the positioning system 1 shown in fig1 and 3 is composed , essentially , of a linear axis mechanism 2 , a clampable ball - and - socket joint 3 and a base 4 . in linear guide 5 of linear axis mechanism 2 , a carriage 6 is guided without play and it can be moved via a threaded spindle 7 . a rotary knob 8 is joined securely to threaded spindle 7 . the pitch of the threaded spindle 7 is designed to be self - locking , i . e . the pitch angle is smaller than the effective angle of friction , so that carriage 6 does not move automatically in linear guide 5 as a result of its weight . the path of carriage 6 moving in linear guide 5 is limited by two end stops 9 , 10 . to form the upper end stop 9 , a closing plate , with the corresponding internal threaded hole for threaded spindle 7 , is attached to the upper end of linear guide 5 . on the one hand , the closing plate forming end stop 9 guides the threaded spindle 7 parallel to linear guide 5 , and on the other hand , however , also prevents carriage 6 from sliding off of linear guide 5 by screwing spindle 7 out too far . similarly , the end stop 10 , which is used as the lower end stop on the lower end of rotary knob 8 , prevents threaded spindle 7 from being screwed in too far , and thus , carriage 6 from sliding out on the opposite end of linear guide 5 . by turning rotary knob 8 , according to the direction of the thread and the selected pitch of threaded spindle 7 , axial displacement of the carriage 6 in guide 5 of linear axis mechanism 2 is effected . carriage 6 can , thus , be moved continuously along the linear axis mechanism 2 between the two end stops 9 and 10 , and due to the self - locking of the threaded drive , maintains its instantaneous position . carriage 6 has a corresponding receiver 11 into which the desired instrument 12 can be manually inserted without play or removed therefrom . receiver 11 for instrument 12 has an opening 13 for a free , active end 14 of the instrument 12 inserted therein . the free , active end 14 of the inserted instrument 12 can , thus , be positioned parallel to the linear guide in axial direction 15 relative to destination 16 in body 17 when the rotary knob 8 is turned . linear axis mechanism 2 , together with threaded spindle 7 , rotary knob 8 , carriage 6 and the instrument 12 inserted in receiver 11 and held there , is joined securely to housing 19 of the clampable ball - and - socket joint 3 using connecting element 18 . ball - and - socket joint 3 has a ball 21 which is securely joined via a column 25 to base 4 , and which can be clamped with reference to the housing 19 by means of clamp screw 20 . when the ball - and - socket joint 3 is unclamped , the entire linear axis mechanism 2 can be turned in all three rotary degrees of freedom 22 , 23 , 24 around the center of ball 21 , which is fixedly joined to the base 4 . via base 4 , positioning system 1 can be securely joined to suitable holders . after attachment of one of these holders to the body , positioning of the system attached to the holder and subsequent clamping of clamp screw 20 , exact positioning of free , active end 14 without play relative to the destination 16 on the body , is thus possible , whereby possibly risky relative movements between the body and the free active end 14 of the instrument are prevented . by loosening clamp screw 20 of ball - and - socket joint 3 , connecting element 18 and the linear axis mechanism 2 which is attached to it , as well as instrument 12 inserted in carriage 6 , together with its free , active end 14 , can be turned around the center of ball 21 of the ball - and - socket joint 3 according to all three rotary degrees of freedom 22 , 23 , 24 . the indicated combination of clampable ball - and - socket joint 3 and linear axis mechanism 2 attached securely to it enables , in combination , four - axis positioning of the free , active end 14 of the selected instrument 12 relative to any destination 16 on the body , i . e ., in the axial direction 15 and in the three rotational degrees of freedom 22 , 23 and 24 . fig2 a and 2b illustrate how clampable ball - and - socket joint 3 works . in fig2 a , the ball - and - socket joint 3 is unclamped . the three dimensional position of the three rotational axes 22 , 23 , 24 is held by spring pretension . in fig2 b , the linear axis is swung to the side and the ball - and - socket joint is clamped . the instantaneous position is secured by a pretensioning spring force and also by the axial force of clamp screw 20 on the ball surface . through conical opening 41 on the bottom of housing 19 of ball - and - socket joint 3 , column 25 leads to base 4 . ball 21 , column 25 and base 4 , thus , form a rigid unit . clamp screw 20 acts on the outer surface of ball 21 via movable ball seat 26 . fig2 b shows how ball 21 is securely clamped when clamp screw 20 is tightened between the contact surfaces of ball seat 26 and the corresponding opposite surfaces of housing 19 . the selected three - dimensional position in the three rotational degrees