Microfracture apparatuses and methods

1. An apparatus comprising:

a cannula having a first end, a second end, and a channel extending between the first end and the second end, the channel having a first transverse dimension between the first end and the second end, a second transverse dimension, and a third transverse dimension positioned between the first transverse dimension and the second transverse dimension; and

a penetrator having a distal end and a first transverse dimension, the penetrator configured to be disposed in the channel of the cannula such that the penetrator is movable between a retracted position and an extended position in which the distal end extends beyond the second end of the cannula by a penetration distance; and

where the channel is tapered from the third transverse dimension toward the second end.

2. The apparatus of claim 1 , where the second transverse dimension is at the second end of the cannula.

3. The apparatus of claim 1 , where:

the third transverse dimension is larger than the second transverse dimension; or

the second transverse dimension is smaller than the first transverse dimension.

4. The apparatus of claim 1 , where:

the third transverse dimension is less than the first transverse dimension; and

the second transverse dimension is closer to the second end than the first transverse dimension is to the second end.

5. The apparatus of claim 1 , where a first tapered portion of the channel that is tapered from the third transverse dimension toward the second end is tapered such that the third transverse dimension of the channel decreases as the channel extends toward the second end of the cannula.

6. The apparatus of claim 5 , where the channel defines a first portion between the first tapered portion of the channel and the second end.

7. The apparatus of claim 6 , where a second tapered portion of the channel is tapered from the first portion toward the second end such that a transverse dimension of the channel increases as the channel extends from the first portion toward the second end of the cannula.

8. The apparatus of claim 1 , where the penetrator is configured to be moved from the retracted position to the extended position to form a microfracture.

9. The apparatus of claim 1 , where the penetrator is configured to be moved from the retracted position to the extended position substantially without rotation of the penetrator.

10. An apparatus comprising:

a cannula having a first portion, a second portion, and a channel extending between the first portion and the second portion, the channel having a first transverse dimension between the first portion and the second portion, a second transverse dimension at the second portion that is smaller than the first transverse dimension, and a third transverse dimension positioned between the first transverse dimension and the second transverse dimension; and

a penetrator having a distal end and a first transverse dimension, the penetrator configured to be disposed in the channel of the cannula such that the penetrator is movable between a retracted position and an extended position in which the distal end extends beyond the second portion of the cannula by a penetration distance; and

where at least a portion of the channel is tapered from the third transverse dimension toward the second transverse dimension.

11. The apparatus of claim 10 , where the third transverse dimension is substantially equal to the first transverse dimension of the channel.

12. The apparatus of claim 10 , the second transverse dimension is positioned at an end of the cannula.

13. The apparatus of claim 10 , where the penetrator is configured to be moved from the retracted position to the extended position substantially without rotation of the penetrator to form in subchondral bone a microfracture.

14. The apparatus of claim 10 , where:

a second portion of the channel is disposed at an angle relative to a first portion of the channel; and

the second portion of the channel includes the portion of the channel that is tapered from the third transverse dimension towards the second transverse dimension such that a cross-sectional area of the channel decreases as the channel extends toward an end of the cannula.

15. The apparatus of claim 14 , where the third transverse dimension is less than the first transverse dimension of the channel.

16. The apparatus of claim 14 , where the second portion of the cannula includes a second tapered portion of the channel that is tapered from the end of the cannula toward the first portion such that a cross-sectional area of the second tapered portion of the channel increases as the channel extends toward the end of the cannula.

17. A method of forming a microfracture in subchondral bone of a patient, the method comprising:

disposing the apparatus of claim 1 adjacent to the subchondral bone; and

advancing the penetrator relative to the cannula, substantially without rotation of the penetrator, until the distal end of the penetrator extends into the subchondral bone to form a microfracture.

18. The method of claim 17 , further comprising:

repeating the steps of disposing and advancing to form a plurality of microfractures in the subchondral bone; and

where the steps of advancing is performed while the apparatus is in contact with the sub chondral bone.

19. The method of claim 18 , further comprising:

actuating a penetrator removal tab coupled to the penetrator to retract the distal end of the penetrator from the subchondral bone.

20. The method of claim 17 , further comprising:

removing the penetrator from the cannula; and

injecting a solution to the microfracture through the channel of the cannula.