fig1 shows a perspective illustration of a screw electrode head 1 , which has a basic cylindrical shape , of an implantable pacemaker electrode line ( see fig3 ), of which the construction is shown in greater detail in fig2 a - 2b . at the distal end , the electrode head 1 has a rounded flange portion 1 a of a first diameter , which is adjoined ( in this order ) by a first longer cylinder portion 1 b of smaller diameter , a second longer cylinder portion 1 c of larger diameter ( which can be bigger , smaller or equal to the first diameter ), and lastly a third longer cylinder portion 1 d , again of reduced diameter again and also below the diameter of the first cylinder portion 1 b . in addition , it can be seen that the electrode head 1 has an open distal end 1 e , in which the distal end of a helical coil 3 can be seen . furthermore , a continuous weld seam 1 f can be seen and fixedly interconnects prefabricated half - shells 1 . 1 and 1 . 2 ( not denoted separately here ) of the electrode head 1 in an integrally bonded manner . fig2 a shows the inner design of the electrode head 1 , together with the first half - shell 1 . 1 of the head housing , and fig2 b shows the second half - shell 1 . 2 of the head housing , in each case again in a perspective illustration . for the sake of improved clarity , the above - referenced portions 1 a to 1 e of the outer contour of the head housing are not denoted again in fig2 a - 2b . it can be seen , however , that both half - shells 1 . 1 , 1 . 2 have a division ( naturally likewise in a half - shell - like manner ) into three chamber segments 1 . 1 a , 1 . 1 b and 1 . 1 c and 1 . 2 a , 1 . 2 b and 1 . 2 c , respectively , adjoining one another in the longitudinal direction . the mentioned chamber segments are separated from one another by partition walls shaped primarily in the form of segments of a circle and having a central aperture , of which merely the more distal partition wall 1 . 1 d of the first half - shell 1 . 1 can be seen in fig2 a , although both partition walls 1 . 2 d and 1 . 2 e can be seen in fig2 b . when comparing the two drawings , it can be easily seen that the half - shells 1 . 1 , 1 . 2 are not identical , but have different projections and returns or stops and centering means , both in the region of the distal flange and of two of the three stepped cylindrical regions and lastly also in the region of the partition walls . inter alia , it is thus ensured that there are overlap regions of sufficient size in the wall of the head housing between the first and second half - shell so as to ensure high mechanical stability and tightness of the rear region of the head housing . it can be seen from fig2 a how the helical coil 3 fills the distal chamber 1 a of the electrode head 1 in the retracted state in its entire length and surrounds , via its proximal end , a ram 5 a of a fixing screw actuation shaft 5 , to which it is fastened ( not visible here ) in an integrally bonded manner ( for example , by means of welding ). in the second chamber 1 b , the fixing screw actuation shaft 5 is surrounded by a ring seal 7 and an x - ray contrast ring 9 in such a way that the periphery of the chamber 1 b is largely filled . in the third chamber 1 c , a contact sleeve 11 for electrically contacting the conductor coil ( not shown here ) of the electrode line body with the ram 5 a or the helical coil 3 can be seen . fig3 shows a longitudinal sectional illustration of the distal end region of an electrode line 10 provided with the electrode head 1 according to fig1 - 2b . besides the electrode head 1 , of which the outer shape and design are shown in fig1 - 2b and are described further above , the electrode line 10 comprises an outer line body ( not shown here ) or outer tube , an outer conductor coil ( likewise not illustrated here ) for contacting a ring electrode 13 , and an inner conductor coil 17 arranged within an inner tube 15 . the fixing screw actuation shaft 5 , already mentioned above , is in turn placed in the interior of said coil , and the contact sleeve 11 , likewise already mentioned further above , is attached to the end of said shaft . the mechanical connection and simultaneous seal between the electrode head 1 and the line body of the line 10 distally in relation to the ring electrode 13 is produced by an inner ptfe ( polyetrafluoroethylene — teflon ) tube 19 . 1 and a substantially likewise tubular outer silicone connection piece 19 . 2 . whereas the ptfe tube 19 . 