Abstract:
The device with a bone plate ( 1 ) and with a temporarily attachable retainer ( 100 ) is used for fixation of, in particular, fragments of a jaw bone. The bone plate ( 1 ) has a longitudinal guide slot ( 40 ) which is open at one end or closed at both ends. The retainer ( 100 ) comprises a disk ( 110 ) which engages partially over the bone plate ( 1 ) and in which a locking screw ( 120 ) sits preferably in a rotatable manner and secure against loss, said locking screw ( 120 ) being intended to be screwed into a bone fragment via the guide slot ( 40 ). At one end, the bone plate ( 1 ) advantageously has areas of members ( 30 ) comprising individual members which can be divided off to obtain the desired length, The device extends the possibilities of screwing the bone plate ( 1 ), so that better adaptability to the particular task is achieved, and also improved rigidity across the edge of the bone plate ( 1 ), while the elasticity of the latter across the surface can be increased by means of less material thickness. The as it were one-piece retainer simplifies handling. A fixing plate is provided for additionally stiffening the screwed-on bone plate ( 1 ) and/or for screwing it at one end. In a second embodiment, the retainer can be, screwed to the underlying bone fragment laterally outside the bone plate ( 1 ).

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a device for osteosynthetic fixation of bone fragments, in particular of fragments of a jaw bone. Devices of this type are fitted intraoperatively in order to mutually fix bone fragments which have become separated from each other. This may be necessary either in the context of osteosynthesis, after accidents in which a bone is shattered into bone fragments, or in the context of orthognathic or maxillofacial treatment for surgical control of abnormal positioning after osteotomy and subsequent positional correction of the bone fragments. Such a device principally spans and fixes two bone fragments together, one part of the device in each case being connected releasably to a respective bone fragment. In order to create the connection between tie temporarily fitted device and the bone fragments, the bone plate (which constitutes the essential structural element of the device) has through-holes in which securing elements sit, in most cases bone screws, which engage in the bone fragments. In these devices it is important that the bone fragments are fixed in a stable manner and in the correct position relative to each other. 
     DESCRIPTION OF THE PRIOR ART 
     DE-C-23 40 880 discloses a solid compression plate which is used for treating jaw fractures and which, spanning the fracture site on the jaw bone, is screwed onto both of the bone compartments to be joined together. In each half of the compression plate there are two oblong holes oriented toward the plate center and toward the fracture site. On the side directed away from the jaw bone, the oblong holes have a countersink with a screw seat configured as a beveled plane surface. At least one oblong hole per half is inclined relative to the plate center. On the side directed toward the jaw bone, the bone plate has a projecting notched web at the center. As a result of the arrangement of the oblong holes and the bevelled screw seats, the bone compartments are compressed at the fracture site when the inserted bone screws are tightened. Because of its rigidity, this plate cannot readily be adapted to the existing bone geometry. The simple hole engagement permits little variability in terms of attachment to the bone compartments, and preliminary provisional fixing prior to final positioning is possible only within very limited ranges of movement. 
     A further refined bone plate for fixation of bone compartments is the subject of WO-A-97 01991. The bone plate described there has at least one continuous screw hole on both its outsides, between which screw holes there is a first axial oblong hole which is limited on both longitudinal flanks by struts lying opposite each other. Moreover, a bracket-shaped retainer is provided for engaging over the bone plate in the transverse direction, i.e. over both struts with the first oblong hole lying between them. The retainer has a second oblong hole which extends transverse to the longitudinal axis of the bone plate and thus also transverse to the first oblong hole. The longitudinal dimension of the second oblong hole corresponds to the width of the first oblong hole. The retainer has two angled guide noses on the outside facing the bone plate, which guide noses engage over and below both struts in the fitted state, so that the retainer is longitudinally displaceable on the bone plate as on a double rail. 
     In use, one outside of the bone plate is screwed securely to a first bone compartment. The retainer is then temporarily mounted on the bone plate in the area of the first oblong hole and is fixed by means of a locking screw inserted into the second bone compartment after positioning of the movable bone compartment. Said positioning is done by means of longitudinal relative displacement between the bone plate and the retainer within the clearance of the first oblong hole and by transverse relative displacement between the locking screw and bone plate and the retainer within the clearance of the second oblong hole. When bone plate and retainer have been fixed thus far and the bone compartments have been oriented with respect to each other, the remaining outside of the bone plate is screwed to the second bone compartment. Thereafter, the locking screw is unscrewed and the retainer is also removed. 
