C6棘突起の形態からみた椎弓形成術後の頚椎のアライメントと安定性

Morphology of the C6 Spinous Process and Cervical Alignment and Stability after Laminoplasty

　頚椎症性脊髄症（CSM）に対するC3-C7椎弓形成術前後での頚椎の配列と安定性の変化をC6棘突起の形態に基づいて分類した2群間で比較検討した．C6棘突起の尖端が二股に分岐したものをbifid型（Bi），分岐していないものをnon-bifid型（NB）とした．NBでは，頚椎前傾は術後に大きくなる傾向があり，前屈時のC7のtiltingが術後有意に増大し，頚椎前弯の喪失はBiに対し有意に大きかった．またC6/7前屈角はBiでは有意に低下したのに対し，NBでは有意に増大した．このようにNBでは好ましくない術後変化がより著明に生じるため，頚椎椎弓形成術の際には特にNBの頚椎ではC7棘突起を温存するのが望ましい．

　The present study compared cervical alignment and flexibility after C3-C7 laminoplasty in two groups of patients with cervical spondylotic myelopathy (CSM) classified according to the morphology of their C6 spinous process. The “bifid” group consisted of patients whose C6 spinous process was bifurcated, and the “non-bifid” group consisted of patients whose C6 tip was not bifurcated. Postoperatively, the cervical spine became more inclined and less lordotic and C7 was tilted more in flexion in the non-bifid group than in the bifid group. The C6-7 flexion angle decreased in the bifid group but increased in the non-bifid group. These unfavorable postoperative changes were more clearly observed in the non-bifid group. Therefore, we recommend that during laminoplasty, at least the C7 spinous process should be preserved in patients with a C6 spinous process of the non-bifid type.