Surgery – Instruments – Orthopedic instrumentation
Patent
1996-04-04
1998-02-03
Buiz, Michael
Surgery
Instruments
Orthopedic instrumentation
606 62, 606 64, 606 98, A61B 1778
Patent
active
057139024
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an osteosynthesis auxiliary with a locking nail, a femoral-neck part and a locking rod associated therewith, for the treatment of subtrochanteric peritrochanteric, and femoral-neck fractures.
An osteosynthesis auxiliary of this kind has been disclosed e.g. in EP 0 321 170 A1. In this known osteosynthesis auxiliary the locking nail serves to guide and hold a femoral-neck screw. For this purpose the locking nail comprises in its proximal region a slanted bore traversing the nail, through which the femoral-neck screw can be passed. At the end of the femoral-neck screw toward the head of the femur a self-cutting thread is provided, with which anchoring in the head of the femur is achieved. In addition, into the proximal end of the locking nail a stay-pin can be inserted, by means of which the femoral-neck screw is secured against rotation. This stay-pin simultaneously cooperates with axial grooves at the circumference of the femoral-neck screw to limit the axial movement of the femoral-neck screw within the slanted bore of the locking nail. Alternatively, the stay-pin can be used to produce a rigid connection between femoral-neck screw and locking nail. One disadvantageous feature of this known construction is that in case of a peritrochanteric fracture it is possible for the head of the femur to twist with respect to the femoral-neck screw. Here it should be kept in mind that a not inconsiderable part of the femoral-neck screw lies within the relatively soft spongiosa of the neck of the femur. Only the self-cutting thread extends into the relatively firm spongiosa of the head of the femur. Under severe stress, this thread is not guaranteed to be rotationally stable with respect to the head-neck fragment, so that the above-mentioned twisting of the head of the femur can result.
The situation is very similar in the case of the osteosynthesis auxiliary according to EP 0 521 600 A1; there too the femoral-neck part is rotationally symmetrical with a threaded section at its free end. No means are provided for axial fixation of the femoral-neck part within the slanted passageway that traverses the locking nail. However, this document discloses that the slanted passageway in the proximal region of the locking nail has a cross section with a shape other than circular or rotationally symmetrical. The section of the femoral-neck part that extends through the slanted passageway in the locking nail has a complementary cross section. By these means the attachment of the femoral-neck part to the locking nail is made rotationally stable. The rotational stability of the neck of the femur itself with respect to the femoral-neck part is, however, not thereby guaranteed, in view of the fact that the section of the femoral-neck part that extends into the spongiosa of the neck of the femur is rotationally symmetrical and is provided at its free end with a rotationally symmetrical thread. Finally, means of increasing the resistance of the locking nail to breakage in the region of the slanted passageway for the femoral-neck part are also lacking. The same applies to the osteosynthesis auxiliary according to EP 0 321 170 A1.
The patent U.S. Pat. No. 4,103,683 discloses the construction of the femoral-neck part as a metal strip with a spiral coiling at its end toward the head of the femur. Moreover, the femoral-neck part so constructed extends at a right angle to the locking nail. In this regard it should be said that the neck of the femur as a rule is inclined at an angle of about 125.degree. relative to the straight part of the femur. This angle may become smaller with increasing age; in any case it is unlikely that in nature the neck of the femur would be inclined at an angle of 90.degree. to the straight part. The consequence is that when this known construction is employed, the possibility cannot be excluded that after some time the femoral-neck part will emerge from the neck of the femur. In addition, the spirally coiled end of the femoral-neck part or the known femoral-neck blade
REFERENCES:
patent: 3433220 (1969-03-01), Zickel
patent: 3561437 (1971-02-01), Orlich
patent: 4103683 (1978-08-01), Neufeld
patent: 4697585 (1987-10-01), Williams
patent: 4895572 (1990-01-01), Chernoff
patent: 4978349 (1990-12-01), Frigg
Buiz Michael
Endocare AG
Reip David O.
LandOfFree
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