     Compared with the earlier state of the art, the bone plate described above resulted in a marked improvement since its flexibility meant that it can be adapted more easily and more accurately to the respective bone geometry. In addition to this, the retainer permits, intraoperatively, an initially approximate and then precise orientation of the two bone compartments which are to be joined together. However, the following shortcomings still remain: 
     a) The retainer and the associated locking screw are two relatively small and separate individual parts and their application is correspondingly awkward. 
     b) The length of the bone plate is fixed and is not adaptable to the particular situation. The firs longitudinal oblong hole located in the bone plate is enclosed on all sides and lies between the screw holes, as a result of which there is limited variability in terms of longitudinal mobility. 
     c) The bone plate can be screwed onto the bone compartments to be joined together only in the area of rigidity; greater variability would also be of advantage here. 
     OBJECT OF THE INVENTION 
     In view of the inadequacies of the devices known hitherto for osteosynthetic fixation of bone fragments with a temporarily attached retainer, the object of the invention is to configure the bone plate belonging to the device in such a way as to improve its adaptability to the particular bone situation by easier deformability, simplified choice of length and greater variability in the setting of locally variable rigidities. In addition, it is intended to provide as great as possible a range of clearance or the bone plate provisionally fixed with a retainer. It is also intended to simplify the handling of the hitherto two-part retainer and bone plate during the operation. Finally, it must be possible for the whole device to be manufactured economically in serial production. 
     SUMMARY OF THE INVENTION 
     In a first embodiment of the fixation device, the bone plate has a longitudinal guide slot which is bordered by plate struts and which is open at one end or closed at both ends. A retainer which can be temporarily attached to the bone plate comprises a disk which engages partially over the bone plate and in which a locking screw sits either in a rotatable manner or fixed, said locking screw being intended to be screwed into a bone compartment via the guide slot. The retainer and bone plate together with the respective bone compartments can be displaced relative to each other within the length and width of the guide slot. A plurality of screw holes are provided on the bone plate, at least at one end. At one end, the bone plate advantageously has an area of members comprising members which can be divided off so as to be able to obtain the desired length in each case. With several possibilities for screwing the bone plate, it is possible to achieve better adaptability to the respective task and improved rigidity across the edge of the bone plate, while the elasticity of the latter can be increased across the surface by means of less material thickness. 
     The disk fitted on the locking screw of the retainer is advantageously secured against dropping. By this means, an as it were one-piece retainer is obtained whose handling is simplified. A fixing plate is provided for additional stiffening of the screwed-on bone plate and/or for screwing the bone plate at one end, which fixing plate can be mounted on the bone plate screwed on at the other end with bone screws through screw holes. 
     In a second embodiment, the retainer attached to the bone plate has a plate which engages partially over the bone plate and which can be screwed to the underlying bone compartment laterally to the outside of the bone plate. 
    
    
     BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS 
     FIG. 1A shows a plan view of a bone plate open laterally at one end, with a horizontal connection web, one area of members on each of two parallel free plate struts, and a guide slot extending between the connection web and the areas of members, and an associated retainer in plan view and side view; 
     FIG. 1B shows the bone plate according to FIG. 1A with a retainer fitted in the guide slot, fitted bone screws, and two symmetrically divided-off holed members; 
     FIG. 1C shows the bone plate according to FIG. 1A enlarged; 
     FIG. 1D shows the retainer according to FIG. 1A enlarged, in a partial cross-sectional side view; 
     FIG. 1E shows the retainer according to FIG. 1A enlarged, in a plan view; 
     FIG. 2A shows the representation according to FIG. 1A, with a narrowing guide slot continuing out between the areas of members; 
     FIG. 2B shows the bone plate according to FIG. 2A, with a retainer fitted in the guide slot between the areas of members, and two symmetrically divided-off holed members; 
     FIG. 3A shows the representation according to FIG. 2A, with a straight guide slot continuing out between the areas of members; 
     FIG. 3B shows the bone plate according to FIG. 3A, with a retainer fitted in the guide slot between the areas of members, and two symmetrically divided-off holed members; 
     FIG. 4A shows the representation according to FIG. 2A, with a vertical connection web; 
     FIG. 4B shows the bone plate according to FIG. 4A, with a retainer fitted in toe guide slot between the areas of members, and two symmetrically divided-off holed members; 
     FIG. 5A shows the representation according to FIG. 2A, with a kidney-shaped connection web; 
     FIG. 5B shows the bone plate according to FIG. 5A, with a retainer fitted in the guide slot between the areas of members, and two symmetrically divided-off holed members; 
