Patent ID: 12207851

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As shown inFIGS.1to4, the modular bone plate according to an embodiment includes at least a first plate member1, a second plate member1′ and optionally a third plate member1″ or further plate members that are to be connected to each other. For connecting the plate members1,1′,1″ connector members2,2′,2″ are provided that are configured to receive at least a portion of a bone anchor100,100′,100″ therein. The bone anchors may be secured, for example, against backing out once they are implanted into the bone via locking members3,3′,3″ that are configured to be inserted into the connector members2,2′,2″, respectively. One or more plug members4may be provided for connecting the plate members instead of using the connector members2,2′,2″. Moreover, end pieces5,5′ may optionally be provided that are configured to be connected to the plate members for forming an end of the bone plate.

InFIG.1, two different types of bone anchors are shown. The bone anchors100,100′ have a shank101with a first shank diameter and a head102,102′ with a first maximum head diameter. The bone anchor100″ has a shank101″ with a second shank diameter smaller than the first shank diameter and a head102″ with a second head diameter smaller than the first head diameter. As depicted in the Figure, the heads102,102″ have a spherically-shaped outer surface portion.

As shown inFIGS.2to4, the bone plate may be assembled from the plate members1,1′,1″ connected by the connector members2,2′,2″ and the plug members4. Then the bone anchors100,100′,100″ may be inserted into the connector members2,2′,2″ and secured by the locking members3,3′,3″.

Turning now in more detail toFIGS.5to8, a plate member1will be described. The other plate members1′,1″ in this embodiment are identical to the plate member1. The plate member1comprises a central plate portion10that has a top surface1aand an opposite bottom surface1b. As bottom surface1bthe surface is defined that faces the bone surface when the bone plate is to be attached to the bone. The plate member1therefore has a thickness in the plate portion10that corresponds to the distance of the top surface1afrom the bottom surface1b. It shall be mentioned that while the plate portion10has a constant thickness in the embodiment shown, the plate portion10may also have a varying thickness, or one or both of the surfaces may be curved or other deviations from a constant thickness may be contemplated.

The plate member1further comprises a first connection portion11that extends laterally away from the plate portion10and that serves for connecting the plate member1to another plate member V. The connection portion11comprises a first hole12with a central axis C, the first hole being at least partially threaded for cooperating with an external thread of the connector member2. Around the first hole, the connection portion11has a substantially circular outer contour forming an edge13. As can be seen in particular inFIGS.6and8, a lower surface of the first connection portion11is flush with the bottom surface1bof the plate portion10. A height of the first connection portion11, however, is smaller than the height of the plate portion10so that an upper surface of the first connection portion11is below the top surface1aof the plate portion10. At an outer end of the first connection portion11opposite to the plate portion10a projection14is formed that constitutes an outermost free end of the plate member1. The projection14extends in a plane perpendicular or at least substantially transverse to the center axis C of the first hole12and has a width in this plane that is smaller than a greatest width of the plate member in said plane. More specifically, the projection14is formed as a lug and has a substantially circular outer contour with the radius of the circle being considerably smaller that the radius of the first hole12. In a circumferential direction, the projection14has a width that is less than a quarter circle of a circumference of the first hole12. In a height direction, i.e. in a direction parallel to the center axis C of the first hole12, the projection14extends from the upper surface of the first connection portion11to a distance from the upper surface.

At a position opposite to the projection14in the plate portion10a groove15is provided that extends within the plate portion10at a distance from the edge13(see alsoFIGS.25and27). The groove15forms the end portion of a recess16that is cut out in the top surface11aof the first connection portion11and that extends substantially transverse to the center axis C of the first hole12. A width of the recess and therefore also of the groove15in a direction perpendicular to the center axis C and perpendicular to a longitudinal axis of the recess16is greater than a width of the projection14. The groove15and the recess16are at a height measured from the bottom surface1bthat corresponds to the height of the projection14. Sidewalls16aof the recess16form a stop for a projection provided at the other plate member as explained more in detail below.

In addition, the plate portion10comprises at the side facing towards the first connection portion11a recess10athat forms a stop for a portion of another plate member when the plate members are to be assembled.

On the side opposite to the first connection portion, the plate member1comprises a second connection portion111with a second hole112having a center axis C′ and an edge113with a substantially circular contour surrounding the second hole112. The second hole112is thread-less. In the second hole112a circumferential shoulder112ais provided at a distance from the upper surface that forms a stop for a connector member2as explained below.

