Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2000-07-19
2002-01-22
Reip, David O. (Department: 3731)
Surgery
Instruments
Orthopedic instrumentation
Reexamination Certificate
active
06340362
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a plate for joining a pelvic fracture, wherein the plate can be fastened by fastening means like screws, nails or the like on either side of said facture to pelvic bone portions to be connected.
Such a plate is known from German patent DE 2 603 087. If a fracture of the pelvis has occured, a plate is fastened to the pelvic for osteosynthesis, i.e. to aid healing of the broken pelvic bone. The plate is placed approximately transversly to the fracture and is fixed to the two portions of the pelvic bone to be connected on either side of the fracture.
The conventional plates are integrally formed as rigid plates, which are secured by means of screws, nails or the like to the bone portions.
The rigid plates, usually made of refined steel, have however drawbacks. The bone portions on either side of the fracture are rigidly fixed to one another with respect to all degrees of freedom. No consideration is made of the fact that the pelvis does not represent a rigid bone system. Rather, the anatomy of the pelvis provides several bone sections, which allow relative movement to one another. In particular, the lower left and right pelvic bones in the region of the coccyx, the pubic arches (arci pubici), are only connected to one another by cartilage, i.e. by the pubic symphysis (symphysis pubica). The cartilage connection between the pubic arches acts as a pivot connection, which allows relative movement of the arches during various human activities, for example walking, lying down or sitting.
A fracture of this cartilage is normally vertical. A plate is spanned across the cartilage transversly to the fracture direction and is fastened to the pubic arches on either side of the cartilage. The fractured cartilage is allowed to heal by holding the two arches together by means of the plate. The conventional rigid plate guarantees support of the two arches, however due to its rigid construction, the plate prevents all other natural movements of the two pelvic bone portions relative to one another, as is the case with the plate known from DE 26 03 087 mentioned above.
The afore-mentioned known plate for fixing a symphysis fracture comprises a plate made of plastics comprising an overall homogenous thickness. The plate is bent in form of a collar comprising two unconnected side parts at its rear side and a front part prolongated over the side parts downwardly and having a central indentation at its rim. The rearward rims of the side parts are tilted relative to each other and rolled round so far that they run parallel to the front side plate plane in an transition region between the front part and the side parts.
Movement of the patient in bed, for example when the patient turns from his back over to his side, causes torques and tensile forces to be exerted on the two lower pelvic bone portions. These forces are transferred to the plate and the screws and nails, because the conventional rigid plate does not allow relative movement of the bone portions. The forces are great enough that they could tear out the screws or nails. When using such conventional plates, the patient must therefore be completely immobilized to avoid pulling out the screws or nails, which, however, is unpleasant for the patient.
The object of the present invention is to provide an improved plate of the mentioned type, where the patient with a pelvic fracture can move without the screws or nails securing the plate to the pelvic bone being torn out and where at the same time it is guaranteed that the pelvic fracture is securely held and can heal.
SUMMARY OF THE INVENTION
According to the present invention, the object underlying the invention is achieved by a plate of the kind mentioned at the outset, comprising:
at least two parts arranged along an axial direction of said plate,
a first engaging means provided on one of said parts,
second engaging means provided on the other of said parts,
wherein said first engaging means and said second engaging means are intended to connect said two parts with each other, and wherein said first and second engaging means are formed such that said two parts are secured to one another in said axial direction and in a transverse direction to a plate plane, and that said two parts are moveable relative to one another in a limited pivotal range.
The two-part configuration of the plate has the advantage over the conventional one-piece rigid configuration that relative motion is allowed between the interconnected pelvic bone portions. Through the interconnection of the two parts with the two engaging means, the two parts are secured to one another in axial direction and in transverse direction to the plate plane, such that the fracture is securely supported transversely to the fracture direction. Thus healing of the fracture is guaranteed, because the engaging means prevent the two pelvic bone portions on either side of the fracture from moving apart.
By providing the two parts to be moveable relative to one another by a certain limited pivotal movement, the advantage is achieved that the bone portions interconnected by the plate can maintain their natural, anatomical relative movement. It is also avoided that the bone screws or nails are torn out of the pelvic bone portions when the patient moves. The plate according to the present invention provides a degree of freedom of relative movement of the two parts within a limited angular range. The limited relative motion of the two parts can be achieved for example in that the engaging means interact with play therebetween.
In a preferred embodiment, the two parts have a limited pivotal movement about a first pivot axis running transversly to the plate plane.
This feature allows the two parts to rotate or pivot by a limited amount relative to one another in the plate plane. The advantage is achieved that the natural movement of the pubic arches is maintained, for example when the patient is standing up and one leg carries more weight than the other.
In a further preferred embodiment, the two parts have a limited pivotal movement about a second pivot axis running in the plate plane transversely to the axial direction.
This allows the two parts to be rotated with respect to one another out of the plate plane. The advantage is achieved that the relative movement of the pubic arches is also maintained, for example when the patient turns over in bed or rises to a sitting position.
In a further preferred embodiment, the two parts are counter-directionally rotatable with respect to one another about the longitudinal axis by a limited angle.
This feature of the plate according to the invention provides the advantage of a further degree of freedom of the relative motion.
In a further preferred embodiment the first engaging means comprises at least one surface oriented substantially transversely to the plate plane and transversely to the axial direction which engages behind a surface of the second engaging means oriented substantially transversely to the plate plane and transversely to the axial direction, and wherein two surfaces are arranged to have play there between.
The two counter-engaging surfaces on the two engaging means engaging behind each other ensure that the two parts of the plate according to the present invention are secured against tensile forces in the axial direction and in transverse direction to the plate plane. In this manner, a mechanically simple connection of the two parts of the plate is advantageously provided. The orientation of the two surfaces can be perpendicular to the plate plane and perpendicular to the axial direction, wherein in this case, two additional overlying engagement surfaces are necessary. These additional surfaces have an orientation approximately parallel to the plate plane, for example in the form of engagement means formed as back cuts to secure the two parts in transverse direction to the plate plane. However, it is more advantageous that the two surfaces are oriented such that they have both a component perpendicular to the plate plane and also a component par
Pierer Wolfgang
Zeidler Hubert
IMPAQ GmbH Medizintechnik
Reip David O.
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