JPH0368696B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a bone nail with a circular cross section for the fixation of femoral fractures, which comprises a bone nail with a circular cross section for fixing femoral fractures. a region having a cross-section different from a circular cross-section near the end, said region having a cross-section different from a circular cross-section being curved about an axis extending primarily parallel to the longitudinal direction of the bone nail; It also relates to tools of the type having concave and convex surfaces partially projecting from a circular cross-section and for exerting forces or rotational moments on the bone nail.

Prior Art The bone nail to which the present invention is directed follows the so-called bone nail bundle fixation principle, in which the bone nail is driven into the medullary canal using curvature and elasticity and is supported by the cortex at its distal end. Advantageously used.

The principle of bone nail bundle fixation is described in the monograph ``Bone nail bundle fixation method'', KHHackethal, Berlin, Goestingen, Heidelberg, 1961. In this case, a stable, well-shaped medullary splint is achieved with multiple resilient steel bone nails. The steel bone nail is driven through an opening in the medullary retainer. In most cases, the curved bone nail completely or partially fills the medullary canal, and the stabilization and thus maintenance of the reduction result is achieved by widening the bone nail in the area of its proximal end (see ref. Page 25, Figure 13 and related explanation). The bone nail bundle fixation principle method utilizes the spring action of the bone nail supported by the cortex within the bone window formed to introduce the bone nail. Biasing of the bone nail after positioning it is an important outcome for treatment. The operation of the bone nail during driving, positioning, and driving of the bone nail is performed from the distal end. In operation, the following movements must therefore be transmitted by the action of appropriate forces: That is, it consists of (1) the driving force that acts impulsively on the rear end of the bone nail in the longitudinal direction of the bone nail, and (2) the rotation of the bone nail that is applied during driving and drives the bone nail. (3) a retraction force that allows the bone nail to be pulled out of the medullary canal once the bone has fully healed.

In order to transmit these forces, a constructionally expensive design is required (page 95 of said document, figs. 66 and 67), in which case the bone nails are assembled in bundles. Special tools are required which require space which is only available to a limited extent due to the location.

According to West German Patent Application No. 2459257, the distal end of the bone nail is configured flat in the form of a small plate, so that a large number of bone nail ends can be arranged side by side and one on top of the other. is publicly known. The small plate-like flat portion makes it possible to transmit a rotational moment to the driving tool when driving a bone nail. Furthermore, this small plate-like flat part is designed to allow the force that should be transmitted to the bone to be transmitted to the bone over a large surface due to the bias applied to the bone nail at the distal end of the bone nail. make it possible to

Furthermore, West German Utility Model No. 75 19 604 discloses a bone nail having the features set out in the generic part of claim 1.

However, in this case, depending on the treatment conditions, the distal end of the bone nail may be brought into full contact with the cortex, and the bone nail may be placed in such a way that the spring force of the bone nail is introduced into the bone through the entire surface. It is not taken into account that it is not always possible to position the distal end of the . The above-mentioned perfect positioning is based on the bone nail bundle fixation method, which uses the principle that the bone nail tips spatially fan out to the sealine of the femoral head in order to achieve accurate reduction and fixation of the fracture. It cannot be achieved from the beginning because it is based on. Known bone nails with a small plate-shaped flat part necessarily have a small plate-like flat part, since in all bone nails the bone nail has a curvature directed in the same direction with respect to the flat part in the nail longitudinal direction. are given a different position than the parallel roof tile arrangement. As a result, the bone nail exerts a chisel-like pressing force on the cortex on the narrow side of the flattened portion, that is, on the sharp edge, and this creates the risk of puncture.

The distal end of the bone nail remains fixed and projects through the window opening formed in the bone, using the edge of the window as a backrest and thus preventing its elastic return to the medullary canal. Therefore, if the flat bone nail end is not satisfactorily positioned, there is a risk of developing a primary pressure ulcer with subsequent infection in the area of the sharp edge of the bone nail end.

The object of the invention as defined in claim 1 is to improve the distal end of the bone nail as defined in the generic part of claim 1 so that the above-mentioned risks are eliminated and the bone nail can still be operated. It allows the reception of all the forces that may otherwise be transmitted, thereby preventing the bone nail from sinking into the cortex of the bone, especially in the case of porous bones.

