棘突起縦割式頚椎椎弓形成術における連通孔性高気孔率ハイドロキシアパタイトスペーサーの吸収過程

Resorption of the Interconnected High-porosity Hydroxyapatite Ceramic Spacers Used in Spinous-process-splitting Cervical Laminoplasty

　背景：棘突起縦割式頚椎椎弓形成術に用いた連通孔性高気孔率ハイドロキシアパタイトスペーサーの吸収過程を調査した．

　対象と方法：術後2年以上経過し，単純X線像と日本整形外科学会頚髄症治療成績判定基準による評価を行った脊髄症患者41例である．

　結果：スペーサーは面よりも角から吸収される例が多く，方向別では背側からの吸収が高度で，平均39カ月では41％のスペーサーが痕跡化あるいは消失した．スペーサーの遅発性脱転はなく，脊髄症状の悪化例もなかった．

　まとめ：本スペーサーは経時的に吸収されたが，それゆえに遅発性脱転は皆無であった．

　Purpose：To elucidate resorption of the interconnected high-porosity hydroxyapatite ceramic spacers used in spinous-process-splitting cervical laminoplasty.

　Methods：Forty-one cases of cervical myelopathy were followed for at least two years, and the degree resorption of the spacers was assessed on radiographs.　The Japanese Orthopaedic Association scoring system for cervical myelopathy was used to make the clinical assessments.

　Results：The spacers were more vulnerable to resorption 1) in younger patients, 2) at the corners of the spacers than at their surfaces, and 3) in the dorsal portion of the spacers than in the other three portions.　At an average postoperative follow-up period of 39 months 41% of the spacers had totally or almost totally vanished on the radiographs.　None of the spacers had dislodged.　No deterioration of the cervical myelopathy was observed.

　Conclusion：Many of the interconnected high-porosity hydroxyapatite ceramic spacers used in spinous-process-splitting cervical laminoplasty had resorbed without any deterioration being observed clinicaly.