Flush anchor snap-off apparatus
An anchor for tensile member(s) includes: a housing having a hollow interior; a collet in the hollow interior of the housing, the collet having a peripheral wall defining a central bore and an exterior surface. The collet is configured to be swaged around the tensile member(s). The collet includes longitudinal grooves in an outer surface of the peripheral wall, each defining a web configured to collapse inward in response to external compressive force. A sleeve has a peripheral wall defining interior and exterior surfaces and is disposed in the housing axially adjacent to the collet. At least one of the collet and the sleeve is tapered and the sleeve and the collet are arranged such that sleeve movement from a first position to a second position will cause the sleeve to bear against the collet, swaging the collet radially inwards around and against the tensile member(s).
1. An anchor for anchoring one or more tensile members to bone, comprising:
a housing extending along a central axis between open first and second ends, and having a hollow interior;
a collet disposed in the hollow interior of the housing, 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, and wherein the collet includes an array of longitudinal grooves formed in an outer surface of the peripheral wall, each groove defining a web configured to collapse inward in response to external compressive force;
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 anchor of claim 1 wherein the longitudinal grooves have a U-shape.
3. The anchor of claim 1 wherein the longitudinal grooves have square internal corners.
4. The anchor of claim 1 further comprising a surface texture configured to enhance grip on a tensile member formed in the central bore.
5. The anchor of claim 1 wherein the housing includes a body portion and an extension portion interconnected by a breakaway connection 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.
6. The anchor of claim 5 , further comprising a mechanical connector formed on the extension portion for connecting the housing to an insertion instrument.
7. The anchor of claim 6 in combination with an insertion instrument, comprising:
a body having a mechanical connector complementary to the threaded 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.
8. The anchor of claim 5 wherein the breakaway structure comprises a plurality of stress-concentrating columns.
9. The anchor of claim 5 , wherein the body portion includes a flange extending radially outward from a second end of the body portion.
10. The anchor of claim 9 , 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.
11. The anchor of claim 9 , 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.
12. The anchor 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.
13. The anchor of claim 12 , 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.
14. The anchor of claim 13 , wherein the body portion includes a transition section axially adjacent the internal flange configured to apply a radially inward force against the collet.
15. The anchor of claim 1 wherein an exterior surface of the housing is formed into male threads, a maximum diameter of the housing being defined by an outer extent of the male threads.
16. A clamp for anchoring one or more tensile members in a closed loop to form a cerclage, comprising:
a housing extending along a central axis between open first and second ends, and having a hollow interior, wherein the housing includes a contoured base with top and bottom surfaces, the top surface defining at least one concave channel communicating with a boss that defines the hollow interior of the housing;
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 and wherein the collet includes an array of longitudinal grooves formed in an outer surface of the peripheral wall, each groove defining a web configured to collapse inward in response to external compressive force;
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.
17. The clamp of claim 16 wherein the at least one concave channel comprises a single central channel.
18. The clamp of claim 16 wherein the at least one concave channel comprises first and second side-by-side channels, wherein the second channel terminates at a convex bearing surface.
19. The clamp of claim 16 wherein the base includes a pair of anchor points flanking the at least one concave channel.
20. The clamp of claim 16 wherein the collet includes longitudinal grooves having a U-shape.
21. The clamp of claim 16 wherein the collet includes longitudinal grooves having square internal corners.
22. The clamp of claim 16 further comprising a surface texture configured to enhance grip on a tensile member formed in the central bore.
23. The clamp of claim 16 wherein the housing includes a channel therein to allow a tensile member to lie flat against it.
24. The clamp of claim 16 wherein the housing includes a body portion and an extension portion interconnected by a breakaway connection 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.
25. The anchor of claim 1 in combination with a tensile member, wherein the tensile member is received in the collet and passes through at least one grommet.