European Spine Journal

, Volume 25, Issue 6, pp 1912–1919 | Cite as

Microendoscopic posterior decompression for the treatment of thoracic myelopathy caused by ossification of the ligamentum flavum: a technical report

  • Satoshi Baba
  • Yasushi Oshima
  • Tomoyuki Iwahori
  • Yuichi Takano
  • Hirohiko Inanami
  • Hisashi Koga
Original Article



Ossification of the ligamentum flavum (OLF) is a common cause of progressive thoracic myelopathy in East Asia. Good surgical results are expected for patients who already show myelopathy. Surgical decompression using a posterior approach is commonly used to treat OLF. This study investigated the use of microendoscopic posterior decompression for the treatment of thoracic OLF.


Microendoscopic posterior decompression was performed on 9 patients with myelopathy. Patients had a mean age of 59.8 years and single-level involvement, mostly at the T10–11 and T11–12 vertebrae. Computed tomography and magnetic resonance imaging were used to classify the OLF. A tubular retractor and endoscopic system were used for microendoscopic posterior decompression. Midline and unilateral paramedian approaches were performed in 2 and 7 patients, respectively. Intraoperative motor evoked potentials (MEPs) of 7 patients were monitored. Pre- and postoperative neurological status was evaluated using the modified Japanese Orthopaedic Association (mJOA) score.


Thoracic OLF for all patients were classed as bilateral type with a round morphology. Improvement of MEPs at least one muscle area was recorded in all patients following posterior decompression. A dural tear in one patient was the only observed complication. The mean recovery rate was 44.9 %, as calculated from mJOA scores at a mean follow-up period of 20 months.


Microendoscopic posterior decompression combined with MEP monitoring can be used to treat patients with thoracic OLF. The optimal surgical indication is OLF at a single vertebral level and of a unilateral or bilateral nature, without comma and tram track signs, and a round morphology.


Ossification of the ligamentum flavum Thoracic myelopathy Microendoscopic posterior decompression Minimally invasive 



We would like to thank Dr Y Yuzawa (Department of Orthopaedics, Iwai Orthopaedic Medical Hospital) for his input in discussions; and Ms. Omuro and Ms. Fukuda for secretarial assistance. We would also like thank all the operating room staff for their technical assistance, and the medical records clerks who helped to collect patient data. This work was partly supported by a grant from the Iwai Medical Foundation.

Compliance with ethical standards

Conflict of interest

The authors declare that there are no conflicts of interest.

Supplementary material

586_2015_4158_MOESM1_ESM.ppt (3.9 mb)
Supplementary material 1 (PPT 4010 kb) Supplemented Fig. 1 Schematic drawings of ossification of the ligamentum flavum (OLF) using axial view on CT scan. The thoracic OLF was classified into 3 types, unilateral (A), bilateral (B), and bridged (C) types. Black area indicates ossified ligamentum flavum. Supplemented Fig. 2 Schematic drawings of ossification of the ligamentum flavum (OLF) using sagittal MRI. The thoracic OLF was classified into 2 types, round (A) or beak (B) types. Black area indicates ossified ligamentum flavum. Supplemented Fig. 3 CT findings which predict dural ossification. A) The “tram track sign,” where there was a hyperdense bony excrescence with a hypodense center. B) The “comma sign,” where there was evidence of ossification of one-half of the circumference of the dura mater


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Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Satoshi Baba
    • 1
    • 2
    • 3
  • Yasushi Oshima
    • 1
    • 2
  • Tomoyuki Iwahori
    • 1
  • Yuichi Takano
    • 1
  • Hirohiko Inanami
    • 1
  • Hisashi Koga
    • 1
    • 4
  1. 1.Department of OrthopaedicsIwai Orthopaedic Medical HospitalTokyoJapan
  2. 2.Department of Orthopaedic SurgeryThe University of TokyoTokyoJapan
  3. 3.Department of OrthopaedicsJapan Community Health Care Organization Tokyo Shinjuku Medical CenterTokyoJapan
  4. 4.Department of Minimally Invasive Spinal SurgeryZhangzhou Zhengxing HospitalZhangzhouChina

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