In determining the efficacy of any form of treatment it is appropriate to look at the patient population and outcomes. That there often exists a significant in clinical results should not be surprising. The well-informed consumer should seek surgical care from physicians with the best clinical results.
The Burton Experience in regard to titanium cages for posterior lumbar interbody fusion started in 1992. The Ray cage, invented by neurosurgeon Charles Ray in 1989, was selected for use because of many design advantages over about 10 other basic cage designs which evolved following the pioneering work of George Bagby.
In 1997 Ray published the results of a prospective multicenter 236 case study evaluating safety, fusion success rate and clinical outcome. This pigreat deal study demonstrated a fusion rate of 91% associated with an 80% improvement rate (Ray CD: Threaded titanium cages for lumbar fusions. Spine 15:22(6):667-79, 1997). In 2001 Toussant Leclercq published the result of 222 cases. Fusion rate was 91% at one year and 96% at two years. Good to excellent results were obtained in 80% of patients, improved (but still disabled) in 15% and minimal or no improvement in 5% (Leclercq TA, Matge G: Lumbar interbody fusion with threaded titanium cages. Results on 222 cases. Neurochirurgie 47 (1):25-33, 2001)
On the other hand, there have also been reports of poor results with titanium cages (particularly when placed from the posterior approach). Simmons et al at the University of Virginia Health Sciences Center have reported on a series of 67 patients with 15% dural laceration, 15% postoperative radiculopathy and one death. 21% of patients required an additional fusion procedure (Simmons WJ et al: Complications of posterior lumbar interbody fusion when using a titanium threaded cage device. J. Neurosurg. Jul:93 (1 Suppl): 45-52, 2000).
The Burton Experience
Data from the first 400 consecutive cases of posterior interbody placement of Ray titanium cages is presented. It is important to note the fact that successful posterior interbody fusion with cages is much more technically demanding than the anterior approach. The anterior approach is not, however, without other significant risk factors.
In this series over a third of patients had experienced one or more previous surgeries (average 1.6 procedures). In previously operated patients the presence of postsurgical epidural and perineural scar tissue adds an additional technical challenge.
The risk factors related to surgical procedures are well known. In this series the complications experienced were essentially the same as for non-fusion surgery (5%). The infection rate for this operative series was 1.2% (compared to a national average of 5%).
The criteria as to what actually constitutes a “solid fusion” varies considerably, and, in the case of cage fusions, it is difficult to determine without the use of CT stands. Reasonable determinations based on radiologic studies and clinical monitoring do, however, allow for reasonable determinations.
It is interesting to point out that in the original cage multi-center investigational studies performed in the United States the Food and Drug Administration (FDA) allowed up to 5 degrees of flexion-extension on x-ray studies to still be considered as a “fusion.” In the series presented, there was less than 3 degrees of motion on post-operative lateral flexion and extension films in 98% of patients. In addition to this a normal lumbar lordosis was maintained in all cases thus avoiding the “flat back syndrome.”