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Using rh-BMP-2 may not guarantee fusion in all cases
Shen HX.Spine. 35(7):747-753. April 2010.
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A large consecutive case series of multilevel fusions treated with recombinant human bone morphogenetic-2 yielded a 10.2% pseudarthrosis rate at 6 months.
“Since the risk of pseudarthrosis increases with the number of fusion levels, a long fusion lever arm may biomechanically overwhelm the biologic advantage of rhBMP-2,” the authors wrote in their abstract. “While rhBMP-2 is known to enhance fusion rates, it does not guarantee fusion in all situations.”
Pseudarthrosis rates after anterior cervical fusion range from 0% to 20% for single-level fusions and up to 50% for multilevel fusions, according to the abstract. Some researchers have theorized that rhBMP-2 may decrease the pseudarthrosis rate.
For their study, Hong Xing Shen, MD, and colleagues studied 127 patients (54 men and 73 women) who had cervical spondylosis and/or disc herniations and underwent anterior cervical fusion with rhBMP-2, structural allograft and plate fixation. The investigators followed the patients for a minimum of 2 years.
In all, 75 patients underwent a 3-level fusion, 34 underwent a 4-level fusion and 18 underwent a 5-level fusion. There were 451 fusion segments; 14 segments (3.1%) in 13 patients (10.2%) had evidence of pseudarthrosis 6 months after surgery.
Of the 13 pseudarthrosis patients, three had a 3-level fusion, six had a 4-level fusion and four had a 5-level fusion. Five asymptomatic patients did not require revision; however, the remaining patients had additional surgery.
In 12 of the 13 pseudarthrosis patients, the nonunion occurred at the lowest fusion level and at the cervicothoracic junction. The number of fusion levels was the only statistically significant pseudarthrosis risk factor, according to the investigators.