     FIG. 6A shows the representation according to FIG. 5A, with a kidney-shaped connection web behind an additional pair of holed members; 
     FIG. 6B shows the bone plate according to FIG. 6A, with a retainer fitted in toe guide slot between the areas of members, and two symmetrically divided-off holed members; 
     FIG. 7A shows the representation according to FIG. 1A, with an additional strip-shaped fixing plate in plan view and side view; 
     FIG. 7B shows the bone plate with screwed-on fixing plate according to FIG. 7A, fitted bone screws, and four symmetrically divided-off holed members; 
     FIG. 7C shows the bone plate according to FIG. 1A and 7A, enlarged; 
     FIG. 7D shows the retainer according to FIGS. 1A and 7A, enlarged in a plan view; 
     FIG. 7E shows the fixing plate according to FIG. 7A, enlarged in a plan view; 
     FIG. 8A shows the representation according to FIG. 7A, with a triangular fixing plate; 
     FIG. 8B shows the bone plate according to FIG. 7B, with a screwed-on fixing plate according to FIG. 8A; 
     FIG. 8C shows the fixing plate according to FIGS. 8A and 8B, enlarged in a plan view; 
     FIG. 9A shows a plan view of a bone plate open laterally at one end, with a horizontal connection web, a guide slot extending from the connection web, and undulating free-ending plate struts, and also an associated retainer and an additional approximately square fixing plate, each in a plan view and side view; 
     FIG. 9B shows the bone plate according to FIG. 9A with screwed-on fixing plate according to FIG. 9A, fitted bone screws, and two strut members symmetrically divided off from the plate struts; 
     FIG. 9C shows the fixing plate according to FIGS. 9A and 9B, enlarged in a plan view; 
     FIG. 10A shows a plan view of a bone plate open laterally at one end, with a horizontal connection web, a guide slot extending from the connections web, and straight free-ending plate struts, and, associated with this, an additional roundish fixing plate with a central web, in a plan view and side view; 
     FIG. 10B shows the bone plate according to FIG. 10A with fitted fixing plate; 
     FIG. 10C shows the fixing plate according to FIGS. 10A and 10B, enlarged in a plan view; 
     FIG. 11A shows the representation according to FIG. 10A, without the central web on the roundish fixing plate; 
     FIG. 11B shows the bone plate according to FIG. 11A, with attached fixing plate; 
     FIG. 11C shows the fixing plate according to FIGS. 11A and 11B, enlarged in a plan view. 
     FIG. 12A shows a bone plate closed laterally at both ends, with kidney-shaped connection webs which each have a pair of holed members mounted in front of them, and a guide slot extending between the holed members, and also an associated retainer, each in a plan view; 
     FIG. 12B shows the bone plate according to FIG. 12A, with a retainer fitted in the guide slot; 
     FIG. 12C shows the bone plate according to FIG. 12A, enlarged in a plan view; 
     FIG. 12D shows the bone plate according to FIG. 12C in a front view; 
     FIG. 13A shows the representation according to FIG. 12A, with an additional pair of holed members at the right-hand end and with a guide slot continuing between the holed members; 
     FIG. 13B shows the bone plate according to FIG. 13A, with a retainer fitted in the guide slot, between the holed members, and with a symmetrically divided-off connection web; 
     FIG. 14A shows the representation according to FIG. 12A, without the holed members in front of the connection webs; 
     FIG. 14B shows the bone plate according to FIG. 14A, with a retainer fitted in the guide slot; 
     FIG. 15A shows a bone plate closed laterally at both ends, with connection webs arranged in the form of a parallelogram and with a guide slot extending between the connection webs, and also an associated retainer, each in a plan view; 
     FIG. 15B shows the bone plate according to FIG. 15A, with a retainer fitted in the guide slot; 
     FIG. 16A shows a plan view of a bone plate closed laterally at both ends, with horizontal connection webs and apertures provided between the connection webs, and an associated laterally fixable retainer in a plan view and side view; 
     FIG. 16B shows the bone plate according to FIG. 16A, with an attached retainer; 
     FIG. 16C shows the bone plate according to FIG. 16A, enlarged in a plan view; 
     FIG. 16D shows the retainer according to FIG. 16A, enlarged in a plan view; 
     FIG. 17A shows the retainer according to FIG. 1D, with a planar disk which is rotatable and nonreleasable on the screw shank; 
     FIG. 17B shows the retainer according to FIG. 17A in a plan view; 
     FIG. 18A shows the representation according to FIG. 17A, with a disk which has locking catches on its underside; 
     FIG. 18B shows the retainer according to FIG. 18A in a plan view; 
     FIG. 19A shows the representation according to FIG. 17A, with a curved disk; 
     FIG. 19B shows the retainer according to FIG. 19A in a plan view; 
     FIG. 20A shows a one-piece retainer with a planar disk sitting securely on the screw shank; 
     FIG. 20B shows the retainer according to FIG. 20A in a plan view; 
     FIG. 21A shows a one-piece retainer with a curved disk sitting securely on the screw shank; and 
     FIG. 21B shows the retainer according to FIG. 21A in a plan view. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A detailed description of illustrative embodiments of the fixation device according to the invention is given below with reference to the attached drawings. 
