GUIDE INSTRUMENT

Abstract: The present invention relates to a guide instrument which is adapted for use at operations for fixation of bone fragments at bone fractures, preferably femoral neck fractures, whereby the bone fragments are intended to be fixed relative to each other by means of at least two bone screws, whereby the guide instrument (1) is adapted for guiding a first and a second drill steel which are adapted for drilling passages in the bone fragments for the bone screws. The guide instrument (1) is designed to permit guiding of the drill steels, driving through of threaded front portions of the bone screws and guiding of uptapped or unthreaded rear portions of said bone screws.

Description: Guide instrument. The present invention relates to a guide instrument which is adapted for use at operations for fixation of bone fragments at bone fractures, preferably femoral neck fractures, whereby the bone fragments are intended to be fixed relative to each other by means of at least two bone screws, whereby the guide instrument is adapted for guiding a first and a second drill steel which are adapted for drilling passages in the bone fragments for the bone screws. At operations for fixation of bone fragments at frac¬ tures, it is important that the bone screws get exact pre¬ determined positions relative to the bone fragments and to each other. For this purpose, bone screws are used having such through center-passages that they can be threaded onto wire-like guide means (so called guide wires) . These wire-like guide means are drilled into the bone fragments during TV-roentgen control to exact positions, whereafter the bone screws are threaded onto the wire-like guide means so that said guide means guide said bone screws when said screws are driven into the bone fragments. Since the wire-like guide means must have room in narrow center passages in the bone screws, they must be thin. This means that the guide means bend easy when they during drilling e.g. come across hard bone after having passed through softer cartilage portions. A wire- -like guide means bent in this way during drilling, may lead to that the bone screw is difficult to advance, fasten or tighten and that it is guided to a wrong posi¬ tion. To remedy this problem by redrilling is time con- suming and the redrilling can be complicated by the pas¬ sage already drilled. The use of wire-like guide means also requires can- nulated bone screws, i.e. bone screws having longitudi¬ nal center passages, which means that the depth of the threads of the bone screws must be limited. The object of the present invention is to remedy or eliminate this problem and this is arrived at according to the invention by means of a guide instrument having pr marily the characterizing features of subsequent claim 1. Since the guide instrument has said characterizing features, it renders it possible to carry through the operation without the use of wire-like guide means and thereby, avoid the problem that such guide means can complicate driving or tightening of the bone screw or guide said bone screw wrong during said driving or said tightening thereof. Furthermore, it is achieved, inter alia, that one can use bone screws without cannulae, i.e. without longitudinal center holes, which means that the threads of the screws can be made deeper and that dril- ling moments are eliminated during drilling. The invention will be further described below with reference to the accompanying drawings, wherein fig. 1 is a section through a guide instrument ac¬ cording to the invention; fig. 2 is a side view of a drill steel which is used together with the guide instrument of fig. 1 and which after drilling a passage in the bone fragment to be fixed, is retained in said bone fragment; fig. 3 is a side view of the guide instrument of fig. 1 located on said drill steel in a guide position relative to said bone fragment; fig. 4 is a side view of the guide instrument of fig. 1 located in the guide position on said drill steel and while guiding of a second drill steel during dril- ling of a second bone passage; fig. 5 is a side view of the guide instrument of fig. 1 located in the guide position on said drill steel, whereby the second drill steel has been removed after drilling a second bone passage; fig. 6 is a side view of the guide instrument of fig. 1 located in the guide position on said drill steel and while driving or tightening a bone screw; fig. 7 is a side view of the guide instrument of fig. 1 located in said guide position on a driving means by means of which