PROBLEM TO BE SOLVED: To provide a navigation system and a guide instrument in which the work such as the excavation work of ostectomy and bone marrow cavity or the component installation can be performed precisely in a short time along a preoperative plan in the artificial joint operation, and also an operator can grasp it intuitively.SOLUTION: First of all, a thighbone side guide instrument 30 provided with a relative angle detector 24 is pressed to an appropriate place of a femoral stem and closely fixed therein, and the osteotomy of the femoral head is performed along an end edge of an abutment fixing part 10A of a fixed guide tool 10, and also an insert center point DX of the femoral stem is grasped. Next, an operator holds a grip part 308 of a stem side guide instrument 300 provided with a relative angle detector 338, and stands a tip of a rasp 340 in the insert center point DX of the stem. In this state, a state of the posture of the relative angle detectors 24, 338 is grasped by a posture detection device 500, and the excavation of the pulp cavity of a thighbone 100 and the insert of the stem are performed in an optimal posture while correcting an angle of the stem side guide instrument 300.SELECTED DRAWING: Figure 5【課題】 人工関節術において、骨切除や骨髄腔の掘削作業あるいはコンポーネント設置などの作業を、術前計画に沿って短時間で的確に行うとともに、術者が直感的に把握することができるナビゲーションシステム及びガイド器具を提供する。【解決手段】 まず、相対角度検出器２４を設けた大腿骨側ガイド器具３０を、大腿骨頸部の該当箇所に押し付けて密着固定し、固定ガイド具１０の当接固定部１０Ａの端縁に沿って大腿骨頭の骨切りを行うとともに、大腿骨ステムの挿入中心点ＤＸを把握する。次に、術者は、相対角度検出器３３８を設けたステム側ガイド器具３００の把持部３０８を持ち、ラスプ３４０の先端を、前記ステムの挿入中心点ＤＸに立てる。この状態で、相対角度検出器２４，３３８の姿勢の様子を姿勢検出装置５００で把握し、ステム側ガイド器具３００の角度を修正しつつ、最適な姿勢で大腿骨１００の髄腔の掘削やステムの挿入を行う。【選択図】図５
