Bone plate system
Bone plate systems are provided for surgical implants and bone repair. The bone plate is multi-tiered for receiving bone anchors screws for securing a plurality of bones or bone fragments in a desired relationship. The plate members include throughbores for receiving a pivot base therein, with head ends of the bone anchors being secured in the pivot bases. The throughbores may permit and define a translation path for the pivot base and the bone anchor secured therein relative to the plate. Pivot members extending between the pivot base and the plate member facilitate pivoting and optional translation of the pivot base relative to the plate. With the bone anchor seated within the pivot base, an apparatus for inhibiting screw back out is employed.
1. A bone plate system comprising:
a bone plate having upper and lower surfaces;
a plurality of throughbores of the bone plate between the upper and lower surfaces, each throughbore extending through the bone plate along a respective bore axis;
straight surfaces of the bone plate extending along opposite sides of one of the throughbores;
a plurality of bone screws each having a head for driving a shank of the bone screw into bone;
a rigid pivot base received in the one throughbore and pivotal about a pivot axis relative to the bone plate, the pivot axis extending laterally across the one throughbore transverse to the bore axis and between the opposite sides of the one throughbore of the bone plate, the pivot base having an opening for receiving the head of one of the bone screws with the pivot base configured to not deform as the one bone screw head is seated in the pivot base opening;
a wall of the pivot base extending around the opening and configured to completely space the one bone screw head from the bone plate with the one bone screw head seated against the rigid pivot base wall such that the seated bone screw head does not contact the bone plate;
straight sides of the rigid pivot base in confronting relation with the straight surfaces of the elongate bone plate to restrict pivotal movement of the rigid pivot base in the one throughbore and the one bone screw received in the pivot base to pivotal movement about the pivot axis;
floor portions of the bone plate extending laterally transverse to the bore axis of the one throughbore from the opposite sides of the one throughbore, the floor portions defining a narrow portion of the one throughbore;
upwardly facing surfaces of the floor portions supporting the pivot base; and
lower surfaces of the pivot base configured to contact the upwardly facing surfaces of the floor portions and limit pivoting of the pivot base in the one throughbore about the pivot axis to less than 180 degrees.
2. The bone plate system of claim 1 wherein the lower surfaces of the pivot base include a first inclined surface and a second inclined surface on opposite sides of the pivot axis that extend transversely to each other, the first inclined surface configured to contact the upwardly facing surface of one of the floor portions and limit pivoting of the rigid pivot base in a first direction about the pivot axis, the second inclined surface configured to contact the upwardly facing surface of the one floor portion and limit pivoting of the rigid pivot base in a second direction about the pivot axis opposite to the first direction.
3. The bone plate system of claim 1 wherein the lower surfaces of the pivot base include:
a pair of first inclined lower surfaces of the pivot base each configured to contact a different one of the floor portions and limit pivoting of the pivot base about the pivot axis in a first direction; and
a pair of second inclined lower surfaces of the pivot base extending obliquely to the pair of first inclined lower surfaces, each second inclined lower surface configured to contact a different one of the floor portions and limit pivoting of the pivot base about the pivot axis in a second direction opposite the first direction.
4. The bone plate system of claim 3 wherein the rigid pivot base includes a pivot member extending laterally outward away from one of the straight sides of the rigid pivot base and connecting the pivot base to the bone plate, the pivot member supported on the upwardly facing surface of one of the floor portions intermediate one of the first inclined lower surfaces and one of the second inclined lower surfaces that are configured to contact the one floor portion.
5. The bone plate system of claim 4 wherein the pivot base includes a second pivot member extending laterally away from the other of the straight sides of the rigid pivot base and pivotally connecting the pivot base to the bone plate, the second pivot member supported on the upwardly facing surface of the other of the floor portions intermediate other of the first inclined lower surfaces and the other of the second inclined lower surfaces configured to contact the other floor portion.
6. The bone plate system of claim 1 wherein the rigid pivot base includes a pivot member pivotally connecting the rigid pivot base to the bone plate, the pivot member having a lower, rounded surface and the upwardly facing surface of one of the floor portions supports the rounded surface of the pivot member.
7. The bone plate system of claim 1 wherein the rigid pivot base includes a pivot member extending laterally outward away from one of the straight sides of the rigid pivot base, the bone plate including a cavity adjacent one of the floor portions into which at least a portion of the pivot member is received for connecting the rigid pivot base to the bone plate.
8. The bone plate system of claim 1 wherein the pivot base wall includes a through aperture in communication with the opening of the pivot base; and
a pin extending through the through aperture of the pivot base wall and connecting the pivot base to the bone plate.
9. The bone plate system of claim 1 wherein the head of the one bone screw includes a resilient portion; and
a locking member configured to expand the resilient portion of the one bone screw head against the rigid pivot base for locking the head of the one bone screw to the rigid pivot base.
10. The bone plate system of claim 1 wherein the one throughbore includes a wide portion above the narrow portion of the one throughbore; and
the rigid pivot base includes a lower narrow portion between the floor portions and an upper wide portion in the wide portion of the one throughbore, the upper wide portion of the rigid pivot base including overhang portions that extend above the floor portions and include the lower surfaces thereon.
11. The bone plate system of claim 1 wherein the floor portions include side surfaces extending downwardly from the upwardly facing surfaces and the rigid pivot base includes a lower portion having outer sides in confronting relation with the side surfaces of the floor portions.
12. The bone plate system of claim 1 wherein the bone plate is elongated along an axis and the one throughbore is axially elongated, the straight surfaces of the bone plate extending axially and permitting translation of the rigid pivot base along the elongated throughbore with the one bone screw head seated against the wall of the rigid pivot base.
13. The bone plate system of claim 12 wherein the bone plate includes an axially elongated cavity along one side of the throughbore adjacent one of the straight surfaces; and
the pivot base includes a pivot member extending outward away from one of the straight sides of the rigid pivot base to position a portion of the pivot member in the axially elongated cavity, the pivot member portion shifting axially in the cavity with translation of the rigid pivot base in the elongated throughbore.
14. The bone plate system of claim 1 wherein the one bone screw head is non-threaded and the pivot base wall is non-threaded and configured to engage the non-threaded bone screw head with seating of the one bone screw head in the opening of the pivot base.