Multiplanar reconstruction（MPR）-CTに基づく至適腰椎椎弓根スクリュー径選択

Selection of Optimal Size Lumbar Pedicle Screws Based on Assessment of Pedicle Diameter by Multiplanar Reconstruction Computed Tomography

　至適腰椎椎弓根スクリュー径決定の指標をmultiplanar reconstruction(MPR)-CTを用いて，冠状断椎弓根横径と椎弓根最短径を比較することで検討した．L1・L2では冠状断椎弓根横径と椎弓根最短径に有意差はなかったが，L3・L4・L5では椎弓根横径より椎弓根最短径は統計学的に有意に小さかった．冠状断椎弓根横径をx，椎弓根最短径(至適椎弓根スクリュー径)をyとすると，回帰式はL1・L2はy＝x，L3はy＝0.88x，L4はy＝0.76x，L5はy＝0.58xとして求められた．

　The purpose of our study was to provide an index for the optimal size of lumbar pedicle screws by comparing the transverse pedicle diameter on the axial plane and minimum pedicle diameter based on multiplanar reconstruction computed tomography (MPR-CT).　Thirty patients with degenerative lumbar diseases who underwent preoperative MPR-CT were the subjects of our study.　There were no differences between the transverse pedicle diameters and minimum pedicle diameters at L1 and L2, but the minimum pedicle diameters at L3, L4, and L5 were significantly smaller than the transverse pedicle diameters (L3：6.55 mm vs. 7.39 mm, p＝0.01；L4：7.14 mm vs. 9.32 mm, p＜0.001；L5：7.68 mm vs. 13.24 mm, p＜0.001.).　We concluded that the index for the optimal size of lumbar pedicle screws is：y＝x at L1 and L2；y＝0.88x at L3；y＝0.76x at L4；and y＝0.58x at L5 (x：transverse diameter on axial plane CT, y：optimal size of the pedicle screw).