Modular intramedullary nail

Information

  • Patent Grant
  • 6569165
  • Patent Number
    6,569,165
  • Date Filed
    Tuesday, March 20, 2001
    23 years ago
  • Date Issued
    Tuesday, May 27, 2003
    21 years ago
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




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 in

FIG. 1

;





FIG. 3

shows a cross-section according to III—III in FIG.


1


;.





FIG. 4

shows an enlarged detail of the distal nail end according to

FIG. 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




Nail


1


is essentially in the form of a cylindrical bar and may be divided into a proximal portion


2


, a middle portion


3


, and a distal portion


4


. 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 portion


2


is cylindrical and is provided with a longitudinal bore


5


comprising a partial internal thread


6


whose core diameter is slightly greater than the diameter of longitudinal bore


5


. Bore


5


serves to receive an insert


7


whose function will be explained later on. The proximal end


11


of the proximal portion comprises two guide grooves


12


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 of longitudinal bore


5


, the internal thread is omitted in order to prevent gripping between the grooves and the fastening screw of the aiming appliance.




Proximal portion


2


is further provided with a throughgoing slot


8


which extends in parallel to the longitudinal axis. A guiding pin


9


, which serves for a rotationally fixed positioning of insert


7


, is disposed inside longitudinal bore


5


and transversally thereto. Underneath longitudinal bore


5


, which extends beyond the longitudinal extension of slot


8


in the distal direction, the proximal portion is provided with a transversal bore at its distal end.




Middle portion


3


and distal portion


4


of the nail have a smaller diameter than the cylindrical proximal portion


2


. Cross-sections II—II and III—III show that the middle portion is provided at its proximal end with a wire groove


13


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 groove


13


exits from the nail below proximal portion


4


, as appears in

FIGS. 3 and 4

, while assuming the shape of a wire channel


13


A.




Bottom


14


of the groove (see

FIG. 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 groove


13


and wire channel


13


A are provided on distal portion


4


, 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 with transversal bores


15


. Point


16


of the nail is parabolical in order to be passed over the line of fracture without a great resistance. Transversal bores


15


, of which preferably at least two are provided, serve to receive the distal fixing screws


17


. As the case may be, a non-represented longitudinal slot may additionally be provided on distal portion


4


.




For the treatment of fractures in the central area of the shaft, the intramedullary nail according to

FIGS. 5 and 6

may be used where the axial and torsional forces are absorbed by fixing screw


18


in transversal hole


10


as well as by a second fixing screw


18


in slot


6


which receives torsional forces exclusively. Instead of fixing screws


18


, fixing bolts


19


(see

FIGS. 7 and 8

) may be used which are provided with hexagon sockets


20


. These fixing screws


18


and fixing bolts


19


constitute the fixing elements


18


. and


19


.




Longitudinal bore


5


is protected against an accretion of tissue into the threaded portion, which would impair the attachment of the explantation instrument, by means of a cap screw


21


. Cap screw


21


is externally threaded and comprises a hexagonal socket


23


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 screw


24


(see

FIGS. 6

or


10


). For this purpose, fixing screw


18


is introduced into longitudinal slot


8


transversally to the longitudinal axis of the nail by means of the proximal aiming appliance (not shown). Subsequently, compression screw


24


is entered in proximal thread


6


of the proximal portion until it contacts fixing screw


18


by its distal end


25


. 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 screw


24


further comprises a shaft portion


26


which is followed by an externally threaded portion


27


of greater diameter, as well as a hexagon socket


28


.




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, an insert


7


is provided which may either be hollow or solid in design. Insert


7


according to the embodiment shown in

FIG. 1 and 5

comprises a through-going longitudinal bore


34


and two guiding bores


29


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 of cap screw


21


approximately corresponds to the external diameter of insert


7


, 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 bores


29


, which are inclined with respect to the longitudinal axis, may have different diameters and serve to receive fixing screws


18


or fixing bolts


19


. The insert further comprises a guiding groove


30


in which guiding pin


9


engages and thus ensures a correct introduction of the insert in such a manner that guiding bores


29


for the fixing screws are aligned with respect to slot


8


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 bores


29


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.




Guiding pin


9


engaging guiding groove


30


can be replaced by other elements for preventing a misalignment of insert


7


. These elements can especially be integrated into the implantation instrument.