An upper surface of the second connection portion111is flush with the top surface1aof the plate portion10and a lower surface of the second connection portion111has a distance from the bottom surface1bof the plate portion10in the height direction. At an outermost end of the second connection portion111a projection114is formed that constitutes an outermost end of the plate member1. The projection114is located at the lower surface of the second connection portion111such that it has the same height as the projection14of the first connection portion11. In a view from the bottom of the plate member1the projection114has a substantially rectangular shape with rounded edges. A thickness of the outermost portion of the projection114depicted inFIG.6, the projection114is connected through a rib114awith the edge113of the second connection portion111. In the same manner as the projection14, the projection114extends in a plane substantially transverse to the center axis (C′) of the second hole (112) and has a width in said plane that is smaller than a greatest width of the plate member in said plane. The plate portion10comprises another recess10bfacing towards the second connection portion111that forms an abutment for the first connection portion11of another plate member.

Opposite to the projection114with respect to the second hole112a groove115is provided in the plate portion10that extends within the plate portion10at a distance from the edge113(see alsoFIGS.25and27). The groove115forms an end portion of a recess116in the lower surface of the second connection portion111, the middle axis of the recess being substantially perpendicular to the center axis of the second hole112. By this design, the connection portions11,111are similar, but inversely shaped in such a manner that the second connection portion111is configured to cooperate with a first connection portion11of another plate member1′ and the first connection portion11is configured to cooperate with a second connection portion111of another plate member1″.

It shall be noted that the plate portion10of the plate member1can have various shapes and lengths. Plate members having the same of a different shape can be combined to form a bone plate. The first and the second connection portions, however, have always the same shape for each plate member1,1′,1″.

Turning now toFIGS.9to12, the connector member2is a substantially cylindrical piece with a top surface2aand an opposite bottom surface2b. An external thread21is provided in at least a portion of the outer surface of the connector member2, wherein the external thread21is configured to cooperate with the threaded first hole12of the plate member1. In addition, the connector member2comprises a passage22that extends from the top surface2ato the bottom surface2bcompletely through the connector member2. The passage22allows to pass a shank101of the bone anchor10,10′,10″ therethrough. In the passage22, at a distance from the bottom surface2ba seat portion23for a head102of the bone anchor is formed. The seat portion23has a spherical segment-shape and is oriented such that the diameter increases towards the top surface2a, so that the head102cannot pass through a lower opening of the connector member2. Adjacent to the top surface2aa substantially cylindrical recess24is provided that has at least in a portion thereof an internal thread24afor screwing in the locking member3. An inner diameter of the recess24may be greater than a greatest inner diameter of the seat portion23, such that the locking member3can be inserted and placed over the head102of the bone anchor. At the top surface2a, a circumferentially extending rim25is formed that extends outward beyond the external thread21. The rim25may comprise recesses26that are open to the outside and serve for easy gripping and inserting of the connector member. A lower surface25aof the rim25serves as an abutment or stop when inserting the connector member2into the holes12,112of the connection portions11,111.

As further shown inFIG.12, adjacent to the bottom surface2b, a conically widening section27may be provided to allow the bone anchor100to pivot in the seat portion23when it is not yet screwed into the bone. A total axial length of the connector member may be such that the top surface2ais in the assembled state flush with the top surface1aof the plate member and the bottom surface2bof the connector member2is flush with the bottom surface1bof the plate member.

Referring toFIGS.13and14, a second connector member2″ is shown that is also depicted inFIGS.1to4. The second connector member2″ differs from the first connector member as shown inFIGS.9to12only in the size of the passage22′. More in detail, the minimum and maximum diameter of the spherical seat portion23″ and of the conically widening portion27″ are smaller compared to the maximum and minimum inner diameter of the seat portion23and of the conically widening portion27of the first connector member2. All other portions and the sizes of the portions are identical to that of the first connector member2. By means of this, the second connector member2″ is configured to accommodate a bone anchor100″ that differs with respect to the size of the head and of the shank. With such a design, the second and the first connector members can be used interchangeably and selectively.

