Surgical instrument positioning device

Claim 1

AN INSTRUMENT FOR USE IN BRAIN SURGERY COMPRISING A THREADED HOLLOW PLUG HAVING A FLANGE PORTION FOR ASSEMBLAGE IN A HOLE FORMED IN THE SKULL OF A PATIENT, SAID THREADED PLUG BEING THE SOLE SUPPORT FOR THE INSTRUMENT HOLDER ON THE PATIENT''S HEAD SERVING TO ESTABLISH A FIRST AXIS PASSING THROUGH THE CENTER OF SAID HOLLOW PLUG LONGITUDINALLY THEREOF, FIRST AND SECOND GUIDEWAYS EXTENDING AT A SELECTED ANGLE WITH RESPECT TO EACH OTHER IN ACCORDANCE WITH A SELECTED SET OF COORDINATES, MEANS FOR DETACHABLY SECURING SAID FIRST GUIDWAY ON SAID FLANGE PORTION SO THAT SAID FIRST GUIDEWAY IS ROTATABLE ADJUSTABLE WITH RESPECT TO SAID HOLLOW PLUG ABOUT SAID FIRST AXIS, SAID FIRST GUIDWAY ESTABLISHING A SECOND AXIS AND CONSTRUCTED TO CONSTRAIN SAID SECOND GUIDEWAY TO SWING ABOUT SAID SECOND AXIS, SAID SECOND GUIDEWAY ESTABLISHING A THIRD AXIS, AN INSTRUMENT HOLDER MOVABLY MOUNTED ON SAID SECOND GUIDEWAY, SAID SECOND GUIDEWAY BEING CONSTRUCTED TO CONSTRAIN SAID INSTRUMENT HOLDER FOR MOVEMENT ABOUT SAID THIRD AXIS, SAID SECOND AND THIRD AXES INTERSECTING EACH OTHER AND SAID FIRST AXIS, SAID INSTRUMENT HOLDER BEING CONSTRUCTED TO DIRECT AN INSTRUMENT THROUGH SAID HOLLOW PLUG ALONG A LINE PASSING THROUGH THE SKULL OF A PATIENT AND THE DIRECTION OF WHICH IN SPACE RELATIVE TO SAID AXES CAN BE DEFINITELY DETERMINED AND MAINTAINED WITH PRECISION, SAID MEANS FOR DETACHABLY SECURING SAID GUIDEWAYS ON SAID FLANGE PORTION FOR ROTATABLE ADJUSTMENT THROUGH SUBSTANTIALLY 360 DEGREES, COMPRISING SURFACE MEANS HAVING A LARGE AREA CONTACT WITH SAID FLANGE PORTION AND MEANS VARYING THE FRICTIONAL ENGAGEMENT BETWEEN SAID SURFACE MEANS AND SAID FLANGE PORTION AND FOR CLAMPING SAID SURFACE MEANS AND SAID FLANGE PORTION TOGETHER WITHOUT RELATIVE ANGULAR DISPLACEMENT THEREOF TO PROVIDE SMOOTH, ACCURATE, INCREMENTAL, HIGHLY STABLE ADJUSTMENT OF SAID INSTRUMENT HOLDER IN SPACE RELATIVE TO SAID SELECTED SET OF COORDINATES.