Outpatient spine surgery is becoming much more viable now than even five years ago.
I have transitioned my practice to doing all of my non-Medicare cervical spine surgeries and more than 50 percent of my non-Medicare lumbar surgeries as outpatients. This includes the larger fusions in the cervical and lumbar spines that used to stay in the hospital two to three days. 
Better techniques in surgical approaches and anesthesia have made this transition possible. I think the trend will continue in the private practice world. In the employed physician model, there is much less incentive for moving to outpatient surgery and ownership in ASCs are more rigorously discouraged if the surgeons take their cases from the balance sheets of their employers.