The Conventional Approach Among the multiple therapeutic modalities and surgical techniques available to treat spinal conditions such as degenerative disc disease, scoliosis, spondylolisthesis, or spinal fracture, one of the more conventional treatments offered to patients is lumbar spinal fusion surgery. With more than 200,000 operations performed each year in the United States1, the open surgical technique of fusing certain lumbar vertebrae together using bone grafts to stabilize movement of the spinal column has proven to be effective for patients with severe mechanical disorders in the spine. However, as with any invasive surgery, the downside of open lumbar spinal fusion surgery is the damage that occurs from the 5- to 6-inch midline incision, muscle dissection and retraction (which, instead of preserving the muscle, contributes to the formation of scar and fibrotic tissue), blood vessel cauterization, and bone removal. Although these disruptions to the normal anatomy are necessary to facilitate the placement of screws and other devices to stabilize the spine, conventional treatment can lead to a lengthy hospital stay (up to five days), prolonged pain and recovery periods, postoperative narcotic use, blood loss, and risk of tissue infection. To minimize these adverse occurrences, a new minimally invasive percutaneous approach in which access to inner organs or other tissue is performed via needle puncture of the skin, has become popular. This new approach is the TranS1 axial lumbar interbody fusion (TranS1 AxiaLIF). In a short period of time, AxiaLIF has demonstrated the potential to change the way spinal fusion surgeries are performed while revolutionizing patient care by dramatically reducing recovery time. The Percutaneous Trans-Sacral Approach The AxiaLIF procedure, which recently received the U.S. Food and Drug Administration market clearance, is a product of five years of clinical development and testing. Dr. Andrew Cragg, a Minneapolis-based interventional radiologist, discovered and patented this percutaneous trans-sacral approach for spinal access. Working in unison at the primary clinical research facility for AxiaLIF, the Toshiba Stroke Research Center's cadre of physicists, chemists, aerospace engineers, neurosurgeons, and neuroradiologists from around the world have helped ensure the continual development of this new, minimally invasive procedure. The facility also houses one of today's most advanced vascular x-ray medical imaging systems available to incorporate catheter-based, image-guided technology with the AxiaLIF procedure. The result has been the dramatic clinical improvement and turnaround associated with the performance of this new spinal procedure. Overview of the New Technique On January 28, 2005, neurosurgeons at the University at Buffalo carried out the first minimally invasive AxiaLIF spinal procedure in the United States. The spinal stabilization procedure involved the placement of an anterior interbody device delivered over a wire and through a small incision. The surgeons applied percutaneous endovascular principles, using catheters and wires guided by modern fluoroscopic imaging technology commonly found in catheterization labs, to access points and target regions. They were able to safely target the lumbar spine and sacrum, and insert a K-wire and tube to provide sufficient space in which to perform the AxiaLIF spinal procedure. In detail, the AxiaLIF is a two-part, 360-degree fusion of the anterior sacrum with the middle columns of the spine. To begin, the procedure requires a two-centimeter percutaneous incision just lateral to the coccyx before the dissection is performed through the incision to define the plane under the sacrum. Once that is achieved, fluoroscopy is used to localize the midline or the median plane of the vertebral body along the sacral plane. This phase of the procedure enables access to the sacrum, the intervertebral disc space between the fifth lumbar vertebra (L5) and the first sacral vertebra (S1), and the L5 vertebral body. With access to the sacrum in this plane, a blunt dissector is used and serves as the tube where a guide K-wire is inserted to create a working channel. Instruments needed to perform the remaining procedure are threaded internally along the spine to the surgical site by following the guide wire. The second half of the procedure involves the placement of an anterior interbody device through the working channel created by the initial procedure. Through the working channel, the L5-S1 intervertebral disc space is drilled out with special miniature disc reamers and endplate scrapers, which are passed through to remove the torn and diseased disc material. The removal of the intervertebral disc enables the L5 vertebral body to be drilled, creating space for inserting screws to stabilize the spine. The screw is then packed with bone grafting material and used to fuse the L5 and S1 vertebrae together. Critical to the success of the AxiaLIF spinal procedure is the visualization of the lumbar spine and sacrum afforded by fluoroscopic imaging. Also, high-resolution imaging of the midline must be maintained at all times during the procedure to avoid the risk of passing the catheters and wires into soft tissues or great vessels. Because the procedure takes place without the benefit of landmarks or cues to help the surgeon identify the patient’s anatomy, an x-ray medical imaging system provides the only assistance for differentiating organs and other soft tissues from the sacral plane. Advances in Patient Care In a recently published clinical study, patients with vertebral fractures, slipped vertebrae, or discogenic (disc-related) back pain who were treated with the AxiaLIF spinal procedure and sent home within 24 hours returned to work within 15 days without requiring intravenous narcotics.2 In contrast, patients undergoing conventional lumbar spinal fusion surgery are discharged in three to five days and do not return to work for one to two months. Some patients could receive the AxiaLIF spinal procedure on an outpatient basis and realistically