1 is arranged within the proximal chamber 1 c of the electrode head 1 and extends beyond a distal region of the inner conductor coil 17 , the silicone connection piece 19 . 2 surrounds a distal end portion of the ring electrode 13 as well as the outer wall of the proximal chamber 1 c ( or , on the basis of the external view , the proximal cylinder portion 1 d ) of the electrode head 1 and interconnects these . suitably shaped fixing ring portions , or locking portions , in the inner wall of the silicone connection piece 19 . 2 or the outer wall of the ptfe tube 19 . 1 , and optionally additional fixing rings or other fixing means , contribute to secure fixing of the interconnected parts in the longitudinal direction of the electrode line in a manner known per se . specific attention should be paid in fig3 to the complete illustration of the ring seal 7 , of which only a distal end - face portion can be seen in fig2 a . it can be seen that the outer contour of the ring seal 7 is stepped or chamfered a number of times . furthermore , a hollow - cylindrical drug storage region 21 is illustrated here in the region of the distal cylinder portion 1 b of the electrode head 1 and ( again in a manner known per se ) serves to store and continuously dispense , in an ongoing manner , an anti - inflammatory steroid when the electrode line is implanted . when the half - shells are already fixedly connected to the cylindrical electrode head 1 , the drug store in the form of a hollow cylinder 21 is slid over and fastened in the distal region . in the shown embodiment , the electrode head 1 is preferably manufactured from peek half - shells , however pu half - shells or housing parts formed from another polymer that can be used in implanted parts can also be manufactured alternatively . in principle , the manufacture from a biocompatible metal , such as , for example , titanium or a titanium alloy or high - grade steel , is also considered , wherein special design provisions have to be made , however , in order to ensure the radiopacity of the length by which the helical coil is screwed out , and specific spring ranges , which are not provided in the above - described embodiment , would possibly have to be provided . the embodiment of the present invention is not limited to the above - described examples and high - lighted aspects , but the present invention can also be implemented in a large number of modifications within the capabilities of a person skilled in the art . fig4 a ( closed shell ) and 4 b ( open shell ) show a perspective illustration of an alternative screw electrode head 101 , which has a basic cylindrical shape of an implantable pacemaker electrode line , of which the construction is shown in greater detail in fig5 - 6 . at the distal end , the electrode head 101 has a rounded flange portion 101 a of a first diameter , which is adjoined ( in this order ) by a first longer cylinder portion 101 b of smaller diameter , a second longer cylinder portion 101 c of larger diameter ( which can be bigger , smaller or equal to the first diameter ), and lastly a third longer cylinder portion 101 d , again of reduced diameter and also below the diameter of the first cylinder portion 101 a . the second longer cylinder portion 101 c of larger diameter can consist of three cylinder portions 101 c ′, 101 c ″ and 101 c ′″, where the diameter of the cylinder portions 101 c ′ and 101 c ′″ is smaller or equal compared to the diameter of the cylinder portion 101 c ″, but the diameter of the cylinder portion 101 c ′ is bigger than the diameter of the rounded flange portion 101 a and also bigger than the diameter of the cylinder portion 101 b . the diameter of the cylinder portion 101 c ′″ is bigger than the diameter of the cylinder portion 101 d . in addition , it can be seen that the electrode head 101 has an open distal end 101 e , in which the distal end of a helical coil 3 can be seen . furthermore , a continuous interface 101 f , i . e ., a weld seam or groove , can be seen where the prefabricated first shell part 101 . 1 and the second shell part 101 . 2 of the electrode head 101 are put together . fig5 shows the inner design of the electrode head 101 , together with the first shell part 101 . 1 and the second shell part 101 . 2 of the head housing , and fig6 shows the second shell part 101 . 2 of the head housing , in each case again in a perspective illustration . for the sake of improved clarity , the above - referenced portions 101 a to 101 e of the outer contour of the head housing are not denoted again in fig5 - 6 . it can be seen in fig5 , however , that the housing of the head 101 , formed out of the shell parts 101 . 