A tissue retractor assembly may be moved through an opening formed in vertebrae in a patient's spinal column. The robotic mechanism may be utilized to form the opening in the vertebrae and to move the contracted tissue retractor assembly into the vertebra. The tissue retractor assembly may include a cannula or scope which is utilized to position the balloon or bladder relative to the vertebra and to conduct the fluid (gas or liquid) into the balloon or bladder to effect expansion of the balloon or bladder. The balloon or bladder may be formed of a biodegradable material. The robotic mechanism may be utilized to position the cannula through which the flow of synthetic bone material or cement is conducted into the space created in the vertebra by expansion of the balloon or bladder.