expect to be up and walking without pain within hours of leaving the operating suite. The first U.S. patient, a 31-year-old woman who had long-standing back pain due to an earlier injury, was presented after she had re-injured her spine and suffered debilitating pain in her back and legs, which required her to take a leave of absence from work and use a cane to walk. Two hours after she underwent the AxiaLIF spinal procedure performed by neurosurgeons at the University at Buffalo, she stated that she had total relief of her back and leg pain and was experiencing only some minor discomfort. This patient was an ideal candidate for the technology because she had no arthritis or degeneration of the vertebrae, which are conditions that are often seen in older patients who require back surgery. As with most minimally invasive procedures, the AxiaLIF spinal procedure is reserved for patients with focal disease; thus patients with widespread arthritis and degenerative disease are not suitable candidates. Despite this limitation, the AxiaLIF spinal procedure is an excellent alternative for approximately 10 to 20 percent of current open lumbar fusion surgery candidates. Providing Training for Widespread Adoption The AxiaLIF procedure requires surgeons to complete comprehensive preclinical and clinical training as part of a certification program. The Toshiba Stroke Research Center serves as a training facility in the United States and abroad for surgeons interested in staying at the forefront of this new, minimally invasive spinal procedure. Using a state-of-the-art training laboratory, surgeons at the facility are trained to perform the procedure using sophisticated image-guided equipment, including the Infinix i-series single-plane vascular x-ray system (Toshiba), which allows surgeons to view real-time x-ray video to guide them during the procedure. In addition to its superior image quality and low radiation dose capabilities, which are required for performing AxiaLIF procedures, the system enables the training to occur safely in a laboratory setting before the actual procedure is performed in the operating room. Additionally, to advance the adoption of new minimally invasive approaches to spine surgery, workshops also are offered to neurosurgery residents at the Toshiba Stroke Research Center. These workshops include basic spinal fluoroscopic anatomy, as well as basic approaches of using fluoroscopic imaging to minimally access the pedicles. The workshop also focuses on vertebroplasty, an image-guided, minimally invasive procedure performed in the catheterization lab to strengthen broken vertebrae. Future Direction of Minimally Invasive Spinal Surgery Due in part to the medical industry’s conventional thinking and a lack of awareness by the public, minimally invasive spine surgery as a trend has been slow to take off. Procedures such as AxiaLIF require specialized techniques and nontraditional ways of visualizing the anatomy that may prove challenging to some seasoned surgeons unwilling to venture too far from their comfort zones. Nevertheless, the positive momentum behind the recent success of the AxiaLIF spinal procedure in the United States and its revolutionary benefit to patients, which validates this unconventional approach to spinal surgery, will undoubtedly trigger wider adoption and foster the next leap in minimally invasive surgical techniques to address other spinal conditions such as percutaneous disc replacement and reconstruction of degenerate spine. Interestingly, it is reported that the next leap is already in its early stages and involves a minimally invasive retroperitoneal or transperitoneal technique of accessing the spine via the tissues that line the wall of the abdominal cavity eliminating the need to make an incision through the abdomen to access the spine for disc replacement. What is certain at this point is that the future direction of minimally invasive spinal surgery will increasingly rely upon the cardiac catheterization lab and the continual development of medical imaging equipment to aid these new approaches to spinal surgery. Dr. Levy can be reached at tel. (716) 887-5311. Do you foresee any future involvement of current cath lab staff or peripheral vascular interventionalists in this lumbar spinal fusion procedure? It is possible that interventionalists with experience in vertebroplasty and kyphoplasty or other minimally invasive spine interventional techniques may be interested in adopting this technology. In the procedures that have been done, were cath lab staff involved at all? An x-ray technologist was in the OR to help run the fluoroscope. How specifically is the cath lab utilized/adapted for use, equipment-wise, for this procedure? In many centers the cath lab is used for vertebroplasty, or percutaneous delivery of bone cement into painful osteoporotic compression fractures. Some perform discograms, which require percutaneous, fluoroscopically guided needle placement into disc spaces. Nucleotomy techniques are performed in cath labs that build on the access techniques for discography and actually remove disc material to help control radicular pain. IDET procedures (thermal annuloplasty, a surgical procedure for chronic back pain relief are performed in cath labs as well. In this procedure, the disc is accessed with a heating catheter, through which energy deposition is thought to inactivate pain-generating nerve endings in damaged discs. In cath labs with this expertise, the AxiaLIF lends itself to skills already mastered by the staff. Equipment trays would be different, but positioning, airway management and a knowledge of the fluoroscopic anatomy already exists. Questions answered by: Lee R. Guterman, PhD, MD, Toshiba Stroke Research Center, School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, New Yorkc
1. Back.com: What’s a bone graft and do I have any options. April 8, 2002.
2. Cragg A, Carl A, Casteneda F, Dickman C, Guterman L, Oliveira C: New percutaneous access method for minimally invasive anterior lumbosacral surgery. J Spinal Disord Tech 17:21-28, 2004.