Abstract:
An orthopedic nail for intramedullary fixation of fractures in long bones has an axially outwardly opening mouth in a first end thereof including a pair of side edge portions and an inward bight portion. A method of fixation of a fracture of a long bone includes driving a distal fastener transverse the bone on a medial frontal plane and axially inserting the mouth end of the nail into the medullary canal with the mouth on the same plane as the distal fastener. The fastener should be received within the mouth and seated against the bight portion due to the axial movement of the nail. A special jig is provided for accurately locating a second distal fastener if one is indicated. A retractable insertion device covers the mouth during nail insertion to reduce the likelihood of snagging vessels.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an intramedullary method and apparatus for fixation of a fracture in a long bone and in particular to a method and apparatus of the type that reduces the fracture and prevents shortening of the bone segments through the use of a locked intramedullary nail. 
     A severely comminuted fracture in a long bone such as a tibia or femur, has a tendency to cause the bone segments created by the fracture to compress, shortening the length of the bone. Traditional treatment to prevent such compression is by skeletal traction. A known alternative is to use a cannulated intramedullary nail that is inserted into an opening made in one end of the bone and looked to the bone segments. A guide wire is first inserted in the opening, that is typically made in the proximal end of the bone, and into the distal bone fragment significantly past the fracture site. The guide wire guides the cannulated nail past the fracture site. Although the intramedullary nail substantially occupies the medullary canal, it is only capable of retaining length and preventing excessive shortening if the bone segments are appropriately fastened, or locked, to the nail. 
     The problem in such a locked intramedullary nail technique is locating the distal aperture(s) in the nail and successfully aligning fasteners, inserted through the bone wall, with the apertures. One known technique is the use of a jig that is accurately retained in relationship to the nail by a portion extending into the bone through the opening made in the proximal end of the bone and which has an external portion that extends parallel the bone with alignment means for aligning fasteners with the apertures in the nail provided along the external portion. While such a technique is quite successful at accurately locating the proximal locking fastener(s), the rather long distance to the distal fasteners allows relative movement between the jig and the nail which distorts the alignment means. Accordingly, alignment with the distal aperture(s) is not assured and damage to the bone wall or to the nail aperture may result. 
     A more accurate technique for locating the distal apertures is an X-ray imaging technique that utilizes a target device. The target device is positioned at the approximate location of the distal nail aperture and iteratively repositioned until a perfect circular image of the nail aperture is produced. This occurs when the target device is located on the centerline of the aperture. Means are provided, relative to the target device, to then locate the insertion point for the fasteners. The problem with such a distal aperture location technique is the cumulative exposure of the patient and the operating team to X-ray radiation which can be excessive if the procedure to properly position the target device results in a large number of attempts. Also, if correct alignment is not obtained, damage to the bone or nail may jeopardize the fixation. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and apparatus for reducing a fracture in a long bone and for producing longitudinal tension between the segments of the bone including an improved technique for location of the distal nail apertures and alignment of the distal locking fasteners with the apertures. 
     An orthopedic nail according to the invention is dimensioned substantially to conform to the shape of the intramedullary canal of the bone to be fixed and has a first terminal end with edge means defining a mouth extending axially outwardly to the terminal end. The mouth has an inward bight portion and a pair of side edge portions that extend outwardly from the bight portion to the terminal end. 
     A method of fixation of a fracture according to the invention includes making an opening sufficiently large to pass the nail in one end portion of the bone, such as the proximal end, and inserting the nail, terminal end first, in the opening. The nail is axially extended through the medullary canal into the opposite, or distal, bone segment with the mouth bight portion oriented generally on a frontal plane. A fastener of diameter substantially smaller than the separation of the mouth side edge portions is inserted transversely through the bone on a medial frontal plane at an estimated location between the side edge portions within the nail mouth. The fastener should be received within the wide mouth of the nail and subsequently seated against the bight portion by the axial movement of the nail. After the seating of the distal fastener is verified, a proximal locking device is installed according to conventional techniques. If a second distal fastener is indicated, an alignment jig according to the invention is provided to accurately locate the position of a transverse distal aperture proximate the mouth and align the fastener with the aperture. In a preferred embodiment, a special insertion tool is provided to substantially close the mouth during movement through the medullary canal to reduce the snagging of vessels. 
