Device for fixation of bone fragments at bone fractures

Background to the invention

The present invention relates to a device for fixation of bone fragments at bone fractures. The device comprises at least two fixation means and a securing plate.

After a bone fracture such as a femur neck fracture, the bone fragments at the fracture need fixing. This is currently done by using suitable fixation means, e.g. bone nails or bone screws.

After the completion of surgery, even as early as when the effects of the anaesthesia have passed and the patient is still confined to bed, but above all when the patient is beginning to be up and walk and stand on the leg, the fixed bone fragments and the fixation means are subject to large forces, particularly to rotational forces downwards and rearwards.

The fixation means alone are often insufficient to counteract these rotational forces and the bone fragments have to be used to help to lock the fracture. If this is not done and the bone fragments are caused to rotate relative to one another by said forces, the result will be shifting of the angular positions of the fixation means to such an extent that they risk substantially crossing one another, thereby keeping the fracture parted and preventing healing.

Brief summary of the invention

The object of the present invention is accordingly to prevent or counteract this and therefore configure the device in such a way that the fixation means are not allowed to rotate and cross one another. To this end, with the device according to the invention, each fixation means has a first fixing portion for fixing the fixation means in an inner bone fragment, a second fixing portion for locking the fixation means to the securing plate disposed on the outside of an outer bone fragment and allowing movement of the outer bone fragment relative to it, so that the fixation means are prevented from changing their angular position relative to the securing plate and relative to one another, and a middle portion which is situated between the fixing portions and runs through the outer bone fragment, along which middle portion the outer bone fragment can slide inwards towards the inner bone fragment in which the fixation means is fixed.

The result of the fixation means being thus fixed to the inner bone fragment and to the securing plate while the outer bone fragment can move towards the inner bone fragment and, in so doing, be guided by the fixation means is that the bone fragments are kept fixed but compression of the bone fragments is nevertheless allowed, the device and the bone

fragments thus being able to absorb the aforesaid rotational forces and control them so that no re-dislocation occurs The fixing of the fixation means in the inner bone fragment and the locking of the fixation means to the securing plate also reduce the risk of screws loosening in cases where the fixation means take the form of bone screws Other objects and advantages of the invention will be apparent to one skilled in the art who examines the attached drawings and the following detailed description of preferred embodiments of and method for fitting the device according to the invention

Brief description of the drawings Fig 1 illustrates in side view upper portions of a femur with a femur neck fracture and a device according to the present invention, showing a securing plate and a first guide sleeve usable in conjunction with said plate for guiding a guide wire drilled into bone fragments which are to be fixed on their respective sides of the fracture,

Fig 2 illustrates in side view the removal of the guide sleeve for the guide wire, Fig 3 illustrates in side view a second guide sleeve for guiding a drill, and a gauge rod for determining how long the fixation means should be,

Fig 4 depicts in side view the second guide sleeve after the removal of the gauge rod,

Fig 5 illustrates in side view the insertion in the second guide sleeve of a drill, provided with a duct, for drilling a hole for a fixation means in the form of a bone screw and for drilling the hole for said bone screw in the bone fragments,

Fig 6 depicts in side view the application of a further second guide sleeve for guiding a drill in the securing plate,

Fig 7 illustrates in side view the further second guide sleeve after the application of a drill with a conical tip therein and the drilling of a second hole for a bone screw in the bone fragments,

Fig 8 illustrates in side view the removal of the further second guide sleeve and the respective drill,

Fig 9 depicts in side view the application of a fixation means in the form of a bone screw in the securing plate for further screwing of the bone screw into the second hole in the bone fragments,

Fig 10 illustrates in side view the bone screw when it has been screwed into the bone fragments,

Fig 1 1 depicts in side view a second bone screw screwed into the first hole in the bone fragments after the guide wire, drill and guide sleeve have been removed,

Fig 12 illustrates the securing plate with bone screws screwed firmly into the plate at an alternative position, and

lastly Figs 13 and 14 depict front views of two different alternative versions of the securing plate

Detailed description of preferred embodiments of the invention The drawings illustrate one of several different methods for fixation of a fracture at the neck of a femur by means of a device according to the present invention As previously indicated, Fig 1 depicts upper portions of a femur with a femur neck fracture 1 , and an outer bone fragment 2 and an inner bone fragment 3 on their respective sides of the fracture A securing plate 4 which forms part of the device according to the present invention for fixation means in the form of bone screws or bone nails, in the version depicted two substantially parallel bone screws 5, 6 (see Figs 9-11 ) for fixing the bone fragments 2, 3, is disposed on the outside of the outer bone fragment 2 The respective bone screws 5, 6 are preferably integral The securing plate 4 is so arranged that it allows movement of the outer bone fragment 2 relative to it, i e it is not connected to the outer bone fragment nor arranged in some other way whereby it would have moved with the latter upon compression of the bone fragments 2, 3 In the femur, a guide wire 7 with a diameter of preferably about 2 4 mm has been drilled through the outer bone fragment 2 and into the inner bone fragment 3 under radioscopy and with guidance by a guide sleeve 8 with an inside diameter of preferably about 2 5 mm The guide wire 7 is intended to guide a drill for drilling a hole for the bone screw 5 in the bone fragments 2, 3 According to the invention, the guide sleeve 8 for the guide wire 7 is applied in the securing plate 4, by preferably being screwed firmly in a threaded hole 9 running through the plate, and having for the purpose an externally threaded forward end portion 10 (see Fig 2 depicting the guide sleeve 8 when it has been unscrewed from the plate 4) This externally threaded forward end portion 10 does of course have an outside diameter corresponding to the diameter of the threaded hole 9 in the securing plate 4, i e preferably about 9-10 mm

