胸椎後縦靱帯骨化症に対する後弯軽減（dekyphosis）を加えた脊髄全周除圧術

Circumspinal Decompression with Dekyphosis Stabilization for Thoracic Myelopathy due to Ossification of Posterior Longitudinal Ligament

　後縦靱帯骨化症（OPLL）が大きく脊髄を圧迫し，脊髄が脊柱管後壁または黄色靱帯骨化との間に挟まれている症例に対して脊髄全周除圧術を行った．まず後方から椎弓切除し，切除すべきOPLLに一致した左右のgutterを椎体に掘り込んでおく．さらに後方インストゥルメンテーションを加え若干の胸椎後弯の軽減を加えた（dekyphosis stabilization）．約3～4週後に前方進入にて，gutterを目安にして手術顕微鏡下にOPLLを切除し，椎体間固定を行った．合計10例に行い，平均経過観察は59.2カ月であった．JOAスコアは術前3.5点，最終経過観察時8.6点であった．全例に骨癒合が得られた．脊髄全周除圧術により，安全・正確で完全なOPLLの除圧操作ができた．

　Circumspinal decompression has been performed in ten patients with thoracic myelopathy due to OPLL, and the patients' neurological status was evaluated. Operative procedure 1st step：Posterior and lateral decompression of the spinal cord are performed. Bilateral gutters along with dural tube are made using a 3 mm-diameter high speed drill into the vertebral body covering the extent of the OPLL to be removed anteriorly. Posterior instrumentation is applied for stabilization of the spine and to reduce thoracic kyphosis by approximately 5-10 degrees (dekyphosis stabilization). 2nd step：4 weeks after the 1st step, anterior decompression is performed with direct vision using an operative microscope, followed by an interbody strut graft. Results：All 10 patients improved and maintained improvement in their neurological status from 3.5 points (pre-operative JOA score) to 8.6 points (postop) with a final follow-up of 59.2 months on average. Discussion and Conclusion：Posterior decompression may provide posterior room for the spinal cord to escape from being compressed by an anterior decompression maneuver such as drilling. Dekyphosis stabilization provides a posterior shift of the spinal cord and reduces the compressive pressure of the OPLL plaque on the spinal cord. The two deep served two important purposes：the extent of the OPLL to be removed was shown, and the gutters helped the surgeon to remove the OPLL in the second step of the operation, as its lateral rim had already been released from the dura. OPLL plaque in the thoracic spine might be most easily, safely, and completely removed or floated through circumspinal decompression with dekyphosis stabilization.