Minimally Invasive Lumbar Interbody Fusion Using Transforaminal Approach

In the surgical treatment of lumbar Spondylolisthesis , there are two basic goals. The first goal is to eliminate the compression of the nerve roots by excision of compressive bone, ligaments, and disc material surrounding the nerve roots. The second goal is to stabilize the two vertebrae by placement of bone grafts, screws, and rods to stabilize the vertebrae and fuse them together.

Traditionally the process of decompression and fusion has been accomplished through a wide surgical exposure of the posterior aspect of the affected vertebrae. A laminectomy is performed to relieve pressure on the nerve roots. Bone graft is removed from the posterior hip bone (iliac crest) through a separate incision. The bone graft is layered on both sides of the exposed spine. Pedicle screws are placed into the vertebrae and connected by rods to immediately stabilize the unstable vertebrae. The bone grafts provide long-term stability once they have fused to the vertebrae (usually 3-6 months). This procedure can require a four- to six-inch incision over the spine, with stripping of the spinal muscles away from the spine over three to four vertebrae to gain adequate exposure. The incision on the hip for harvesting of the bone graft is usually three to four inches long. Both of these incisions remain painful for many weeks after surgery, prompting the quest for better methods.

The evolution of minimal access surgical techniques (MAST), new instrumentation ( METRx, Sextant ) , new techniques to achieve fusion ( BMP, TANGENT ), and surgical image guidance technology (Stealth, ISO-C3D C-arm ) have made is possible to achieve the goals of decompression, stabilization and fusion through multiple small incisions, minimizing surgical exposure of the spine, decreasing blood loss, reducing post-operative pain and shortening recovery time. The procedure can be done without harvesting bone graft from a separate incision. The fusion process takes place between the vertebrae within the disc space (interbody fusion), rather than around the sides of the vertebrae. An interbody fusion is believed to be a more stable fusion with a higher rate of success. The procedure performed to fuse the vertebrae through the level of the disc space is called a posterior lumbar interbody fusion or a transforaminal interbody fusion.

The following photographs illustrate a minimal-access technique used to perform a TLIF on a patient with spondylolisthesis. ISO C-3D images are combined with the Stealth surgical navigation system to guide instruments through small incisions to defined points on the spine.

The guidance system is, in turn, combined with the Sextant pedicle screw and rod insertion system to precisely place pedicle screws through half-inch incisions for the treatment of spinal instability.

The discectomy and interbody fusion is performed through a one-inch incision using the METRx tubular retractor system.

A reference frame is attached to the spine through a small incision so the Stealth camera can “see” the spine.

A scan is performed with the ISO-C 3D C-arm and images are transferred ot the Stealth station computer.

The locations for the skin incisions are plotted with the image guidance system.

An image guided probe is passed through a small incision to locate screw entry points on the pedicles.

The probe is replaced with a guide wire.

The pedicle screws are attached to screw inserters and passed over the guide wires and screwed through the pedicles into the vertebral bodies.

The guide wires are removed and the Sextant arc is attached to the screw extenders. A ¼-inch rod attached to the end of the arc is passed through a ¼-inch incision to engage the heads of the screws. The rod is locked in place, and the Sextant arc and screw extenders are removed.

Rod placed through 1/4" incision to engage 2 screws

X-ray showing rod engaging screws.

Images courtesty of Medtronic, Inc. - Artist's illustration of rod instertion.

Earthchannel Media Animation

A one-inch incision is made opposite the two pedicle screws and a METRx tube is positioned through the spinal muscles. Using microsurgical technique and image guidance, a discectomy and interbody fusion is performed.

A Patient's Story:

Theresa Ledbetter is an assistant director of human resources at the University of Tennessee . Over a three-year period she developed progressive low back and bilateral leg pain (sciatica). Diagnostic studies demonstrated an unstable spondylolisthesis at the lumbo-sacral junction. After considering the various surgical options and having failed to respond to non-surgical treatment, Mrs. Ledbetter chose to have minimal access surgery. She underwent a posterior lumbar interbody fusion and pedicle screw fixation using Stealth image guidance and METRx systems.

She was discharged two days after surgery and returned to work in seven weeks.

At one year after surgery, Mrs. Ledbetter states that she feels fabulous.

“My quality of life has improved 100%.”

-- Theresa Ledbetter

A Patient's Story:

Mr. William Schmidt is the president of a sports marketing company and an Olympic Bronze medalist. He had surgery in 1992 for a herniated lumbar disc. Over the next decade, Mr. Schmidt developed increasing back and leg pain. Diagnostic studies showed degenerative lumbar spondylolisthesis and stenosis at the level of the previous disc herniation. On December 15, 2003, he underwent a posterior lumbar interbody fusion (PLIF) and pedicle screw fixation using the Stealth and Sextant systems.

William was walking the next morning and allowed to return home on the second post-operative day.

“Surgery absolutely improved my life. I couldn't function before surgery, and now I have no limitations on my daily life. I could have gone anywhere in the US for surgery, but I chose to stay in Knoxville .”

-- William Schmidt, July 2005

Mr. Schmidt is a low-handicap golfer and rides motorcycles for relaxation.

A Patient's Story:

Jackie Hill is a surgical nurse at University Hospital who was previously treated for a herniated disc by microsurgical discectomy. She made a good recovery, but within six months, developed recurrent back and leg pain. Repeat x-rays and MRI scan showed the development of a degenerative spondylolisthesis at the level above her previous surgery. After failing to respond to non-surgical treatment, she underwent interbody fusion and pedicle screw fixation using minimal access surgical technique in February, 2004.

She experienced an uneventful recovery, leaving the hospital after three days and returning to work full time within six weeks.

In September 2005, Jackie says, “I love it. I'm productive now.” She works in the pre-operative unit and frequently talks to patients admitted to have the same operation, offering encouragement and reassurance for their prognosis.