Threaded fusion cages for lumbar interbody fusions. An economic comparison with 360 degrees fusions

This study compared the surgical and hospitalization costs, operating times, and blood loss attributable to lumbar interbody fusions at one and two lumbar levels by the use of two device systems: 1) the Ray Threaded Fusion Cage, and 2) an anteroposterior interbody technique with pedicle screw and rod stabilization (360 degrees fusion). The clinical efficacy and complication rate of each method were similar.

Data were analyzed to compare the newer threaded fusion cage method with the well established 360 degrees technique.

Interbody bone grafts are a proven concept to obtain solid spinal fusions. A variety of mechanical means are used to stabilize the graft material during the fusion growth and have been shown to be important in facilitating both the rate and ultimate quality of the fusion.

In a cohort of 50 prospectively selected patients having severe, disabling back pain with discal degeneration, 25 received Ray Threaded Fusion Cages and 25 had anteroposterior interbody fusion procedures using pedicle screws (360 degrees technique) over the period 1991 to 1995. All implants were performed by the same surgeon in the same hospital. All fusions were judged solid by established radiologic criteria. Cost comparisons were made from pertinent medical records using inflation-corrected 1995 U.S. dollars.

The average combined (surgeon, hospital, anesthesiologist) costs attributed to one-level threaded fusion cage procedures were $25,171, and $41,813 to equivalent 360 degrees procedures, a difference of 40% or $16,642. Costs for two-level cases were $33,113 and $47,320, respectively, differing by 30% or $14,207. The average saving through preferential use of the threaded fusion cage was $14,639 per case, or $365,966 for the 25-patient subgroup. Ten of the 360 degrees fusion cases required later instrumentation removal, adding $8,635 to the costs of each such case, a final difference of $22,889 compared with an equivalent threaded fusion cage case. The actual collections on threaded fusion cage cases were 81% of billed costs and the actual collections on 360 degrees cases were 73% of billed costs.

Assuming that the fusion success, clinical outcome, and complication rates are sufficiently similar between these two techniques, the striking improvement in overall surgical and hospitalization costs, surgical time, and blood losses provided by the threaded fusion cage technique can be major decision points in method selection. Further, no threaded fusion cage case having a normal adjacent level preoperatively developed a fusion transition syndrome over a followup period from 3 to 29 months (averaging 24 months) that required a second fusion procedure, and no cage had to be removed because of instrumentation-associated pain, although each of these problems are known to occur in at lease 10% of pedicle screw implants. Ten of the 25 (40%) 360 degrees fusion cases in this study required subsequent instrumentation removal, although no case has required adjacent level surgery for transition syndrome.