US20050273103A1 - Modular intramedullary nail - Google Patents

Abstract

An intramedullary nail, comprises a proximal portion, a middle portion and a distal portion. The proximal portion has a longitudinal slot and the distal portion has at least one transversal bore. The proximal portion has a longitudinal axis and a longitudinal bore extending over the longitudinal extension of the slot in the distal direction. The longitudinal bore has an internal thread. An insert which is intended to be inserted in the longitudinal bore. The insert comprises a guiding bore in the form of a slot which is intended to receive fixing elements. The alignment of the guiding bore of said insert is transverse with respect to the longitudinal axis of the proximal portion. The insert has a compression screw adapted to be screwed into said internal thread of the longitudinal bore of the proximal portion to move a fixing element in the direction of the longitudinal axis of the intramedullary nail.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation of U.S. patent application Ser. No. 10/354,290, filed Jan. 30, 2003, which is a continuation of U.S. patent application Ser. No. 09/812,916, filed Mar. 20, 2001, which is a divisional of U.S. patent application Ser. No. 09/180,991, filed Jul. 21, 1999, which is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/IB98/00406 filed Mar. 19, 1998, published in English, which claims priority from European Application No. 97810164.0 filed Mar. 19, 1997, all of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
• The present invention refers to a modular intramedullary nail, more particularly to a modular femoral intramedullary nail comprising a nail which is composed of a proximal portion, a middle portion and a distal portion, said proximal portion having a longitudinal slot and said distal portion having at least one transversal bore.
• So-called unreamed locking intramedullary nails have been used for the treatment of fractures of tubular bones for some time now. Lately, the indications of such intramedullary nails have been extended to include proximal fractures of the femur shaft, these fractures existing in a great diversity while their treatment is extremely complex. As a consequence, a great number of intramedullary nails have been developed which take into account the different types of fractures. These nails only distinguish themselves by the manner in which the proximal fixing screws are positioned according to the type of fracture. This leads to an expensive storage of a large number of nails and instruments. Furthermore, it is increasingly difficult for the surgeon and the nurses to master a great number of different implant systems in such a manner that an optimum treatment of fractures is ensured.
• WO-94/13219 describes an unreamed intramedullary nail of modular structure which allows a considerable reduction of the number of required intramedullary nails by its diversity in use. The intramedullary nail is provided with a cylindrical sleeve which is adapted to be slid over its proximal end in a telescopic manner and whose design allows different modes of attachment in order to adapt the intramedullary nail to the required application. However, such a telescopic attachment is not optimal with respect to biomechanical aspects, which must be considered as essential on account of the great loads at the proximal femur, and furthermore, the proximal portion of the nail is additionally thickened by the attached sleeve, thus resulting in negative effects with respect to the vascularization of the neck area of the femur head. Finally, the telescopic attachment compulsorily lengthens the nail, resulting in a modification of its original length.
• DE 85 33 134 U describes a device for treating a bone fracture, which comprises a proximal hollow portion accepting a threaded bolt for fixing a screw in a transversal slot. This device is designed for a particular type of fracture and does not permit the reduction of required intramedullary nails.
SUMMARY OF THE INVENTION
• On the background of this prior art, it is the object of the present invention to provide a modular intramedullary nail and a relating method where the above-mentioned drawbacks are eliminated and which has an increased biomechanical stability and ensures a better vascularization. This object is attained by an intramedullary nail wherein the proximal portion comprises a longitudinal bore extending over the longitudinal extension of said slot in the distal direction and an insert which is intended to be inserted in said longitudinal bore, said insert comprising at least one guiding bore which is intended to receive fixing elements.
BRIEF DESCRIPTION OF THE DRAWINGS
