Spine Cages Help to Restore Correct Spinal Alignment

Peer Reviewed

In recent years the excitement about the development and use of spine cages has escalated. However, unless you are a spine specialist, you may find it difficult to appreciate what all the commotion is about. Lets face it, for most people, spine cages are not an everyday topic of conversation. Most people do not know what spine cages are, how they are used, and how they benefit patients.


To begin, a brief introduction to cages is needed to help you understand why these devices are so important in spine surgery today ... and tomorrow.

Cages: An Overview
A cage is a small hollow cylindrical device, usually made of titanium, with perforated walls.


cage interbody device color photo


These devices are sometimes called 'interbody cages.' The word 'interbody' refers to where these cages are used (i.e. the disc space between two vertebrae). The purpose of using cages is often to restore lost disc height resulting from a collapsed disc and to relieve pressure on nerve roots.



spinal segment labeled disc vertebral body spinal cord nerve root color drawing


Lost disc height is restored when the cages, packed with bone graft are inserted into the space between the two vertebrae. Basically what happens is the bone graft, which has been neatly packed into and around the cages, begins to grow through the perforated walls of the cages eventually forming a solid bond (or 'fusion') holding the vertebrae together. This process is known as 'interbody fusion.' You could loosely compare cages to building blocks and bone graft to the mortar that binds the structure together. The end result is fusion, a strong and stable construct.

ltcage2.gif x-ray lateral view lt cage lumbar l5-s1instrumentation fixation fusion
Example of an LT Cage™
inserted between L5 and S1
X -ray illustrating LT Cage™
placement between L5 and S1

Patients who are to undergo surgery due to degenerative disc disease, disc herniation or low-grade spondylolisthesis may have cages implanted during their surgical procedure. These conditions can cause vertebrae to grate against each other during motion and cause nerve impingement when a disc is damaged. A solid cage fusion can eliminate the motion, increase the space for the nerve roots, stabilize the spine, restore spine alignment, and relieve pain.


disc problems labeled normal degenerated bulging herniated thinning osteophyte formation color drawing


Cage Development: A Brief History
Remarkably, the history of cages begins with horses. Several decades ago Dr. George Bagby, an orthopaedic surgeon from Spokane, Washington invented the first cage. "Bagby's Basket," as it was called, became popular when a horse named Seattle Slew; the first unbeaten Triple Crown Winner, was diagnosed with "Wobbler's Syndrome," a degenerative condition causing serious neck instability.

Working with an equine veterinary specialist, Dr. Bagby implanted his cylindrical stainless steel "basket" into Seattle Slew's spine.

After securing the basket in place, it was packed with the horse's own bone graft. In time the bone graft grew into and around the basket creating a solid fusion and saving Seattle Slew from certain death. After the Seattle Slew episode, several years passed without any notable cage developments. Then in the late 1980's significant advancement was made when Dr. Stephen D. Kuslich, a spine surgeon from Minneapolis, Minnesota converted Dr. Bagby's design into a cage suitable for human use. Dr. Kuslich's cage, a threaded hollow titanium cylinder with thick perforated walls, was designed for the posterior (back) part of the spine. His cage design quickly caught the attention of his peers.

Since then, several surgeons, including myself became involved to develop anterior cage systems.

Anterior Placement: Why?
An anterior approach, meaning through the front of the body, allows the surgeon to work through the abdomen to reach the spine. In this way spine muscles located in the back are not damaged or cut; avoiding muscle weakness and scarring. In addition, minimally invasive surgical techniques serve to dramatically accelerate patient recovery. Over 90-percent of my patients who have undergone this procedure have gone home the morning after surgery.

The Next Generation of Cages Today
In recent years cages have undergone numerous modifications to improve their effectiveness. Some of these cages include the BAK™ , Ray TFC™ , the Contact Fusion Cage™ , and INTER FIX™ .


ltcage.jpgLT Cage™


Although, as a patient, you don't need to understand all the technical details about cages, we thought we would highlight some basic details about a specific cage. One of the newest and most technically advanced is the LT Cage™ . Surgeons are reporting very good results using this cage as a result of its unique design elements. For example:

  • The LT Cage™ is tapered (similar to a door wedge). This cage's tapered shape helps to restore the spine's correct alignment or curves; an essential goal of spine surgery.
  • Often surgeons use two cages next to each other in surgery. The problem in the past has been the curved sides of cages make it difficult to get the cages close together. The LT Cage™ has flat sides, meaning that cages can be placed very close together. This might sound like a small change, but it is an important development to help cages succeed in creating strong constructs.
  • The perforations or holes in the cage walls are larger thus helping create fusion by allowing for increased bony growth in and around the cage.
  • The LT Cage ™ is titanium, which makes it very strong and durable. There are no reported cases of an LT Cage™ failing structurally. In addition, its titanium construction allows the cage to be seen by CT or MRI scanning.

Will a Cage be Used in Your Surgery?
Hundreds of thousands of people suffer from degenerative disc disease, disc herniation or low-grade spondylolisthesis. Thankfully, surgery is not necessary for the vast majority of patients as non-surgical treatments most often provide relief from symptoms. However, for those patients who do require surgery, we hope this article will help you better understand what the surgeon means when he discusses your surgical options and refers to using cages. If you want to learn more about cages, see the links following this article.

And remember, if you are scheduled for surgery, patients who are motivated to maintain a healthy lifestyle and take responsibility for their care, make great patients! Their commitment to health puts them in the fast lane for a more rapid recovery from surgery.


Updated on: 02/01/10
Jean-Jacques Abitbol, MD
A significant evolution in intervertebral body cage development has occurred in the past decade. Doctor Zdeblick gives a very precise overview describing recent cage technologies. These devices have proved successful in restoring intervertebral height while promoting fusion. The LT cage represents the most current technology. The unique shape allows for restoration of a natural alignment while preventing complications see with other devices. These cages are designed for anterior placement often performed through a minimally invasive approach thereby avoiding disturbing the posterior muscles, which can be disabling.