I tore a ligament connecting my spine and tore a low back muscle to go with it. I took about a month off from pretty much all lifting. along with physical therapy 3x/week i started incorporating lifts I could do without any pain. so lots of upper body and belt squats, reverse hypers, leg curls and extensions, lunges... lots of chest supported
row variations and pull up variations. 3 months in and I'm going heavy to/beyond failure again on those exercises. didn't lose any muscle mass and got stronger on my press days. going to start incorporating barbell work back in real light. I don't expect to lose much besides being detrained. might still be a few months out from going heavy. just don't stop altogether