• The invention is explained in more detail hereinafter with reference to drawings of several embodiments of the invention.
• FIG. 1 shows an assembly of the different elements of the intramedullary nail in a partly sectioned view according to a first embodiment of the invention;
• FIG. 2 shows a cross-section according to II-II inFIG. 1;
• FIG. 3 shows a cross-section according to III-III inFIG. 1;.
• FIG. 4 shows an enlarged detail of the distal nail end according toFIG. 1;
• FIG. 5 shows the intramedullary nail for treating fractures in the central area of the shaft according to a second embodiment of the invention;
• FIG. 6 shows the intramedullary nail for treating fractures in the central area of the shaft with means of a compression screw according to a third embodiment of the invention;
• FIG. 7 shows the intramedullary nail for treating proximal femur fractures with means of a retrograde respectively an antegrade fixation according to a fourth embodiment of the invention;
• FIG. 8 shows the intramedullary nail for treating proximal femur fractures with means of a retrograde respectively an antegrade fixation according to a fifth embodiment of the invention;
• FIG. 9 shows the intramedullary nail for treating fractures in the central area of the shaft according to a sixth embodiment of the invention; and
• FIG. 10 shows the intramedullary nail for treating fractures in the central area of the shaft with means of a compression screw according to a seventh embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
• Nail1 is essentially in the form of a cylindrical bar and may be divided into aproximal portion2, amiddle portion3, and a distal portion4. The illustrated nail for the femur is adapted to the anatomy of the femur and therefore curved according to a so-called antecurvation. The distal portion as well as the middle portion are so dimensioned that the nail can be introduced into the intramedullary channel without drilling by means of a guiding wire. Within other embodiments cannulated nails can be used.
• Proximal portion2 is cylindrical and is provided with alongitudinal bore5 comprising a partialinternal thread6 whose core diameter is slightly greater than the diameter oflongitudinal bore5. Bore5 serves to receive aninsert7 whose function will be explained later on. Theproximal end11 of the proximal portion comprises twoguide grooves12 which serve for the rotationally fixed guidance of the non-represented driving bow on which, according to the indication, the corresponding aiming appliance is fastened in an angularly stable manner. Therefore, at this end oflongitudinal bore5, the internal thread is omitted in order to prevent gripping between the grooves and the fastening screw of the aiming appliance.
• Proximal portion2 is further provided with athroughgoing slot8 which extends in parallel to the longitudinal axis. A guidingpin9, which serves for a rotationally fixed positioning ofinsert7, is disposed insidelongitudinal bore5 and transversally thereto. Underneathlongitudinal bore5, which extends beyond the longitudinal extension ofslot8 in the distal direction, the proximal portion is provided with a transversal bore at its distal end.
• Middle portion3 and distal portion4 of the nail have a smaller diameter than the cylindricalproximal portion2. Cross-sections II-II and III-III show that the middle portion is provided at its proximal end with awire groove13 intended to receive a guiding wire, the wire groove extending from the distal portion to the proximal side and being inclined with respect to the longitudinal axis of the nail. As a consequence,wire groove13 exits from the nail below proximal portion4, as appears inFIGS. 3 and 4, while assuming the shape of awire channel13A.
• Bottom14 of the groove (seeFIG. 2) is rounded in order to provide an optimum guidance of the guiding wire and to prevent possible notch tensions in the bottom of the wire groove. This kind of guidance allows a safe and controlled introduction of the nail by means of the guiding wire while preventing, in contrast to a cannulation, the formation of a non-vascularized clearance.
• As already mentioned above,wire groove13 andwire channel13A are provided on distal portion4, which means that the design of the guiding means for the guiding wire allows a nail which need not be entirely cannulated while the cross-section of the nail, which is smaller due to the wire groove, reduces the risk of a fat embolism in the course of the introduction of the nail.
• However, in order to carry out the invention, it is not absolutely necessary to provide the middle and the distal portions with a wire groove and a wire channel. A central cannulation of the intramedullary nail is also possible.
