Impactor

1. An impactor for transmitting an assembly force to a component of an orthopaedic implant, the impactor comprising:

(i) a first member having first and second ends, wherein the first end has a surface which is adapted to have an assembly force applied to it,

(ii) a second member having first and second ends, wherein the first end is adapted to directly or indirectly transmit the assembly force applied to the first member to the component of the orthopaedic implant,

wherein one of the first and second members has a bore extending within it from its second end which defines a longitudinal axis, and the second end of the other of the first and second members is received in the bore so that one of the first and second member can slide within the bore in a telescoping manner,

and wherein the impactor includes a main spring acting between the first and second members, the main spring being retained in a compressed condition within the first and second members,

and wherein the impactor further comprises an indicator which can move between first and second positions, the indicator being biased from the first position towards the second position and held in the first position by a latch, and wherein the indicator is released from the latch to move towards its second position when the extent of compression of the main spring by the application of an assembly force exceeds a threshold, wherein one of the latch and the indicator is acted on directly or indirectly by one of the first and second members to cause the indicator to be released from the latch to move towards its second position, wherein the latch can move between a first latch position wherein it engages the indicator to retain it in its first position and a second latch position wherein the indicator is released to move towards its second position and the latch is biased towards the first latch position.

2. The impactor of claim 1 , wherein the compression force is at least about 1.0 kN.

3. The impactor of claim 1 , wherein the movement of the indicator between the first and second positions involves movement of the indicator along the second member.

4. The impactor of claim 3 , which includes a resiliently deformable part which acts on the indicator directly or indirectly, biasing it from its first position towards its second position.

5. The impactor of claim 1 , wherein movement of the indicator between its first and second positions after it has been released from the latch is substantially independent of movement of the second member relative to the first member in response to the application of an assembly force to the first member.

6. A system for use in an orthopaedic surgical procedure, which comprises an impactor of claim 1 and a hammer for applying an assembly force to the first end of the first member.

7. The impactor for transmitting an assembly force to a component of an orthopaedic implant, the impactor comprising:

(i) a first member having first and second ends, wherein the first end has a surface which is adapted to have an assembly force applied to it,

(ii) a second member having first and second ends, wherein the first end is adapted to apply the assembly force directly or indirectly to a component of an orthopaedic implant and thereby to transmit the assembly force applied to the first member to the component of the orthopaedic implant,

wherein one of the first and second members has a bore extending within it from its second end which defines a longitudinal axis, and the second end of the other of the first and second members is received in the bore so that one of the first and second member can slide within the bore in a telescoping manner,

and wherein the impactor includes:

(iii) a main spring acting between the first and second members, and

(iv) an indicator which can move between first and second positions, the indicator being biased from the first position towards the second position and held in the first position by a latch, and wherein the indicator is released from the latch to move towards its second position when the extent of compression of the main spring by the application of an assembly force exceeds a threshold; and

wherein one of the latch and the indicator is acted on directly or indirectly by one of the first and second members to cause the indicator to be released from the latch to move towards its second position and wherein the latch can move between a first latch position wherein it engages the indicator to retain it in its first position and a second latch position wherein the indicator is released to move towards its second position and the latch is biased towards the first latch position.

8. The impactor of claim 7 , wherein the main spring is retained in a compressed condition within the first and second members so that it exerts a compression force against the first and second members, and so that an assembly force applied to the first member does not compress the main spring further unless the assembly force exceeds the compression force.

9. The impactor of claim 7 , wherein the compression force is at least about 1.0 kN.

10. The impactor of claim 7 , wherein the movement of the indicator between the first and second positions involves movement of the indicator along the second member.

11. The impactor of claim 10 , which includes a resiliently deformable part which acts on the indicator directly or indirectly, biasing it from its first position towards its second position.

12. The impactor of claim 7 , wherein movement of the indicator between its first and second positions after it has been released from the latch is substantially independent of movement of the second member relative to the first member in response to the application of an assembly force to the first member.

13. A system for use in an orthopaedic surgical procedure, which comprises an impactor of claim 7 and a hammer for applying an assembly force to the first end of the first member.