a bone screw is advanced or fastened; fig. 8 is a side view of the guide instrument of fig. 1 located in said guide position on said driving means and during fastening or tightening of a bone screw in a first bone passage; fig. 9 is a side view of the two bone screws driven to their fixed positions in the bone fragments; fig. 10 is a side view of a driving means connected with a bone screw and provided with a handle for unscre¬ wing the bone screw; and fig. 11 is a side view of a handle located on a bone screw for unscrewing thereof from the bone fragment. The guide instrument 1 illustrated in the drawings is adapted to be used at operations for fixation of bone fragments 2, 3 at bone fractures, preferably femoral neck fractures. Hereby, the femoral neck 4 (collum) illustra¬ ted in the drawings has a fracture 5 and said bone frag- ment 2 consists of the bone on one side of the fracture 5, while the bone fragment 3 on the other side of the fracture 5 is the femoral head (caput) . The bone fragments 2, 3 are fixed relative to each other by means of bone screws 6, 7 and each such bone screw 6 and 7 has a threaded front portion 8 with exter¬ nal threads 9 and a rear portion 10 without threads. Each bone screw 6, 7 is designed so that the outer diameter Dl of the external threads 9 is greater than the outer diameter D2 of the unthreaded or untapped por- tion 10 (see e.g. fig. 6) . The outer diameter D2 of the unthreaded portion 10 of every bone screw 6, 7 may e.g. be 6 mm or about 6 mm and the outer diameter Dl of the external threads 9 of each bone screw 6, 7 may be 8 mm or about 8 mm. Furthermore, each bone screw 6, 7 may have a total length of about 125 mm and the threaded front portion 8 thereof a length of about 20 mm. Each bone screw 6, 7 has a point 11 with drilling properties and at the rear a transverse groove 12 for con¬ nection of a drive means 13 or 14. Each bone screw 6, 7 may also have a rear opening 15 with internal threads for fastening of a screw retainer 16 (see fig. 11) which can be used for unscrewing the bone screw 6 or 7. The bone screws 6, 7 are preferably solid in that respect that they have no longitudinal center passages extending therethrough (which has been necessary at those prior art bone screws which have been used in connection with wire-like guide means) . For carrying through the operation, one also uses a first drill steel 17 for drilling a first bone passage 18 in the bone fragments 2, 3 for one of the bone screws 6, 7 and a second drill steel 19 for drilling a second bone passage 20 in said bone fragments 2, 3 for another of said bone screws 6, 7. Each drill steel 17, 19 pre¬ ferably has a point 21 with a smaller diameter D3 than the diameter D4 of the portions 22 of each drill steel 17, 19 located behind said point or tip 21. The diameter D3 of the point 21 is preferably about half as large as the diameter D4 of said portions 22. The diameter D3 may e.g. be 3,5 mm and the diameter D4 6,0 mm. The total length of said drill steel 17 and/or 19 can be about 210 mm and the length of said point 21 about 30 mm. Pre- ferably, the first drill steel 17 can be somewhat shorter than the second drill steel 19. In the guide instrument 1 there is drilled a first and a second passage 23 and 24, which extend in parallel with each other and which are open towards a rear side 25 as well as a front side 26 of the guide instrument 1. These passages 23, 24 are adapted to said drill steels 17, 19 so that said passages 23, 24 are fit for said drill steels 17, 19 and vice versa. Thus, the diameter D5 of each passage 23, 24 is only somewhat greater, pre- ferably 0,1 - 0,4 mm greater that the largest diameters D4 of each drill steel 17 and 19. Thus, the diameter D5 of each passage 23, 24 may be 6,2 mm. In said passages 23, 24 in the guide instrument 1, internal threads 27 and 28 respectively, are cut and these internal threads 27, 28 are adapted to the exter¬ nal threads 9 on the threaded front portions 8 of the bone screws 6, 7 so that said portions 8 can be driven through the respective passage 23, 24. The internal threads 27, 28 are preferably designed to that they guide the threaded front portion 8 of the bone screw 6, 7 driven through the respective passage 23, 24. The largest diameter D6 of the internal threads 27, 28 is preferably only somewhat greater, e.g. 0,4 - 1,0 mm greater than the outer diameter Dl of the external threads 9 on the threaded portions 8 of the bone screws 6, 7. In the present embodiment, the diameter D6 may be e.g. 9,0 mm. The first and second passages 23, 24 