Greater use of spinal fusion has not lowered risk of repeat back surgery

Despite new implant technologies and surgical techniques leading to increased rates of spinal fusion surgery, the percentage of patients requiring further low-back surgery after spinal fusion has actually increased since the early 1990s, reports the Sept. 1 issue of the journal Spine, published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.

Brook I. Martin, M.P.H., and colleagues of the Center for Cost and Outcomes Research at the University of Washington, Seattle, analyzed rates of spinal fusion and repeated low-back surgery during two periods: 1990-93 and 1997-2000. Spinal fusion is an operation done to fuse together adjacent vertebrae in patients with certain types of chronic low back pain. The analysis included about 2,500 patients undergoing some type of surgery on the lumbar spine (lower back) during each period.

During the 1990s, the percentage of patients undergoing spinal fusion more than doubled: from about nine percent during 1990-93 to 19 percent during 1997-2000. The increase was largely related to the introduction of new surgical hardware and techniques—for example, "cages" implanted to guide the growth of bone grafts for spinal fusion and biological enhancements such as bone graft substitutes.

However, as the rate of spinal fusion surgery increased, so did the proportion of patients who later required another low-back operation. Of patients undergoing spinal fusion during 1990-93, about 12 percent had another lumbar spine operation within four years. For patients undergoing spinal fusion during 1997-2000, this figure increased to 14 percent. After adjustment for other factors, the risk of repeated low-back surgery after spinal fusion increased by about 16 percent from the beginning to the end of the decade.

Among patients undergoing spinal fusion in 1997-2000, the risk of repeated lower back surgery within the first year was about 40 percent higher than for patients initially operated on in the early 1990s. After the first year, reoperation rates were similar between the two periods.

Consistent with previous data, the findings show that the use of spinal fusion surgery has increased dramatically in recent years—especially since the U.S. Food and Drug Administration's approval of "cage" devices for spinal fusion in 1996. However, some recent studies have questioned the true benefits of spinal fusion.

For patients undergoing initial low-back surgery, the need for an additional operation is an important indicator of overall success. "Repeat lumbar spine operations are generally undesirable, implying persistent symptoms, progression of degenerative changes, or treatment complications," Mr. Martin and colleagues write.

Their results suggest that the rapid growth of spinal fusion surgery has been accompanied by an increase, not a decrease, in the need for repeated spinal surgery. "A higher proportion of fusion procedures and the introduction of new spinal implants between 1993 and 1997 did not reduce reoperation rates," the authors conclude. They highlight the need for efforts to better identify patients most likely to benefit from spinal fusion surgery, as well as to demonstrate the safety and effectiveness of new surgical devices and techniques.

Recognized internationally as the leading journal in its field, Spine is an international, peer-reviewed, bi-weekly periodical that considers for publication original articles in the field of spine. According to the latest ISI Science Citation Impact Factor, it is the leading subspecialty journal for the treatment of spinal disorders. Only original papers are considered for publication with the understanding that they are contributed solely to Spine. Visit the journal website at http://www.spinejournal.com.