Bone plate arrangement

p0001The invention relates to a bone plate assembly comprising a bone plate and at least one bone screw, wherein the bone plate has a through hole for direction indeterminate receiving the shaft of the bone screw and make both parts form corresponding cooperating bearing surfaces.

p0002The cooperating contact surfaces of bone plates and bone screws are running angularly movable, in general, in particular with a spherical bearing surface of the screw head. This is to the effect that the fastening of the bone plate to the bone independently of the bone screw direction comes about, which may differ from the perpendicular to the bone plate toward accidental or deliberate, to take account of anatomical conditions (DE-PS 29 38 202).

p0003Also known bone screws with a flat design of the bearing surfaces on the screw head and the platen (DE-OS 28 32 555, Figure 2), but are used only for secondary purposes, if it is either in the bone fixed screws towards mutual on an accurate system the bearing surfaces does not arrive or a short screw shaft in soft bone material can be swiveled so when tightening without disadvantage that its direction adjusts to the coaxial to the bearing surfaces direction.

p0004The direction of the screw to the bone plate bone fragment is determined in each case, that the surface of the bone fragment is pressed to the surface of the bone plate by the screw and thus this must take place in the same direction.

p0005The invention is based, to broaden the applications of bone plates the task.

p0006The inventive solution is that the bearing surfaces are formed in the direction of determining with respect to a direction deviating from the perpendicular to the bone plate direction. Preferably, the bearing surfaces are flat or consistent conical.

p0007The invention provides the ability to grant the screw to the bone plate bone fragment a direction that is predetermined by the direction of the bone screw and the bearing surfaces and need not necessarily be dependent on the matching direction of the surface of the bone fragment and the surface of the bone plate. The Erfidnung permits accordingly, including those bone fragments impose a predetermined direction, which have no simple, can be brought to the bone plate according to the relief or the bone plate is not conformable to bending.

p0008The invention opens the possibility of an operational method in which the direction of a bone fragment during the attachment of the bone plate is selectively changed. For this purpose, the screw hole is generally perpendicular is first prepared for the bone plate and screwed the bone screw in this direction. When coming together at the end of screwing the screw, the bearing surfaces, they look for the same shape to create each of the screw clamping, whereby the screw is rotated until it runs coaxially with the bearing surfaces.

p0009Achieving and maintaining the desired direction is thus dependent on a close contact of the bearing surfaces together. Generally, this is when the operation achieved by the screw clamping. However, there are cases where the load on the bone fragment with the screw clamping required for safe installation of the bearing surfaces together is undesirable or where the system can not be ensured by the screw clamping alone in the long run. For these cases, it is expedient to provide the bone plate with a cover plate, which under pressure on the head of the bone screw can be connected to it.

p0010The invention is explained in more detail below with reference to the drawing which illustrates an advantageous embodiment. Therein:<dl id="dl0001"><dt>Fig. 1</dt><dd>an enlarged partial longitudinal section through a bone plate assembly,</dd><dt>FIG. 2</dt><dd>a plan view of the bone plate part shown in Figure 1 and</dd><dt>Fig. 3</dt><dd>a side view of a bone plate assembly as applied to three vertebrae.</dd></dl>

p0011The bone plate 1 includes a through hole 2, which is designed as a slot in the longitudinal direction of the bone plate to the shaft 3 of a bone screw not to impose restrictions angle in this direction. Radius of the through hole 2, the bone plate includes a recess 4 to form a support surface 5, which is opposite to the longitudinal direction of the bone plate inclined and flat.

p0012The bone screw associated with the shaft 3, the screw head 6 has a bottom support surface 7, which is also flat and perpendicular to the screw longitudinal axis running eighth

p0013If the bone screw (but need not extend) screwed into the dashed manner indicated in the direction 9, which runs approximately perpendicular to the plate in a bone fragment, then in the final stage of the tightening under the influence of the force acting in the longitudinal axis of the screw screw clamping the bearing surface 7 of the screw head will rest against the bearing surface 5 of the plate, so that a pivoting in the direction of the arrow 10 is made, is to complete installation of the bearing surfaces achieved together. This pivoting of the shaft 3 of the screw receiving bone fragment by the angle 11 can be achieved.

p0014When it seems impracticable aufzuüben the screw clamping required for pivoting on the bone fragment or if due to the nature of the surface of the fragment geometric reasons the pivoting is not possible, or if the maintenance of the desired angular position is not sufficient to ensure due to the screw clamping, one uses the belonging to the bone plate 1 cover plate 12, which is pressed by the screws 13 so against the screw head 6, that the bearing surfaces 5, 7 held together with safety.

p0015In the application example shown in FIG. 3, the problem, the vertebral body 14 from the position shown with dashed lines, it has taken as a result of an accident, establish illustrated by solid lines in the anatomically correct position. Two bone plates 1 are screwed in a symmetrical arrangement on both sides of the spinous processes with the illustrated vertebrae, the bone plate in the area of ​​righted the vertebral body 14 has an inclined support surface 5, adjacent its angle relative to the longitudinal direction of the bone plate about the tilt angle of the righted vertebral body towards the vertebrae corresponds. If now the bone screws screwed parallel to the main direction of the vertebral body through the pedicle approaches Besides the spinal canal in the vertebral body, as this depends on when creating the screw head 6 on the contact surface 5 in the desired manner, which can be supported and secured by the cover plate 12th