Friction-fit implantable devices and assemblies
An implantable device may be configured to couple to a bone screw for spinal fixation. The implantable device may include one or more friction-fit features to allow the implantable device to maintain its orientation before being locked into place by a set screw. For example, an implantable device may include a body comprising a sidewall. The sidewall may define a first passage extending within the sidewall and parallel to a vertical axis of the body, and a slot extending through the sidewall and in communication with the first passage. The device may further include a pressure member coupled to the body. The pressure member may include a distal surface for engaging the head of the bone screw. The device may further include a biasing member at least partially within the first passage of the body for applying a downward force on the pressure member.
1 . An implantable device configured to couple to a head of a bone screw, the implantable device comprising:
a body comprising a sidewall defining:
a first passage extending within the sidewall and parallel to a vertical axis of the body; and
a slot extending through the sidewall and in communication with the first passage;
a pressure member coupled to the body such that the sidewall at least partially surrounds the pressure member, the pressure member comprising a distal surface configured to engage the head of the bone screw; and
a first resilient biasing member positioned at least partially within the first passage of the body and configured to apply a downward force on the pressure member relative to the body.
2 . The implantable device of claim 1 , wherein the pressure member comprises a lateral surface defining an engagement feature, and
wherein the first resilient biasing member comprises:
a first pin positioned through the slot of the body and in the engagement feature of the pressure member; and
a spring positioned within the first passage of the body and configured to apply, via the first pin, a downward force on the pressure member relative to the body.
3 . The implantable device of claim 2 , wherein the engagement feature comprises an opening in the lateral surface of the pressure member.
4 . The implantable device of claim 2 , wherein the first pin comprises:
a first portion positioned in the engagement feature; and
a second portion positioned within the slot.
5 . The implantable device of claim 1 , wherein:
the sidewall of the body further defines a second passage extending within the sidewall and parallel to the vertical axis of the body, and
the implantable device further comprises a second biasing member positioned at least partially within the second passage of the body and configured to apply a downward force on the pressure member relative to the body.
6 . The implantable device of claim 5 , wherein:
the body comprises a first vertical tab extending proximally from a base of the body and a second vertical tab extending proximally from the base of the body,
the first passage is defined within the first vertical tab and offset from a center of the first vertical tab, and
the second passage is defined within the second vertical tab and offset from a center of the second vertical tab.
7 . The implantable device of claim 1 , further comprising a set screw configured to apply a downward pressure on the pressure member and the head of the bone screw.
8 . An implant, comprising:
a body comprising a first arm and a second arm extending vertically from a base of the body, wherein:
the first arm defines a first vertical tunnel within a sidewall of the first arm, and
the second arm defines a second vertical tunnel within a sidewall of the second arm;
a pressure cap positioned within a cavity of the body between the first arm and the second arm;
a first spring positioned within the first vertical tunnel;
a second spring positioned within the second vertical tunnel; and
a first biasing member comprising a first pin attached to a first cross pin such that the first cross pin extends transverse to the first pin,
wherein the first spring and the second spring are configured to apply a downward force on the pressure cap relative to the body, and wherein the first spring is configured to apply the downward force on the pressure cap via the first biasing member.
9 . The implant of claim 8 , wherein:
the first arm comprises an external surface defining a first tool engagement feature,
the first vertical tunnel is offset from the first tool engagement feature,
the second arm comprises an external surface defining a second tool engagement feature, and
the second vertical tunnel is offset from the second tool engagement feature.
10 . The implant of claim 8 , further comprising an expandable ring positioned within the cavity of the body and adjacent to the base of the body and the pressure cap.
11 . The implant of claim 10 , wherein an interior surface of the base of the body is configured to:
restrict the expandable ring from expanding when the expandable ring is in a first vertical position relative to the body; and
allow the expandable ring to expand to accept a head of a bone screw when the expandable ring is in a second vertical position relative to the body, the second vertical position being proximal to the first vertical position.
12 . The implant of claim 8 , wherein the first vertical tunnel is offset from a center of the first arm.
13 . The implant of claim 8 , wherein the first vertical tunnel is aligned with a center of the first arm.
