Orthopaedic rod/plate locking mechanism

• US 6,524,315 B1
• Filed: 08/08/2000
• Issued: 02/25/2003
• Est. Priority Date: 08/08/2000
• Status: Expired due to Term

• Current Assignee: Depuy Acromed Incorporated (Johnson & Johnson)
• Original Assignee: Depuy Acromed Incorporated (Johnson & Johnson)
• Inventors: Doherty, Thomas V., Selvitelli, David M., Reynolds, Martin A.
• Primary Examiner(s): Philogene, Pedro
• Application Number:
  US09/633,057
• Time in Patent Office: 931 Days
• Field of Search: 606/70, 606/71, 606/72, 606/73, 606/69, 606/61, 606/60, 623/17.11, 623/17.15, 623/17.16
• US Class Current: 606/70
• CPC Class Codes: A61B 17/7044 also having plates, staples or washers bearing on the vertebrae
• CPC Class Codes: A61B 17/7053 with parts attached to bones or to each other by flexible wires, straps, sutures or cables
• CPC Class Codes: A61B 17/7055 connected to sacrum, pelvis or skull

Abstract

An orthopaedic junction or anchor assembly for anchoring a linkage such as a rod or cable used for fixation or reduction. The assembly includes a slotted bolt that fits through an apertured plate, and a support platform that fits over the bolt, capturing the plate in a one-piece assembly for convenient installation. The base of the bolt is recessed in the plate and a cap or nut tightens down to secure the linking member, e.g., a rod or cable, in the bolt slot, simultaneously clamping the bolt to fix both its position and its orientation on the plate. The support platform has the form of a generally annular washer with an upper surface including a transverse groove on which the rod seats, and a lower surface abutting the plate. A sleeve potion may extend within and buttress the surrounding wall of the plate. The plate may take various forms, such as a hook or offset arm, an occipital T-plate, or a vertebra plate. In one embodiment the support platform is swaged to the bolt, allowing the bolt to rotate freely, and slide along the slot of the bone plate as a captive assembly, keeping all the components together without constraining the alignment during installation. Other embodiments employ mating ridge and groove, or other detents circumferentially on the bolt shaft and the inner face of the support, to snap and retain the pieces together. When the rod or other linkage has been positioned, a lock nut or cap then fastens onto the bolt to seat the rod against the support platform and lock both the position of the bolt and the angular orientation of its slot. Tightening the nut or cap pushes the rod downward to seat on the support plate and pulls the bolt upward to press the base of the bolt against the bottom of the plate. The bottom surfaces of the support washer as well as the plate-facing surface of the base may be roughened or textured to engage the plate, or otherwise increase resistance to rotational and lateral movement once the rod has been positioned and the nut is torqued down.

Claims

1. An orthopaedic fixation assembly, comprising:

a bone plate having a front face, a back face and an elongate aperture extending through the front and back faces, the bone plate being securable to a bone;

a bolt having a bolt base, a bolt shaft and a slot in the shaft, the bolt being sized for insertion through the aperture so that the bolt base contacts the back face of the bone plate, the bold shaft extends through the front face of the bone plate, and the bolt is rotatable within the aperture and movable along the aperture in a direction in which the aperture is elongated; and

a support platform consisting of a single washer having a back face and an opposed front face, the support platform configured to fit about the bolt shaft so that the back face of the support platform rests against the front face of the bone plate and the front face of the support platform cooperates with the slot for holding an elongate bone fixation element;

wherein the bolt and the support platform are adapted to be secured together to hold the bone plate between the bolt base and the back face of the single support platform.

2. The assembly of claim 1, wherein the support platform includes a sleeve portion that fits within the aperture.

3. The assembly of claim 2, wherein the support platform sleeve portion extends partially through the bone plate.

4. The assembly of claim 1, wherein the back face of the bone plate has a counter-machined recess around the aperture and the bolt base is round and fits within the counter-machined recess for rotation therein.

5. The assembly of claim 1, wherein the bolt shaft has an outer diameter in a support platform mating region and a radially protruding element that extends outwardly beyond the bolt shaft outer diameter and the support platform is formed as a split washer and expands to slide over the radially protruding element and reverses its expansion to be captured by the radially protruding element.

6. The assembly of claim 5, wherein the radially protruding element is a protruding circumferential ridge.

7. The assembly of claim 5, wherein the bolt shaft outer diameter is defined within a recess on the bolt shaft.

8. The assembly of claim 7, wherein the recess is circumferential.

9. An orthopaedic fixation assembly, comprising:

a bone plate having a front face, a back face and an elongate aperture extending through the front and back faces, the bone plate being securable to a bone;

a bolt having a bolt base, a bolt shaft and a slot in the shaft, the bolt having an outer diameter in a support platform mating region and being sized for insertion through the aperture so that the bolt base contacts the back face of the bone plate, the bold shaft extends through the front face of the bone plate, and the bolt is rotatable within the aperture and movable along the aperture in a direction in which the aperture is elongated; and

a support platform in the form of a split washer having a back face and an opposed front face, the support platform configured to fit about the outer diameter of the bolt shaft so that the back face of the support platform rests against the front face of the bone plate and the front face of the support platform cooperates with the slot for holding an elongate bone fixation element;

wherein the bolt shaft includes a radially protruding element that extends outwardly beyond the bolt shaft outer diameter and the support platform expands to slide over the radially protruding element and reverses its expansion to be captured by the radially protruding element.

10. The assembly of claim 9, wherein the support platform includes a sleeve portion that fits within the aperture.

11. The assembly of claim 10, wherein the support platform sleeve portion extends partially through the bone plate.

12. The assembly of claim 9, wherein the back face of the bone plate has a counter-machined recess around the aperture and the bolt base is round and fits within the counter-machined recess for rotation therein.

13. The assembly of claim 9, wherein the radially protruding element is a protruding circumferential ridge.

14. The assembly of claim 9, wherein the bolt shaft outer diameter is defined within a recess on the bolt shaft.

15. The assembly of claim 14, wherein the recess is circumferential.

16. The assembly of claim 9, wherein the aperture is elongated and the assembly includes a single support platform.