Ann: 36-Month Results of Phase 3 Trial in Chronic Low Back Pain, page-191

That's one purpose of keeping the control the same (to reduce effect of placebo). A patient getting an injection of anything in the spine may think it has helped even if it's just saline.

But another purpose of keeping the same injection media is to control for the effect of the media itself. If HA does decrease pain on its own (which other trials have shown it does, look at its uses in intraarticular injections in knees for arthritis) then using just HA as a control helps to prove the effect of the treatment is the cells, not HA.

The purpose of a trial is to prove the treatment works. Would you consider there is a problem simply giving patients a costly injection without evidence that it is superior to HA alone?

This is the last I'll speak of this. If people don't understand this aspect of trial design at this stage then further harping on won't help, and it sounds like others here are sick of hearing me