Bone implant and method of controlling the bone implant

1 . A method of controlling an implant with respect to a bone that is one of a metacarpal, metatarsal, and phalangeal bone of one of a foot or hand, the method comprising the steps of:

obtaining an implant having a body with a lengthwise axis, the body having a leading end and a trailing end and external threads extending around the lengthwise axis,

wherein the external threads comprise first and second threaded lengths with the body having an unthreaded shank portion between the first and second threaded lengths,

the first and second threaded lengths respectively having first and second roots each with a diameter, wherein the diameters of the first and second roots are approximately the same;

directing the implant through an exposed surface of the bone into a passage in the bone and turning the body in a first turning direction around the lengthwise axis to thereby cause the external threads to engage a bone surface bounding the bone passage so as to cause the implant to advance in a first assembly direction relative to the bone into an operative position,

the trailing end of the implant body is one of flush with or below the exposed bone surface with the implant in the operative position;

obtaining a removal tool having a first fitting;

with the implant in the operative position, operatively engaging the first fitting with a cooperating fitting on the implant body at or adjacent to the trailing end so that the first fitting is in lengthwise overlapping relationship with the external threads at the trailing end of the implant body and can be moved to thereby: a) turn the body in a second turning direction around the lengthwise axis that is opposite to the first turning direction; and b) draw the body oppositely to the first assembly direction; and

with the implant in the operative position and the first fitting engaging the cooperating fitting on the body, controlling the removal tool so as to a) turn the body in the second turning direction; and b) draw the body oppositely to the first assembly direction by exerting a force on the body oppositely to the first assembly direction through the removal tool to thereby withdraw the implant from its operative position.

2 . The method of controlling an implant with respect to a bone according to claim 1 wherein the implant has an axial through passage between the leading and trailing ends of the body.

3 . The method of controlling an implant with respect to a bone according to claim 2 wherein the passage in the bone is a medullary canal and the step of directing the implant into the passage comprises directing a guide pin into the medullary canal, engaging the body with the guide pin so that the guide pin extends into the axial through passage on the implant, and guiding the body along the guide pin.

4 . The method of controlling an implant with respect to a bone according to claim 1 wherein the first and second threaded lengths each has threads with a pitch, and the pitch of the threads on the first threaded length is substantially the same as the pitch of the threads on the second threaded length.

5 . The method of controlling an implant with respect to a bone according to claim 1 wherein the first and second threaded lengths each has threads with a pitch and the pitch of the threads on the first threaded length is different from the pitch of the threads on the second threaded length.

6 . The method of controlling an implant with respect to a bone according to claim 1 wherein the step of turning the body in the first turning direction comprises turning the body through a second fitting on an assembly tool with the second fitting engaged with the body, the second fitting having an axis that aligns with the lengthwise axis of the body with the second fitting engaged with the body, the body and second fitting configured so that with the second fitting engaged with the body the second fitting and body overlap axially relative to the second fitting axis and lengthwise body axis.

7 . The method of controlling an implant with respect to a bone according to claim 6 wherein the second fitting has a peripheral surface extending around the axis of the second fitting and an axial length of the peripheral surface of the second fitting extending away from the body with the second fitting engaged with the body has a diameter less than or equal to a diameter of the unthreaded shank portion.

8 . The method of controlling an implant with respect to a bone according to claim 6 wherein the second fitting has a peripheral surface extending around the axis of the second fitting, the trailing end of the implant has an outer diameter, and an axial length of the peripheral surface of the second fitting extending away from the body with the second fitting engaged with the body has a diameter less than or equal to the outer diameter of the trailing end of the body.

9 . The method of controlling an implant with respect to a bone according to claim 8 wherein the bone passage is a medullary canal and the bone has articular cartilage with a thickness thereon and the step of directing the implant into the bone passage comprises directing the implant through the thickness of the articular cartilage, and the axial length of the peripheral surface of the second fitting is at least equal to the thickness of the articular cartilage.

10 . The method of controlling an implant with respect to a bone according to claim 6 wherein the second fitting has a peripheral surface extending around the axis of the second fitting, the external threads extend from a root portion with a diameter, and a part of the second fitting that is axially overlapped with the body has a diameter that is less than or equal to the diameter of the root portion.

11 . The method of controlling an implant with respect to a bone according to claim 6 wherein the body has an axially extending receptacle into which the second fitting is directed with the second fitting engaged with the body.

12 . The method of controlling an implant with respect to a bone according to claim 11 wherein the first fitting has threads that engage threads on the body, and the threads on the body extend axially towards the leading end of the body to beyond the axially extending receptacle into which the second fitting is directed.

13 . The method of controlling an implant with respect to a bone according to claim 12 wherein the axially extending receptacle has a diameter that is greater than a diameter of a portion of an axial through passage that is surrounded by the threads on the body that engage the threads on the first fitting.

14 . The method of controlling an implant with respect to a bone according to claim 1 wherein the root on the first threaded length has first threads with a crest diameter, the root on the second threaded length has second threads with a crest diameter, and at least a portion of the second threads has a crest diameter greater than a crest diameter of at least a portion of the first threads.

