Holding instrument and medical device

A retainer configured to hold a screw to be placed inside a human body, the screw having a hole that is recessed from a proximal end of the screw in an axial direction of the screw, the hole having a first polygonal shape on a cross-section,

• the retainer comprising
• a shaft,
• a tubular body through which the shaft is inserted, and
• a strip-shaped protruding member protruding from a tip of the tubular body in a longitudinal direction of the tubular body,
• wherein
• the shaft includes a tip part insertable into the hole of the screw with the tip part extending from the tip of the tubular body,
• the tip part of the shaft has a cross-section missing a portion that constitutes a part of an outer edge of a second polygonal shape similar to the first polygonal shape, the portion being defined by a groove extending in a longitudinal direction of the shaft, the protruding member being configured to be inserted into the groove,
• the groove has a bottom surface that is a tapered surface inclined toward the tip of the shaft so as to approach the part of the outer edge of the second polygonal shape,
• at a state in which the tip part of the shaft is placed in the hole, advancing the tubular body toward the tip of the shaft with respect to the shaft so as to expose the tip part of the protruding member from the groove brings the tip part of the protruding member and the tip part of the shaft into firm contact with an inner surface of the hole of the screw to allow the retainer to hold the screw, and
• at a state in which the screw is held by the retainer, retracting the tubular body toward a proximal end of the shaft with respect to the shaft so as to release the contact of the tip part of the protruding member and the tip part of the shaft with the inner surface of the hole of the screw detaches the screw from the retainer.