1 , 101 . 2 , has a division ( naturally likewise in a half - shell - like manner ) into three chamber segments 101 a , 101 b and 101 c , adjoining one another in the longitudinal direction . the mentioned chamber segments are separated from one another by partition walls shaped primarily in the form of segments of a circle or a ring and having at least a central aperture , of which both partition walls 101 d and 101 e can be seen in fig5 . in fig6 , merely the more distal partition wall 101 d can be seen , because it is connected to the second shell part 101 . 2 . the two shell parts 101 . 1 and 101 . 2 can be held together by one or two rings which can be slid over the cylinder parts 101 c ′ and 101 c ′″. the rings can preferably manufactured from peek , pu or from another polymer that can be used in implanted parts . in principle , the manufacture from a biocompatible metal , such as , for example , titanium or a titanium alloy such as platinum / iridium or high grade steel , is also considered . in addition , at least one of the rings can be an x - ray contrast ring , consisting at least in parts of a radiopaque material such as , i . e ., platinum / iridium . in addition or alternatively , the housing parts , in particular , the first and second shell parts 101 . 1 and 101 . 2 , of the head housing are expediently welded or adhesively bonded together . when comparing the two drawings , it can be easily seen that the half - shells 101 . 1 , 101 . 2 are not identical , but have different projections and returns or stops and centering means , both in the region of the distal flange and of two of the three stepped cylindrical regions and lastly also in the region of the partition walls . inter alia , it is thus ensured that there are overlap regions of sufficient size in the wall of the head housing between the first and second half - shell so as to ensure high mechanical stability and tightness of the rear region of the head housing . due to the asymmetric form of the two shell parts 101 . 1 and 101 . 2 , it is sufficient if the two shell parts 101 . 1 and 101 . 2 are held together by one or two rings which can be slid over the cylinder parts 101 c ′ and 101 c ′″. in this case the housing parts , in particular , the first and second shell part 101 . 1 and 101 . 2 , of the head housing do not necessarily need to be welded or adhesively bonded together . it can be seen from fig6 , that the second shell part has a pin 12 so that the helical coil acting as a fixation screw can be rotated out from the head housing in distal direction . it can be seen from fig5 and 7 how the helical coil 3 fills the distal chamber 101 a of the electrode head 101 in the retracted state in its entire length and surrounds , via its proximal end , a ram 5 a of a fixing screw actuation shaft 5 , to which it is fastened ( not visible here ) in an integrally bonded manner ( for example , by means of welding ). in the second chamber 101 b , the fixing screw actuation shaft 5 is surrounded by a ring seal 7 in such a way that the periphery of the chamber 101 b is largely filled . in the third chamber 101 c , a contact sleeve 11 for electrically contacting the conductor coil ( not shown here ) of the electrode line body with the ram 5 a or the helical coil 3 can be seen . one or more of the helical coil 3 , the fixing screw actuation shaft 5 and the ram 5 a of the fixing screw actuation shaft 5 can consist at least in part of a radiopaque material . in case both rings are made as x - ray contrast rings and at least the ram 5 a of the fixing screw actuation shaft 5 consists at least in part of a radiopaque material , it is possible to inspect how far the helical coil acting as a fixation screw has been rotated out from the head housing in distal direction . it will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teachings of the disclosure . the disclosed examples and embodiments are presented for purposes of illustration only . other alternate embodiments may include some or all of the features disclosed herein . therefore , it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention , which is to be given the full breadth thereof . additionally , the disclosure of a range of values is a disclosure of every numerical value within that range .
an electrode head of an implantable electrode line , including an elongate housing which has a longitudinal axis and includes at least two housing parts , which are cylinder - segment - shaped at least in portions and are fixedly joined together .