椎弓切除後の頚椎亜脱臼に椎弓根スクリュー固定術が有用であった1例―三次元的X線透視法を用いて

Cervical Pedicle Screw Fixation for Traumatic Cervical Vertebra Subluxation after Laminectomy. Case Report

　頚椎椎弓根スクリュー（以下PS）の登場により後方のみでの短分節再建が可能になった．今回われわれは，椎弓切除術後に外傷によって頚椎亜脱臼を生じ，PS固定術を行った症例を経験したので報告する．われわれは，三次元的X線透視を用い，PS固定術を施行した．術後CTでスクリュー刺入位置は良好であり，順調に骨癒合も得られている．PSの刺入精度を上げるため，今日ではナビゲーションシステムが導入されている．しかし，椎弓切除例ではリファレンスアームが立てづらいため，ナビゲーションを用いてPS刺入することは困難である．三次元的X線透視下で正確にpedicle axis viewを確保し，PS刺入点と角度に十分な注意を払えば，今回のような解剖学的指標の乏しい症例においても安全にPS刺入を行うことができる．頚椎椎弓切除後に亜脱臼を生じた症例に対し，三次元的X線透視法を用いたPS固定術は有用であった．

　Cervical pedicle screw fixation has recently been used to treat patients who require cervical reconstruction. We report the case of a 50-year-old man with a past history of laminectomy in whom cervical pedicle screw fixation guided by 3-dimensional X-ray images was performed to treat a traumatic cervical vertebra subluxation. The patient was followed up in the outpatient clinic, and achieved bone union. The four pedicle screws were accurately inserted inside the pedicle without perforating the cortex of the pedicles. The X-ray navigation system is useful for performing surgery of the cervical spine, because it enables relatively safe and accurate surgery by transpedicular screw fixation. However, it is impossible to attach the stereotactic reference arc to the spinous process in patients who have undergone laminectomy in the past, and application of the navigation system in such patients is limited. We have been using 3-dimensional X-ray images to guide insertion of the screws. If the entry points of the screws can be positioned accurately, it is possible to insert the pedicle screws safely in patients with few anatonical landmarks. 3-dimensional X-ray images were useful as a means of improving the accuracy of screws placement during cervical pedicle screw fixation.