Union Patterns of Local Autogenous Bone Grafts Using Metal Cages, Allogenic Bone, and Local Autogenous Bone Around the Cages During Posterior Lumbar Interbody Fusion: A Retrospective CT Analysis

ABSTRACT

STUDY DESIGN: Retrospective study. OBJECTIVES: To conduct an analysis of the union rate and union patterns of local autogenous bone grafts using metal cages, allogenic bone, and local autogenous bone around the cages in posterior lumbar interbody fusion (PLIF). SUMMARY OF LITERATURE REVIEW Local autologous bone grafting using metal cages is regarded as an effective method for union during PLIF without iliac bone harvesting. There are few studies about the additional bone grafting except using metal cages. MATERIALS AND METHODS: Thirty-nine patients (68 segments) with postoperative computed tomography (CT) results from 6 to 18 months after PLIF were included. We used 2 metal cages filled with local autogenous bone intraoperatively (region C). We also grafted allogenic bone between 2 cages (region A) and local autogenous bone at the side of the cages (region B). Retrospective analyses of the coronal CT sections were performed using the modified Bridwell criteria for assessing the presence of union. A quantitative evaluation was performed using a scoring system that assessed the proportion of radiopaque parts of the union mass. RESULTS: Among the 68 segments, union was observed in 64 segments, resulting in a union rate of 95.6%. The union rates in regions A, B, and C were 86.8%, 89.7%, and 94.1%, respectively. Trabeculation and the quantitative evaluation of union bone showed a statistically significant trend for improvement from regions A to C (p<0.001). CONCLUSIONS: In this study, the complementary effect of additional bone grafting other than local bone grafting was not proven, but it was effective in increasing the fusion area at around 90%. Keeping the height of disc space with the cages, additional bone grafting using local autogenous and allogenous bone may be used as an effective method for stable union.