In this case, the invention is based on the recognition that a chisel-like effect on the surrounding bone region or surrounding tissue region can only be prevented if sharp edge bends and high pressure forces are avoided. The solution found is that, in particular when transmitting torque with the aid of screw spanner-like tools, technically speaking, cross-sections with sharp edges (triangular, square or polygonal cross-sections are usually chosen) Therefore, it is necessary to find a shape that allows a dense bundle of bone nails to be obtained without creating a narrow chisel-like surface edge. On the basis of By having a circular arc on the cylindrical bone nail surface corresponding to an angle of less than 120° when viewed, or by having a notch limited to an appropriate length in the longitudinal direction of the bone nail, the bone nail can assume any position without creating undesirably high surface pressures that damage the cortex in the implanted state.

A particular advantage of the solution of the invention, besides the fact that only simple tools are required to produce such a bone nail, is that its operation is carried out with a simply constructed device. This is something that can be done.

The invention will now be explained with reference to the drawings: In FIG. 1 a bone nail 2 is shown. In this case, the area shown enlarged in FIGS. 1a to 1c is surrounded by a dashed line. The notch 8 of the bone nail 2 is located inside the curvature of the bone nail. This curvature can consist of various curvatures and bends distributed over the entire length of the bone nail, such that when used for fixation of a femoral neck fracture, the bone nail end holding the notch 8 will On the back side opposite to the notch 8, the cortex can be contacted without damaging it.

A semicircular recess 8 is arranged at the distal end of the bone nail according to the invention, which is shown enlarged in FIGS. 1a to 1c. The rounding of the notch 8 extends in the direction of the rounding in the nail surface, and the notch 8 is set back relative to the outer end of the nail. In the region of the longitudinal edge of the bone nail, the recess 8 transitions into the cylindrical outer circumferential surface of the bone nail via a lightly contoured profile.
A transparent opening 9 is provided at the bottom of the notch. The opening forms a passage towards the opposite extent of the outer circumferential surface of the bone nail and occupies a smaller area than the notch 8. The cutout 8 has an upper limiting surface 10 which extends substantially horizontally. The limiting surface connects directly or indirectly to the transparent opening 9 in an area close to the distal end of the bone nail. Areas 11 and 12 serving to introduce the rotational moment are provided on the sides of the recess 8. Advantageously, the recess 8 is provided on one side.

FIG. 2a shows a cross section of the bone nail shown in FIGS. 1 to 1a. The cutting plane is indicated in FIG. 1b. In this case, the notch 8 is cold deformed so that areas 11 and 12 extend beyond the circular bone nail cross section and are arranged symmetrically with respect to the diameter line 13, which is shown in dash-dotted lines. It is formed like this. Anteriorly curved, in the longitudinal direction of the bone nail, the range in which the cross section does not change over one section in the longitudinal direction of the bone nail or does not exceed the maximum contour, in the range beyond the circular cross section of the bone nail,
It is likewise constructed symmetrically with respect to line 14, indicated in dash-dotted lines, so that the inner contour allows manipulation with a tool, indicated by dashed line 15. In this way, the tool can be easily inserted and manipulated. This can be achieved by arranging the regions 11, 12 symmetrically constructed at 120° or 180° radially.

As can be seen from this cross section, the cross section of the bone nail has only a slight deviation from the disc shape in the area of the cutout 8, except for the cutout 8 and the open opening 9. The cross-sectional shape may be slightly oval or oval or triangular with rounding. In the case of an elliptical design, the axial ratio is preferably 1:
1.1 and 1:1.2, the longer half-axis being oriented parallel to the plane area in which the recess 8 is provided. The slightly eccentric deformation of the cross section of the bone nail end in the area of the recess 8 as described above corresponds to the advantageous manufacturing method of the bone nail according to the invention, in which the recess 8 is formed by a cold deformation method. This is accomplished by typing. The resulting eccentricity is such that when driving a bone nail with a sleeve that is suitably adjusted and fitted over the bone nail, the eccentricity at the distal end of the bone nail is This is sufficient to apply a rotational moment that allows a controlled introduction of the bone nail with respect to the desired direction.

Furthermore, as can be seen in FIG. 2a, the recess 8 is arranged in the lateral region of the recess 8 due to the rounding according to the invention in such a way that no chisel-like pressure forces are produced on the bone or tissue parts. The fact that the narrow and limited surface area and the resulting high compressive force acting on the bone or tissue area means that the notch 8 is not located directly at the end of the bone nail, but from this end. This can also be avoided by forming an undeformed bone nail region at the bone nail end, which is placed at a small distance and rests on the bone or tissue over a large area.

