臨床整形外科45巻11号

2010年11月発行

Lecture

骨強度と骨質

著者： 斎藤充¹ 丸毛啓史¹

所属機関： ¹東京慈恵会医科大学整形外科

ページ範囲：P.986 - P.993

　骨強度は骨密度と骨質で規定されている．臨床的にも高い骨密度で骨折することや，薬剤により骨密度を高めても新たに骨折を起こす症例がある．こうした症例は，決して稀ではなく，骨の材質劣化が強い場合に，骨密度非依存性に骨折リスクが高まる．骨は材質学的には，鉄筋コンクリートに例えられる．鉄筋がコラーゲンであり，コンクリートはハイドロキシアパタイトである．コラーゲンは骨の重量当たりでは20％であるが，体積当たりに換算すると骨の50％はコラーゲンで占められている．コラーゲンの分子間をつなぎ止める架橋には，骨にしなやかさを与える酵素依存性の生理的架橋(善玉架橋)と，酸化や糖化といった老化や生活習慣病に関わる要因によって誘導される非生理的架橋(悪玉架橋)とが存在する．非生理的架橋の本体は，終末糖化産物(advanced glycation end products：AGEs)である．ペントシジンはAGEs架橋の代表的構造体であり，骨質を評価するマーカーとしてエビデンスが集積されてきた．コラーゲン架橋の異常は骨粗鬆症のみならず，加齢や生活習慣病，ステロイド投与，関節リウマチなどで誘導され，骨の代謝回転の亢進とは独立した機序で骨強度を低下させる．

参考文献

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