Sometimes you have to be ultra-patient, and stand still for a while to avoid falling back downhill again. Long term progress may require doing very little right now. If you cannot lift heavy weights or any weights at all for the upper body right now, then you have to accept that. To go against what your body is telling you risks making this situation much worse and making recuperation take months longer.
Sometimes, we suffer set backs. We ALL do, it's not just you. If you are an enthusiastic exercise lover, injuries are going to happen. It's not IF, it's WHEN.
You may lose strength gains in the upper body. But, you will get it back eventually. Having built strength once, you can always get it back. Muscles have memory. You build it back faster subsequently, faster than the time it took to build it originally.
What you need to figure out in the meanwhile is what to do to stay sane while the body heals. So, you do cardio and make movement patterns that are non-weight bearing and natural movements. Are you able to do planks? If you can bear the weight of your own body, then you can do yoga and planks, which will prevent excessive loss of strength. Can you swim? You could also think about investing now in different forms of exercise, that vary the stresses placed upon the body and the movement patterns of the arms, to avoid this problem surfacing again once healed. So: can you swim? It's excellent for upper and lower body and cardiovascular system, and the resistance is provided by the water itself. No weights needed. Can you do punches from kickboxing? If you can, then again, kickbox, boxing and martial arts (all of Cathe's MMA stuff from STS shock cardio series) are all ways to maintain strength while you heal.
Can you hold weights while you work the lower body? You may need to focus on lighter weights and higher reps for the lower body for a while, to avoid the strain on the elbows of holding 20 pound dumbbells, for example. Also, if you use the barbell across the shoulders for lower body work, this again puts less strain on the elbows.
Hope this helps,
Clare