     The invention is capable of significantly reducing the cumulative exposure to X-ray radiation and reducing the likelihood that damage to the bone or the nail may result in abandonment of the procedure or inadequate fixation. In addition, the present invention avoids the requirement for an incision at the fracture site and substantially reduces the severity of the incision required at the distal fastener site. In addition, the invention is efficient because it requires only one insertion tool and alignment jig set for a particular bone for the multiplicity of nail sizes required to fix fractures due to the variation in patient bone size. 
     These and other related objects, advantages and features of this invention will become apparent upon review of the following specification in conjunction with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sagittal view of an orthopedic nail according to the invention; 
     FIG. 2 is the orthopedic nail in FIG. 1 rotated 90° about a longitudinal axis; 
     FIG. 3 is an enlarged sectional view of an orthopedic nail taken along the lines III--III in FIG. 1; 
     FIG. 4 is a front view of a bone having a compound fracture therein, illustrating a distal guide pin being driven into the bone according to the method of the invention; 
     FIG. 5 is the same view as FIG. 4 illustrating attachment of a cannulated distal fastener and the use of a proximal alignment jig to attach the proximal locking fastener according to the method of the invention; 
     FIG. 6 is the same as FIGS. 4 and 5 showing the use of a second-distal-fastener alignment jig according to the invention to locate a second distal fastener; 
     FIG. 7 is an enlarged sagittal view of the second-distal-fastener alignment jig taken along the lines VII--VII of FIG. 6; 
     FIG. 8 is an enlarged anterior view of an orthopedic nail insertion device according to the invention; and 
     FIG. 9 is an enlarged sagittal view of a preferred embodiment of the apparatus prepared for axial insertion of the orthopedic nail in the medullary canal. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now specifically to the drawings, and the illustrated embodiments depicted therein, an elongated orthopedic nail 10 is dimensioned to substantially conform to the shape of the medullary canal of the bone to be fixed (FIG. 1). Nail 10 has a first, terminal end 12 and an edge means 14 defining a mouth 15 extending axially outwardly toward end 12. Edge means 14 includes an inward bight portion 16 and a pair of side edge portions 18a and 18b extending away from the bight portion 16. In one embodiment, side edge portions 18a, 18b diverge outwardly from the bight portion. A first transverse aperture 20 extends through opposing wall portions of nail 10 at a second, opposite end 13 thereof spaced a first predetermined longitudinal distance X from a second end 13 of the nail. An optional second transverse aperture 22 extends through opposing wall portions of nail 10 spaced a second predetermined longitudinal distance Y from bight portion 16. 
     Nail 10 is made from an alloy such as titanium alloy and is tubular, having a wall 25 defining an outer wall surface 24 and an inner wall surface 26 (FIG. 3). Inner wall surface 26 is threaded for the outermost several centimeters at second end 13. A pair of transverse slot portions 28a and 28b are formed in nail wall 25 at second end 13. 
     Referring to FIG. 4, a long bone, such as a femur, is shown at 30 severed into a first, proximal bone segment 34 and a second, distal bone segment 36 at fraction site 32. In order to reduce the fracture and provide longitudinal tension between the bone segments 34 and 36, an opening 38 is made, which in the illustrated embodiment, is in the proximal end 39 of bone 30, by conventional techniques. Opening 38 is illustratively located in the trochanteric fossa and is reamed to a diameter 1 or 2 millimeters greater than the diameter at the widest portion of nail 10. Bone segments 34 and 36 are reduced by manual manipulation and terminal end 12 of nail 10 is inserted through opening 38 into the medullary canal. With bight 16 oriented on a generally frontal plane, nail 10 is axially extended through the medullary canal until it is substantially enclosed within bone 30. Care must be taken to assure bight 16 is oriented on a generally frontal plane after insertion. Slot portions 28a, 28b, which are oriented on the same plane as bight portion 16 in the illustrated embodiment, may be used as indicating means for indicating the angular orientation of the nail. 