preferably have straight guide surfaces 29 in the longitudinal direction of said passages for guiding the drill steels 17, 19 and the untapped or unthreaded portions 10 of the bone screws 6, 7. These guide surfaces 29 preferably have a length L which is substantially greater, e.g. three times greater than the width B of that part of the internal threads 27, 28 which separates said guide surfaces 29 from each other. The guide surfaces 29 however, do not necessarily have to be straight, but may have an arcuate shape which is adap¬ ted to an arcuate shape between the external threads 9 of the bone screws 6, 7. Each internal thread 27 and 28 respectively, runs preferably along a helical line 30 which extends around each passage 23 and 24 respectively, with at least four turns. Preferably, only one internal thread 27, 28 runs around each passage 23, 24 from the inlet of said passage to the outlet thereof as is shown in fig. 1. Thus, in summary, it is apparent from the guide instrument 1 described above that the diameter D5 of each passage 23, 24 is adapted to the diameter D4 of each drill steel 17, 19 as well as to the diameter D2 of the untapped rear portion 10 of each bone screw 6, 7. Thus, it is also apparent that the diameter D6 of the internal threads 27, 28 provided along each passage 23, 24 is adapted to the diameter Dl of the threaded front portion 8 of each bone screw 6, 7. Hereby, the guide instrument 1 permits: a) that the drill steels 17, 19 are guided by the bone passages 18, 20 during drilling; b) that it can be fixedly attached to the drill steels 17, 19 before fastening or advancing the bone screws 6, 7; c) that the bone screws 6, 7 can be driven there- through for fastening in the bone fragments 2, 3; and d) that the untapped rear portions 10 of the bone screws 6, 7 are guided when the threaded front portion 8 of each bone screw 6, 7 is driven into each bone fragment 2, 3. The operation with the guide instrument 1 begins by drilling the first bone passage 18 (see fig. 2) along the femoral neck 4 by means of the first drill steel 17. The drill steel 17 is provided with position marks 31 and a measuring sleeve 32 is threaded onto said drill steel and brought to engage the bone fragment 2. When a mark 31 during drilling is situated at the rear edge of the measuring sleeve 32, it is possible to determine how far into the bone fragment 3 the drill steel 17 has pe- netrated and to stop drilling at the correct depth. When the first bone passage 18 has been drilled, the first drill steel 17 remains seated therein but the measu¬ ring sleeve 32 is removed from the drill steel 17. There¬ after, the guide instrument 1 is threaded onto the first drill steel 17 and fixedly attached to the bone fragment 2 in a predetermined position e.g. by bringing a fixation tip 33 into engagement with said bone fragment 2. When the guide instrument 1 has attained said pre¬ determined position relative to the bone fragment 2 and is retained therein by the first drill steel 17 and the fixation tip 33, its second passage 24 is used for gui- ding the second drill steel 19 by means of which the second bone passage 20 is drilled (see fig. 4) . The bore depth of this second bone passage 20 is determined by com¬ paring the position marks 31 on the second drill steel 19 with the rear or backside 25 of the guide instrument 1. When the drilling of the second bone passage 20 is finished, the second drill steel 19 is removed and the guide instrument 1 is maintained in its guiding position by the first drill steel 17 and the fixation tip 33 (fig. 5) . If cortex or eventually any other part of the bone fragment 2 is hard, threads for the bone screw 6 can be cut in the bone passage 20 by means of a manually pivo- table thread tap (not shown) which is driven through the second passage 24. Thereafter, the drive means 13 is connected with the bone screw 6 by inserting a trans- verse tongue 34 on said drive means 13 into the trans¬ verse groove 12 of the bone screw 6 and then, the bone screw 6 is driven by means of the drive means 13 through the second passage 24 of the guide instrument 1. Hereby, the threads 28 in the second passage 24 guide the threa- ded portion 8 of the bone screw 6 so that it is correct¬ ly oriented relative to the drilled second bone passage 20 when said threaded portion 8 leaves the second bone passage 20. When the bone screw 6 is driven so far into the second bone passage 20 that the threaded portion 8 thereof has left the guide instrument 1, the untapped or unthreaded portion 10 of the bone screw 6 is guided