     The following observation applies to the whole of the following description. If reference numbers are given in a figure for the purposes of clarity but are not mentioned in the directly related text of the description, reference is made to their mention in previous or subsequent figure descriptions. In the interest of clarity, repeated mention of components in subsequent figures is in most cases omitted insofar as the drawings clearly show that these are “recurring” components. 
     FIGS. 1A and 1C 
     The fixation device consists of a bone plate  1 , in this case laterally open at one end and with a horizontal connection web  10 , and also of a retainer  100 . Two mutually parallel and spaced-apart plate struts  20  extend from the connection web  10 , and at their ends they are each provided with an area of members  30  comprising in each case three holed members  31  which lie closely opposite each other in pairs. Extending between the connection web  10  and the area of members  30  there is a guide slot  40  which in the area of members  30  is constricted to a three-times narrowed gap  41  and emerges diametrically opposite the connection web  10 . The holed members  31  are eye-shaped and each have a central screw hole  32  and a transition web  33  to the adjacent holed member  31 . Consequently, the central pair of holed members  31  has two diametrically opposite transition webs  33  per holed member  31 , which transition webs  33  establish the connection to the inner pair and outer pair of holed members  31 . The two plate struts  20  adjoin the inner pair of holed members  31  opposite the transition webs  33 , while the outer pair of holed member  31  only have transition webs  33  directed toward the central pair of holed members  31 . A theoretical longitudinal axis A can lie longitudinally through the bone plate  1 , said bone plate  1  being symmetrical with respect to said longitudinal axis A. The connection web  10  has two screw holes  12  lying on the longitudinal axis A, between which screw holes  12  there are two apertures  14  spaced symmetrically apart from the longitudinal axis A. The apertures  14  are used for engagement of a holder instrument known per se for bringing the bone plate  1  to the application site during the operation. 
     The retainer  100  consists of a circular disk  110  in which a locking screw  120  sits centrally. Disk  110  and locking screw  120  can together form one part or are connected to each other in such a way that the locking screw  120  is rotatable in the disk  110  but the disk  110  cannot come loose from the locking screw  120 . 
     FIG. 1B 
     The retainer  100  is intended to be mounted on the bone plate  1  which has first been screwed onto the first bone compartment. Screwing by means of bone screws  2  at one end could be carried out both or the areas of members  30  and on the connection web  10  via the screw holes  12 , the latter alternative being generally followed. After rough adjustment of both bone compartments, the retainer  100  is placed on the bone plate  1  and the retainer  100  is first screwed loosely onto the second bone compartment by means of the locking screw  120  so that the bone plate  1  under the retainer  100  remains movable in order to permit fire adjustment of both bone compartments relative to each other. The locking screw  120  penetrates through the guide slot  40  and engages in the underlying second bone compartment, and the disk  110  of the retainer  100  spans the distance between both plate struts  20 . For fine adjustment, relative movements between both bone compartments are therefore still possible, i.e. the bone plate  1 , with the screwed-on bone compartment, and the other bone compartment with the attached retainer  100  can be moved relative to each other in the range of clearance which remains for the retainer  100  with locking screw  120  within the guide slot  40 . 