14 . A method for assembling an implantable device, the method comprising:
providing a body comprising a sidewall defining:
a passage extending within the sidewall and parallel to a vertical axis of the body; and
a slot in communication with the passage;
positioning a pressure cap within a cavity of the body, the pressure cap comprising a lateral surface defining a pin engagement hole;
positioning a spring within the passage of the body;
compressing the spring proximally within the passage;
retaining the spring in a compressed state such that the compressed spring is disposed proximal of the pin engagement hole of the pressure cap;
inserting a first pin through the slot of the body and in the pin engagement hole of the pressure cap, wherein the first pin defines a bore extending through the first pin and transverse to a central axis of the first pin; and
inserting a second pin into the passage of the body, through the bore of the first pin, and into the spring.
15 . An implantable device configured to couple to a head of a bone screw, the implantable device comprising:
a body comprising a sidewall defining:
a first passage extending within the sidewall and parallel to a vertical axis of the body; and
a slot extending through the sidewall and in communication with the first passage;
a pressure member coupled to the body such that the sidewall at least partially surrounds the pressure member, the pressure member comprising a distal surface configured to engage the head of the bone screw and comprising a lateral surface defining an engagement feature; and
a first biasing member positioned at least partially within the first passage of the body and configured to apply a downward force on the pressure member relative to the body, the first biasing member comprising:
a first pin positioned through the slot of the body and in the engagement feature of the pressure member; and
a spring positioned within the first passage of the body and configured to apply, via the first pin, a downward force on the pressure member relative to the body,
wherein:
the first pin defines a pin opening extending through the first pin in a direction transverse to a longitudinal axis of the first pin,
the first biasing member further includes a second pin coupled to the first pin and extending through the pin opening, and
at least a portion of the spring is positioned around a proximal portion of the second pin.
16 . The implantable device of claim 15 , wherein:
the first passage comprises a distal opening, and
the second pin is configured to be received into the first passage through the distal opening.
17 . The implantable device of claim 15 , wherein the first pin comprises screw threads at the pin opening, and wherein the second pin comprises screw threads configured to engage the screw threads of the first pin.
18 . An implantable device configured to couple to a head of a bone screw, the implantable device comprising:
a body comprising a sidewall defining:
a first passage extending within the sidewall and parallel to a vertical axis of the body; and
a slot extending through the sidewall and in communication with the first passage;
a pressure member coupled to the body such that the sidewall at least partially surrounds the pressure member, the pressure member comprising a distal surface configured to engage the head of the bone screw and comprising a lateral surface defining an engagement feature; and
a first biasing member positioned at least partially within the first passage of the body and configured to apply a downward force on the pressure member relative to the body, the first biasing member comprising:
a first pin positioned through the slot of the body and in the engagement feature of the pressure member; and
a coil spring positioned within the first passage of the body and configured to apply, via the first pin, a downward force on the pressure member relative to the body.
19 . An implant, comprising:
a body comprising a first arm and a second arm extending vertically from a base of the body, wherein:
the first arm defines a first vertical tunnel within a sidewall of the first arm, and
the second arm defines a second vertical tunnel within a sidewall of the second arm;
a pressure cap positioned within a cavity of the body between the first arm and the second arm;
a first spring positioned within the first vertical tunnel;
a second spring positioned within the second vertical tunnel; and
a first biasing member comprising a first pin attached to a first cross pin such that the first cross pin extends transverse to the first pin,
wherein:
the first spring and the second spring are configured to apply a downward force on the pressure cap relative to the body,
the pressure cap comprises a lateral surface defining a first pin engagement feature,
a first end of the first cross pin engages the first pin engagement feature,
a proximal end of the first pin is positioned within the first vertical tunnel, and
the first spring is configured to apply the downward force on the pressure cap via the first biasing member.
20 . The implant of claim 19 , further comprising a second biasing member comprising a second pin attached to a second cross pin such that the second cross pin extends transverse to the second pin,
wherein:
the lateral surface of the pressure cap further defines a second pin engagement feature,
a first end of the second cross pin engages the second pin engagement feature,
a proximal end of the second pin is positioned within the second vertical tunnel, and
the second spring is configured to apply the downward force on the pressure cap via the second biasing member.