Supra condylus bone nail

Abstract: A supra-condylar bone nail of body-compatible material having an elongated shank with a distal end and a proximal end to be inserted from the distal end of a femur from below the condylus, said shank having a first bend spaced from said distal end lying in a plane parallel to the medial plane of the human body and a second bend spaced a greater distance from said distal end than said first bend and lying in said same plane, said shank in the proximal portion further having at least one transverse bore for a bone screw and in the distal portion at least a transverse bore between said distal end and said bend for the accommodation of a condylar screw penetrating said condylar.

Description: The invention refers to a bone nail. Frequently, in cases of fractures of the femur bone nails are applied which are driven into the intermedullary bone canal from proximal. It is also known to apply so-called locking nails which have transverse bores to be fixed on both sides of the fracture. Fractures in the condylus area of the bone necessitate a very long bone nail. Furthermore, the danger exists that the bone is pierced through in the area of the condylus by which cartilage is damaged. EP-A-0 381 462 discloses a bone nail, particularly for a tibia having an elongated shank with a distal end and a proximal end. The shank has a first bend-off spaced from the distal end and lying in a plane. It has further a second bend spaced a greater distance from the distal end and lying in the same plane. The shank in the proximal and in the distal portion has at least one transverse bore between the end and the bend-off. The transverse bores are designed to accommodate a bone screw in order to lock the nail in the bone canal. In US-A-2 489 870 a bone fastening device is disclosed having a generally oval shaped plate with inwardly projecting prongs to be piercing into the bone portion in the distal range of a tibia. The plate is fastened on a sleeve-like nut which can be screwed onto a threaded portion of an elongated bolt having a head at the other end thereof. The bolt is inserted into a bore drilled transversely through fibula and tibia and allows to exert a pressure between the plate and the head of the bolt in order to compress the bone portions. The object of the invention is to provide a bone nail which can be used as supra condylus nail for the treatment of fractures in the condylus portion of the femur. This object is attained by features of claim 1. The invention provides for a supra condylus bone nail. The bone nail according to the invention has an elongated shank which is relatively short if compared with known femur nails. The maximum length is for example 230 mm. The bone nail according to the invention is driven into a bore which ends at the distal end between the condylii and which follows the intermedullary canal. For the drilling of the bore and the insertion of the nail it is necessary to bend the knee and to laterally displace the patella. For the surgical operation this does not meet any obstacle. In view of the function of the knee the position of the bore is not critical since it is located remote from the sliding areas of the condylii on the plateau of the tibia. The bone nail includes two bends-off. The first begins at a distance from the distal end of about a quarter or a third of the length of the nail. The angle for example is 8°. The second bend-off begins in the last third of the nail length if looking from the distal end and has approximately an angle of 3°. Both bends-off are lying in a plane parallel to the sagittal plane of the human body. Furthermore, the nail has transverse bores in the distal and the proximal portion, with the bores extending transverse to the mentioned plane wherein the nail is bent-off. The bores are adapted to accommodate bone screws. The bone nail according to the invention is to be applied to fractures in the condylus area, with at least one condylus screw being adapted to fix segments of the fracture in the distal area of the nail. The diameter of the nail according to the invention which is approximately between 10 and 12 mm may be held constant for different lengths. Preferably, according to an embodiment of the invention a set of bone nails can be provided having the same diameter, however, a different length, with the length difference occurring only in the proximal portion behind the second bend-off while the remaining portion is approximately 120 to 130 mm if looking from the distal end and remains substantially constant. In order to allow application of a condylus screw for a fracture of the condylus portion the invention provides that the condylus screw has a nut which is threaded onto a threaded portion of the shank of the condylus screw. Nut and head of the screw are flat and thin. By means of such a condylus screw segments of the fracture can be effectively compressed and retained at the nail. The shank and the nut have an axial throughbore, in particular for the guidance of the nut. A guiding lance may be threaded through the throughbore. According to another embodiment of the invention, the frontal side of the proximal portion of the shank has a skid-shaped flattening. This facilitates the driving and sliding in of the nail and avoids undesired damages of the bone. The shank of such a condylus screw is smooth. According to an embodiment of the invention the shank of the condylus screw is conically enlarged toward the end of the shank, and the nut includes a conical extension wherein the inner thread is formed to accommodate the threaded portion of the screw shank. The invention is explained in more detail along accompanying drawings. Fig. 1 shows diagrammatically the proximal portion of a femur including a bone nail according to the invention. Fig. 2 shows the underview of the femur of Fig. 1. Fig. 3 shows a front view of the distal portion of the femur with a bone nail according to the invention. Fig. 4 shows a lateral view of the bone nail according to the invention. Fig. 5 shows a cross section through a condylus screw for a bone nail of Fig. 4. Fig. 6 shows a cross section through a nut for the screw of Fig. 5. In Fig. 1 the distal portion of a femur 10 is shown which accommodates a bone nail 12. The bone nail 12 is inserted through a bore 14 which is made from below of the condylus retrograde (see Fig. 2). In a plane parallel to the sagittal plane the bone nail 12 which is solid and made of body compatible metal or metal alloy has a first distal portion 16, an intermediate portion 18 and a proximal portion 20. Distal portion 16 and proximal portion 20 have three transverse bores 22 or two transverse bores 24, respectively. Between the portions 16, 20 a first bend-off 26 is provided with an angle of 8°. A weaker bend-off is to be seen between portion 18 and portion 20 as shown at 28. This bend-off has an angle of approximately 3°. At the distal end the bone nail 12 has diametrically opposed recesses 30 for the engagement of a driving instrument. Furthermore, the distal end may have an axial threaded bore (not shown). It also serves for the engagement with a driving or retracting instrument. In Fig. 3 it can be seen that the condylus portion of the femur 10 has a oblique fracture. The fracture line is designated with 32. Two bone screws 34, 36 having a drill tip are extended through two of the three transverse bores 22 and serve for the fixation of the bone nail 12 in the femur, with the lower screw 36 penetrating both segments of the fracture. A particular condylus screw 38 is extended through the distal transverse bore 22. The structure of the screw is to be explained in more detail along Figs. 5 and 6. The condylus screw 38 has a thin smooth shank 40 which conically enlarges towards a head 42 as shown at 44. The head 42 is relatively thin and has a large diameter. The head 42, furthermore, has an inner hexagon 46 for a corresponding rotary tool. At the free end shank 40 has an outer threaded portion 48. A nut 50 in Fig. 6 has a flat head 52 similar to head 42 and an inner hexagon 54. A conical extension 46 joins to head 52 which is hollow and has an inner threaded portion 58 by which nut 50 can be threaded onto a threaded portion 48 of the condylus screw. As can be seen in Fig. 5, shank 50 and also head 46 are provided with a throughgoing axial bore 60 for the accommodation of a guiding lance. As can be seen in Fig. 3 by means of the condylus screw shown in Figs. 5 and 6 a compression force can be exerted onto the fracture segments. The diameter of shank 40 is such that it can be extended through the bores 42 with relatively small clearance. In Fig. 4 the bone nail 12 is more clearly illustrated as to the dimensions thereof. It can be seen furthermore that the proximal end of nail 20 is pointed as shown at 52. Furthermore, it has a flattening 54 frontally faced which forms a skid for the introduction of nail 12. It is again mentioned that the nail 12 may have different lengths. From the distal end up to the bend-off 28 all nails have the same length independent of their total length. Merely the portion between bend-off 28 and the proximal end the nails of a set of nails have different length. The diameter of nail 12 is constant for all lengths.

