's not a huge weight/strength difference , "bad" intent from the person applying the hold, or a very bad referee, this move should not have a high injury ratio compared to other holds.
In some competittions the referees don't actively stop the matches when they see submissions locked in, and wait for the tap. I'd say that for white belts, the referees should intervene more to stop bouts when they see the integrity of one of the competitors is in danger. With referees that intervene more, i'm sure you can add more submissions that "seem" to be more dangerous. I think it's safe to say that most blues know when to tap, and maybe the referee should intervene less, or only with certain submissions.
My take is that twisting submissions (heelhooks, twisting kneebars) and spine submissions (neck cranks, hip cranks) should only be allowed at black belt competitions (they're the pro's). The rest? Some at white, some at blue, more at purple. I see no reason as to why a purple belt shouldn't be allowed to use a much larger arsenal of submissions.
Human anatomy has more than just neck and arms - why limit ourselves to attacking those?
P.S. - What happens if you scream in BJJ because of pain? In sambo it's the same as tapping, the referee will stop the bout, no clue if it also applies for BJJ.