     A sagittal, cutaneous incision is made at the distal portion of the leg in the vicinity where mouth 15 is estimated to be located. In one embodiment, a guide pin 40 is percutaneously inserted transverse the bone on a medial frontal plane by the use of a drill 44. Pin 40 has a tip with cutting means thereon (not shown) to penetrate the bone and is rotatably held in the drill by a chuck 42. After guide pin 40 is inserted within the bone, the drill and chuck are detached therefrom and conventional imaging technique is used to determine the position of pin 40 with respect to mouth 15. If pin 40 is located between sidewall 18a and 18b it is thus within mouth 15. If it is determined that pin 40 has not been successfully located within mouth 15, then a second transverse guide pin is inserted percutaneously in the same fashion and imaging technique is utilized to determine that the second guide pin has been positioned within mouth 15. No special targeting device is needed in association with the disclosed imaging techniques and no more than two exposures should be required to position a guide pin within mouth 15. 
     With guide pin 40 positioned within mouth 15, a distal fastener 46 is inserted into the bone cannulated with guide pin 40 (FIG. 5). In a preferred embodiment, fastener 46 is a hollow, 6.5 mm, self-tapping screw made from a titanium alloy or the like and which has a head 48 with a hex or fluted socket that is selected to be compatible with the tip of a screwdriver shaft 50a. Such a fastener is manufactured by Orthomed Company. Because distal fastener 46 is hollow, it can be cannulated with guide pin 40 to assure successful insertion into bight portion 16 of mouth 15. With fastener 46 positioned within mouth 15, nail 10 is then further axially thrust to seat bight portion 16 against the distal fastener. 
     An alternative method for seating bight portion 16 against distal fastener 46 is to first drill a transverse distal opening on the medial-frontal plane of the bone and attach the distal fastener to the bone walls. A nail, in which the mouth side edge portions preferably diverge outwardly, is inserted through opening 38 into the medullary canal and axially extended through the canal. Bight portion 16 must be oriented on the same plane as the distal fastener, as mouth 15 approaches the distal fastener. With bight portion 16 and the distal fastener on the same plane, the diverging walls of the mouth will receive the fastener and seat the bight portion against it. 
     After the distal fastener is attached, a conventional technique may be used to lock proximal bone segment 34 to the nail. In the illustrated embodiment, a proximal fastener alignment jig 52 is attached to second end 13 of nail 10 by a threaded shaft 58 that extends through a hollow body 54 and threadably engages the threads on inner wall surface 26 (FIG. 5). A pair of ears (not shown) on body 54 may be provided to engage transverse slot portions 28a and 28b in order to angularly orient alignment jig 52 with the nail. A handle 56 extending from shaft 58 may be provided. A lateral arm 60 extends from body 54 and terminates in an apertured socket 62. The location of socket 62 and the axial aperture therein, are preselected to be in axial alignment with aperture 20 in the nail. A diameter-reducing sleeve (not shown) may be inserted into socket 62 and a drill bit 64 of a diameter to fit the sleeve is passed through the socket 62 and transversely through the bone using drill 44. The drill bit and sleeve are removed and a self-tapping proximal fastener 66 is engaged by the tip of a screwdriver blade 50b, inserted through socket 62 and threaded into the proximal opening formed by the drill in the bone. Because of the predetermined orientation of alignment jig 52 with nail 10, proximal fastener 66 will be aligned with aperture 20 and will pass therethrough. 
