Testing of double-stranded allografts used in ACL reconstruction

We used bovine tibiae and two-stranded human anterior tibialis tendon grafts to compare biomechanical properties of two tibial fixation devices, the Milagro Interference Screw (Milagro) and the Bio-Intrafix Soft Tissue Tibial Fixation System (Bio-Intrafix). A total of 24 constructs (12 with each type of fixation) underwent biomechanical testing with 12 matched constructs undergoing uniaxial loading to failure (rate of 1 mm/sec) and the other 12 matched constructs undergoing cyclic loading (10,000 cycles at 1 Hz with a loading range of 125 to 375 N). All constructs failed by slippage of one or both ends of the anterior tibialis graft past the fixation device. One of the six Bio-Intrafix specimens failed before 10,000 cycles; four of the six Milagro specimens failed before 10,000 cycles. Bio-Intrafix, which is designed for a four-stranded graft, provided superior fixation to a traditional bioabsorbable interference screw in a two-stranded soft tissue graft at one of the weakest links in anterior cruciate ligament reconstruction surgery.