後方進入腰椎椎体間固定術（PLIF）において椎間を持ち上げすぎると隣接椎間障害を来す

Excessive Distraction of Lumbar Disc Space Induces Early Degeneration of the Adjacent Segment after Posterior Lumbar Interbody Fusion (PLIF)

　L4腰椎変性すべり症に対しL4/5単椎間後方進入腰椎椎体間固定術（PLIF）を施行し2年以上追跡した85名を対象に，単純X線像，CTを用い隣接椎間障害（ASD）に対する危険因子を検討した．L4/5固定椎間高は，ASD（－）群（58例）の3.1/1.3mm（術直後/最終）に対し，画像的ASD（＋）群（14例）は4.4/1.5mm，臨床的ASD（＋）群（13例）は6.2/4.3mmと有意に持ち上げられており，過度の持ち上げがASDの危険因子であることが示された．臨床的ASD（＋）群の11例はL3/4の手術が追加されていた．

　Posterior lumbar interbody fusion (PLIF) for lumbar spondylolisthesis usually results in an excellent outcome, but the problem of so-called adjacent segment disease (ASD) remains unresolved. ASD at L3/4 was investigated in 85 patients with L4 spondylolisthesis treated by L4/5 PLIF with uniform pedicle screws and interbody cages who had been followed up for more than two years (mean, 38.8±17.1 months). The patients were divided into three groups according to the final outcome：a group without ASD (n＝58), a group with radiological ASD (n＝14), and a group with clinical ASD (n＝13). Eleven patients in the third group were reoperated to treat L3/4 lesions. L4-5 disc height distraction by cage insertion in the three groups was 3.1 mm, 4.4 mm, and 6.2 mm, respectively, and the latter two values were significantly higher than the first value. Excessive distraction of the L4/5 disc space proved to be a significant risk factor for radiological and clinical ASD at L3/4.