FIG. 7

shows the retrograde respectively antegrade fixation of a fracture by means of an insert


31


for a intramedullary nail according to a fourth embodiment comprising a single guiding bore


29


but which is otherwise identical to insert


7


. In this

FIG. 7

as well as in

FIG. 8

, it is visible how guiding pin


9


engages in guiding groove


30


of the insert and thus precisely aligns the insert with respect to longitudinal slot


5


. It further appears that, an insertion of the sleeve with one of its ends


32


facing in the distal direction or with the other end


33


facing in the distal direction allows either a retrograde or an antegrade fixation. In this case, as in the case according to

FIG. 8

the cap screw


21


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 of insert


7


for a intramedullary nail according to a fifth embodiment with two guiding bores


29


in the case of a retrograde respectively an antegrade fixation of the fracture. The considerations with regard to insert


31


according to

FIG. 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 a throughgoing slot


45


which extends in parallel to the longitudinal axis. Underneath longitudinal bore


5


, which extends beyond the longitudinal extension of slot


8


in the distal direction, the proximal portion does not contain a transversal bore at its distal end. Insert


7


comprises at least one guiding bore


29


. In the embodiment shown insert


7


comprises two guiding bores


29


which are oriented transversal to the longitudinal axis


46


of insert


7


respectively proximal portion


2


. Fixing screws


18


are received within said guiding bores


29


whereby another screw is provided in the distal portion


4


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 a compression screw


24


to effect an active compression fixation. First of all insert


7


comprising a longitudinal guiding slot


39


is introduced and fixed by means of the cap screw


21


. Then, the fixing screw


18


is pushed through the longitudinal guiding slots


39


and


8


in a direction transversal to the longitudinal axis


46


of the nail. The initial position of the fixing screw is marked with numeral


18


′. Finally, the compression screw


24


is inserted into the internal thread


6


of the proximal portion until contacting the fixing screw


18


in the position


24


. The shaft of the compression screw


24


transverses the hollow cap screw


21


. As the compression screw


24


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. The distal end


25


of the compression screw


24


touches the fixing screw


18


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 a nail


1


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 the longitudinal bore


5


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.



Claims
  • 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.
  • 2. An intramedullary nail, comprising:a) a proximal portion, a middle portion and a distal portion, said proximal portion having a longitudinal slot and at least one transversal hole; b) the proximal portion having a longitudinal bore extending over said slot in the distal direction, so that a first fixing screw intended to be inserted in the transversal hole to absorbs axial and torsional forces and so that a second fixing screw intended to be inserted in said slot receives torsional forces exclusively.
  • 3. The intramedullary nail of claim 2, further including a cap screw to be fastened in the longitudinal bore of the proximal portion.
  • 4. The intramedullary nail of claim 2, further including a compression screw to be screwed into an 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.
  • 5. A method of treating fractures, comprising the steps of:(a) placing a nail in the intramedullary space of a bone, the nail having a longitudinal axis and a proximal portion, a middle portion and a distal portion, the proximal portion having a longitudinal slot and the distal portion having at least one transverse bore, whereby the proximal portion includes a longitudinal bore extending over the slot in the distal direction and having an internal thread; (b) introducing at least one distal fixing screw in the at least one transversal bore; (c) introducing a hollow insert in said longitudinal bore, the insert having a guiding bore in the form of a slot; and (d) driving one fixing element in the slot of the insert and through the longitudinal slot of the nail; (e) introducing a compression screw into the internal thread of the longitudinal bore of the proximal portion; and (f) screwing the compression screw into the internal thread of the longitudinal bore so that the compression screw is inserted in the hollow insert and moves the fixing element in the direction of the longitudinal axis of the intramedullary nail to displace the proximal fragment of the bone relative to the nail until the fracture is closed and an interfragmentary compression is obtained.
Priority Claims (1)
Number Date Country Kind
97810164 Mar 1997 EP
CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. patent application Ser. No. 09/180,991, filed Jul. 21, 1999, now U.S. Pat. No. 6,228,086 the disclosure of which is hereby incorporated by reference herein.

US Referenced Citations (4)
Number Name Date Kind
4875475 Comte et al. Oct 1989 A
5653709 Frigg Aug 1997 A
6106528 Durham et al. Aug 2000 A
6228086 Wahl et al. May 2001 B1