THREADED FUSION CAGES FOR LUMBAR INTERBODY FUSIONS - AN ECONOMIC COMPARISON WITH 360-DEGREES FUSIONS

Study Design. This study compared the surgical and hospitalization cos ts, operating times, and blood loss attributable to lumbar interbody f usions at one and two lumbar levels by the use of two device systems: 1) the Ray Threaded Fusion Cage, and 2) an anteroposterior interbody t echnique with pedicle screw and rod stabilization (360 degrees fusion) . The clinical efficacy and complication rate of each method were simi lar. Objectives. Data were analyzed to compare the newer threaded fusi on cage method with the well established 360 degrees technique. Summar y of Background Data. Interbody bone grafts are proven concept to obta in solid spinal fusions. A variety of mechanical means are used to sta bilize 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 patient s having severe, disabling back pain with discal degeneration, 25 rece ived Ray Threaded Fusion Cages and 25 had anteroposterior interbody fu sion procedures using pedicle screws (360 degrees technique) over the period 1991 to 1995. All implants were performed by the same surgeon i n the same hospital. All fusions were judged solid by established radi ologic criteria. Cost comparisons were made from pertinent medical rec ords using inflation-corrected 1995 U.S. dollars. Results. The average combined (surgeon, hospital, anesthesiologist) costs attributed to on e-level threaded fusion cage procedures were $25,171, and S41,813 to e quivalent 360 degrees procedures, a difference of 40% or $16,642. Cost s for two-level cases were $33,113 and $47,320, respectively, differin g by 30% or $14,207. The average saving through preferential use of th e threaded fusion cage was $14,639 per case, or $365,966 for the 25-pa tient subgroup. Ten of the 360 degrees fusion cases required later ins trumentation removal, adding $8,635 to the costs of each such case, a final difference of $22,889 compared with an equivalent threaded fusio n cage case. The actual collections on threaded fusion cage cases were 81% of billed costs and the actual collections on 360 degrees cases w ere 73% of billed costs. Conclusions. Assuming that the fusion success , clinical outcome, and complication rates are sufficiently similar be tween these two techniques, the striking improvement in overall surgic al 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 norm al adjacent level preoperatively developed a fusion transition syndrom e over a follow-up period from 3 to 29 months (averaging 24 months) th at required a second fusion procedure, and no cage had to be removed b ecause of instrumentation-associated pain, although each of these prob lems 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 subse quent instrumentation removal, although no case has required adjacent level surgery for transition syndrome.