Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2000-04-27
2002-10-08
Philogene, Pedro (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C606S062000, C606S064000
Reexamination Certificate
active
06461360
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a locking nail for the repair of femur shaft fracture and trochanteric femur fractures.
2. Description of the Prior Art
An osteosynthetic aid for the repair of intertrochanteric or subtrochanteric femur fractures which is designed as a locking nail with an open cloverleaf profile is known from the reference EP 0 528 128. The locking nail has inclined bores in its proximal section for guiding and holding a femoral neck screw. The locking nail has an axial longitudinal slit at its distal section. The locking nail also has a bend at the transition between a proximal partial section and a distal partial section. Disadvantageous in this known locking nail is the fact that it is difficult to introduce into the medullary space.
SUMMARY OF THE INVENTION
The object of the present invention is to create a more advantageous locking nail for the repair of femur shaft fractures.
This object is satisfied in particular by a locking nail comprising a proximal nail section and a distal nail section adjoining the latter, with these nail sections having bores for the reception of bone screws, and with the distal nail section having a curvature extending in an anterior-posterior plane and corresponding substantially to the antecurvature of the femur; and with the proximal nail section having at least over a partial section a continuous curvature, in particular with constant radius of curvature, extending in a lateral-medial plane. The term “continuous curvature” will be understood in the following to mean that the curvature has no point with a discontinuity or a bend respectively, which can be mathematically described in such a manner that the first derivative of the curvature plot has no discontinuity or no jump-like change.
In an advantageous embodiment the proximal nail section, starting from the distal nail section, has a transition section and a securing section adjoining the latter with bores for the reception of the bone screws, with the transition section and the securing section having a continuous curvature with a constant radius of curvature.
The locking nail in accordance with the invention is suitable in particular for the repair of femur shaft fractures, also in connection with trochanteric femur fractures, with the locking nail being manufactured with lengths of about 300 mm to 500 mm due to the inter-individually differing shaping of the femur. The locking nail is distinguished by a good mechanical hold in the medullary cavity and has a good rotational security. A transverse bore through which a bone screw is introduced in order to firmly hold the locking nail axially and in the direction of rotation is arranged in the lower distal nail section. The proximal nail section preferably has an inclined through-bore through which a femoral neck screw can be introduced.
The locking nail in accordance with the invention is preferably designed as a continuous hollow tube, in particular as a cylindrical hollow tube, and consists of a body-compatible, non-corroding material such as titanium or a titanium alloy. A guide wire is preferably introduced into the continuous hollow tube. The locking nail could however also be designed in the shape of a bar and have no hollow inner space extending in the axial direction.
An advantage of the locking nail in accordance with the invention is the fact that the latter can be introduced into the medullary space of the femur without a greater exertion of force even in an embodiment with low elasticity. The embodiment with low elasticity ensures a very good mechanical hold and a good support function in the medullary cavity.
The locking nail in accordance with the invention is designed in such a manner that the latter is preferably introduced into the femur or into its medullary space respectively starting from the trochanter major, with the introduction point being located slightly laterally with respect to the tip of the trochanter major. Since the trochanter major is arranged closer to the surface of the skin in comparison with the previously usual introduction location at the femur, the introduction via the trochanter major has the advantage that a smaller opening of the operation field is required, which in particular reduces the danger of infections. In addition the trochanter major is more easily accessible in the activities required during the operation. A locking nail was usually introduced into the medullary space in the region of the fossa piriformis. Blood vessels, etc. are also present at this location, however, so that the introduction via the trochanter major is more sure to avoid damage to these blood vessels. In an advantageous embodiment the locking nail has a securing section with a relatively small cross-section. This enables a locking nail to be formed with a smaller total cross-section, which has an advantageous effect on the introduction into the medullary space and in addition requires only a small opening of the operation field.
The locking nail which is known from the cited reference has at the transition location between the distal and the proximal nail section a bend location and is therefore difficult to introduce into the medullary space in spite of the elasticity produced by the longitudinal slit in the distal nail section since the medullary space has a curved extent and this nail lies in contact at certain locations at the medullary space wall or at the spongiosa and can be introduced into the medullary space only with a greater exertion of force. The locking nail in accordance with the invention with the curved proximal nail section has the advantage that the latter takes into account the anatomical shape of the medullary space in such an advantageous manner that it can be introduced without a greater exertion of force. In contrast to short locking nails, the locking nail in accordance with the invention, which is designed to be very long, must be rotated during the introduction into the medullary space by a partial rotation about its longitudinal axis. The locking nail in accordance with the invention has the property that the latter rotates into the correct final position by itself during the introduction into the medullary space since the outer shape of the locking nail is formed in imitation of the shape of the medullary space with respect to essential aspects. The locking nail which is known from the cited reference has a bend at the transition location between the proximal and distal nail section, which prevents a rotation of its own accord during the introduction into the medullary space. The locking nail which is known from the cited reference has the further disadvantage that the nail which is introduced into the medullary space is only rotatable to a limited extent since material protrudes into the longitudinal slit and forms an obstacle during the rotation. Since the locking nail in accordance with the invention does not necessarily require a longitudinal slit, it can also be manufactured more economically.
The locking nail in accordance with the invention can have a low elasticity and nevertheless be surely introduced without a greater exertion of force into the medullary space. Through the design of the locking nail in accordance with the invention a greater force, which is directed approximately radially outwardly and in particular weakens or destroys the femur corticalis, is avoided during its introduction into the medullary space. Through this it is also enabled that the femur is held together in its anatomically correct position. It is known that an unfavorably designed locking nail can cause the femur having the fracture to adapt to the shape of the locking nail, which has the result that the fixed femur has a faulty position or a deviation from the normal position respectively.
REFERENCES:
patent: 2518019 (1950-08-01), Kane
patent: 4135507 (1979-01-01), Harris
patent: 4475545 (1984-10-01), Ender
patent: 4622959 (1986-11-01), Marcus
patent: 5374235 (1994-12-01), Ahrens
patent: 5697930 (1997-12-01), Itoman et al.
patent: 57139
Philogene Pedro
Sulzer Orthopedics Ltd.
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