Mechanical evaluation of a ligament fixation system for ACL reconstructionin the tibia on a canine cadavre model

Object : Excellent fixation df an artificial ligament in bone is mandatory for initial stability. ACL reconstruction with the LARS artificial ligament may fail if anchorage to bone is inadequate. The weak metaphyseal bone of the proximal tibia is prone to inadequate fixation. This study evaluates th e initial mechanical stability of two techniques with an interference screw on the tibial side of an ACL reconstruction with the LAPS ligament. Method s: Six left tibias were obtained from 1 to 3 year old mongrel dog weighing 20 to 26 kg, ACL straight line reconstruction according to the technique de scribed by J.P. Laboureau was performed with a 4.5 mm drill. Two tunnels we re created in the tibia, one oblique and one transverse, the latter 2 cm be low the former. Reconstruction was done with a 30-fiber LARS ligament and a 5.2 mm x 15 mm conical titanium cannulated interference screw. Group I had an interference screw in the oblique tunnel and group II had an interferen ce screw in the transverse tunnel. Pull-out tests were performed parallel t o the oblique tunnel on an Instron 8521 machine at a speed of 5 mm per minu te until failure. The oblique tunnel was tested first then the transverse t unnel. Results : Group I (n = 6): sliding value = 238 +/- 115 N. Group II ( n = 6): sliding value = 998 +/- 145 N. This is statistically significant (p < 0.001, student t - test), Conclusion : One interference screw in a trans verse tibial tunnel for ACL reconstruction with the LARS ligament is 4 time s more resistant on loading and impact than an oblique screw.