I need help from all spine surgeons, spine biomechanists or anyone
familiar with spinal anatomy:

Could effacement of the thecal sac in the lumbar region be caused by a a
single traumatic event? Can a herniated disc which is encroaching into
the spinal canal cause effacement of the thecal sac? To me effeacement
means a thinning of the thecal sac which would require a long term
process to develop. Am I correct in assuming this? Or can effacement
mean a compression of the thecal sac by a heriated disc?

Thank you in advance,

Fabian

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Fabian E. Pollo, Ph.D.
Director, Motion and Performance Lab
Orthopaedic Surgery
Baylor University Medical Center
Dallas, TX 75246