by the guide surfaces 29 of the second passage 24 so that said bone screw 6 is directed in parallel with the second bone passage 20 until said bone screw 6 is screwed home or tightened therein (fig. 6) . This can be deter¬ mined by driving in the bone screw 6 so far that a posi¬ tion mark 35 on the drive means 13 (or a front position mark of two position marks 35, 36 on the drive means 13) is located at the backside 25 of the guide instru¬ ment 1. Then, the drive means 13 is left on the bone screw 6 so that said screw through its adaptation to the se¬ cond passage 24 in the guide instrument 1, can retain said instrument in guide position along with its fixa¬ tion tip 33 when the first drill steel 17 is removed from the first bone passage 18 and from the first pas- sage 23 in the guide instrument 1 (fig. 7) . If cortex or eventually any other part of the bone fragment 2 is hard, threads for the bone screw 7 may then be cut by means of the abovementioned, manually pivotable thread tap, which in this case is driven through the first passage 23. Now, a transverse tongue 34 on the drive means 14 is connected with the transverse groove 12 of the bone screw 7 and said bone screw 7 is driven through the first passage 23 until it is screwed home or tightened in the first bone passage 18 (fig. 8) , which is the case when the position mark 35 on the drive means 14 is situated at the backside 25 of the guide instrument 1. During faste¬ ning or advancement, the threaded portion 8 of the bone screw 7 will be guided by the threads 27 in the first passage 23 and the untapped portion 10 of said bone screw 7 guided by the guide surfaces 29 in said first passage 23, so that said bone screw 7 is guided in paral¬ lel with the first bone passage 18 along the entire dri¬ ving distance thereof. Thereby, both bone screws 6, 7 have been driven or advanced under guidance to their intended positions in the femoral neck 4 and the bone fragments 2, 3 have been fixed by means thereof. This means that the drive means 13, 14 and the guide instrument 1 can be removed (fig. 9) . For pivoting or rotating the drive means 13, 14, a separate tommy bar 37 is preferably used. For being able to connect said tommy bar with the drive means 13, 14, each of said drive means 13, 14 is provided at the rear with two planar, bevelled surfaces, by means of which an oval end portion 38 is obtained. The tommy bar 37 has an oval end opening 39 into which the end portion 38 fits, so that said tommy bar 37 can be connected with each drive means 13, 14 for rotation thereof. The tommy bar 37 is preferably also positionable at an arm 40 on the guide instrument 1 and can thereby be used as a handle therefor. When the femoral neck 4 has healed, the bone screws 6, 7 can be removed by unscrewing them from their bone passages 18, 20. This can be done by connecting a drive means 13, 14 with the bone screw 6, 7, connect the tommy bar 37 with the drive means 13, 14 and then pivot or rotate the bone screw 6, 7 in an inscrewing direction (fig. 10) . Instead of using a drive means 13, 14 for unscrewing the bone screws 6, 7, one can use the tommy bar 37 to¬ gether with the screw retainer 16, which has a threaded end portion 41. This end portion can be fastened or dri¬ ven into the threaded rear opening 15 of the bone screw 6, 7 for connecting the tommy bar 37 with the bone screw 6, 7 so that said bone screw can be unscrewed by means of said tommy bar 37 (fig. 11) . The invention is not limited to the embodiment de¬ scribed above and shown in the drawings, but may vary within the scope of the following claims. Thus, the guide instrument 1 can be used at other bone fractures than femoral neck fractures, the bone screws 6, 7 can be of another type than shown, the guide instrument 1 can be designed for guiding more than two bone screws, the bone screws 6, 7 and/or drill steels 17, 19 and/or passages 23, 24 can have other diameters than those men¬ tioned, the drill steels 17, 19 can be designed other- wise than described (the drill steels 17, 19 may e.g. be designed without narrow points 21) , at least one thread 27, 28 can be provided around each passage 23, 24 and these threads 27, 28 can have another shape than shown if necessary for fitting in with the external threads 9 of the bone screws 6, 7 and the guide instrument 1 can have one or more other fixing portions than a fixing tip 33 of the illustrated design. Instead of the removing members illustrated in fig. 10 and 11 for removing or withdrawing the bone screws 6, 7, removing members of other types may be used.