Claims: A bone nail of body-compatible material having an elongated shank with a distal end and a proximal end to be inserted in a bone canal, the shank having a first bend-off (26) spaced from the distal end lying in a plane and a second bend-off (28) spaced a greater distance from the distal end than the first bend-off and lying in the same plane, the shank in the proximal portion further having at least one transverse bore (24) for a bone screw and in the distal portion at least a transverse bore (22) between the distal end and the first bend-off (26) for the accommodation of a further screw (34, 36, 38), characterized in that a condylus screw (38) is provided having a smooth shank (40) and a flat head (42), the shank being adapted to be inserted through a distal transverse bore (22) and having a threaded portion (48) at the free end thereof, a nut (50) having an inner threaded portion (58) adapted to be threaded onto said threaded portion (48) of the shank, the nut (50) having a flat head (52), the shank (38) having a throughbore aligned with throughbores in the heads (42, 52) of the screw (38) and the nut (50), respectively. The bone nail of claim 1, wherein said shank is circular in cross section and has a diameter of between 10 and 12 mm. The bone nail of claim 1 or 2, wherein the front side of said proximal end of said shank has a skid-shaped flattening (54). The bone nail of claim 1, wherein said distal portion has two or three transverse bores (23). The bone nail of one of the claims 1 to 4, wherein said shank is conically enlarged (44) towards said head (52), and said nut (50) has a conical extension (56) wherein said inner thread (58) is formed. A set of bone nails of claim 1, wherein all bone nails have a constant diameter and the same length between said distal end and said second bend-off (28) and having different length between said proximal end and said second bend-off (28).

Inventors: ASCHE GERNOT, HARDER HANS ERICH, HEINZ THOMAS HEINRICH ANTON, HORNBERGER KLAUS, SCHNETTLER REINHARD, VECSEI VILMOS, ASCHE, GERNOT, DR. MED., HARDER, HANS ERICH, HEINZ, THOMAS HEINRICH ANTON, DR., HORNBERGER, KLAUS, DR. MED., SCHNETTLER, REINHARD, DR. DR. MED., VECSEI, VILMOS, PROF. DR. MED., Vécsei, Vilmos, Prof. Dr. med.
Applicants: STRYKER TRAUMA GMBH
Application year: 1997
Main classification: A61B17
IPC codes: A61B17