This invention offers, the field where stress distribution improves the cave (48) in at least outside the computer and the cave which are penetrated completely and, the medullary nail which it possesses (30). With one example, as for the medullary nail, the notch which it adjoins, to the cave of the notch and the like which inclines (32,56,70,84) it includes, it improves the stress distribution of the medullary nail in the field around the outer part opening of the cave. With one example, as for the notch, the inclined section (78,94), namely the field where the outer part opening of the cave is demarcated is included. With the other examples, as for the notch, the roll off (60), namely the outer part opening of the cave is demarcated demarcates the even part substantially.本発明は、横穴(48)が貫通した本体と、横穴の少なくとも外側において応力分布が向上された領域と、を有する髄内釘(30)を提供する。一実施例では、髄内釘は、傾斜した切欠き部などの、横穴に隣接した切欠き部(32,56,70,84)を含み、横穴の外側開口部の周りの領域における髄内釘の応力分布を向上させる。一実施例では、切欠き部は、傾斜部(78,94)、すなわち横穴の外側開口部を画定する領域を含む。その他の実施例では、切欠き部は、逃げ部(60)、すなわち横穴の外側開口部を画定する実質的に平坦な部分を画定する。