     After fine adjustment of both bone compartments relative to each other, the locking screw  120  is tightened so that the disk  110  presses on the two plate struts  20  with a clamping effect, and the set position of he two bone compartments is thus fixed. The bone screws  2  on the connection web  10  are now introduced into the screw holes  12 . If the full length of the plate struts  20  with the extending areas of members  30  is not needed, the excess number of holed members  31  can be divided off. In order to avoid sharp edges, the appended transition webs  33  are also divided off. The length in which the bone plate  1  is used, the screw holes  32 ,  12  which are fitted with bone screws  2 , and the question of whether bending of the bone plate  1  is carried out for adjustment, all depend on the local bone geometry and on the intended end result. 
     When both ends of the bone plate  1  are screwed onto the two bone compartments by means of bone screws  2 , i.e. in the area of members  30  and on the connection web  10 , the retainer  100  has then fulfilled its temporary function. The locking screw  120  is unscrewed from the underlying bone compartment and the retainer  100  is removed from the bone plate  1 . 
     FIGS. 1D and 1E 
     At the center of the circular disk  110  of the retainer  100  there is a through-bore  11  with a countersink  112  on the upper side  113  of the disk. In this illustrative embodiment, the bore  111  has an internal thread. The lower part of the screw head  122  of the locking screw  120  is partially embedded in the countersink  112 . The screw shank  123  with the external thread  121  penetrates through the bore  111 , said external thread  121  and internal thread of the bore  111  engaging in one another. The disk  110  therefore cannot fall from the locking screw  120 . On its upper side, the screw head  122  has an engagement contour  124 , in this case a circular slit, for application of a conventional screwing instrument. As will be described later (see FIGS.  17 A through  21 B), there are other possible ways of preventing the disk  110  from falling from the locking screw  120 . 
     FIGS. 2A and 2B 
     This embodiment of the bone plate  1  differs in that the bone plate  1  as a whole is wider, so that the plate struts  20  lie farther apart and a wider guide slot  40  is obtained. Thus, the areas of members  3 C with the holed members  31  on both plate struts  20  also lie farther apart, as a result of which a larger gap  41  is obtained. The guide slot  40  is as it were continued by the adjoining gap  41 . This in particular permits an extended longitudinal range of clearance upon fine adjustment, since the retainer  100  can be screwed-in within an extended guide slot  40 , in other words within the areas of members  30 . The locking screw  120  now sits between the holed members  31 . 
     FIGS. 3A and 3B 
     An extended guide slot  40  which likewise also extends via the gap  41  between the areas of members  30  has been generated here by having all the holed members  31  with screw holes  32  pointing outward, i.e. they do not protrude into the path of the gap  41 , as a result of which the gap  41  has smooth edges toward the holed members  31 . This also opens up the possibility of positioning the retainer  100  with locking screw  120  not only in the guide slot  40 , but also, as is illustrated, in its continuation, within the gap  41 . 
     FIGS. 4A and 4B 
     In contrast to FIG. 2A, the connection web  10  is arranged vertically. The two apertures  14  lie on the longitudinal axis A, while the screw holes  12  are spaced apart symmetrically from the longitudinal axis A. In the illustrative embodiment shown, the plate struts  20  with the adjoining areas of members  30  lie so far apart that once again a guide slot  40  is obtained which is extended by the gap  41 . The retainer  100  can thus be positioned along the entire length of the guide slot  40  and adjoining gap  41 . 
     FIGS.  5 A and SB 
     As is shown here, the connection web  10  can also be given a kidney-shaped configuration. The two screw holes  12  located therein are once again spaced apart symmetrically from the longitudinal axis A; an aperture  14  lies on the longitudinal axis A. Otherwise, this embodiment is identical to the previous embodiment. 
