Spinal Problems Are Improved With The Aid Of A University Of Florida-Made Implant

October 11, 1996

GAINESVILLE—After four unsuccessful back surgeries, Alice McKay thought she would battle the excruciating pain caused by degenerative disc disease for the rest of her life. Then the 44-year-old Bell, Fla., resident met a University of Florida physician who suggested something new that possibly could end her pain.

Today, six months after the latest surgery, McKay is able to walk and enjoy fishing again thanks to an implant called the MD-I. Known as a bone dowel, the MD-I is a piece of natural bone tissue that joins two vertebrae in patients with degenerative disc problems or instability in the lumbar spine so the spine can become more normal. Its advantages over existing vertebral stabilizing implants have given many patients the opportunity to return more quickly to the activities they once enjoyed.

“In many spinal patients like Mrs. McKay, the bone dowel may be a better option than traditional back surgery,” said UF orthopaedic surgeon

Dr. Michael Mac Millan. “Routine spinal surgery comes with a price.”

Mac Millan is referring to the amount of tissue disruption and trauma that the surgery causes.

“Surgeons can operate on a spine, but in the process they have to cut tissue, such as the muscles that are important in supporting the back,” he said.

Other bone or metal devices exist, but the size, cut and strength of the new dowel may be the key to improved surgery. The dowel measures the diameter of a dime, is 18 to 20 millimeters round and is 1 1/2 inches long. Its strength equals or exceeds that of most dowel material.

“Because the dowel is small and circular, it can be placed in a long tube, which is inserted into the spinal column through small incisions in the torso. The faulty disc is then removed, a hole is drilled and the dowel is inserted. This method cuts down on the amount of dissection and preserves the back muscles,” Mac Millan said.

Surgery that normally would take six hours is cut down to three or four hours.

The UF Tissue Bank Inc., which manufactures the dowel, recently entered into an exclusive agreement with Sofamor-Danek of Memphis, Tenn., a major spine implant company. As part of the agreement, the tissue bank creates dowels that may be used by surgeons for other joints including the ankle. A patent for the dowel is pending.

Several physicians throughout the country are using the bone dowel and other versions successfully.

Dr. Nick E. Grivas, a neurosurgeon with Mercy Medical Center in Charlotte, N.C., and the dowel’s designer, has been inserting a smaller version of the dowel for neck stabilization for more than a year-and-a-half.

“My experience with the dowel has been highly successful,” Grivas said. “Other dowels can collapse or be displaced, but the new dowel is made of cortical bone, which is taken from long bones that makes it stronger.”

Because bone occurs naturally in the body, there is less chance of rejection than with metal dowels.

“Over a one- to two-year period, the body will replace the dowel with natural bone,”

Mac Millan said. “You can compare the replacement process to having a red brick wall and you want a white brick wall that matches your house instead. Rather than knocking the brick wall down, you take out a red brick and replace it with a white brick. The body does this in relationship to the dowel. A piece of the bone dowel is taken out and is replaced with the body’s bone until all necessary bone in the dowel is replaced with the patient’s own bone. The reconstructed spine looks natural and has a better chance of survival.”

Another advantage to the bone dowel is, if problems should occur, it can be removed more easily than a metal dowel, which would require cutting out bone.