Transforaminal lumbar interbody fusion (TLIF) is a proven yet still evolving procedure that can be extremely successful in the right patient. When it comes to interbody fusion implants, there are several challenges surgeons face with both traditional and expandable technologies.
Due to their small footprints, both traditional and expandable TLIF implants are difficult to place on the anterior cortical ring. Plus, their small graft windows don’t offer the graft area that may be necessary to achieve fusion successfully.
"Because of the limitations of the anatomy, there are some cages that aren't able to fit into the intervertebral space," says Richard Fessler, MD, PhD, of Rush University Medical Center in Chicago. "The consequence is a large patient or osteoporotic patient can experience a cage that breaks through the endplate of a vertebral body and crushes into the body so we lose the disc height we were trying to gain."
Traditional TLIF implant placement can require aggressive bone removal and/or impaction, which can make the procedure more traumatic. Furthermore, the normally narrow surgical corridor constrains the size of the interbody device that can be inserted. In most TLIF patients, surgeons are unable to place a sufficiently large implant that can be placed on the anterior third of the apophyseal ring to restore disc height, foraminal volume and stability via a large footprint while minimizing the risk of subsidence and providing an optimal fusion environment.
"When we are trying to gain access to the spine, surgeons sometimes place both the traversing and exiting nerve roots at risk because of the implant's size and we have to impact the implants," says Jeffrey Coe, MD, of Silicon Valley Spine Institute in Campbell, Calif. "The expandable TLIF technologies, like the Luna 3D, can meet these needs by allowing both expansion in a cephalocaudal direction and mediolateral direction and in most cases create lordosis. It's like a ship in a bottle; you can get in a larger ultimate device through a smaller aperture."
Luna 3D offers these benefits and more, as only Luna 3D expands in multiple directions. First, Luna 3D expands in a circular diameter of 25mm to engage a much broader area of vertebral endplate. It then expands in height up to 13mm with 0° lordosis or up to 15mm with 8° of lordosis. Once expansion is complete, the surgeon then injects bone graft into the large, contained graft chamber.
Luna 3D’s non-impacted, posterior delivery is performed through a 6 to 11 mm insertion cannula, minimizing nerve retraction and preserving the vertebral endplates.
"The nice thing about the Luna cage is that it can be put into a relatively small opening posteriorly — like a TLIF — and once it's in the intervertebral space it expands like an ALIF implant," says Dr. Fessler. He has seen benefits for patients, including:
• Less muscle dissection
• Less blood loss
• Large fusion footprint
• Lower pain scores
• Faster hospital discharge
• Quicker recovery
"The first time I saw the technology, it was so logical and provided advantages because the implant goes through a small opening and expands to cover a wide part of the intervertebral endplates," says Dr. Fessler. "It was a no-brainer; the technology we wanted all along."
The procedure essentially allows surgeons to place a large ALIF-like implant through a TLIF approach achieving direct and indirect decompression in one approach, including the placement of copious bone graft material in direct contact and apposition to the bony endplates.
"You want to have a device that is right for the patient," says Dr. Coe. "The reason why that is important is because we want to be able to adapt to each patient's anatomy and their particular condition. There is greater emphasis now on spinal surgery for the prevention of inadvertent lumbar kyphosis and the preservation of the normal spinal alignment. Even if you are not a spinal deformity surgeon, it's important not to create a deformity with a lumbar fusion procedure. If you pay attention to your patient’s lordosis initially, you have a much greater chance of having him or her avoiding major deformity surgery down the line."
Surgeons have two different lordotic options — 0° or 8° of lordosis — to accommodate sagittal alignment restoration. The bone graft after expansion feature ensures the graft is in contact with the endplates and under compression in accordance with Wolff’s law.
"For many years I shied away from doing TLIFs," says Dr. Coe. "One of the reasons was the potential for subsidence with small footprint cages. Furthermore creating lordosis was challenging. But when I was first introduced to the Luna technology, I found an option where I could do TLIFs again at L5-S1 and even L4-5 where the lateral approach was not the right choice for a particular patient. It's revitalized TLIF as an option in my surgical practice."
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This article is sponsored by Benvenue Medical.
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