     FIGS. 6A and 6B 
     In this alternative embodiment, the kidney-shaped connection web  10  on the bone plate  1  has been made narrower, apertures  14  have been completely omitted, and a pair of holed members  31 ′ have been mounted in front of the screw holes  12  in the connection web  10 , symmetrical with the longitudinal axis A. The additional holed members  31 ′ extend the possibilities of securing the bone plate  1  and thus also of setting different rigidities of the bone plate  1 . At one end, each additional holed member  31 ′ adjoins one of the plate struts  20 , and at the other end each holed member  31 ′ has a transition web  33 ′ which adjoins the connection web  10  in alignment with the plate strut  20 . With sufficient distance transverse to the longitudinal axis A between the holed members  31 ′, so that the screw shank  123  of the locking screw  120  can pass through the interspace between the pair of holed members  31 ′ and if appropriate also through the interspace between the screw holes  12 , a gap  41 ′ is also obtained at the side of the connection web  10 , which gap  41 ′ extends the guide slot  40  in this direction as far as the connection web  10 . Bone plate  1  and retainer  100  can now be displaced relative to each other along the length of the guide slot  40  and the extensions via the gaps  41 ,  41 ′ at both ends. The retainer  100  is shown in its position in the gap  41  within the areas of members  30 , but the bone plate  1  can also be fixed with the locking screw  120  sitting in the guide slot  40  or in the gap  41 ′. As in all thee previous representations, an unnecessary pair of holed members  31  and transition webs  33  are divided off from the areas of members  30  of the bone plate  1 . 
     FIGS. 7A and 7C through  7 E 
     The bone plate  1  and the retainer  100  correspond to the embodiment according to FIGS. 1A and 1D. A strip-like fixing plate  200  is provided to increase the rigidity of the screwed-on bone plate  1  after removing the temporarily fitted retainer  100 . The fixing plate  200  has screw holes  232  which are congruent with respect to a pair of screw holes  32  arranged on both sides of the longitudinal axis A of the bone plate  1 . On the underside of the fixing plate  200  directed toward the bone plate  1 , depressions  201  are arranged around the outlet of the two screw holes  232 , into which depressions  201  the pair of holed members  31  of the bone plate  1  come to lie. 
     FIG. 7B 
     The fixing plate  200  can be attached to the screwed bone plate  1  while the retainer  100  is still fitted. The attached fixing plate  200  spans, underneath it, the two holed members  31  lying on both sides of the longitudinal axis A, and the turned-in bone screws  2  sit with their heads on the upper side of the fixing plate  200 , while the shanks of the bone screws  2  penetrate the screw holes  232  in the fixing plate  200  and also the screw holes  32  in the holed members  31  of the bone plate  1  and engage in the underlying bone compartment. As has been described above, in the screwed state the screw holes  12  in the connection web  10  are likewise fitted with bone screws  2  in order to screw this side of the bone plate  1  to the other bone compartment. In the example shown here, two pairs of holed members  31  were not needed and were divided off, each contiguous with the adjoining holed member  31 , together with transition webs  33 . 
     FIGS. 8A through 8C 
     Compared with the previous group of FIGS. 7A through 7E, the fixing plate  200  is now triangular and, in the third corner, which lies on the longitudinal axis A, it has a further screw hole  232  in addition to the two screw holes  232  present in the strip-shaped fixing plate  200 . In order to be able to apply the fixing plate  200  correctly to the bone plate  1  in each of the three possible positions of rotation, depressions  201  are located on the underside of the fixing plate  200 , at the outlets of all three screw holes  232 . In the assembled state, one pair of holed members  31  of the bone plate  1  lies with its screw holes  32  congruent, under the fixing plate  200 , with respect to the screw holes  232 , which are screwed by means of bone screws  2 . The third and as it were free screw hole  232  of the fixing plate  200  can also be used for inserting a bone screw  2 , which then engages directly in the underlying bone compartment. 
     FIGS. 9A through 90 
     The difference with this bone plate  1 , laterally open at one end and with a horizontal connection web  10 , is that the plate struts  20  originating at the connection web  10  end in an undulating area of members  30  and do not have any holed members  31 , and the guide slot  40  thus extends from the connection web  10  to the outlet at the free ends of the plate struts  20 . There are no changes to the connection web  10  or to the retainer  100 ; by contrast the fixing plate  200  is modified in conjunction with the modified ends of the plate struts  20 . Since holed members  31  with screw holes  32  have been omitted in this case at the free end of the plate struts  20 , the fixing plate  200  has, in addition to the previous stiffening function, the main function of allowing this end of the bone plate  1  to be screwed to the underlying bone compartment. 
     The free ends of both plate struts  20  have outwardly curving and systematically reseating bulges symmetrical with respect to the longitudinal axis A, so that on each plate strut  20  an area of members  30  is obtained comprising a plurality of strut members  35  of identical shape and lying in line. The fixing plate  200  has an approximately square configuration for this bone plate  1  and has two spaced-apart screw holes  232  lying on the longitudinal axis A. On the underside of the fixing plate  200 , complementary with the shape of the areas of members  30 , there are two depressions  201  which are likewise symmetrical with respect to the longitudinal axis A and which consequently extend in the direction of extent of the areas of members  30 . 