of freedom 22 , 23 , 24 is thus securely fixed . when loosening the clamp screw 20 shown in fig2 a , conversely , the unclamped ball will not allow tilting of the entire positioning system , but the selected position will continue to be maintained by friction . this is done by axially prestressed spring element 42 acting on ball seat 26 , even after loosening of clamp screw 20 , and with the correspondingly preselected prestress securing the three - dimensional position of the ball - andsocket joint by frictional engagement , but still allowing manual movements of the entire system . the entire linear axis mechanism 2 , together with inserted instrument 12 and housing 19 of ball - and - socket joint 3 , thus can be swung around the center of ball 21 in all three of the rotational degrees of freedom 22 , 23 , 24 , the friction of prestressed spring element 42 on the ball surface , even with clamp screw 20 loosened , preventing tilting of the system . the primary dimensions of the entire system are , for example , an overall height above the surface of the body of roughly 100 mm and a total width of 40 mm . in fig3 a combination of the described positioning system 1 and a surgical retractor 27 for intraoperative use is shown as a first preferred embodiment . in this case , positioning system 1 , together with linear axis mechanism 2 and the clampable ball - and - socket joint 3 , is joined with its base 4 securely to any retractor 27 . after inserting retractor 27 into body opening 28 which is made , for example , by a surgical tissue incision , and subsequent spreading of retractor 27 in body opening 28 , retractor 27 , together with the positioning system 1 attached to it , is securely joined to the body . by manipulating the four axes of movement 15 , 22 , 23 and 24 , thus , intraoperatively , the free active end 14 of any instrument 12 which is clamped securely into the positioning system can be precisely guided to any destination 16 located in body 17 . if positioning is to be done on structures which are no longer visible with the naked eye , the position of the free active end in the body opening can be visually monitored , for example , by a microscope . here , positioning system 1 is located on retractor 27 such that optical axis 30 of the microscope or naked eye 29 is not hidden by positioning system 1 itself or its parts . preferred body openings 28 in which positioning system 1 can be used intraoperatively with a suitable retractor 27 are , for example , incisions in soft tissues , the external auditory canal , the mastoid antrum or openings in the skull bone for neurosurgery . accordingly , preferred destinations 16 on the body , at which free active end 14 of positionable instrument 12 is to be pointed are among others , microsurgical structures on or in the spinal column , within the skull , in the external auditory canal , on the ear drum , in the opened cavities of the middle ear ( malleus , incus , stapes ), on the bone wall between the middle and inner ear ( promontorium ), on the liquid - filled inner ear , on the auditory nerve , in the vestibular organ , or in the eye cavity . suitable instruments 12 for use in positioning system 1 in conjunction with suitable retractors 27 are , among others , piezoelectric hearing aid transducers for electromechanical vibrational stimulation of the auditory ossicle chain , exciter coils for electromagnetic stimulation of permanent magnets fixed to the chain , optical fibers for guiding surgical laser light ( for example , for cutting , drilling , coagulating or obliterating tissue or bone structures ), optical fibers for guiding measurement laser light ( laser doppler vibrometry ), a flexible miniature endoscope for inspection in the entire skull area , probe microphone , and small noise sources for intraoperative audiometry ( hearing threshold determination , measurement of otoacoustic emissions ) and electrodes for electrocochleographic derivation of body potentials , such as the sum action potential ( sap ) or microphone potential ( mp ). as a second preferred embodiment , fig4 shows a combination of positioning system 1 and a head support 31 for noninvasive , diagnostic or therapeutic use of instruments anchored to the skull . in the version shown here , the positioning system 1 is securely joined with its base 4 to a head support 31 . opening width 32 of the head support 31 is , preferably , roughly 200 mm , and width 32 can be set , optionally and without play , via a knob 33 and an interior threaded drive by moving two receiving arms 34 and 35 towards ( closing ) or away ( opening ) from one another . knob 33 for adjustment of opening width 32 , in this case , can be operated either by the wearer of head support 31 himself / herself or by a qualified specialist ( physician , nurse , assistant ) in order to attach head support 31 to the head of the patient by clamping on both sides . positioning system 1 with its base 4 is attached securely to one of two receiving arms 35 . this side is called the working