gms | German Medical Science

The success of anterior cruciate ligament reconstruction depends on the strength of fixation, but there is a lack of information on the behavior of the graft fixation under physiological loading.

We used 42 fresh frozen human cadaver knees (45.6 ± 10.6 years) and compared the following three fixation methods: (1) Endobutton with Mersilene tape No. 4, (2) interference screw 25 x 9 mm, and (3) cancellous screw 6.5 x 35 mm with 3 Ethibond No. 5 sutures. Bone-patellar tendon-bone-grafts were placed isometrically in the femur and anchored in one of the previously described ways.

Dynamic tests were performed under cyclic loading conditions (30 to 300 N, 1 cycle/sec, up to 60,000 cycles, 8 specimen / fixation method) in a material testing machine. The displacement of the bone plug of the graft in the femur with respect to the femur itself were recorded.

Differences in failure site and number of cycles until failure were found: none of the Endobutton fixation, three of interference screw fixations, all cancellous screw fixation failed. All failures occurred at the fixation site. In all groups the displacement between the fixed bone plug in the femur and the femur itself increased up to 60,000 cycles, it was lessest for interference screw fixation.

The results indicate that the cancellous screw can´t be recommended because of early failure. Because a high movement of the fixed bone plug results clinically a poor postoperative outcome, the Endobutton technique must be viewed critically in this point.