Minimally invasive spine surgery is transforming spinal surgery both in the United States and internationally. These procedures performed by expert surgeons are improving surgical outcomes and decreasing the recovery time in a predictable fashion. New developments and improvements in traditional techniques continue to advance the field at a rapid pace. To paraphrase an old car commercial; this isn't your father's spine surgery.
Improved spinal implants compatible with minimally invasive surgical approaches expand the range of conditions that can be treated. Expandable implants can be placed in a collapsed configuration into the disc space then enlarged to the desired shape. This is analogous to placing a small model ship into a bottle then expanding it to full size. The small implant can be placed through a small tube without injury to normal tissues. The implants can also re-establish the normal balance of the spine in multiple planes to improve both the short-and long-term outcomes of the surgery.
Other implants promote bone healing by unique surface coatings, metallic composition, and structural design. These are made by modern manufacturing techniques including 3D printing and computer design. In my opinion, the most exciting design promotes forces at the nanotechnological level imparting a signal to the cells to make bone and secrete growth factors.
Traditional implants such as pedicle screws are constantly improved so as to be more adaptable to minimally invasive surgery.
Another major advancement is intra-operative computer navigation. In the operating room in real time, the spine can be imaged and surgery performed by touching the skin or other landmarks. Surgical implants can be placed by visualization on a computer screen with extreme accuracy and safety without dissecting or injuring normal tissue. I routinely utilize this technology in the cervical, thoracic and lumbar spine. It can also be used to navigate soft tissue which is very useful in redo surgery, where normal spinal landmarks are missing, and in endoscopic surgery. Future developments will probably include the combination of computer navigation and robotic surgery.
Surgical approaches have also been modified to minimally invasive strategies. The far lateral approach to the lumbar spine has been a significant advance in deformity and now in routine spinal surgery. It can be done through a tubular retractor with very little dissection. The main drawback has been neurologic injuries in a small number of patients. The oblique lateral approach was then developed to address this problem and has been a dramatic improvement. This approach can also be done through a tubular retractor without major dissection with no neurologic or vascular injury. Both of these techniques are extremely useful in deformity surgery to correct spinal imbalance with minimal surgical injury.
Soft tissue procedures can also be performed with tubular or endoscopic techniques to address a specific nerve compression at a specific site. In addition, multiple level, bilateral and far lateral decompressions can be performed through single scope portals or multiple portals depending on the pathology. These strategies can be employed to achieve the same anatomical effectiveness without the pain and morbidity of open surgery.
Another new and exciting development is preoperative computer surgical planning. This is especially applicable to deformity (scoliosis) surgery. The specific type of osteotomy can be calculated and modeled on a computer screen before the surgery to achieve the optimal result. The specific implants and even the bending of the rods can be determined and made available preoperatively. This planning is then combined with intraoperative computer navigation in order to achieve precision surgery. We can combine minimally invasive techniques with open techniques in these complex cases dramatically improving outcomes and decreasing surgical morbidity.
Motion devices in the cervical and lumbar spine are not necessarily minimally invasive but they are implanted through small open procedures with minimal morbidity. They stabilize the spinal segment and maintain more normal motion and mechanics of the spine. Long term outcome studies are now showing superiority of motion over time. A relatively new posterior (intra-laminar) motion-sparing device can be used instead of fusion in selective cases.
Biologics are the newest frontier in spine surgery. These include growth factors and stem cells. Growth factors have been studied for decades in both animals and humans. An FDA approved growth factor, INFUSE, has been utilized in spine surgery for years with excellent results in obtaining fusion healing and excellent surgical outcomes. However, the intense inflammation associated with INFUSE caused unanticipated complications especially when used in an off-label fashion. Growth factors are powerful agents that work well when experienced surgeons use them appropriately. Stem cells obtained from the bone marrow combined with collagen carriers and utilized with modern spinal implants have been very effective in obtaining spinal fusion without inflammatory complications. In my practice, bone marrow-derived mesenchymal stem cells have replaced growth factors and other bone graft harvested tissues.
Regenerative medicine seeks to restore injured or worn out tissues with biologic treatments. In spine, we are studying the use of bone marrow-derived stem cells injected into degenerative disc and joints of the spine. Other studies — an FDA IDE trial and a trial outside U.S. — have shown the ability of immature cartilage cells or a patient's own disc cells expanded in culture and re-implanted into the disc to relieve pain. The results are preliminary with small numbers but show significant promise. Animal studies have demonstrated the ability to regenerate the disc but human studies are planned for the near future outside the U.S. The FDA is very concerned about the nature of these therapies, so all our treatments are compliant with FDA guidelines.
The power of these new technologies and treatments lies in the ability to use them alone or in combination depending on the specific diagnosis. The technical learning curve for a surgeon is significant. The body of knowledge necessary to implement these strategies is vast. This new frontier requires a new mindset or paradigm from the diagnosis of the painful condition to the planning and execution of the surgery to the postoperative care. Many surgeons claim they perform minimally invasive surgery but few actually know all the elements necessary to achieve optimal results. The field continues to evolve generating excitement, hope and opportunities for patients and surgeons.