Analysis of Migration Patterns of Disk Fragments and Contributing Factors in Extruded Lumbar Disk Herniation

Abstract

Background: The exact location of migrated extruded lumbar disk fragments is an important consideration in selecting a treatment plan. However, few descriptive reports of the migration pattern of extruded lumbar disk fragments are available. Objective: To examine the distribution of disk fragments and possible contributing factors that affect their migration. Design: Retrospective descriptive study. Setting: Tertiary university outpatient and inpatient clinic. Patients: A total of 164 patients diagnosed with a symptomatic extruded lumbar disk from January 2011 to December 2012. Methods: Lumbar spine magnetic resonance imaging scans of patients were retrospectively reviewed. The term “migration” was defined as the horizontal and vertical displacement of extruded material away from the opening in the annulus through which the material has extruded. Migration of the disk material was recorded in both the horizontal and vertical plane. In the horizontal plane, migration was recorded as central, paracentral, subarticular, or foraminal. In the vertical plane, migration was recorded as rostral or caudal. Main Outcome Measurements: The pattern of migration and the associated factors (age and the level of herniation) were analyzed. Results: Rostral and caudal migration was observed in 27% (95% confidence interval [CI], 21%-35%) and 73% (95% CI, 66%-79%) of the patients. Central, paracentral, subarticular, and foraminal migration was observed in 6% (95% CI, 3%-11%), 67% (95% CI, 60%-74%), 18% (95% CI, 13%-25%), and 9% (95% CI, 5%-14%) of the patients, respectively. A significant increase was observed in the incidence of rostral migration with increasing age (P ¼ .048). A significant association was also noted between migration in the horizontal plane and increasing age (P ¼ .01). A significant increase occurred in the incidence of foraminal extrusion with increasing age (P ¼ .01). A significant association was found between migration in the vertical plane and horizontal plane; in patients with foraminal herniations, migration was always rostral (P < .001). Conclusion: The migration of extruded lumbar disk materials follows some general patterns. The results of this study may help spine interventionists and surgeons choose appropriate treatments for patients who have radiculopathy associated with lumbar disk extrusions.