Child's Nervous System

, Volume 34, Issue 9, pp 1767–1770 | Cite as

Mechanical relationship of filum terminale externum and filum terminale internum: is it possible to detether the spinal cord extradurally?

  • Mayank Patel
  • Marc Vetter
  • Emily Simonds
  • Maia Schumacher
  • Tyler Laws
  • Joe Iwanaga
  • Rod Oskouian
  • R. Shane TubbsEmail author
Original Paper



Intradural transection of the filum terminale (FTI) is often used to treat tethered cord syndrome. Recently, some have proposed that the extradural part of the filum terminale (FTE) can be sectioned with equal results but with fewer complications. Therefore, the present cadaveric study aimed to evaluate the anatomical foundation of such procedures.


A posterior lumbosacral approach was performed on five fresh-frozen cadaveric specimens to expose both the FTI and FTE. Tension was then applied to the FTE and observations and measurements made of any movement of the FTI. Other morphological measurements (e.g., length, diameter) of the FTI and FTE were also made.


Although very minimal movement of the FTI was seen in the majority of specimens following tension on the FTE, no specimen was found to have more cranial movement of the conus medullaris or cauda equina. The mean length and diameter of the FTI was 52.2 and 0.38 mm, respectively. The mean length and diameter of the FTE was 77 and 0.60 mm, respectively. The force necessary to move the FTI with tension applied to the FTE had a mean of 0.03 N. The average distance that the FTI moved with distal FTE tension was 1.33 mm. All specimens had a thecal sac that terminated at the S2 vertebral level. And no specimen had a low-lying conus medullaris, cutaneous stigmata of occult spinal dysraphism, or grossly visible adipose tissue in either the FTI or FTE.


Based on our studies, tension placed on the FTE has very little effect on the FTI and no obvious effect on the conus medullaris or cauda equina. Therefore, isolated transection of the FTE for a patient with tethered cord syndrome is unlikely to have significant effect. To our knowledge, this is the first study to quantitate the distal forces needed on the FTE to move the FTI.


Filum terminale externum Filum terminale internum Tethered cord syndrome Anatomy Cadaveric 


Compliance with ethical standards

Conflict of interest

The authors have no conflicts of interest to report.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • Mayank Patel
    • 1
  • Marc Vetter
    • 1
  • Emily Simonds
    • 1
  • Maia Schumacher
    • 1
  • Tyler Laws
    • 1
  • Joe Iwanaga
    • 1
  • Rod Oskouian
    • 1
  • R. Shane Tubbs
    • 1
    • 2
    Email author
  1. 1.Seattle Science FoundationSeattleUSA
  2. 2.Department of Anatomical SciencesSt. George’s UniversitySt. George’sGrenada

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