As can be seen inFIGS.15to18, the plug member4is formed as a substantially cylindrical part with a solid cylinder having a top surface4aand an opposite bottom surface4b. At an outer surface of the plug member an external thread40is formed and the plug member has such a size that it can be inserted into the first hole12and the second hole112when they overlap in the assembled state as shown inFIGS.1to4. Thereby, the plug member engages with its external thread40the internal thread of the first hole12of the first connection portion11. At the top surface4a, the plug member4comprises an annular rim41that extends in a radial direction beyond the external thread40. A lower surface41aof the rim serves as an abutment or stop when the plug member4is inserted into the first hole12and the second hole112. In addition, plurality of engagement portions for a driver in the form of circumferentially arranged recesses42are provided in the top surface4aof the plug member4. The recesses42may be located at a distance from the outer edge of the rim41and outside a center of the top surface4a. In a top view, the recesses42may have an elongate, circular segment-shaped contour. It shall be noted that the engagement portions may also be shaped like the recesses26of the rim25of the connector member or may be realized as a polygon recess in the center of the plug member4. A total height of the plug member may be such that the top surface4aand the bottom surface4bare flush with the top surface1aand the bottom surface1bof the plate member1, respectively.

The locking member3will be explained more in detail referring toFIGS.1to4. The locking member3is a substantially cylindrical part with a top surface3aand a bottom surface3band with an external thread30that is configured to cooperate with the internal thread24aof the connector member2. Adjacent to the bottom surface3ba recess31is provided that serves for accommodating a portion of the head of the bone anchor therein. The recess31may have a spherical segment-shape adapted to the shape of the head102of the bone anchor100so that the locking member3may contact the head and exert pressure onto the head when the locking member3is inserted into the connector member2. In the top surface3aa plurality of recesses32in the form of pockets may be provided that are arranged on a circular line around the center of the locking member3and at a distance from an outer edge of the locking member3. The recesses32serve for engagement with a tool, such as a driver, used to insert and tighten the locking member3. Moreover, in the top surface3a, a central hole33may be provided. A height of the locking member3may be such that the top surface3ais substantially flush with the top surface1aof the plate portion10or projects only to a small extent above the top surface1aof the plate portion10.

Referring now toFIGS.19and20, the first end piece5is a substantially ring-shaped piece with a top surface5aand a bottom surface5band an internal thread50. At one side, a projection51is provided that corresponds in size and shape to the projection14of the first connection portion. In other words, the projection51is formed as a lug that extends from the upper surface5aoutward and extends in a height direction to a distance from the lower surface5b. Opposite to the projection51a recess or cutout52is provided in the top surface5aof the first end piece5that corresponds in shape and size to the recess16of the first connection portion11of the plate member1. In other words, the recess52has a width that is greater than the width of the connection portion51and extends perpendicular to a center axis of the ring. A depth of the recess52also substantially corresponds to the thickness of the projection51. The first end piece5is configured to cooperate with the second connection portion111of the plate member1.

Referring toFIGS.21and22, the second end piece5′ is also a ring-shaped part that has a top surface5aand a bottom surface5b. At one side, a projection51′ extends outward from below the lower surface5b. The projection51′ has an elongate substantially rectangular shape with rounded edges that is similar to that of the projection114of the plate member1. More in detail, a thickness of the projection51′ is such that the projection51′ can be inserted into the groove15of the first connection portion11of the plate member1. At an inner wall of the ring of the second end piece5′ an annular step or abutment52ais formed serving as a stop for the connector member. The second end piece5′ is configured to cooperate with the first connection portion11.

The plate members, the connector members, the plug members and the locking members as well as the bone anchors may each be made of a bio-compatible material, for example of tita-nium or stainless steel, of a bio-compatible alloy, such as NiTi-alloys, for example Nitinol, of magnesium or magnesium alloys, or from a bio-compatible plastic material, such as, for example, polyether ether ketone (PEEK) or poly-L-lactide acid (PLLA). Moreover, the parts can be made of the same or of different materials.

The assembly of the modular bone plate will now be described with reference toFIGS.1to4. To connect the plate members1,1′,1″ the plate members are oriented such that the first connection portion11of a first plate member1overlaps with the second connection portion111of a second plate member1′, or in the case of three plate members, the first connection portion11of the second plate member1′ overlaps with the second connection portion111of the third plate member1″. Thereby, the projections114of the second connection portion enter through the recess16into the groove15of the first connection portion11. Simultaneously, the projection14of the first connection portion enters through the recess116into the groove115of the second connection portion111. When the projections are fully introduced into the grooves, the first hole12and the second hole112are concentric. The bottom surfaces1band the top surfaces1aof the plate portions10and the connection portions11,111are substantially flush, as can be seen in particular inFIGS.2and4. The outermost portions of the edges13,113abut against the recesses10a,10bof the plate portion10.

