The spinal column is made up of building blocks of bones separated by discs that act as shock absorbers and spacers between the vertebrae (bones).
A rounded back offers little or no support to the spinal column when lifting and that's often why, generally over time and through repetition, that we injure the spine - we're asking the spinal column to take on the load of lifting instead of engaging muscle meant to do the heavy lifting.
Use proper body mechanics & engage the back and gluteal muscles:
TAke a wide stance, pull your abdomen in, fold at the hips, bend the knees, lead with the chest to come up, stiffen your back by pulling your shoulder blades down your back and use your buttock muscles. When you "stiffen" your back you're engaging the muscles that support the spinal column.
P.S. The idea of using your legs to lift is outdated and can harm the knees. (Dr. Stuart McGill) Use your glutes instead.
The glutes or buttock muscles are the strongest and largest muscles in the body. Use them when lifting by contracting (pull them in/ squeeze the butt).