The Variation in the Lumbar Facet Joint Orientation in an Adult Asian Population and Its Relationship with the Cross-Sectional Area of the Multifidus and Erector Spinae

STUDY DESIGN: Cross-sectional study of healthy volunteers. PURPOSE: We aimed to investigate the variation in the lumbar facet joint orientation in an adult Asian population. The relationship between the facet joint orientation and muscle cross-sectional area (CSA) of multifidus and erector spinae was also clarified. OVERVIEW OF LITERATURE: Several studies have reported that lumbar pathologies, such as lumbar spondylolysis and degenerative spondylolisthesis, were related to the horizontally shaped lumbar facet joint orientation at the lower lumbar level. However, data regarding variations in the facet joint orientation in asymptomatic subjects have not been well documented. METHODS: In 31 healthy male adult Asian volunteers, the facet joint orientation and CSA of multifidus and erector spinae were measured using magnetic resonance imaging at the L4–5 and L5–S1 levels. Variation in the facet joint orientation was examined using coefficients of variation (CV). Pearson's product-moment coefficient was used to investigate the relationship between the facet joint orientation and CSA of multifidus and erector spinae. RESULTS: Lumbar facet joint orientation had a wider range of variation at L5–S1 (CV=0.30) than at L4–5 (CV=0.18). The L4–5 facet joint orientation had a weak but significant correlation with the CSA of erector spinae (r=0.40; p=0.031). The CSA of the multifidus had no relationship with the facet joint orientation at the L4–5 (r=0.19; p=0.314) and the L5–S1 level (r=0.19; p=0.312). CONCLUSIONS: The lumbar facet joint orientation was found to have a wide variation, particularly at the L5–S1 in the Asian adult population, and the facet joint orientation had a relationship with the CSA of the erector spinae at the L4–5.