Radiographic Assessment of Lumbar Facet Distance Spacing and Pediatric Spondylolysis

Study Design. Retrospective radiographic review. Objective. The purpose of this article was to explore the relationship between interfacet spacing and pediatric spondylolysis. Summary of Background Data. Recent literature suggests that a potential cause of spondylolytic defects in adults is a narrowed interfacet spacing in the lower lumbar spine. This lack of space places them at increased risk for pars fractures with repetitive lumbar hyperextension. This relationship has not been explored in a pediatric population. Methods. The anteroposterior lumbar spine radiographs of 41 pediatric patients with spondylolytic defects were compared with 41 unaffected controls. A standard digital caliper was used to measure interfacet distance. Vertebral body width and interpedicular distance were recorded as internal standards to control for varying vertebral size. Statistical analysis exploring the relationships of interfacet distances between the affected and unaffected groups was performed using a Mann-Whitney U test. Results. The absolute increase in interfacet distance between adjacent levels was significantly smaller at the L4/L5 level in spondylolytic individuals (P = 0.023). When interpedicular distance was used to standardize for vertebral body size, a significantly smaller increase in the interpedicular distance was noted at the L4/5 level in spondylolytic individuals (P = 0.026). Similar results were obtained when body width was used to standardize for vertebral body size (P < 0.001). A similar trend was noticed at the L3/4 level when standardizing with interpedicular distance although these results were not significant (P = 0.098). Conclusion. A likely explanation for the etiology of lumbar pars defects is insufficient caudal increase in lumbar interfacet spacing. Further prospective studies are necessary to determine if unaffected individuals with a narrowed interfacet spacing are at increased risk of developing spondylolytic defects later in life.