     The previously described procedure will, in many circumstances, be sufficient to retain bone segments 34 and 36 in tension and prevent longitudinal shrinkage of the bone length. If indicated, a second distal fastener may be inserted by the use of a distal fastener alignment jig 70 (FIGS. 6 and 7). Jig 70 is an elongated member having an edge means defining circular openings 72 and 76 at one end thereof and a slotted opening 74 at an opposite end thereof passing entirely through the jig. Openings 72 and 76 are spaced apart by the Y dimension and slotted opening 74 is spaced from opening 72 so as to include within its perimeter the proximal fastener. 
     In use, opening 72, which is slightly larger than screwdriver shaft 50a, is generally aligned with distal fastener 46 and screwdriver shaft 50a or the like passed through opening 72 and engaged with distal fastener 46 (FIG. 6). This provides means for longitudinally orienting the jig with the nail. The slotted opening 74 is aligned with proximal fastener 66 and a screwdriver shaft 50b, or the like, is passed through opening 74 and is engaged with fastener 66. This provides means for orienting alignment jig 70 on the same frontal plane as the nail. 
     With jig 70 properly positioned, opening 76 will be aligned with the centerline of aperture 22 and provide means for aligning the second distal fastener with aperture 22. A sleeve (not shown) is placed in opening 76 to reduce the diameter to the appropriate size and a drill bit 64, driven by a drill 44, is passed through the sleeve to make a transverse opening in the bone. The drill bit will pass through the aperture 22 in nail 10 as it drills through the bone. Drill bit 64 and the sleeve are withdrawn and a second distal fastener (not shown) is inserted through opening 76 in jig 70 and into the bone using a screwdriver shaft 50a. 
     The reason for slotting opening 74 is to accommodate the multiplicity of nail sizes that are required to provide fixation of a particular long bone on various patients. The distance between the distal fastener and the proximal fastener will vary depending on the length of the nail. However, the distance between the two distal fasteners Y may be, and preferably is, constant for all nail sizes for a particular bone. Thus, one jig 70 may be used to accurately position the second distal fastener for all such nail sizes. 
     In a most preferred embodiment, the insertion of nail 10 into the medullary canal is preceded by the insertion of a guide wire 88 through opening 38 and into the medullary of the distal segment 36. Imaging is used to verify that guide wire 88 is properly positioned in the distal bone segment. With guide wire 88 in place, the nail 10 may be cannulated with the guide wire and inserted into the medullary canal. In order to reduce the likelihood that forwardly extending mouth 15 will snag vessels and the like as it is moved forwardly inside the medullary canal, a special insertion tool is provided. Insertion tool 80 has an elongated head 82 which is configured to the inside surface of terminal end 12 of the nail and which has a central axial shaft 83a defined therethrough (FIG. 8). Head 82 is connected to a T-handle 86 at an opposite end of the insertion tool by a multiplicity of elongated resilient members 84. A central axial shaft 83b is defined through T-handle 86 aligned with shaft 83a in the head. The purpose of resilient members 84 is to bias head 82 into engagement with the inside surface of terminal end 12 and to accommodate variation in spacing between the head and the T-handle so that one insertion tool may be used with various nail lengths. When head 82 is positioned inside nail 10 and forwardly within mouth 15 it substantially closes the mouth (FIG. 9). Accordingly, mouth 15 will be less likely to snag vessels during insertion. 
     In use, insertion tool 80 is inserted telescopingly within nail 10. The T-handle 86 is received within transverse slot portions 28 and head 82 is biased by members 84 fully forward inside the nail. With the insertion tool within the nail, the assembly is inserted into the medullary canal cannulated with guide wire 88, which is telescopingly received within shafts 83a and 83b. The T-handle may be used to provide forward thrust to the nail and to control the rotational alignment of the nail during insertion. Once the nail is substantially fully inserted within the medullary canal, a rearward pull on T-handle 86 will withdraw the insertion tool. The guide wire 88 is also then withdrawn. 
     With the nail properly inserted in the medullary canal, the insertion tool and guide wire withdrawn and the proximal and distal fasteners inserted, the incisions are closed in a conventional fashion. 
     Changes and modifications in the specifically described embodiments can be carried out without departing from the principles of the invention which is intended to be limited only by the scope of the appended claims.