After the removal of the guide sleeve 8 for the guide wire 7, a second guide sleeve 1 1 , with an inside diameter of preferably about 6 5 mm and an externally threaded forward portion with the same outside diameter as the first guide sleeve, is applied in, i e screwed into, the threaded hole 9 in the securing plate 4 (Fig 3) This guide sleeve 11 is intended to guide a drill 13, which has running through it a duct 12 for the wire guide 7 (see Figs 5-10), for drilling the hole for the bone screw 5 in the bone fragments 2, 3 When the second guide sleeve 11 has been attached to the securing plate 4, a gauge rod 14 is inserted at the rear of this guide sleeve and through the sleeve towards the bone 2, 3 The gauge rod 14 can be used in a conventional manner to indicate how far the drilling should go or how long the bone screw 5 should be for optimum function In Fig 4 the gauge rod 14 has been removed

The hole for the bone screw 5 can now be drilled Accordingly, as illustrated in Fig 5, the drill 13 provided with the duct 12 is introduced through the guide sleeve 11 towards the bone fragment 2 and the drilling of the hole for the bone screw 5 is commenced, using a suitable drive device 15 The drill 13 has an outside diameter of preferably about 6 5 mm and fits exactly in the guide sleeve 11 The drill 13 is guided by the guide sleeve 11 to a correct position against the bone fragment 2 and thereafter by the guide wire 7 through the bone fragment 2 and past the fracture 1 into the bone fragment 3 Monitoring that the hole for the bone screw 5 is of a correct length is carried out with advantage at the rear of the guide sleeve 1 1 , where the drill 13 or the drive device 15 bears suitable markings 16 This entails the drill 13 being halted about 2 cm from the tip of the guide wire 7, i e about 2 cm before reaching the point to which the bone screw 5 is intended to be screwed in

After any necessary adjustment of the securing plate 4 sideways, a further second guide sleeve 1 1 is now applied as per Fig 6 in a second threaded hole 9 running through the plate Alternatively, a guide sleeve 8 for a guide wire 7 may be applied first and the same procedure as before, with the same parts as above, may be carried out With advantage, although not depicted in the drawings, guide sleeves of desired kinds 8, 11 may already from the outset be applied in the respective threaded holes 9 in the securing plate 4 to give the surgeon a better grasp for correct control of the guide wire 7 and the respective drills 13, 17 The guide sleeve 11 in the version depicted is intended to guide a drill 17 without a duct for the guide wire but with a conical tip (see Fig 7) This solid drill 17 is driven in to a desired position for the bone screw 6 by means of the drive device 15 The correct length is read with advantage at the rear of the guide sleeve 11 , where the drill 17 or the drive device 15 bears suitable markings 16 (Fig 7) The drill 17 and the guide sleeve 1 1 for it are removed (Fig 8), leaving a hole 18 for the bone screw 6 in the bone fragments 2, 3, which hole is shorter than the distance to which the bone screw is intended to be screwed in

The bone screw 6 can now, by means of a first fixing portion in the form of a threaded forward end portion 19, be screwed in through the free threaded hole 9 in the securing plate 4 (see Fig 9) and into the hole 18 in the bone fragments 2, 3 in order to fix these bone fragments Alternatively, the threaded forward end portion 19 of the bone screw 6 may be somewhat smaller and only be in contact with, i e ride on, the threads in the threaded hole 9 in the plate 4 For example, the thread on the threaded forward end portion 19 of the bone screw 6 may be about 8 mm, while the thread in the threaded hole 9 in the securing plate 4 may, as previously indicated, be about 9-10 mm The bone screw 6 is screwed in by using a suitable tool, in the version depicted a suitable type of screwdriver 20 Alternatively it is of course possible to conceive of using for this purpose the same drive device 15 as for the drills 13, 17 The bone screw 6 is screwed in until the second fixing portion in the form of a threaded rear end portion 21 thereof engages in the threaded hole 9

I fig. 11 ar borret 13, styrhylsan 11 for borret samt styrtraden 7 borttagna. Ben- skruven 5, fόretradesvis motsvarande utformad som benskruven 6, ar inskruvad i det efter avlagsnande av namnda delar fria gangade halet 9 i plattan 4 och i det med hja ^' lp av borret 13 utformade halet 23 (fig. 10) i benfragmenten 2, 3 fδr fixering av benfragmenten. Ett stabilt fόrband melian fasthallningspiattan 4 och benskruvarna 5, 6 som fδr- hindrar att benskruvarna andrar sitt vinkellage relativt plattan och relativt varandra sa att benskruvarna korsar varandra, har erhallits. Dessutom ar benfragmenten 2, 3 optimalt fixera- de med hjalp av benskruvarna 5, 6.

