@Ss11263 while I cannot speak specifically about using a child carrier with a back injury, I had great success using the Deuter Kid Comfort for several years when my son was young; I found it to be comfortable and supportive, however again, I do not have a back injury. Since it sounds like you've tried both the Osprey and Deuter, perhaps you could order the Thule Sapling, get it fit at your closest REI store, and be able to decide between the models? Hope this helps!

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