ABSTRACT
Since the Bagby and Kuslich cage (BAK cage, Spine-Tech, Minneapolis, MN) received FDA approval for lumbar interbody spinal fusion in 1996, interbody cage usage by spine surgeons has grown significantly. In the last 5 years, more than 80,000 lumbar interbody fusion cages have been placed, and in the United States over 5000 cages are surgically placed each month (1). The initial prospective multicenter clinical trial of the BAK interbody fusion system by Kuslich et al. claimed promising results: 98.3% fusion at 36 months, 91% return-to-work at 36 months, 85% pain improvement at 24 months, and 90.7% functional improvement at 24 months (2). To quote the authors verbatim, who incidentally were also involved in the innovation of the BAK cage, ‘‘carefully selected middle-aged patients with chronic low back pain secondary to degenerative disk disease can be treated effectively and safely by skilled surgeons using the BAK device for oneand two-level interbody fusion.’’ However, there were some basic design flaws with the study, including a follow-up of only 25% of the original group who underwent the procedure. Needless to say, not everyone has been able to reproduce these results. O’Dowd et al. reported an overall failure rate requiring revision of 31% of the cages due to clinical failures at a mean period of 15 months (3). Elias et al. reported a radiographic failure rate of 28% and additonal surgery rate of 21% (4).
