Mechanisms for strut length measurement

A strut for use with an external fixation system, the strut comprising:

• a first joint proximate a first end of the strut, the first joint configured to couple to a first ring of the external fixation system;
• a second joint proximate a second end of the strut, the second joint configured to couple to a second ring of the external fixation system;
• a threaded rod having a first end coupled to the first joint;
• a tube that receives the threaded rod;
• a fluctuation counter coupled to the tube;
• and
• a needle coupled to the fluctuation counter, the needle extending through a bore in the tube, the needle having a free end in contact with the threaded rod,
• wherein the strut is an adjustable-length strut whereby the threaded rod is moveable axially into or out of the tube, and while the threaded rod moves into or out of the tube, the free end of the needle is configured to maintain contact with the threaded rod.