side 37 of the head support . a conical retaining element 36 can be made , for example , like an ear speculum which , when necessary , can be placed on gimbals in receiving arm 35 to equalize small spatial angles . it is inserted into the external auditory canal of the wearer ( patient ) with visual monitoring , if necessary , with the aid of a microscope . conical retaining element 36 , moreover , has a conical inside opening 40 which provides space for the free , active end 14 of the instrument 12 clamped in positioning system 1 and also for visual control . on the receiving arm 34 on the opposite side 39 of head support 31 , selectively , a second conical support , similar to support 36 , or an earmuff element 38 in the form of a half shell , is attached . the second conical support or earmuff element 38 is , respectively , inserted into the auditory canal or placed over the outer part of the opposite ear . when earmuff element 38 is used , as is shown in fig4 some of the pretensioning force is transferred over a large area to the skull bone area which surrounds the outer ear by reducing the opening width 32 . this prevents compressive forces from being applied at points and the associated undesirable feeling of pressure associated with it , and the force applied for support is distributed over a large area of skin . after inserting conical retaining element 36 of working side 37 into the outer auditory canal and the subsequent placement of the earmuff element 38 on the outer ear of the opposite side 39 , by carefully reducing opening width 32 of head support 31 , the two retaining elements , i . e ., retaining element 36 and earmuff element 38 , can be caused to approach one another until the entire head support 31 is clamped on the skull of the patient . by deforming earmuff element 38 and by blocking conical retaining element 36 in the outer auditory canal , a secure filling of the entire head support 31 on the skull of the patient is ensured . by means of conical inside hole 40 in conical retaining element 36 , after clamping head support 31 on the skull of the patient , the free , active end 14 of instrument 12 , attached in positioning system 1 , can be positioned without play so as to prevent relative movements between the skull and target points 16 on the skull . the set position of the positioning system can be fixed via the already described clamping means of the positioning system ( see fig2 a and fig2 b ). one preferred body opening 28 in which positioning system 1 can be used noninvasively or with minimal invasiveness , using a suitable head support 31 , is the external auditory canal of a human . accordingly , preferred destinations 16 on the body , at which the free , active end 14 of the positionable instrument 12 is to be noninvasively pointed , among others , are microsurgical structures in the auditory canal itself , on or in the eardrum or the manubrium which is fused directly to the inside of the eardrum , and which represents the outermost point of the auditory ossicle chain which can be reached noninvasively through the auditory canal . in local , minimally invasive use of this second embodiment , after opening the eardrum , moreover , positioning of the instrument relative to the anatomical structures of the air filled middle ear ( malleus , incus , stapes ) or the bony wall between the middle and inner ear ( promontorium ) is possible . for noninvasive use of positioning system 1 in conjunction with suitable head supports 31 , all instruments described with reference to the first preferred embodiment are equally applicable . while various embodiments in accordance with the present invention have been shown and described , it is understood that the invention is not limited thereto , and is susceptible to numerous changes and modifications as known to those skilled in the art . therefore , this invention is not limited to the details shown and described herein , and includes all such changes and modifications as are encompassed by the scope of the appended claims .
temporarily fixable positioning system for secure , play - free fastening to the human body , preferably to the human skull has a base , a clampable ball - and - socket joint , a linear axis mechanism fixed securely to it and a carriage guided along the linear axis mechanism for receiving an actuator or sensor instrument . for intraoperative use , the positioning system is combined with a retractor . a head support is provided for noninvasive diagnostic or therapeutic applications . the combination of the axial degree of freedom of linear axis with the three rotational degrees of freedom of the ball - and - socket joint allows four - axis , in situ positioning of the instrument on or in the skull , especially in the external auditory canal and an opened middle ear . the positioning system in combination with one of the holders enables precise positioning of an active end of a guided instrument relative to sensitive anatomical structures while avoiding risky relative movements .