Artificial lumbar disc replacement shows benefit over fusion

Study results show disc replacement to treat degenerative disc disease improves disability and pain scores.

New research comparing artificial lumbar disc replacement to circumferential fusion in patients with degenerative disc disease and discogenic pain showed statistically significant improvement in disability and pain scores for those receiving the artificial disc.

Rick Sasso, MD, an orthopedic surgeon at the Indiana Spine Group, Indianapolis, presented the preliminary results from this prospective, randomized, multicenter trial at the Spine Arthroplasty Society Global Symposium on Motion Preservation Technology in New York City. Sasso is an investigator participating in the FDA Investigational Device Exemption (IDE) trial of the FlexiCore artificial disc replacement (Stryker Spine).

Sasso’s results focused on 68 patients from two centers in Indianapolis and Oklahoma City. Forty four of them received the FlexiCore disc replacement and 24 control patients underwent circumferential fusion involving an anterior femoral ring and posterior pedicle screw, and an autogenous iliac crest bone graft. Overall the study involved 400 patients randomized in a 2:1 ratio to artificial disc replacement or fusion surgery. Final results won’t come for another year or two.

Patients could participate in the trial if they manifested degenerative disc disease, had a preoperative pain score of at least 40 on the Visual Analog Scale (VAS), had a preoperative low back disability score of at least 40 on the Oswestry Disability Index (ODI), and proved unresponsive to standard nonoperative treatment. Surgeons reported an average age 36 years, and an average Body Mass Index (BMI) of 28. Artificial disc replacement and control groups did not differ at baseline for BMI, sex or age. Operative time averaged 82 minutes and the estimated blood loss was less than 100 cc. The average length of hospital stay was two days in the artificial disc group and three days in the control group.

While the ODI showed statistically significant improvement in both groups, improvement in the artificial disc replacement group continued over 12 months. The researchers found a similar pattern for VAS scores. They based preliminary results at 12 months on 11 patients in the artificial disc group and five in the control arm.

The researchers found no evidence of spontaneous fusion across the segment in patients who underwent artificial disc replacement and all of the discs showed movement. In addition, surgeons reported no expulsions, migrations of the disc or vascular sequelae. Two patients experienced complications that required reoperation — one patient with an L5 radiculopathy involving an osteochondral fragment and another with a disc herniation above the level of the original involvement one year postoperatively.

Surgeons typically treat degenerative disc disease, a common cause of back pain, with fusion. As an alternative, the FlexiCore disc is a uniarticular ball-and-socket device with a fixed axis of rotation and surfaces composed of a cobalt chrome alloy. The device features a domed base plate coated with a titanium plasma spray to promote long-term bone on-growth formation. Spikes in the domed base plate provide additional stability.

For more information:
Sasso R. Metal-on-metal artificial lumbar disc replacement versus circumferential fusion for the treatment of discogenic pain: A prospective randomized study. Presented at the Spine Arthroplasty Society Global Symposium on Motion Preservation Technology. May 4-7, 2005. New York.