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FEATURE

Histomorphometric Evaluation of Intervertebral Implants

Imaging tool facilitates bone integration analysis

by Dr. Michel Assad & Ron Goldman

June 2003

Have you ever experienced a persistent shooting pain in the lower back, permeating down one or both legs? Aching so intense that bending or straightening of the back is impossible? For more than 65 million Americans who experience lower back pain, the condition, at best, can be a temporary inconvenience; at worst, it can be debilitating. In the most critical situations, the root of the problem can sometimes be attributed to disc degeneration, which affects approximately 12 million people in the United States between the ages of 20 and 80.

Intervertebral discs are flexible pads securely fixated between vertebrae. Circular in shape, measuring approximately one inch in diameter and a quarter of an inch thick, they are comprised of a cartilage material that acts as a spacer between vertebrae and allows for flexibility and movement. The discs are held in place by a combination of intricate ligaments and muscle tissues. As a result of age, injury or repeated stress, intervertebral discs can collapse, resulting in excruciating pain and immobilization.

SURGICAL INTERVENTION
There are several treatment alternatives available. For some, the traditional method calls for arthrodesis, an invasive surgery that is performed to join together or fuse adjacent vertebrae. Potential surgical techniques to treat this condition include the combination of a metallic hollow cage and bone grafting taken from the patient's pelvic bone or from a bone bank to stimulate healing between adjacent vertebrae. The metallic cages secure vertebrae in place until new bone grows between them.

Although these methods have been around for a reasonably long period of time, spinal and neurosurgeons have reported many disadvantages of spinal cage implants with the use of autologous bone grafting. Such problems include long operative times, significant blood loss, graft harvest site morbidity and high non-union rates.

Biorthex, a Montreal-based biotechnology firm, recently developed a biomaterial named porous nitinol. "The beauty of this technological platform is such that once in place, surrounding cells will lodge themselves within the material, thus secreting a bone matrix bridge between adjacent vertebrae. The material is unique in nature since it acts as a device that promotes rapid tissue in-growth and the formation of bone tissues inside the implant," commented Benoît Sicotte, President and CEO of Biorthex, Inc.