The outer surface of the bone nail facing the notch 8 forms a range that ensures reliable contact with the upper edge of the bone window even if the bone nail is introduced with a twist of more than ±90° when viewed in the axial direction. do. Since the bone nail end has a cross-section that differs relatively only slightly from a circular cross-section, the parallel arrangement of the bone nail in the bone nail layer also results in a noticeable space in the area of the notch 8. is possible without the additional need for

In FIG. 2b, a number of bone nails 8 are shown in section, deliberately arranged in a bundle. In this case, the different contact areas of the adjacent bone nails cause the practitioner to move in the direction of the notch 8, even though the bone nails have areas 11, 12 beyond the circular cross section. This allows bone nail placement without the need for attention to accurately position the bone nail in between. Rather, the formation of a tight bone nail bundle is also possible if the individual bone nails are arranged at different angular values.

In this case, regions 11 and 12 extend beyond the circular cross-section of the bone nail 2 at the locations of the cavities 21 to 25 between closely spaced adjacent bone nails. Said regions 11, 12 protrude into the space unfilled by material between the circular cross-sections of the bone nail, allowing the bone nail to be placed tightly. In the area 22, the raised areas of the two bone nails are arranged in a space area formed by the three bone nails adjacent to each other so that they do not interfere with each other.

As can be seen from Figure 2b, the distal bone nail end does not have to contact the cortex along a straight line, but can simply follow a curved surface. In this case, the limit line of the space provided for reduction and fixation by the bone nail can be imagined as the tangent to the bone nail shown in the upper part of FIG. 2b. The advantage of placing the bone nail in a tight band and using less space is also obtained with respect to the corresponding bone nail end on the opposite side, which is not shown.

Furthermore, the space provided between the circular sections of the bone nail can be occupied by the raised areas 11 and 12 even if the notches 8 are not located at the same height.

In FIG. 3, at the distal end of the bone nail 2,
The lower extent of the tool 31 is shown which engages to apply pushing and pulling forces or turning moments. A number of variant embodiments are shown in dashed lines in the drawings, which can be used in various combinations.

If the end of the bone nail 2 is configured as an ellipse or an oblong in the area of the notch, it can be used as a driving tool in the non-circular shape of the bone nail end, unlike the shape shown in FIG. It has matched notches to transmit the moment necessary for rotation of the bone nail during driving.

On the other hand, in the case of non-circular cross-sections and circular cross-sections, the tool shape shown in Fig. 3 can be used both for driving bone nails with rotation and for pulling bone nails. Can be used.

The holding part 32 of the tool 31 is provided with a hook-like extension, on which a jaw 33 adapted to fit into the notch 8 is provided. Surface 10 of bone nail 2
The acting surface 34 allows the bone nail to be withdrawn from the bone after the treatment is completed. Different lengths (dashed line 35
a) and whose free end is rounded for introduction into the open-air opening 9;
is used.

In order to avoid that the hook-shaped addition part with the surface 34 slips off when applying a rotational moment to the bone nail or when pulling the bone nail out, a locking part 36 is provided in the part of the tool that comes into contact with the notch 8. It is being This locking part 36 can have various different constructions. It can be configured as a corresponding jaw of a pincer that can grasp the distal end of the bone nail 2 or the bone nail 2.

On the other hand, the embodiment shown in broken lines is also possible. Although this embodiment is fixedly connected to the opposite side of the tool 31 that engages in the notch 8,
It is shortened and slightly rounded. The tool 31, which is constructed in one and fixed manner, can therefore be pushed over the bone nail end with a lateral tilt. If the tool is guided coaxially with respect to the bone nail, a slippage of the part 33 that engages in the recess 8 is reliably avoided.

When the tool 31 is configured in a pincer shape,
The variant embodiment indicated by the dot-dashed line 36b is advantageous. This elongated structure is provided with a through hole 37 which is engaged with an elongated pin 35a. With this configuration, the strength of the bond between the tool and the bone nail can be additionally increased if it is necessary to apply a particularly large force to pull out the bone nail.

