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

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