Migration patterns of herniated disc fragments: a study on 1,020 patients with extruded lumbar disc herniation.

ABSTRACT

BACKGROUND CONTEXT Herniated disc fragments are known to migrate in various directions within the spinal canal. To date, no comprehensive studies have been undertaken to examine the migration patterns of herniated disc material using a standard nomenclature and classification system. PURPOSE: To report migration patterns of extruded lumbar disc fragments. STUDY DESIGN: A review of magnetic resonance (MR) images. PATIENT SAMPLE A total of 1,020 consecutive Azeri patients with symptomatic extruded lumbar intervertebral disc herniation. OUTCOME MEASURES: Migration patterns of extruded lumbar disc fragments in vertical and horizontal planes and their association with age, gender, body mass index (BMI), and the level of herniation. METHODS: High-quality axial and sagittal MR images of the lumbar spine were used. Disc material that was displaced away from the site of extrusion, regardless of continuity, was considered "migrated." The migration patterns observed were rostral or caudal in the vertical plane and central, paracentral, subarticular, foraminal, or extraforaminal in the horizontal plane. RESULTS: In the vertical plane, rostral and caudal migrations were observed in 27.8% and 72.2% of the patients, respectively. The number of rostral migrations increased significantly with increasing age and in higher levels in the lumbar spine (p<.001 for both). Radiculopathy was significantly more frequent in caudal migrations than in rostral migrations (78.9% vs. 65.1%, p<.001). There was no significant association between gender or BMI and migration patterns in the vertical plane. In the horizontal plane, central, paracentral, subarticular, foraminal, and extraforaminal migrations were reported in 17.3%, 74.2%, 4.3%, 2.5%, and 1.8% of the patients, respectively. The youngest (median age 39 years, interquartile range [IQR] 13 years) and the oldest (median age 55 years, IQR 15 years) groups of patients (p<.001) had the most formainal and extraforaminal migrations, respectively. Radiculopathy was present in 66.5%, 76.8%, 88.6%, 96%, and 27.8% of the patients with central, paracentral, subarticular, foraminal, and extraforaminal migrations, respectively (p<.001). No significant association was found between gender, BMI, or the level of herniation and migration pattern in the horizontal plane. CONCLUSIONS: Caudal and paracentral migrations are the most common patterns of migration in patients with extruded lumbar disc herniation in the vertical and horizontal planes, respectively. Age and the level of herniation may affect the migration patterns of herniated lumbar disc material.