Benskruvarna 5, 6 ar emellertid genom det slata mittpartiet 22 dessutom utformade att medge att benfragmenten 2, 3 komprimeras saledes att det yttre benfragmentet 2 glider fran fasthallningspiattan 4 i riktning inat mot det inre benfragmentet 3, vari benskruvarna ar fastskruvade. Fasthallningspiattan 4 kommer i sadant tillfalle, genom sin lasning vid benskruvarna 5, 6, att komma bort fran sin anliggning mot det yttre benfragmentet 2 (visas schematiskt i fig. 12 genom mellanrummet 24 melian fasthallningspiattan och det yttre ben- fragmentet). Detta har dock ingen betydelse for fδrbandets hallfasthet och funktionen fδr- samras inte.

I fig. 13 och 14 visas alternativa utfόranden av fasthallningspiattan 4. Fasthallningspiattan 4 har i dessa utfδranden tre gangade hal 9 for benskruvar.

De gangade halen 9 for benskruvarna fόrlόper i alia de visade utfόrandena i huvud- sak parallellt med varandra saledes att benskruvarna 5, 6 likasa kommer att fδrlόpa i huvud- sak parallellt med varandra. Ett parallellt fόrlopp pa fixeringsorganen underlattar namligen glidfόrskjutningen av det yttre benfragmentet 2 langs fixeringsorganen (langs mittpartiet 22 da ^' rav) for kompression av benfragmenten.

Fasthallningspiattan 4 enligt fδreliggande uppfinning kan fόrutom for larbens- hals(collum)frakturer aven anvandas for t.ex. όverarms(humerus)frakturer.

Eftersom det vid operationer for fixering av benfragment vid benbrott ar viktigt att fixeringsorganen erhaller exakt fόrutbestamda lagen i fόrhallande till benfragmenten och till varandra, ar det en fόrdel att anordningen enligt uppfinningen dessutom medger anbringning av styrhylsor fδr styrning av borr for att borra hal for benskruvarna i benfragmenten och/eller styrhylsor for styrning av styrtradar for namnda borr i samma hal i fasthallningspiattan som ar avsedda for fixeringsorganen. Detta har inneburit att operationspersonalen inte langre behόver halla reda pa ett onόdigt stort antal olika delar for genomfόrande av en operation, tiden for ingreppet blir kortare och riskerna och komplikationerna for patienterna minskar.

Det ar for en fackman uppenbart att anordningen enligt fόreliggande uppfinning kan modifieras och andras inom ramen for efterfόljande patentkrav utan att franga uppfinningens ide och andamal. Saledes kan, sasom angivits ovan, fasthaliningsplattan 4 anvandas for styrhylsor 8 for styrtrad och darefter for styrhylsor 11 for borr eller t.ex. direkt for styrhylsor 11

for the bone screws in the bone fragments, and/or guide sleeves for guidance of guide wires for said drills, in the same holes in the securing plate as are intended for the fixation means This means that surgical staff need no longer keep count of an unnecessarily large number of different items for performing an operation, operating time becomes shorter and risks and complications for patients are reduced

It will be obvious to one skilled in the art that the device according to the present invention can be modified and altered within the scope of the claims set out below without departing from the idea and objects of the invention Thus, as indicated above, the securing plate 4 may be used for guide sleeves 8 for guide wires and thereafter for guide sleeves 1 1 for drills or, for example, immediately for guide sleeves 11 for drills The securing plate 4 may of course also be used only for guide sleeves 8 for guide wires, followed by drill guidance solely by guide wire, without special guide sleeves for drills The securing plate 4 may also be used for bone screws of different kinds from the bone screws 5, 6 described above or for other types of fixation means, e g bone nails A bone nail may have a sleeve and, disposed therein, a pin arranged for movement in the sleeve so that at least a forward portion of the pin can be driven outwards through at least one side aperture in the sleeve, in which case this forward portion constitutes a first fixing portion in the form of at least one hook which engages in the inner bone fragment, and the respective bone nail has in addition a second fixing portion of the type described above As the density in the inner bone fragment is greatest at its centre, it is of advantage if the respective bone nail is applied in such a way that the forward portion of the pin is caused, during the driving, to engage in the central portions of the bone fragment The respective bone nail may also be so configured as to achieve engagement in the central portions of the inner bone fragment For example, where there is a threaded second fixing portion, the threads therein may be so disposed and/or configured that said result is achieved Having the forward portion of the pin in the respective bone nail pointing towards the centre of the inner bone fragment not only means that the bone nails have a better grip in the inner bone fragment but also counteracts the risk of rotation or other movement of the bone nails Said first and second fixing portions of the fixation means may also be other than threaded portions The size and choice of material of the constituent items of an operating set may vary as necessary and desired