Claims: Claims : 1. Guide instrument which is adapted for use at ope¬ rations for fixation of bone fragments at bone fractures, preferably femoral neck fractures, whereby the bone frag¬ ments (2, 3) are intended to be fixed relative to each other by means of at least two bone screws (6, 7), where¬ by the guide instrument (1) is adapted for guiding a first and a second drill steel (17, 19) which are adap¬ ted for drilling passages (18, 20) in the bone fragments (2, 3) for the bone screws (6, 7), c h a r a c t e r i - z e d i n that the guide instrument (1) has a first and a second passage (23, 24) and internal threads (27, 28) provided along each such passage (23, 24) , that each bone screw (6, 7) has a threaded front portion (8) with external threads (9) , the diameter (Dl) of which is grea- ter than the diameter (D2) of an untapped or unthreaded rear portion (10) of the bone screw (6, 7), that each passage (23, 24) has a diameter (D5) which is adapted to the diameter (D4) of each drill steel (17, 19) as well as the diameter (D2) of the untapped or unthreaded rear por- tion (10) of each bone screw (6, 7), and that the inter¬ nal threads (27, 28) provided along each passage (23, 24) have a diameter (D6) which is adapted to the diameter (Dl) of the external threads (9) on the threaded portion (8) of each bone screw (6, 7) . 2. Guide instrument according to claim 1, c h a ¬ r a c t e r i z e d i n that the internal threads (27, 28) are designed so that the outer threads (9) on the threaded portion (8) of each bone screw (6, 7) are gui¬ ded by the internal threads (27, 28) in the guide instru- ment (1) when each bone screw (6, 7) is driven or advan¬ ced through the respective passage (23, 24) in the guide instrument (1) . 3. Guide instrument according to claim 1 or 2, c h a r a c t e r i z e d i n that a largest diameter (D6) of the threads (27, 28) in the guide instrument (1) is only somewhat greater, preferably 0,4 - 1,0 mm greater, than the outer diameter (Dl) of the external threads (9) on the threaded portions (8) of the bone screws (6, 7) . 4. Guide instrument according to any preceding claim, c h a r a c t e r i z e d i n that the diameter (D5) of the first and second passages (23, 24) provided in the guide instrument (1) is only somewhat greater, pre¬ ferably 0,1 - 0,4 mm greater, than a largest diameter (D4) on the first and second drill steel (17, 19) and also only somewhat greater, preferably 0,1 - 0,4 mm grea¬ ter, than a diameter (D2) on the untapped or unthreaded portions (10) of the bone screws (6, 7) . 5. Guide instrument according to any preceding claim, c h a r a c t e r i z e d i n that the first and se- cond passages (23, 24) in the guide instrument (1) have in the longitudinal direction of said passages (23, 24) straight guide surfaces (29) for guiding the first and second drill steels (17, 19) and for guiding untapped or unthreaded portions (10) of the bone screws (6, 7) . 6. Guide instrument according to claim 5, c h a ¬ r a c t e r i z e d i n that the guide surfaces (29) has a length (L) which is substantially greater, prefer¬ ably three times greater, than the width (B) of that part of the threads (27, 28) which separates the guide surfaces (29) from each other. 7. Guide instrument according to any preceding claim, c h a r a c t e r i z e d i n that each internal thread (27, 28) in the guide instrument (1) runs along a helical line (30) which extends in at least four turns around res- pective passage (23, 24) in the guide instrument (1). 8. Guide instrument according to any preceding claim, c h a r a c t e r i z e d i n that each drill steel (17, 19) has a point (21) with a smaller diameter (D3) than the diameter (D4) of the portions (22) of the drill steel (17, 19) located behind said point (21) and that the diameter (D3) of the point (21) preferably is about half as large as the diameter (D4) of said portions (22) located behind said point (21) . 9. Guide instrument according to any preceding claim, c h a r a c t e r i z e d i n that each drill steel (17, 19) has position marks (31) for determining how far in the drill steel (17, 19) has penetrated, whereby pre¬ ferably a measuring sleeve (32) is threaded onto each drill steel (17, 19) against which measuring sleeve (32) one can compare the position of the marks (31) for determi¬ ning the depth of penetration of the drill steel (17, 19). 