     In the screwed state, the fixing plate  20 C lies over the two areas of members  30 , the latter being partially embedded in the depressions  201 . By means of bone screws  2  which penetrate the screw holes  232  on the fixing plate  200  and the screw holes  12  on the connection web  10  of the bone plate  1 , the latter is screwed to both bone compartments. Excess strut members  35  which are not needed are cut off from the areas of members  30 . 
     FIGS. 10A through 10C 
     Here, the free ends of the plate struts  2 C are designed straight and without any area of members  30 , so that the guide slot  40  extends uniformly from the connection web  10  to the end of the plate struts  20 . The roundish fixing plate  200  has two spaced-apart screw holes  232  which lie on the longitudinal axis A and between which there are two apertures  214  symmetrical with respect to the longitudinal axis A. The apertures  214  have the same role as the apertures  14  in the bone plate  1 . On the underside of the fixing plate  200 , and congruent with respect to the extent of the plate struts  20 , there are two groove-like depressions  201  running parallel with the longitudinal axis A. A raised central web  202  thus remains between the depressions  201 , in the axial area of the screw holes  232 . The fixing plate  200  could be fitted on the plate struts  20  along the entire length of the latter, but in practice, because of the screwing of two bone compartments and the rigidity which is to be achieved, it is best to arrange the fixing plate  200  only near the ends of the plate struts  20 . In the assembled state, the plate struts  20  are partially embedded in the depressions  201 . 
     FIGS. 11A through 11C 
     The only difference from the previous group of FIGS. 10A through 10C is that the depressions  201  on the underside of the fixing plate  200  are not divided by a central web  202 , and instead the depression  201  extends continuously almost to the upper and lower edges of the fixing plate  200 . 
     FIGS. 12A through 12D 
     The bone plate  1  is closed laterally at both ends and has kidney-shaped connection webs  10  at both ends. The left-hand connection web  10  has two spaced-apart screw holes  12  symmetrical with respect to the longitudinal axis A, and, connected to these via transition webs  33 ′, a pair of holed members  31 ′. The right-hand side and the left-hand side of the bone plate  1  are identical, i.e. symmetrical with respect to a vertical axis B perpendicular to the longitudinal axis A. In order to maintain the system, an area of members  30  on the right-hand side is defined in each case by two pairs of holed members  31  which are in turn connected to each other via transition webs  33 . The connection web  10  is situated on the outside. Extending between the holed members  31 ′ and the area of members  30  is the guide slot  40  which is adjoined to the right and left by the gaps  41 ,  41 ′, which are narrow, so that there is no widening of the guide slot  40 . The guide slot  40  is flanked by the plate struts  20  which extend parallel with the longitudinal axis A and which connect the area of members  30  to the forward holed members  31 ′. The plate struts  20  have a lesser thickness than the other parts of the bone plate  1 . This favors bending of the bone plate  1 , from the flat configuration of the bone plate  1 , adapted to the specific bone geometry. There is a higher degree of rigidity in the plane, as it were across the edge. The greater material thickness outside the plate struts  20  gives the bone screw  2  fitted into the screw holes  12 ,  32  a more stable fit. The retainer  100  is positioned inside the guide slot  40 . 
     FIGS. 13A and 13B 
     The only difference from the previous group of FIGS. 12A through 12D is that the area of members  30  now has a third pair of holed members  31 , and the holed members  31  and the screw holes  12  with the forward holed members  31 ′ are at a greater distance from the longitudinal axis A, so that widened gaps  41 ,  41 ′ are obtained which result in lengthening of the guide slot  40  at both ends. The retainer  100  is positioned inside the gap  41 , and the outer unnecessary pair of holed members  31  is cut away together with connection web  10  and transition webs  33 . 
     FIGS. 14 and 14B 
     Compared with FIG. 12A, the bone plate  1  shown here is reduced at both ends by the pair of forward holed members  31 ′ and a pair of holed members  31  from the area of members  30 . The guide slot  40  (the retainer  100  can consequently only be positioned here) accordingly extends only between the area of members  30  and the screw holes  12 . This bone plate  1  is of symmetrical construction with respect to the longitudinal axis A and the vertical axis  3 . 
