Mechanical properties of soft tissue femoral fixation devices for anterior cruciate ligament reconstruction

Purpose: To evaluate femoral soft tissue fixation for anterior cruciate ligament reconstruction. Hypothesis: Femoral fixation devices have different ultimate strengths and slippage under cyclic loading. Study Design: Controlled laboratory study. Methods: Thirty-three porcine femora were used to study interference screw (9), Endobutton (8), Rigidfix cross-pin (8), and BioTransfix cross-pin (8) fixation methods. Fixation slippage was evaluated under cyclical load from 50 N to 250 N using a materials testing machine. Ultimate load was determined with a single load to failure. Results: Total graft slippage was greater (P <.001) for the Rigidfix (6.02 +/- 2.12 mm) and the interference screw (5.44 +/- 3.25 mm) compared to the Endobutton (1.75 +/- 0.97 mm) and the Bio-Transfix (1.14 +/- 0.53 mm). All techniques showed the greatest slippage during the first 100 cycles (Rigidfix 84%, Endobutton 70%, interference screw 56%, and Bio-Transfix 55%). The failure load for the interference screw technique (539 +/- 114 N) was lower (P =.0008) than for the other 3 techniques (737 +/- 140 N for Rigidfix, 746 +/- 119 N for Bio-Transfix, and 864 +/- 164 N for Endobutton). Conclusions: The interference screw and the Rigidfix fixation demonstrated inferior fixation biomechanics compared to the BioTransfix and the Endobutton techniques.