Preconditioning and Cyclic Loading

Subsequent to graft insertion and tibial fixation of the constructs, testing was started with 10 precycles between +0.5 and −8.0 mm of displacement, respectively (simulating ROM from 90° to 0° of knee flexion) at a frequency of 0.5 Hz (step 3). In step 4, the machine moved to a displacement of 0 mm, corresponding to a simulated knee flexion angle of 75°, and the digital displacement was set to zero. At this position, the graft was retensioned on the femoral site to approximately 200 N, and knots were tied on the femoral ALD. Then, position-controlled cyclic loading started between +0.5 and –8.0 mm of displacement (simulating ROM from 90° to 0° of knee flexion) for 1000 cycles at 1 Hz (step 5). Upon completion, load-controlled cyclic loading from 10 to 250 N and 500 N, respectively, simulating a progressive rehabilitation protocol (steps 6 and 7), was performed before a pull to failure at 50 mm/min (step 8) at a knee flexion angle of 90°.

Data were recorded at an acquisition rate of 500 Hz, and the mode of failure was noted. All specimens were constantly kept moist using a physiologic saline solution during preparation and testing.