     FIGS. 15A and 15B 
     In contrast to preceding FIGS. 14A and 14B, the connection webs  10  are now no longer kidney-shaped, and instead they represent the narrow sines or a bone plate  1  having the overall shape of a parallelogram. The two screw holes  12 ,  32  in each case thus no longer lie on two common theoretical verticals, and each upper screw hole  12 ,  32  is offset to the right. The guide slot  40  in which the retainer  100  is fitted extends once again between the connection web  10  and the area of members  30 . 
     FIGS. 16A,  16 C and  16 D 
     A bone plate  1  closed laterally at both ends, with two outer horizontal connection webs  10 , and a laterally attachable retainer  100 ′ are shown. The bone plate  1  is constructed symmetrically with respect to longitudinal axis A and vertical axis B. The connection webs  10  correspond to the embodiments according to FIG. 1A. A guide slot  40  has been dispensed with here, since the retainer  100 ′ has the bore  111 ′ for introducing the locking screw  120  toward the outside. To increase the rigidity of the bone plate  1 , but while maintaining the bending capacity for the purpose of adaptation to the particular bone geometry, transverse reinforcement struts  21  are provided in addition to the parallel plate struts  20 . The reinforcement struts  21  extend between the two connection webs  10 . 
     The shackle-shaped retainer  100 ′ is designed to engage over the bone plate  1  parallel with he vertical axis B and has the bore  111 ′ on the lower periphery. The notches  114 ′ let in on both sides are complementary to the position of the screw holes  12  so that the retainer  100 ′ can stand near a screw hole  12  and also between two screw holes  12 , without colliding with the bone screws  2  which are to be screwed in and have raised screw heads. On its underside, the retainer  100 ′ has, above the bore  111 ′, a groove  101 ′, in the width of the bone plate  1  in order to partially enclose the latter from the top. The retainer  100 ′ and the locking screw  120  (see FIG. 1A) can be two separate parts or car. form an inseparable unit. A conventional bone screw  2  can be used as locking screw  120 . 
     FIG. 16B 
     In the assembled state, the bore  111 ′ of the retainer  100 ′ lies laterally outside the bone plate  1 , so that the associated locking screw  120  can be screwed into the underlying bone compartment, but not tightened at first. A still loosely screwed-on retainer  100 ′ once again permits the relative movements for fine adjustment of both bone compartments relative to each other. In this fine adjustment, the retainer  100 ′ can be swivelled about the axis of the locking screw  120  and can be moved along the longitudinal axis A on the bone plate  1 . After said fine adjustment, the bone plate  1  is screwed in fully and the retainer  100 ′ is then removed. 
     FIGS. 17A and 17B 
     In this alternative, compared with FIGS. 1D and 1E, the central through-bore  111  in the circular disk  110  of the retainer  100  is not provided with an internal thread. However, in order to prevent the disk  110  from falling from the locking screw  120 , the bore  111  on the disk  110  is only minimally larger than the core diameter of the screw shank  123  and at any rate smaller than the external diameter of the screw shank  123 . To achieve this, it is possible to caulk or flange an initial larger bore  111 , so that the screw shank  123  can be passed through first. The locking screw  120  sitting in the disk  110  thus remains rotatable and the disk  110  is secured against falling off. 
     FIGS. 18A and 18B 
     In contrast to the preceding embodiment, the disk  110  has, on its underside, four locking catches  115  offset through 90° on the outer edge. In the assembled state, two opposite locking catches  115  engage around the plate struts  20  of a bone plate  1  positioned under the retainer  100  parallel with the vertical axis B. The other two locking catches  115  lying on the longitudinal axis A penetrate into the guide slot  40 . 
     FIGS. 19A and 19B 
     In contrast to the embodiment according to 
     FIGS. 17A and 17B, the disk  110  is curved with a concave contour in relation to the point of the locking screw  120  fitted in the disk  110 . In the assembled state, the curve gives a certain spring tensioning which can be advantageous for better contact pressure of the disk on the underlying bone plate  1 . 
     FIGS. 20A and 20B 
     The retainer  100  could also be made in one piece, with a disk part  110  sitting under the screw head  122 . When the screw part  120  turns, the disk part  110  then always turns with it. 
     FIGS. 21A and 21B 
     The retainer  100  designed as one piece now has a curved disk part  110  according to FIGS.  19 A and