Minimally invasive screw extension assembly

Patent metadata

Field	Value
Publication number	US-10064662-B2
Application number	US-201615236036-A
Country	US
Kind code	B2
Filing date	Aug 12, 2016
Priority date	Aug 12, 2016
Publication date	Sep 4, 2018
Grant date	Sep 4, 2018

Abstract

A screw extension assembly for use in minimally invasive spinal surgery, the assembly has an inner slotted shaft and an outer shaft, a rod reducer and a removable nut. The combination when assembled is configured to move a spinal fixation rod into a slotted rod receiving spinal implant where it is seated and affixed thereto. The screw extension assembly further has a locking knob rotationally coupled to a proximal end of the outer shaft, wherein the inner shaft has one or more cam grooves and the locking knob has a pin extending into and guided by said cam groove causing the outer shaft to translate longitudinally upon rotation of the locking knob relative to the inner shaft toward an engaged position locking the deflectable legs in the coupled position to the slotted rod receiving implant.

First claim

What is claimed is:

1. A screw extension assembly for use in minimally invasive spinal surgery, the assembly comprising:
an inner slotted shaft, the inner slotted shaft being an elongated hollow tubular shaft having a proximal end, a distal end and a slotted distal end portion having a pair of slots open through the distal end defining a pair of deflectable leg extensions, each leg extension having a projection configured to engage a groove on an outer surface of a slotted rod holding element of a rod receiving implant thereby coupling the inner shaft to the slotted rod holding element adjacent slots at the distal end of the leg extensions having a plurality longitudinal edges keyed to abut proximal walls of the slotted rod holding element to prevent rotation;
an outer shaft configured to receive and pass over the inner shaft; the outer shaft having a pair of slots open through a distal end with longitudinal rails adjacent edges of each slot of the outer shaft to slide along each edge of the slots of the leg extensions of the inner shaft along at least a portion of the slots; and
wherein the outer shaft, when moved inwardly toward the distal end of the inner shaft into an engaged position, locks the deflectable legs in a coupled position to the grooves of the slotted rod holding element and wherein the inner shaft at the distal end has the projections extending from the distal end, the projections of the inner shaft engage the grooves of the slotted rod holding element clipping the deflectable legs onto the slotted rod holding element when the outer shaft is moved to engage an inner side of the slotted rod holding element, in the engaged position a chamfered end of the outer shaft engages the distal end of the inner shaft and covers a portion of the slotted rod holding element along an inner surface of the slot, and when in the engaged position the slotted rod holding element is held externally by the deflectable legs and internally by the end and locked from rotation by the chamfered end.

2. The screw extension assembly of claim 1 wherein a proximal portion adjacent the proximal end of the inner shaft has a threaded portion.

3. The screw extension assembly of claim 2 wherein the threads of the threaded portion have longitudinal extending grooves aligned to receive the longitudinal rails of the outer shaft.

4. The screw extension assembly of claim 3 wherein the grooves are aligned with the edges of the slots forming a keyed pathway allowing the longitudinal rails to slide relative to the inner shaft toward the distal end on assembly.

5. The screw extension assembly of claim 1 wherein the pair of slots in the inner shaft and the pair of slots in the outer shaft are aligned to pass rods therethrough.

6. A screw extension assembly for use in minimally invasive spinal surgery, the assembly comprising:
an inner slotted shaft, the inner slotted shaft being an elongated hollow tubular shaft having a proximal end, a distal end and a slotted distal end portion having a pair of slots open through the distal end defining a pair of deflectable leg extensions, each leg extension having a projection configured to engage a groove on an outer surface of a slotted rod holding element of a rod receiving implant thereby coupling the inner shaft to the slotted rod holding element adjacent slots at the distal end of the leg extensions having a plurality longitudinal edges keyed to abut proximal walls of the slotted rod holding element to prevent rotation;
an outer shaft configured to receive and pass over the inner shaft; the outer shaft having a pair of slots open through a distal end with longitudinal rails adjacent edges of each slot of the outer shaft to slide along each edge of the slots of the leg extensions of the inner shaft along at least a portion of the slots, wherein the outer shaft, when moved inwardly toward the distal end of the inner shaft into an engaged position, locks the deflectable legs in a coupled position to the grooves of the slotted rod holding element; and
a locking knob rotationally coupled to a proximal end of the outer shaft, wherein the inner shaft has one or more cam grooves and the locking knob has a pin extending into and guided by said cam groove causing the outer shaft to translate longitudinally upon rotation of the locking knob relative to the inner shaft toward an engaged position locking the deflectable legs in the coupled position to the slotted rod holding element.

7. The screw extension assembly of claim 6 wherein the one or more cam grooves has a cam over pocket feature in a distal end of the cam groove, the cam over pocket locks the locking knob at or past an engaged position.

8. The screw extension assembly of claim 7 wherein the cam over pocket at the distal end of the cam groove rotationally moves the locking knob in the absence of forward longitudinal translation of the outer shaft to the inner shaft at a locked position.

9. The screw extension assembly of claim 6 further comprises:
a rod reducer, the rod reducer being a hollow tube with a distal end to push a rod received in the aligned slots of the assembly when the rod reducer is placed over the inner and outer shaft.

10. The screw extension assembly of claim 9 further comprises:
a nut having female threads for engaging the threaded proximal end of the inner shaft and wherein the nut when tightened abuts a proximal end of the reducer and pushes the reducer inwardly to move a rod received in the aligned slots of the assembly into the slotted rod holding element.

11. The screw extension assembly of claim 10 wherein the threads of the proximal end of the inner shaft has a pitch sufficient to allow the nut to auto-rotate, solely due to the weight of the nut, to abut the proximal end of the reducer and further rotation pushes the reducer inwardly to seat a rod in a rod seating position.

12. The screw extension assembly of claim 10 wherein the nut is removable and separate from the outer shaft.

13. The screw extension assembly of claim 10 wherein the outer shaft has flats in the proximal portion and the locking knob has flats configured to align with the flats of the outer shaft when the locking knob is rotated to a locked position allowing the reducer with complimentary internal flats to non-rotationally move relative to the assembly as the nut pushes the reducer.

Assignees

• Amendia Inc

Inventors

• Gunn Joshua David
• Cain David Brett

Classifications

• A61B17/7086 Primary

  Rod reducers, i.e. devices providing a mechanical advantage to allow a user to force a rod into or onto an anchor head other than by means of a rod-to-bone anchor locking element; rod removers · CPC title

• A61B17/7085

  for insertion of a longitudinal element down one or more hollow screw or hook extensions, i.e. at least a part of the element within an extension has a component of movement parallel to the extension's axis · CPC title

• A61B17/00234

  for minimally invasive surgery (A61B17/0218, A61B17/0469, A61B17/12013, A61B17/1285, A61B17/29, A61B17/320016 take precedence) · CPC title

• A61B17/708 Primary

  with tubular extensions coaxially mounted on the bone anchors · CPC title

• A61B17/8665

  Nuts · CPC title