• The lower section of the distal portion is provided withtransversal bores15.Point16 of the nail is parabolical in order to be passed over the line of fracture without a great resistance.Transversal bores15, of which preferably at least two are provided, serve to receive thedistal fixing screws17. As the case may be, a non-represented longitudinal slot may additionally be provided on distal portion4.
• For the treatment of fractures in the central area of the shaft, the intramedullary nail according toFIGS. 5 and 6 may be used where the axial and torsional forces are absorbed byfixing screw18 intransversal hole10 as well as by asecond fixing screw18 inslot6 which receives torsional forces exclusively. Instead of fixingscrews18, fixing bolts19 (seeFIGS. 7 and 8) may be used which are provided withhexagon sockets20. Thesefixing screws18 and fixingbolts19 constitute thefixing elements18. and19.
• Longitudinal bore5 is protected against an accretion of tissue into the threaded portion, which would impair the attachment of the explantation instrument, by means of acap screw21. Capscrew21 is externally threaded and comprises ahexagonal socket23 which allows to fasten the screw.
• In the treatment of a fracture of the central shaft area, an active compression fixation can be effected by means of a compression screw24 (see FIGS.6 or10). For this purpose, fixingscrew18 is introduced intolongitudinal slot8 transversally to the longitudinal axis of the nail by means of the proximal aiming appliance (not shown). Subsequently,compression screw24 is entered inproximal thread6 of the proximal portion until itcontacts fixing screw18 by itsdistal end25. As the compression screw is now further entered, the proximal fragment of the bone is displaced relative to the nail until the fracture is closed and an interfragmentary compression is obtained.Compression screw24 further comprises ashaft portion26 which is followed by an externally threadedportion27 of greater diameter, as well as ahexagon socket28.
• As an essential extension of the field of applications of the intramedullary nail according to the invention, more particularly for an antegrade or a retrograde fixation, aninsert7 is provided which may either be hollow or solid in design.Insert7 according to the embodiment shown inFIGS. 1 and 5 comprises a through-goinglongitudinal bore34 and two guidingbores29 which are inclined with respect to the longitudinal axis, more than two guiding bores being possible, but at least one such bore being provided. In this case, the external diameter ofcap screw21 approximately corresponds to the external diameter ofinsert7, thus allowing its fastening. A subsequent displacement of the insert in the longitudinal bore is thus prevented, i.e., a precisely defined positioning of the insert with respect to the longitudinal axis is ensured. Furthermore, the clamping action excludes any microscopic movements between the inner wall of the bore and the insert which might result in an undesirable abrasion. Finally, the insert increases the biomechanical stability of the nail by a bracing effect.
• Guiding bores29, which are inclined with respect to the longitudinal axis, may have different diameters and serve to receive fixingscrews18 or fixingbolts19. The insert further comprises a guidinggroove30 in which guidingpin9 engages and thus ensures a correct introduction of the insert in such a manner that guiding bores29 for the fixing screws are aligned with respect to slot8 of the nail. In order to facilitate the insertion, the guiding groove is enlarged in the manner of a funnel at both its ends. For a retrograde fixation of the fracture, guiding bores29 are preferably aligned at an angle of 120° to 150° with respect to the longitudinal axis, while they are preferably aligned at an angle of 125° to 150° with respect to the longitudinal axis in the case of an antegrade fixation.
• Guidingpin9 engaging guidinggroove30 can be replaced by other elements for preventing a misalignment ofinsert7. These elements can especially be integrated into the implantation instrument.
• FIG. 7 shows the retrograde respectively antegrade fixation of a fracture by means of aninsert31 for a intramedullary nail according to a fourth embodiment comprising a single guiding bore29 but which is otherwise identical to insert7. In thisFIG. 7 as well as inFIG. 8, it is visible how guidingpin9 engages in guidinggroove30 of the insert and thus precisely aligns the insert with respect tolongitudinal slot5. It further appears that, an insertion of the sleeve with one of itsends32 facing in the distal direction or with theother end33 facing in the distal direction allows either a retrograde or an antegrade fixation. In this case, as in the case according toFIG. 8 thecap screw21 serves to fasten the insert by a clamping action and furthermore as a protection against an accretion of tissue into the threaded portion.
