An adapter for receiving a medical technical device and a position detecting system , comprising: a. a first holding element and a second holding element , wherein the first holding element has a receiving opening with a longitudinal extension direction, and wherein the second holding element is movably supported in the receiving opening of the first holding element ; b. a spring disposed between the second holding element and a bottom surface fixed at a bottom side of the first holding element , wherein the restoring force of the spring is directed in the longitudinal extension direction of the first holding element and acts on the second holding element ; c. a first insertion opening completely passing through the first holding element and a second insertion opening completely passing through the second holding element , both for insertion of the medical technical device , wherein the first and second insertion openings are configured transverse to the restoring force of the spring and can be brought into congruence by a force acting counter to the restoring force of the spring , whereby a receiving state of the adapter is defined, and wherein without the force acting counter to the restoring force of the spring , a clamping state of the adapter is defined; d. a first displacing element fixed at the top side of the second holding element and having a thread on its outer face; e. a second displacing element connected to the thread of the first displacing element via a counter-thread, such that by a rotational movement of the second displacing element the thread of the first displacing element can be moved in the direction of the restoring force of the spring into the second displacing element , until a movement proof clamping state of the adapter is thereby achieved; and f. a fixing element for fixing the position detecting system . a. a first holding element and a second holding element , wherein the first holding element has a receiving opening with a longitudinal extension direction, and wherein the second holding element is movably supported in the receiving opening of the first holding element ; b. a spring disposed between the second holding element and a bottom surface fixed at a bottom side of the first holding element , wherein the restoring force of the spring is directed in the longitudinal extension direction of the first holding element and acts on the second holding element ; c. a first insertion opening completely passing through the first holding element and a second insertion opening completely passing through the second holding element , both for insertion of the medical technical device , wherein the first and second insertion openings are configured transverse to the restoring force of the spring and can be brought into congruence by a force acting counter to the restoring force of the spring , whereby a receiving state of the adapter is defined, and wherein without the force acting counter to the restoring force of the spring , a clamping state of the adapter is defined; d. a first displacing element fixed at the top side of the second holding element and having a thread on its outer face; e. a second displacing element connected to the thread of the first displacing element via a counter-thread, such that by a rotational movement of the second displacing element the thread of the first displacing element can be moved in the direction of the restoring force of the spring into the second displacing element , until a movement proof clamping state of the adapter is thereby achieved; and f. a fixing element for fixing the position detecting system . <EOS>