10. Guide instrument according to any preceding claim, c h a r a c t e r i z e d i n that the guide instru¬ ment comprises a fixation tip (33) which is adapted to be brought into engagement with the bone fragment (2) in which the inlet to a bone passage (18) is located and which is adapted to fix the guide instrument (1) in a certain position relative to said bone fragment (2) . 11. Guide instrument according to any preceding claim, c h a r a c t e r i z e d i n that a first passage (23) of the two passages (23, 24) in the guide instrument (1) permits location of said guide instrument on the first drill steel (17) when said drill steel remains seated in said first, thereby drilled bone passage (18) , while the second passage (24) in the guide instrument (1) permits guidance of the second drill steel (19) during drilling of the second bone passage (20) when the guide instru¬ ment (1) is located on the first drill steel (17) , and that said first and second passages (23, 24) in the guide instrument (1) are designed for guiding the untapped or unthreaded portion (10) of each bone screw (6, 7) when said bone screw through said first and second passage (23, 24) in the guide instrument (1) is driven or advan¬ ced into the respective bone passage (18, 20) . 12. Guide instrument according to any preceding claim, c h a r a c t e r i z e d i n that one of the bone screws (6, 7) through the second passage (24) in the guide instrument (1) is driven into the second bone pas¬ sage (20) while the guide instrument (1) is located on the first drill steel (17) when said drill steel remains seated in the first bone passage (18) , and that after removal of the first drill steel (17) from the first bone passage (18) and from the first passage (23) in the guide instrument (1) , a bone screw (7) is driven into said first bone passage (18) through said first passage (23) . 13. Guide instrument according to any preceding claim, c h a r a c t e r i z e d i n that at least one drive means (13 and/or 14) for driving or fastening at least one bone of the screws (6 and/or 7) is adapted to at least one of the passages (23 and/or 24) in the guide instrument (1) , so that the drive means (13 and/or 14) can be inserted into and pivoted or rotated relative to said passage (23 and/or 24) , and that said drive means (13 and/or 14) has at least one position mark (35 and/or 36) which is adapted to mark that the bone screw (6 and/ /or 7) is advanced or driven sufficiently far into the bone passage (18 and/or 20) when said bone screw (6 and/ /or 7) is situated at a backside (25) of the guide instru- ment (1) . 14. Guide instrument according to any preceding claim, c h a r a c t e r i z e d i n that a drive means (13) for driving or fastening at least one of the bone screws (6, 7) is adapted to at least the second passage (24) in the guide instrument (1) so that said drive means (13) can be used for retaining the guide instrument (1) in a guiding position for guiding a bone screw (7) during dri¬ ving thereof into the first bone passage (18) when another bone screw (6) has been driven into or fastened in the second bone passage (20) and the connection of the drive means (13) therefor with said latter bone screw (6) is maintained. 15. Guide instrument according to any preceding claim, c h a r a c t e r i z e d i n that the bone screws (6, 7) used at the guide instrument (1) are solidly designed in that respect that they lack center passages extending in the longitudinal direction thereof. 16. Guide instrument according to any preceding claim, c h a r a c t e r i z e d i n that a tommy bar (37) for unscrewing the bone screw (6, 7) from the bone pas¬ sage (18, 20) can be connected with said bone screw (6, 7) either through a drive means (13, 14) or through a screw retainer (16) which can be mounted on the tommy bar (37) . 17. Guide instrument according to claim 16, c h a ¬ r a c t e r i z e d i n that the tommy bar (37) is provided as a handle on the guide instrument (1) .

Inventors: HANSSON LARS JOHAN HENRIK, HANSSON, LARS, JOHAN, HENRIK
Applicants: HANSSON LARS JOHAN HENRIK, HANSSON, LARS, JOHAN, HENRIK
Application year: 1995
Main classification: A61B17
IPC codes: A61B17