• FIG. 8 shows the use ofinsert7 for a intramedullary nail according to a fifth embodiment with two guidingbores29 in the case of a retrograde respectively an antegrade fixation of the fracture. The considerations with regard to insert31 according toFIG. 7 apply in an analogous manner.
• FIG. 9 shows a intramedullary nail for treating fractures in the central area of the shaft according to a sixth embodiment of the invention. The nail is cannulated and comprises athroughgoing slot45 which extends in parallel to the longitudinal axis. Underneathlongitudinal bore5, which extends beyond the longitudinal extension ofslot8 in the distal direction, the proximal portion does not contain a transversal bore at its distal end.Insert7 comprises at least one guiding bore29. In the embodiment showninsert7 comprises two guidingbores29 which are oriented transversal to thelongitudinal axis46 ofinsert7 respectivelyproximal portion2. Fixing screws18 are received within said guiding bores29 whereby another screw is provided in the distal portion4 to stabilise a fracture of the central area of the shaft.
• FIG. 10 shows a intramedullary nail for treating fractures in the central area of the shaft according to a seventh embodiment of the invention using acompression screw24 to effect an active compression fixation. First of allinsert7 comprising alongitudinal guiding slot39 is introduced and fixed by means of thecap screw21. Then, the fixingscrew18 is pushed through thelongitudinal guiding slots39 and8 in a direction transversal to thelongitudinal axis46 of the nail. The initial position of the fixing screw is marked with numeral18′. Finally, thecompression screw24 is inserted into theinternal thread6 of the proximal portion until contacting the fixingscrew18 in theposition24. The shaft of thecompression screw24 transverses thehollow cap screw21. As thecompression screw24 is now further entered, the proximal fragment of the bone is displaced relative to the nail until the fracture is closed and an interfragmentary compression is obtained. Thedistal end25 of thecompression screw24 touches the fixingscrew18 in the position shown in unbroken lines.
• The intramedullary nail shown and described is to be used for femur fractures. It is clear that the nail can also be provided for treatment of other fractures, e.g. fractures of the tibia or the humerus. The basic advantage of the modular system of this intramedullary nail using inserts which do not enlarge the space used for the nail is maintained.
• It follows from the preceding description that anail1 as well as a limited number of inserts allow to treat all kinds of femur, tibia and humerus shaft fractures as well as the most different proximal femur, tibia or humerus fractures. Besides, the shape of the inserts and thus also of thelongitudinal bore5 receiving the insert is independent from the diameter or the length of the nail. Furthermore, there is no need for a left-hand and a right-hand form of the nail, which is an essential advantage with respect to the use and the storage of this implant. The corresponding left-hand or right-hand embodiment of the nail is determined by a mere 180° turn when introducing the insert. It further follows from the description that other embodiments of the intramedullary nail such as reconstruction nails can be used according to the inventive idea.
• Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims (1)

1. An intramedullary nail, comprising:

a) a proximal portion, a middle portion and a distal portion, said proximal portion having a longitudinal slot and said distal portion having at least one transversal bore;

b) the proximal portion having a longitudinal axis and a longitudinal bore extending over said slot in the distal direction, said longitudinal bore having an internal thread; and

c) a hollow insert which is intended to be inserted in said longitudinal bore, said insert comprising at least one guiding bore in the form of a slot which is intended to receive fixing elements;

d) the alignment of the at least one guiding bore of said insert being transverse with respect to the longitudinal axis of the proximal portion;

e) said insert comprising a compression screw adapted to be screwed into said internal thread of the longitudinal bore of the proximal portion and adapted to be inserted in the hollow insert so as to move the fixing element in the direction of the longitudinal axis of the intramedullary nail.

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