This is a commonly performed procedure to address certain disabling lower back conditions. In a Posterior Spinal Fusion, an incision is made on the back and the painful segment of the spine is fused together using bone graft material and titanium rods and screws. The most common indication is for spondylolisthesis, or slippage of the vertebra. This is caused by arthritis involving the joints of the lower back and results in instability. It is commonly associated with spinal stenosis, or pinching of the nerves in the lower back by bone spurs. Patients typically present with lower back pain and leg pain, often with numbness and weakness. Surgery usually takes about 1-2 hours and usual hospital stay is 2-3 nights.