Relative motion of tendon limbs in a loop tendon graft

The biomechanical data derived from the standard tensile testing machines may not be able to show the relative motion of the graft limbs. This paper uses a digital stereo image recording system, synchronized with the standard test machine, to determine the relative motion of a looped tendon graft. Bovine flexor tendon was used to create the looped graft and then the graft was passed through a tunnel in a foam block and fixed with an interference screw. The structure was then mounted in a testing machine. The tendon limbs surfaces were speckled just moments before test, and two cameras synchronized with the test machine were capturing the movements of the speckles. Following a cyclic loading from 50 - 250 N at 1.0 Hz for 500 cycles, a load-to-failure test was carried out at a rate of 20 mm/min. The load-displacement data and the corresponding images of the graft were used to examine the mechanical properties of the graft structure and the relative motion of the individual graft limbs. There was no significant difference between the mechanical properties of the grafts structure. The average displacement of the grafts structure was 6.95 mm, while the average relative motion between the loop limbs up to the point of the graft failure was 0.3 mm.