Fixation device
A method and apparatus are disclosed for providing a compression fixation between a first and further component. The apparatus comprises an elongate body having a head end and a tip end and comprising a screw thread including a first region in which the screw thread has a corresponding first pitch and a further region, extending from the tip end, in which the screw thread is tapered and has a corresponding further pitch that continually decreases away from the tip end.
1. Apparatus for providing a compression fixation between a first and further component, comprising an elongate body having a head end and a tip end and comprising a screw thread including:
a first region in which the screw thread has a constant outer diameter and a corresponding first pitch that is constant between adjacent turns; and,
a further region, extending by about 1.5 to 2 revolutions of the screw thread from the tip end to the first region of the screw thread, in which the screw thread is tapered and has a corresponding further pitch that continually decreases away from the tip end;
wherein the first region of the screw thread blends into the further region of the screw thread at a location of the elongate body where the first region of the screw thread begins to taper inward towards the tip end.
2. The apparatus as claimed in claim 1 , further comprising:
the further pitch continuously decreases from the tip end to the first region of the screw thread.
3. The apparatus as claimed in claim 1 , further comprising:
a distance between adjacent turns of the screw thread along the elongate body constantly decreases from the tip end to a location where the distance between adjacent turns becomes constant.
4. The apparatus as claimed in claim 1 wherein the constant pitch of the screw thread in the first region is selected from about 0.5 to 3.5 mm, about 2.0 to 2.5 mm and between 2.0 and 2.5 mm.
5. The apparatus as claimed in claim 1 , further comprising:
the further region of the screw thread has a varying pitch that varies by decreasing continuously and constantly away from the tip end.
6. The apparatus as claimed in claim 1 , further comprising:
the screw thread in the further region extends more than one revolution around the elongate body.
7. The apparatus as claimed in claim 1 , further comprising:
a crest of the screw thread in the first and further regions has a common radius.
8. The apparatus as claimed in claim 1 wherein the first region of screw thread comprises a straight thread and the further region of screw thread comprises a tapered thread that blends into the straight thread.
9. The apparatus as claimed in claim 1 , further comprising:
the elongate body comprises a central through passage extending from the tip end to the head end; or
the elongate body comprises a cannulation extending from the tip end to the head end.
10. The apparatus as claimed in claim 1 , further comprising:
the elongate body comprises a head portion that extends from the head end to a cylindrical threaded portion, that provides said first region of the screw thread, and that comprises a substantially cylindrical body including a driver element at the head end, for receiving a mating end of a driver member, and a thread origin where an outer surface of the cylindrical body is recessed to form a start of the first region of the screw thread and the cylindrical threaded portion and optionally the driver element comprises a hex-shaped recess in the head portion for receiving a working end of an orthopaedic screwdriver.
11. The apparatus as claimed in claim 1 , further comprising:
the head portion includes at least one visible indicia element having a position associated with a location of a start site of the further region of the screw thread at the tip end of the elongate body.
12. The apparatus as claimed in claim 1 , wherein the elongate body is integrally formed.
13. The apparatus as claimed in claim 1 , wherein an overall length of the elongate body is selected from about 20 to 40 mm and about 25 to 35 mm.
14. The apparatus as claimed in claim 1 , wherein an overall outer diameter of the elongate body is selected from about 5 to 15 mm and about 6 to 12 mm.
15. The apparatus as claimed in claim 1 , wherein the first component comprises a bone region and the further component comprises one or more of a further bone region or a ligament or at least one artificial fibre.
16. A method of providing a compression fixation between a bone and at least one further component, comprising:
screwing an apparatus for providing compression between the bone and the at least one further component into a pre-prepared tunnel in the bone, the apparatus comprising:
an elongate body having a head end and a tip end and comprising a screw thread including:
a first region in which the screw thread has a constant outer diameter and a corresponding first pitch that is constant between adjacent turns; and,
a further region, extending by about 1.5 to 2 revolutions of the screw thread from the tip end to the first region of the screw thread, in which the screw thread is tapered and has a corresponding further pitch that continually decreases away from the tip end;
wherein the first region of the screw thread blends into the further region of the screw thread at a location of the elongate body where the first region of the screw thread begins to taper inward towards the tip end; and
as the elongate body is screwed into the tunnel, advancing the elongate body at an advancement rate that continually reduces from an initial start rate until a constant rate of advancement is reached, said constant rate being slower than the start rate.
17. The method as claimed in claim 16 whereby the advancement rate indicates a linear distance travelled by the elongate body per revolution as the elongate body is rotated.
18. The method as claimed in claim 16 , further comprising:
providing a continuous reduction in advancement rate via a region of a screw thread of the elongate body that has a pitch that continuously decreases away from the tip end.
19. The method as claimed in claim 16 , further comprising:
the step of screwing comprises simultaneously rotating the elongate body and urging the elongate body in a desired direction along the tunnel.