title: Posterior epidural migration of sequestrated lumbar disc fragments into the bilateral facet joints:  case report.
abstract: BACKGROUND
  Symptomatic lumbar disc herniation is common. Migration of a free disc fragment is usually found in rostral, caudal, or lateral directions. Posterior epidural migration is very rare. We report the first case with posterior epidural migration and sequestration into bilateral facet joints of a free disc fragment.
  
  
  METHODS
  A 78-year-old female presented with low back pain and right leg pain. Plain radiographs showed lumbar spondylolisthesis. Magnetic resonance imaging revealed a posterior epidural mass and intrafacet mass, which was hypointense on T1-weighted images and hyperintense on T2-weighted images. The lesion in the left L3-4 facet joint had rim enhancement, whereas the right one was not contrasted after gadolinium injection. Preoperative differential diagnosis included abscess, tumor, hematoma, or synovial cyst. An interbody cage fusion at L3-4 and L4-5 for spondylolisthesis was performed, and a hybrid technique was applied with the Dynesys flexible rod system at L3-S1 for multisegment degenerative disc disease. The lesion proved to be an epidural disc fragment with sequestration into bilateral facet joints.
  
  
  CONCLUSIONS
  A free disc fragment should be considered in the differential diagnosis of posterior epidural lesions, and even in the facet joint.
authors: Department of Surgery, Sin-Lau Hospital, Tainan, Taiwan.
authors: Tzuu-Yuan
authors: TY
authors: Huang
authors: Kung-Shing
authors: KS
authors: Lee
authors: Tai-Hsin
authors: TH
authors: Tsai
authors: Yu-Feng
authors: YF
authors: Su
authors: Shiuh-Lin
authors: SL
authors: Hwang