Biomechanics of two types of bone-tendon-bone graft for ACL reconstruction

We measured the initial fixation strength of a new graft, bone-hamstring-bone (BHB), for reconstruction of the anterior cruciate ligament (ACL) in 79 porcine knees and compared it with that of the normal porcine ACL and of the bone-patellar tendon-bone (BPB) graft. All specimens were subjected to ultimate load to failure and cyclic loading tests to assess the amount of graft slippage. The ultimate load to failure for the intact ACL was 1266 +/- 250 N, for the BPB graft 663 +/- 192 N and for the BHB graft 354 +/- 92 N (p < 0.01). After cycling to 235 N (the maximum load for all groups without failure) the average residual displacements after removal of the load for the ACL, BPB and BHB grafts were 0.031 +/- 0.013 cm, 0.078 +/- 0.033 cm, and 0.322 +/- 0.222 cm, respectively (p < 0.01). For the BHB graft the load to failure was less and the amount of graft slippage was more than for the BPB graft. Neither form of reconstruction was as strong as the intact ACL.