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Threaded Fusion Cages for Lumbar Interbody Fusions: An Economic Comparison With 360° Fusions

Ray, Charles Dean, MD, FACS, FRSH (Lond)


Study Design. 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° fusion). The clinical efficacy and complication rate of each method were similar.

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

Summary of Background Data. 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.

Methods. 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° 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.

Results. The average combined (surgeon, hospital, anesthesiologist) costs attributed to one-level threaded fusion cage procedures were $25,171, and $41,813 to equivalent 360° 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° 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° cases were 73% of billed costs.

Conclusions. 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 follow-up 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° fusion cases in this study required subsequent instrumentation removal, although no case has required adjacent level surgery for transition syndrome.

From the Spinal Research and Education Foundation, Norfolk, Virginia.

The author developed and patented the fusion cage devices reported here; all rights are now owned by U.S. Surgical Corp. The author has a potential indirect financial interest (royalties) from the TFC devices and has purchased shares of U.S. Surgical Corp. The Ray TFC Threaded Fusion Cages and instruments are manufactured by Surgical Dynamics, Inc., a subsidiary of U.S. Surgical Corp., 111 Glover Avenue, Norwalk, Connecticut 06856. The pedicle screw devices are at this time classified as investigational by the United States Federal Food and Drug Administration (U.S. FDA). The Ray-TFC system has been fully approved by the FDA, and the study was conducted under an approved Investigational Device Exemption protocol.

Acknowledgment date: February 3, 1996.

First revision date: May 10, 1996.

Acceptance date: July 29, 1996.

Device status category: 1.

Address reprint requests to: Charles Dean Ray, MD, FACS, FRSH (Lond); Spinal Research and Education Foundation; 880 Kempsville Road, Suite 1100; Norfolk, VA 23502.

© Lippincott-Raven Publishers.