Flush anchor snap-off apparatus
An apparatus for anchoring one or more tensile members to bone includes: an anchor, including: a housing having a hollow interior, and including a body portion and an extension portion interconnected by a breakaway structure configured to retain structural integrity under a first predetermined tensile load and to separate under a second predetermined tensile load which is greater than the first predetermined tensile load; a collet disposed in the hollow interior, the collet having a peripheral wall defining a central bore for accepting one or more tensile members therethrough; a sleeve having a peripheral wall and being disposed in the hollow interior of the housing, so as to be movable parallel to the central axis; and wherein the sleeve and the collet are arranged such that axial movement of the sleeve will cause the collet to swage radially inwards around and against the one or more tensile members.
1. An apparatus for anchoring one or more tensile members to bone, comprising:
an anchor, including:
a housing extending along a central axis between open first and second ends, and having a hollow interior, the housing including a body portion and an extension portion interconnected by a breakaway structure which is configured to retain structural integrity under a first predetermined tensile load and to separate under a second predetermined tensile load which is greater than the first predetermined tensile load;
a collet disposed in the hollow interior of the body portion, the collet having a peripheral wall defining a central bore for accepting one or more tensile members therethrough and an exterior surface, wherein the collet is configured to be swaged around and against the one or more tensile members;
a sleeve having a peripheral wall defining opposed interior and exterior surfaces, the sleeve disposed in the hollow interior of the housing and positioned generally axially adjacent to the collet, so as to be movable parallel to the central axis between first and second positions; and
wherein at least one of the exterior surface of the collet and the interior surface of the sleeve is tapered and the sleeve and the collet are arranged such that movement of the sleeve from the first position to the second position will cause the interior surface of the sleeve to bear against the exterior surface of the collet, causing the collet to swage radially inwards around and against the one or more tensile members.
2. The apparatus of claim 1 wherein the breakaway structure comprises a plurality of stress-concentrating columns.
3. The apparatus of claim 1 , wherein the body portion includes a flange extending radially outward from a second end of the body portion.
4. The apparatus of claim 3 , wherein:
the breakaway structure comprises a plurality of stress-concentrating columns; and
each of the stress-concentrating columns intersects the flange within a recess that is positioned below an outer surface of the flange.
5. The apparatus of claim 1 , wherein the body portion is generally cylindrical in shape, the body portion has an outer diameter of about 3 to 12 mm, and the flange has an outer diameter of about 5 to 20 mm.
6. The apparatus of claim 1 , wherein the body portion includes an internal flange disposed at the first end configured to block axial movement of the collet in one direction.
7. The apparatus of claim 6 , wherein the collet and the internal flange of the body portion are further configured such that axial movement of the collet towards the first end of the body portion will cause the internal flange to bear against the exterior surface of the collet, causing the collet to swage radially inwards around and against the one or more tensile members.
8. The apparatus of claim 7 , wherein the body portion includes a transition section axially adjacent the internal flange configured to apply a radially inward force against the collet.
9. The apparatus of claim 1 , further comprising a connector formed on the extension portion for connecting the housing to an insertion instrument.
10. The apparatus of claim 9 , further comprising an insertion instrument including:
a body having a connector complementary to the connector of the extension portion of the housing;
a hollow pushrod extending through the stem and slidably movable between retracted and extended positions; and
a driving mechanism operable to move the pushrod between the retracted and extended positions.
11. The apparatus of claim 1 wherein the sleeve and the housing each include retention elements, the retention elements collectively configured to permit movement of the sleeve from the first position to the second position and to mutually engage each other so as to prevent the sleeve from moving out of the second position.
12. The apparatus of claim 11 when the retention elements comprise predetermined dimensions of the sleeve and the housing effective to permit radial clearance between the sleeve and the housing in the first position and to define a radial interference between the sleeve and the housing and the second position.