P34. Multiple anterior bridging bone using newly designed anterior bridging cage (ABC) in posterior lumbar interbody arthrodesis

Abstract

BACKGROUND CONTEXT A number of spine surgeons place bone graft materials into anterior disc space as well as the void of cages to expect bridging bone at the extra-cage area. However, there have been no lumbar cages enabled to communicate anterior extra-cage grafted bone and intra-cage grafted bone. PURPOSE To introduce the newly designed lumbar cage, anterior bridging cage (ABC) with 4 anterior holes in ogival shape, which design enables to communicate anterior extra-cage grafted bone and intra-cage grafted bone and to first demonstrate the multiple anterior bridging bone (ABB) between anterior extra-cage area and intra-cage area and interconnecting bridging bone between two ABC cages. STUDY DESIGN/SETTING Prospective cohort radiographic study (ClinicalTrials.gov NCTD2485574). PATIENT SAMPLE Consecutive 101 patients with 133 surgical levels were enrolled from May 2015 to Dec 2017. The mean age of patients was 66.44 (95%Cl, 64.94-68.13) and the number of male and female was 31 and 70. OUTCOME MEASURES Bridging scores using post operative 1-year multi-direction computed tomographic (CT) scan and clinical outcomes analysis. METHODS The conventional bilateral transforaminal interbody fusion was performed in all enrolled patients. Anterior bone grafts were prepared by each 6cc volume of half-mixed local auto-bone and artificial or allograft bone at the right and left prepared disc space and then, each ABC cage filled with local auto-bone was inserted bilaterally into disc space. All bridging scores were evaluated in post-operative 1-year CT scan and evaluated by 2 spine surgeons twice. The scores of bridging bone were divided into the intra-cage grafted bridging bone (InGBB, scored 1 to 3 at right and left cages), extra-cage grafted bridging bone (ExGBB, scored 1 to 3 at anterior, posterior, right, left, intermediate area between cages) and anterior bridging bone (ABB, scored 0 to 2 at medial, lateral, superior and inferior holes at each cage). In all area, the higher the score, the more complete bridging bone. Radiographic fusion was determined as if 3 in InGBB and/or in ExGBB were evaluated. RESULTS In reliability assessment, intra-class correlations were ranged 0.82 to 0.87 in InGBB, 0.70 to 0.89 in ExGBB, and 0.65 to 0.81 in ABB and inter-class correlation were 0.77 to 0.78 in InGBB, 0.68 to 0.83 in ExGBB, and 0.56 to 0.74 in ABB. The average scores of InGBBs in right and left sides were 2.43(2.38-2.47) and 2.47(2.44-2.53) resepctively. In ExGBB, the average scores significantly higher in anterior (2.40, 2.35-2.44) compared to posterior (2.11, 2.05-2.17), right (1.48, 1.45-1.55), left (1.50, 1.45-1.55), and intermediate (1.91, 1.83-2.13) (p CONCLUSIONS InGBB and ExGBB demonstrated the acceptable ranges of reliability values. In addition to InGBB, ExGBB was important radiographic findings to determine fusion status and especially, anterior ExGBB was significantly frequent. The ABB score was the highest in a medial hole of the ABC cages and each cage had an average 1.9 holes with complete bridging. Such multiple anterior bridging bones between anterior ExGBB and InGBB as well as interconnecting bridging bone between cages through medial holes might be helpful to sustain stable lumbar interbody fusion process. FDA DEVICE/DRUG STATUS Unavailable from authors at time of publication.