Modular intramedullary nail

Abstract: The modular femoral intramedullary nail comprises a nail portion (1) which is composed of a proximal portion (2), a middle portion (3), and a distal portion (4), the proximal portion (2) having a longitudinal slot (8) and the distal portion (4) having at least one transversal bore (15). The proximal portion (2) is provided with a longitudinal bore (5) extending over the length of said longitudinal slot (8) for the purpose of receiving an insert (7). Said insert (7) is provided with one or two guiding bores (29) which are inclined with respect to the longitudinal axis or oriented in a transversal direction and intended to receive fixing screws (18), fixing bolts (19), or blades. Such a widely applicable modular intramedullary nail offers a high biomechanical stability while the proximal end of the bar is not additionally thickened or lengthened.

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. DE 94 01 916 U1 (The preamble of claim 1 is based on this document.) discloses an intramedullary nail having in the proximal portion to axially spaced longitudinal slots. An insert which can be threaded into an internal thread of the proximal portion of the nail has two transverse bores axially spaced and aligned with the longitudinal slots if the insert is threaded into the proximal portion of the nail. By means of the cooperation of the external thread of the insert and the internal thread of the proximal portion fixing screws extending through the bores of the insert and of the longitudinal slots of the proximal portions can be subject to pressure in axial direction for compression purposes of the bone fracture. 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 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 slot which is intended to receive fixing elements. Brief Description of the Drawings The invention is explained in more detail hereinafter with reference to a drawing of one embodiment of the invention. The only figure shows an intramedullary nail for treating fractures in the central area of the shaft with means of a compression screw according to an embodiment of the invention. Detailed Description of the Preferred Embodiment A nail 1 is essentially in the form of a cylindrical bar and may be divided into a proximal portion 2, a middle portion, and a distal portion the latter not shown. 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 of the proximal portion comprises two guide grooves (not shown) 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. The lower section of the distal portion of nail 1 may be provided with transversal bores (not shown). 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 which allows to fasten the screw and to hold the insert 7 in place. 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. As shown further the intramedullary nail 1 for treating fractures in the central area of the shaft uses 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 a 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.

Claims: An intramedullary nail, more particularly a modular femoral intramedullary nail, comprising a nail (1) which is composed of a proximal portion (2), a middle portion and a distal portion, said proximal portion (2) having a longitudinal slot (8) and said distal portion having at least one transversal bore, wherein the proximal portion (2) comprises a longitudinal bore (5) extending over the longitudinal extension of said slot (8) in the distal direction and comprising an internal thread and an insert (7) which is intended to be inserted in said longitudinal bore (5), said insert (7) comprising at least one guiding bore which is intended to receive a fixing element (18) and compression means to exert a compression force onto a fixing element (18) extending through the slot (8) and the guiding bore, characterized in that said insert (7) comprises only one guiding bore in form of a longitudinal slot (39), and in that the compression means comprise a compression screw (24) which is adapted to be screwed into said internal thread (6) of the longitudinal bore (5) of the proximal portion (2) to move the fixing element (18) in the direction of the longitudinal axis (46) of the intramedullary nail (1). The intramedullary nail of claim 1, wherein the alignment of the guiding slot (39) of insert (7) is inclined with respect to the longitudinal axis (46) of the proximal portion (2) and in that said insert (7) is adapted to be inserted and locked in said longitudinal bore (5) with one end (32) facing in the distal direction for a retrograde fixation and with the other end (33) facing in the distal direction for an antegrade fixation. The intramedullary nail of claim 1, wherein the alignment of the guiding slot (39) of insert (7) is transversal with respect to the longitudinal axis (46) of the proximal portion (2). The intramedullary nail according to one of claims 1 to 3, wherein a guiding pin (9) engages in the longitudinal bore (5) of said proximal portion (2), and wherein said insert (7) is provided with a corresponding guiding groove for its correctly positioned insertion. The intramedullary nail according to one of claims 1 to 4, wherein the longitudinal bore (5) of said proximal portion (2) is internally threaded (6) for the provision of a cap screw (21). The intramedullary nail according to one of claims 1 to 5, wherein said fixing element (18) comprises fixing screws (18), fixing bolts or blades. The intramedullary nail of claim 1, wherein the alignment of the guiding slot (39) of insert (7) is transversal with respect to the longitudinal axis (46) of the proximal portion (2). The intramedullary nail according to one of claims 1 to 7, wherein said insert (7) and/or said nail (1) is hollow or solid.

Inventors: BUEHREN VOLKER, MITTELMEIER WOLFRAM, WAHL THOMAS, BUEHREN, VOLKER, MITTELMEIER, WOLFRAM, WAHL, THOMAS, Bühren, Volker
Applicants: STRYKER TRAUMA GMBH
Application year: 1998
Main classification: A61B17
IPC codes: A61B17