Thereafter, the connector members are screwed into the threaded first hole12of the first connection portion until the lower surface25aabuts against the stepped portion112aof the second connection portion111. Thereby, the plate members are firmly connected. The abutment of the connector member against the stepped portion112aresults in a compressing force which the connector member2exerts onto the second connection portion111towards the first connection portion11of a neighbouring plate member. By means of this, the strength of the connection is enhanced. In addition, the design of the projection and groove results in an enhanced stiffness against bending forces that may act onto the bone plate.

Turning now toFIG.23, the versatility of the modular bone plate is shown. A first connector member2can be used with a first bone anchor100having a first shank diameter and a first head diameter. Depending on the clinical application, instead of the first connector member2, a second connector member2″ can be used together with a second bone anchor102″ having a smaller shank diameter and a smaller head diameter. Further, if a bone anchor is not necessary at a particular position of the bone plate, a plug member4can be used instead of the connector members to close the holes.

Once the bone plate has been assembled from the plate members and the connector members, the modular bone plate can be placed onto the bone without the members falling apart. When the modular bone plate has been placed onto the bone, the bone anchors100,100′,100″ can be inserted so that the spherical head of each bone anchor is seated in the seat portion23,23′ of a corresponding connector member2,2′,2″. Each bone anchor may assume various angular posi-tions with respect to the bone plate, because the head is accommodated in the seat in the manner of a ball and socket joint.

Once one or several bone anchors have been placed, the locking member3can be screwed into the connector member2to secure the bone anchor100in the plate and prevent backing out of the bone anchor. The locking member3may be used to press onto the head102of the bone anchor or may be used to just provide a closure for the passage22in the connector member2without contacting the head.

Referring again toFIGS.1to4, the end pieces5,5′ may be used to form an end area of the bone plate that has the same or substantially the same thickness as other areas of the bone plate. The first end piece5that resembles the first connection portion is connected with its projection51to the groove115of the second connection portion111of a plate member1so that the holes of the end piece5and of the second connection portion111overlap. The second end piece5′ is connected with its projection51′ to the groove15of the first connection portion11, so that the holes of the end piece5′ and of the first connection portion11overlap.

InFIGS.24and25the modular bone plate ofFIG.1is shown in a curved configuration. To achieve this, the plate members1,1′ are rotated in one direction one relative to the other until the projections114of the second connection portion111abut against the wall of the groove15of the first connection portion11at the transition to the recess16. Simultaneously, the projections14of the first connection portion abut against the wall of the groove115of the second connection portion111at the transition to the recess116. Also, the first end piece5is rotated with respect to the first plate member1so that its projection51abuts against the wall of the groove115of the second connection portion111. The second end piece5′ may be or may not be rotated, depending on the requirements for the bone plate. The maximum curvature of the bone plate is defined by the maximum angle that can be achieved when rotating the plate members relative to each other which is limited by the above described abutment.

InFIGS.26and27the modular bone plate ofFIG.1is shown in a curved configuration with a curvature opposite to the curvature of the modular bone plate shown inFIGS.24and25. To achieve this, the plate members are rotated one relative to the other in the opposite direction compared to that shown inFIGS.24and25and the projections abut at the opposite side of the wall of the grooves at the transition to the recess, respectively.

It shall be noted that any angled configuration between the two maximum angles shown inFIGS.24and25at the one hand andFIGS.26and27at the other hand can be arranged. It is also possible to have various curvatures along the whole length of the bone plate.

FIG.28shows a modified embodiment of the modular bone plate with a further type of a plate member1″″ that is substantially T-shaped. The plate member1′″ comprises a second connection portion111at one end and an end portion110that extends substantially transverse to the second connection portion111. The end portion110may have one or more holes120with connector members2to be placed therein.

It should be clear that the plate members can be designed in many configurations and are not limited to the specific embodiments shown above. For example, the contour of the plate members may vary, the plate members can be angled in a plane perpendicular to the axis of the holes or also in a plane containing the axis of the holes. The holes may have an axis that is inclined with respect to the top and/or the bottom surface of the plate portion.

The seat portion in the connector member may be shaped other than spherical, for example con-ical. The seat may also have a shape that prevents an angled insertion of the bone anchor or permits angled insertion only in a specific direction or specific plane. In this case the bone anchor may also have a head with another shape.

The locking member may be omitted or designed in another shape. The end pieces may be omitted.