Biomechanical And Clinical Study Of Four Strand Hamstring Tendon Graft Femoral Fixation Devices In Anterior Cruciate Ligament Reconstruction

The anterior cruciate ligament(ACL) is the primary structure to sustain the stability for the knee;it has double functions of guiding physiological motions and restraining unphysiological motions.The rupture of ACL may lead to disability and degeneration of the knee,so it is necessary to reconstruct the ACL of the knee.There are a variety of ACL fixation devices available,BPTB and quadrupled hamstring tendon are widely used in recent years.However,the fixation devices of grafts are still the weak point in ACL reconstruction.Successful restoration of ACL function requires rigid fixation with sufficient stiffness to withstand the rehabilitation exercise and to avoid the failure before the healing of tendon-to-bone.For different grafts,there are many different fixation devices.Optimal femoral fixation technique for hamstring-tendons graft is still discussed;it is an important tissue valued approach.Objective:To evaluate the biomechanics of different femoral fixation devices for hamstring tendon grafts.To evaluate the curative effect of Rigid-fix for the fixation of hamstring grafts on both femur and tibia side in ACL reconstruction.Methods:Different femoral fixations were used in every cadaver knee.After 1000 Cyclic Loading between 50 and 200N,stiffness,maximal load,failure load and displacement evaluation were used to study the biomechanics of reconstruction of ACL. From June of 2007 to January of 2008,twelve cases with ACL ruptures were reconstructed under arthroscopy with hamstring grafts,and the grafts were fixed with Rigid-fix cross-pin on both femoral and tibial side.After semitendinosus/gracilis were harvested,the hamstring grafts were pre-tensioned and woven,the diameter of four or five strands grafts was 7-8mm.The tibia tunnel was positioned and drilled on ACL stump of tibial crest,and the femoral tunnel was drilled through the additional anteromedial approach,the depth of femoral tunnel was 30mm.Insert Rigid-Fix guide through tibial and femoral tunnel,drill the sleeve and interlocking trocar through the Rigid-Fix guide,and keep the two sleeve fixed to the lateral femur and tibia.Pull the tendon graft into the femoral tunnel through tibial tunnel.Insert the Rigid-fix cross pins into its' approach from femur and tibia one by one.When insert the second,third,fourth cross pin,the graft should be kept tensioned.Then,tie a knot through tibial bony bridge using the Enthibond thread switched to the end of tendon grafts.The end,observe the tension of tendon grafts and the impingement of fossa intercondylica under arthroscopy.Results:Maximal load and failure load:Endobutton＞Rigid-fix＞Hamstring tendons knot＞Interference screw,the fixation strength of Endobutton is larger than the others(P＜0.01),the fixation strength of Rigid-fix is larger than interference screw(P＜0.05).There were not statistical difference between Rigid-fix and hamstring tendons knot,hamstring tendons knot and interference screw;Stiffness:Rigid-fix=hamstring tendons knot＞interference screw＞Endobutton;Displacement after cyclic loading: hamstring tendons knot＞Rigid-fix＞Endobutton＞interference screw,and there hasn't statistical difference in stiffness and displacement between the groups.With an eleven months follow-up evaluation,all of the patients' injured knee are stable,the average Lysholm knee score was elevated from 62.5to 94.5.Arthrometer device values were less than 3 mm of sagittal displacement in 10 patients and 3-5mm in 2 patients. Postoperative Lachman was negative in 10 patients and weakly positive in 2 patients. According to the IKDC scores,10 patients reported normal function,2 patients reported nearly normal function,and no patient reported abnormal function.Conclusion:The biomechanics of each of the four femoral fixation devices can satisfy the desire of ACL reconstruction,but the biomechanics of Rigid-fix is more balance and outstanding.The method of graft fixed both in the femur and the tibia using absorbable cross pins is approval.In this way,the graft is stabilized near the joint line,it allows 360 Degree bone to graft contact,and promotes the hilling of tendon to bone.In our practice,very good results have been obtained with the use of this technique.