INCREASING NEUROFORAMINAL VOLUME BY ANTERIOR INTERBODY DISTRACTION INDEGENERATIVE LUMBAR SPINE

Study Design. This study quantified changes in the size of the stenoti c neuroforamen in degenerative lumbar spines. The volume and area of t he neuroforamen were measured before and after the application of ante rior distraction using the BAK interbody fusion system. Objective. To quantitatively assess the neuroforaminal area and volume when the BAK interbody fusion system is applied to lumbar spines with neuroforamina l stenosis. Summary of Background Data. The spatial relationship betwe en the nerve root and the osseous and nonosseous elements of the neuro foramen is clinically important. Few studies have focused on changes i n neuroforaminal size in the lumbar spine after anterior interbody dis traction. No previous study has assessed the neuroforaminal volume. Me thods. The BAK instrumentation system was applied anteriorly at L4-L5 and L5-S1 intervertebral discs in nine degenerative cadaver lumbar spi nes. The neuroforaminal volumes of L4-L5 and L5-S1 were measured from silicon molds taken of the neuroforamen. In addition, computed tomogra phy and circular blunt probes were used to determine the neuroforamina l areas. The disc height was recorded from lateral radiographs. Result s. After the BAK instrumentation, the volume of the neuroforamen incre ased significantly-by 22.9% for L4-L5 and 21.5% for L5-S1. The posteri or disc height increased by 37.1% at L4-L5 and 45.1% at L5-S1, The neu roforaminal areas significantly increased-by 29.0% at L4-L5 and 33.8% at L5-S1. There was good correlation between the volume and the poster ior disc height (R(2) = 0.50) and the volume and the area of the narro west portion of neuroforamen (R(2) = 0.56). Conclusions. The results i ndicated that anterior systems such as the BAK system, which increase disc heights, can significantly increase neuroforaminal volume and are a, providing adequate space for the nerve root and improving neurofora minal stenosis.