A medical instrument has a connector configured for being fixed to a spine support, and a rib support connected to the connector and configured for supporting the rib. The medical instrument has a pair of an upper hook and a lower hook provided on the rib support. One of the upper hook and the lower hook is fixed to the rib support so as to be vertically adjustable. The rib support is connected to the connector to be movable in a direction along the rib.
