腰椎変性すべり症に対するpedicle screw併用後側方固定術の術後長期における矢状面アライメント

Degenerative Lumbar Spondylolisthesis Treated by Posterolateral Fusion Combined with Pedicle Screw Fixation. A Radiographic Study of Sagittal Alignment Based on Long-Term Results

　腰椎変性すべり症に対するpedicle screw併用後側方固定術後に9年以上が経過し，直接検診できた31例（男10例，女21例，平均年齢59.8歳）に対し長期成績を調査した．術後の矯正位は保持されなかった．後弯位すべり群は平行・前弯位すべり群に比し，前弯度の小さな固定角となってしまい，術前からの腰椎前弯減少とあいまって脊柱矢状面バランスが前方偏位する傾向にあった．術後の腰椎前弯増減には近位腰椎前弯増減が関与していた．後弯位すべり例には近位腰椎前弯増加などの代償機能が働かないと矢状面バランスの前方偏位が生じるおそれがあるため，後方椎体間固定術のほうが適切と考えられた．

　We conducted a long-term radiographic study of degenerative lumbar spondylolisthesis treated with posterolateral fusion (PLF) combined with pedicle screw fixation. This combination did not maintain corrected sagittal alignment during follow-up. Patients in the kyphotic listhesis group tended to show a forward shift in sagittal balance associated with hypolordotic alignment of fused segments. When compensatory mechanisms, such as a compensatory increase in proximal lumbar lordosis, did not function properly, the forward shift in sagittal balance occurred more often in patients with less preoperative lumbar lordosis and a long-term postoperative hypolordotic fused segment in the kyphotic listhesis group than in those in the parallel or lordotic listhesis group . PLF combined with pedicle screw fixation therefore requires careful consideration before being selected as the treatment modality for a particular kyphotic degenerative spondylolisthesis, even though radiographic differences did not affect the clinical outcome during follow-up.