Fixation device and method of manufacture and use
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 farther pitch that continually decreases away from the tip end.
1 . A method of providing a compression fixation via an interference fit between a bone and at least one further component, comprising:
screwing an elongate body comprising a head end, a tip end and a screw thread into a pre-prepared tunnel in a bone, wherein:
the elongate body advances at a predetermined initial advancement rate as the tip end is initially screwed into the tunnel, and
after initially advancing at the initial advancement rate, the elongate body advances at a continually decreasing advancement rate until the elongate body reaches a constant advancement rate; wherein a continuous reduction in the continually decreasing advancement rate is provided via a distal tip region of the screw thread, that has a pitch that continuously decreases away from the tip end, and that blends into a central substantially cylindrical region of the screw thread that provides the constant advancement rate and that has a constant pitch.
2 . The method of claim 1 , wherein each of the initial advancement rate, the continually decreasing advancement rate, and the constant advancement rate indicate a linear distance travelled by the elongate body per revolution as the elongate body is rotated.
3 . The method of claim 1 , wherein screwing the elongate body comprises simultaneously rotating the elongate body and urging the elongate body in a desired direction along the tunnel.
4 . The method of claim 1 , wherein the pre-prepared tunnel is selected from a tibial tunnel and a femoral tunnel.
5 . The method of claim 1 , further comprising:
prior to screwing the elongate body, inserting at least one guide wire along the pre-prepared tunnel in the bone.
6 . The method of claim 5 , further comprising:
passing the elongate body over the at least one guide wire via a cannulation in the elongate body.
7 . The method of claim 1 , further comprising:
prior to screwing the elongate body, providing at least one graft component in an opening at an end of the pre-prepared tunnel.
8 . The method of claim 1 , further comprising:
prior to screwing the elongate body, using a locating notch as a guide to align a corresponding start point of the screw thread at a desired location.
9 . The method of claim 8 wherein the start point of the thread is orientated so as to begin cutting into the bone rather than into a graft.
10 . The method of claim 1 , wherein advancing the elongate body provides a compression fixation to secure a graft with respect to the bone.
11 . The method of claim 1 , wherein the at least one further component comprises at least one of a further bone or ligament or artificial fibre.
12 . The method of claim 1 , wherein screwing the elongate body is performed by a driver that comprises a handle and a shaft shaped for engaging the elongate body.
13 . The method of claim 12 , wherein the driver is cannulated so as to be usable with a guide wire.