A surgical distraction device is provided for applying extending or tensioningforce non-invasively to a patient's skeleton or to an implant which comprisesanchoring means for attaching first and second components of the device to abone or to adjoining bones, said components being connected by a linkage of anextendible length, a magnet connected to the linkage via a reduction gearboxand actuating means located externally of the patient for generating a movingor varying electro-magnetic field, thereby causing the magnet to rotate andthe linkage to be extended.
