中足部骨折の一部分としての舟状骨骨折治療の小経験

Mechanism and Treatment of Navicular Fractures in Patients with Multiple Midtarsal Fractures

　舟状骨を含む中足部骨折の5例に対し，マルチスライスCTを撮影し病態を検討した．マルチスライスCTにより，細部にいたる骨折の状況が把握でき，舟状骨のほか多部位の中足部骨折を合併した複合損傷として診断が可能となった．われわれは今回，複合損傷の位置により，内側列集中型と均等分散型に分類した．また，この2つの治療方法は分けて考えるべきであり，足部内転および短縮変形の予防として，補助的ピン固定によるLisfranc-Chopart関節間・仮固定が有用であった．本症例の治療は全例に手術加療を施行し，短期調査ではあるが足部変形や足長の変化はなく歩行は可能となった．中足部骨折の中には，今回のように，X線像のみでは十分な術前計画を立てることが困難であったことから，マルチスライスCTによる詳細な検討が不可欠なものもあると考えた．

　Five patients with multiple midtarsal fractures that included a navicular fracture were treated surgically.　Full weight-bearing with arch support was allowed 8.2 weeks postoperatively.　There were no obvious foot deformities or shortening, and all patients were satisfied with the results, but the follow-up has been short.　Multi-planar reconstruction CT images were advantageous for detecting even minor hidden fractures, and they were informative for overall and detailed diagnosis of the injury and for preoperative planning.　Fracture distributions of all cases were plotted and could be classified into two types： (1) a medial column stress concentrated type caused by the impact of an axial load on the medial aspect of the foot, and (2) a uniform stress distribution type, that caused by abduction force against the forefoot or equal axial compression medial aspect and lateral aspect of the foot.　The treatment strategy should be different, because the medial column concentrated type is at risk of adduction deformity, and the uniform distribution type might become complicated by shortening of the foot.　These deformities can be prevented by these adequate temporary fixations through Lisfranc-Chopart joints.