[Brief explanation of drawings]

The drawings show advantageous embodiments of the invention, FIG. 1 being a side view of a bone nail according to the invention, FIG.
Figures 1b and 1c show a bone nail according to the invention.
An enlarged side view of the distal bone nail end of the embodiment; FIG. 2a is a cross-sectional view of the bone nail end of the same embodiment; FIG. 2b is a second
FIG. 3 is a sectional view of a tool for applying force or rotational moment to the bone nails. 2... Bone nail, 8... Notch, 9... Penetration opening, 1
0...Restriction surface, 11,12...Range, 13,14
...Dotted chain line, 20, 21, 22, 23...Hollow chamber, 31...Tool, 32...Holding part, 33...
Jiyo, 34... Surface, 35... Pin, 40... Fixing member, 41... Additional portion, 42, 43... Notch, 44, 45... Bone screw.

Claims (1)

[Scope of Claims] 1. A bone nail with a circular cross section for the fixation of femoral fractures, the nail having a circular cross section near one end for introducing forces and/or moments during the procedure. comprises a region with a different cross-section, said region having a cross-section different from the circular cross-section being curved about an axis extending primarily parallel to the longitudinal direction of the bone nail; The convex surface projects only slightly from the cylindrical outer surface of the bone nail, and the surface area is continuously curved. and is connected to a tank-shaped notch 8 including a concave surface, and is characterized in that when the bone nail 2 is curved, the notch 8 is present on the inside of the curve over the entire length of the bone nail 2. A bone nail for fixing femoral fractures. 2 Areas 11, 12 projecting from the circular cross-section of the bone nail 2, which serve to transmit rotational moments to the bone nail 2 by form-fitting, are arranged so that the circular cross-section of the bone nail 2 when the bone nail 2 is tightly bound is 2. A bone nail according to claim 1, in which the bone nail protrudes from the cylindrical surface of the bone nail only to the extent that it fits into the spaces 21-25 remaining between the surfaces. 3. The range 11,1 protruding from the circular cross section
3. A bone nail according to claim 1 or 2, wherein the nails are radially symmetrically arranged over an angle of 120 or 180°. 4 Notch 8 and area 1 protruding from the circular cross section
1 and 12 are formed by cold deformation, any one of claims 1 to 3.
Bone nail as described in section. 5 Surface 10 limiting the notch 8 near the bone nail end
A bone nail according to any one of claims 1 to 4, wherein the bone nail is flat and forms part of a cross section of the bone nail oriented approximately at right angles to the axis. . 6. In the area of the notch 8 there is provided a transparent opening 9, which opens into the bone nail surface area facing the notch 8 and which is wider than the bone nail surface area occupied by the notch 8. Any one of claims 1 to 5 having a significantly smaller cross section
Bone nail as described in section. 7. Bone nails with a circular cross section for fixation of femoral fractures, with a cross section different from the circular cross section near one end for introducing forces and/or moments during the procedure. concavities and convexities partially projecting from the circular cross-section, comprising a region, said region having a cross-section different from the circular cross-section, said region being curved about an axis extending primarily parallel to the longitudinal direction of the bone nail; with a convex surface projecting only slightly from the cylindrical outer surface of the bone nail, and a continuously curved surface area with a trough-like surface including a concave surface. The bone nail is connected to the notch 8 in order to drive a bone nail of the type that exists inside the curvature over the entire length of the bone nail 2 when the notch 8 curves the bone nail 2. In a tool 31 for generating a force or a rotational moment, a jaw 3 is provided with a protuberance aligned with said notch 8.
3. A tool for driving a bone nail for fixing a femoral fracture. 8. The jaw 33 has a surface 34 that generates force on a notch surface that forms a part of the cross section of the bone nail.
A tool according to claim 7. 9 Locking members 36, 36 supported by the portion of the cylindrical surface of the distal bone nail end facing the notch 8 and keeping the tool surface and bone nail surface in contact with each other.
9. A tool according to claim 8, comprising: a, 36b. 10. The device according to claim 9, wherein the locking member consists of a projection 36a or, if the tool is of tongue-shaped construction, a corresponding jaw 36b and/or a slidable locking bar. tool. 11 This is a tool for driving a bone nail with a transparent opening in the notch 8, and pins 35, 35a are provided as centering members, and when the jaw is in the engaged state, the pins 35, 35a are 11. A tool according to any one of claims 7 to 10, which engages or passes through a transparent opening provided in a bone nail.