People with degenerative disc disease in the lumbar (lower) spine who undergo disc replacement fare better in the short term – and at least as well overall – compared with those who have fusion surgery, according to a review of seven studies published online in ANZ Journal of Surgery. This analysis builds on existing evidence.

Degenerative disc disease, a common cause of low back pain, occurs when one or more discs – gel-filled cushions between the bones of the spine (vertebrae) – rupture or deteriorate. Unlike other “degenerative” conditions, symptoms from the disc problems often improve in a few weeks with minimal treatment. However, a small proportion of people have persistent symptoms that may require surgery.

For decades, the gold standard has been lumbar fusion, which removes the damaged disc(s) and fuses adjacent vertebrae to prevent motion-related pain. But only 60 to 80 percent of patients who undergo lumbar fusion have satisfactory pain relief, according to Jeffrey S. Fischgrund, MD, a professor of orthopaedic surgery at Oakland University William Beaumont School of Medicine in Rochester, Mich. “And fusing one level in the spine may lead to accelerated [disc] degeneration – and a new source of pain – in the adjacent levels," he says. Plus, it reduces mobility.

Artificial disc replacement (ADR) – sometimes called artificial intervertebral disc replacement (AIDR) – is a surgical alternative to fusion procedures. The damaged disc is removed and replaced with an artificial implant – in this case, a sliding polyethylene core between two metal endplates. The aim is to maintain the spine's normal motion and biomechanics.

"ADR preserves motion, theoretically resulting in less adjacent segment issues," Dr. Fischgrund says. "But the adoption of this procedure has been relatively low, as the results have not lived up to initial expectations."

Because ADR is controversial, investigators at the Royal Australasian College of Surgeons in North Adelaide, Australia, decided to find out just how safe and effective the procedure really is.

Between 2005 and 2012, they searched electronic databases for clinical studies comparing lumbar fusion and ADR, eventually finding six randomized controlled trials (comprising nine studies) and one nonrandomized comparative study that met their criteria. The studies used four types of artificial discs and three different fusion procedures. The largest study included 688 patients and the smallest 67 patients. Most were followed for two to five years after surgery.

To evaluate safety, researchers looked at the number of adverse events such as infection and nerve or blood vessel injury that occurred after both ADR and fusion. Overall, they found little difference, although two studies reported significantly more life-threatening complications after fusion.