環椎後弓部分欠損を伴う小児環軸関節回旋不安定症の1例

Atlantoaxial Rotatory Subluxation in the Absence of Posterior Arch of the Atlas : A Case Report

　強い頚部痛を主訴とする環椎後弓部分欠損を伴う小児環軸関節回旋不安定症の1例を経験した．症例は4歳の女児で，3歳時から特に誘因なく頚部痛を訴えるようになった．神経症状はなく，前屈および左回旋制限を認め，外観は左斜頚位であった．C2/3椎弓の癒合，環椎後弓右側の欠損および軸椎右側上関節突起形成不全を認めた．右後弓欠損があるため，片側骨移植テープ固定のBrooks法による環軸関節固定術を行った．術後に疼痛は改善し，術後9カ月の単純X線像で環軸椎の骨癒合が確認され，良好な結果を得た．

　Pediatric atlantoaxial rotatory subluxation is rare.　We report a case of pediatric atlantoaxial rotatory subluxation and aplasia of posterior arch of the atlas.　The patient was a 4-year-old girl with severe neck pain, who had complained of neck pain since she was 3-years-old.　Examination revealed no neurological deficits, but range of motion testing revealed limitations in flexion and left rotation, and she exhibited torticollis.　Union of the C2/3 lamina was observed on radiographs, and CT showed aplasia of the right posterior arch of the atlas and aplasia of the atlantoaxial joint.　The evidence of aplasia seemed to be related to the instability of the atlantoaxial joint.　Unilateral bone grafting was performed for the atrantoaxial joint (Brooks method).　The neck pain resolved after surgery.　Bone union was observed on radiographs 9 months after surgery.　Unilateral bone grafting was successful in treating pediatric atlantoaxial rotatory subluxation and aplasia of posterior arch of the atlas.