Sorry to hear about ur back problems mine pale in comparison. Good luck with the treatment . I have my fingers crossed for you. One thing have learned as i have gotten older is to listen to my body and when it says stop I stop. I know from my own personal experience that squats are a great overall excercise but they do put tremdous pressure on your lower back . i no longer do them but count on leg presses and lunges to work my quads as effectively. Dead lifts also put a lot of pressure on the lower back so i do without as well. I am pushing harder and harder each day and continue to be successful while staying injury free. Good luck.