15 . The method of controlling an implant with respect to a bone according to claim 1 wherein the removal tool has a leading end and a graspable handle spaced from the leading end that can be engaged to turn the removal tool and the first fitting, and the removal tool has a tapered guide portion that extends to beyond the threads on the first fitting towards the leading end.

16 . The method of controlling an implant with respect to a bone according to claim 1 wherein with the implant in the operative position, the trailing end of the body is recessed below the external surface of the bone.

17 . The method of controlling an implant with respect to a bone according to claim 1 wherein the exposed surface of the bone is at a joint.

18 . The method of controlling an implant with respect to a bone according to claim 17 wherein there is articular cartilage at the exposed surface of the bone through which the implant is directed.

19 . A method of controlling an implant with respect to a bone that is one of a metacarpal, metatarsal, and phalangeal bone of a foot or hand, the method comprising the steps of:

obtaining:

a) an implant comprising:

a body with a lengthwise axis, the body having a leading end and a trailing end and external threads extending around the lengthwise axis,

the external threads extending around the lengthwise axis of the body at or adjacent each of the leading end and trailing end of the body with a length portion of the body unthreaded between the leading and trailing ends of the body,

the body having a shank portion with a diameter and an axial through passage between the leading and trailing ends of the body,

the body further having a receptacle with threads extending around the receptacle; and

b) a removal tool with a length and a first fitting having threads,

the threads around the receptacle on the body spaced from the trailing end of the implant body;

directing the body in an assembly direction through an exposed surface on the bone into a passage in the bone at an articular joint and turning the body in a first direction around the lengthwise axis to cause the external threads on the body to engage a bone surface bounding the passage to thereby advance the implant into an operative position wherein the trailing end of the implant is one of flush with or below the exposed bone surface; and

with the implant in the operative position, engaging the threads on the removal tool with the threads around the receptacle so that the body follows movement of the first fitting as the first fitting is: a) turned in a direction opposite to the first direction; and b) drawn in a direction oppositely to the assembly direction to thereby allow the implant to be separated from the bone,

wherein the removal tool has a leading end that is directed into the receptacle to guide the threads on the first fitting up to the threads on the body for engagement with the threads on the body.

20 . The method of controlling an implant with respect to a bone according to claim 19 wherein with the first fitting engaged with the body the first fitting overlaps the body over a first axial length and the first fitting has an axial length: a) extending away from the trailing end of the implant body that is at least equal to the first axial length; and b) having a diameter that is less than or equal to the diameter of the body shank portion.

21 . The method of controlling an implant with respect to a bone according to claim 19 wherein with the first fitting engaged with the body the first fitting overlaps the body over a first axial length and the first fitting has an axial length: a) extending away from the trailing end of the body that is at least equal to the first axial length; and b) having a diameter that is less than or equal to a diameter of a root away from which the external threads project.

22 . A method of controlling an implant with respect to a bone that is one of a metacarpal, metatarsal, and phalangeal bone of a foot or hand, the method comprising the steps of:

obtaining an implant having a body with a lengthwise axis, the body having a leading end and a trailing end and external threads extending around the lengthwise axis at or adjacent the leading end and the trailing end of the body with a length portion of the body unthreaded between the leading and trailing end of the body;

directing the implant through an exposed surface of the bone at an articular joint into a passage in the bone and turning the body in a first turning direction around the lengthwise axis to thereby cause the external threads to engage a bone surface bounding the bone passage so as to cause the implant to advance in a first assembly direction relative to the bone into an operative position,

the trailing end of the implant body is one of flush with or below the exposed bone surface with the implant in the operative position;

obtaining a removal tool having a first fitting;

with the implant in the operative position, operatively engaging the first fitting with a cooperating fitting on the body at or adjacent to the trailing end so that the first fitting can be moved to thereby: a) turn the body in a second turning direction around the lengthwise axis that is opposite to the first turning direction; and b) draw the body oppositely to the first assembly direction; and

with the implant in the operative position and the first fitting engaging the cooperating fitting on the body, controlling the removal tool to: a) turn the body in the second turning direction; and b) draw the body oppositely to the first assembly direction to thereby withdraw the implant from its operative position,

wherein the first fitting has threads that engage threads on the cooperating fitting on the body,

wherein the external threads and the threads on the first fitting are opposite-handed,

wherein the step of operatively engaging the first fitting comprises turning the first fitting relative to the body around the lengthwise axis in the second turning direction,

wherein the removal tool has a stepped diameter region adjacent a leading end of the removal tool with a first diameter portion and a second diameter portion is projected into an axially extending receptacle on the body,

wherein the stepped diameter region has an annular shoulder facing in one direction which abuts to an oppositely facing edge on the body with the first fitting fully operatively engaged with the body,

whereby with the first fitting fully engaged with the body, the first fitting is blocked from further turning relative to the body in the second turning direction and the threads on the first fitting bind, and thereby become locked, with the threads on the cooperating fitting on the body so that a part of the body is fixedly held between the threads on the first fitting and the annular shoulder facing in the one direction.