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Studies suggest fixing ACL grafts under low tension during reconstruction surgery

The research won its author the 2007 ISAKOS Albert Trillat Young Investigator's Award.

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FLORENCE — Japanese investigators reported that adjusting ACL graft tension to about 20° optimized the position of the tibia and femur and their loads during ACL reconstruction.

Tatsuo Mae, MD, PhD, Osaka, Japan, received the Albert Trillat Young Investigator's Award during the 2007 International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine Congress, held here, for his two-part cadaver study, the first to explore the effects of initial tension and load on grafts used for ACL reconstruction surgery.

Mae and colleagues studied the effects of initial ACL graft tension by analyzing how it affected the load on and position of the tibia and femur. They looked closely at the ACL and PCL in the coronal, axial and sagittal planes using a robotic system.

In the first part of the study, the researchers analyzed the effects of ACL tension and graft force in seven intact human cadaver knees, performing the experiments first on knees with intact ACLs and then on ones with the ACL transected.

Researchers gradually added loads to the knee joints and flexed them from 0° to 90°, recording the 3-D path in which they moved. They repeated the experiments, applying anterior-posterior drawer load to 100 N to the tibias and recording those paths.

After transecting the ACLs, researchers reconstructed them with quadrupled hamstring tendons (two each, semi-tendinosis and gracilis tendons), and current surgical and graft fixation techniques. Mae and colleagues then re-tested the knees at 20° flexion, setting graft tension at 22 N, 44 N and 88 N of femoral and tibial load.

"With increased ACL tension regarding the relative position between the femur and tibia, the tibia moves posteriorly and laterally, and proximally with external and valgus rotation," Mae said. "As intact force in the femoro-tibial joint increased, not only did the ACL force increase, but the PCL force did, too. So, ACL graft tension in ACL reconstructions should be set as low as possible."

Researchers wrote in the abstract of part two of their study, which mainly focused on optimal knee flexion angle during graft fixation: "In the ACL reconstruction with quadrupled hamstring tendons, the initial tension to the graft should be adjusted around 20°."

For more information:

• Tatsuo Mae, MD, PhD, can be reached at the Shoulder and Sports Medicine Service, Osaka Kosei-nenkin Hospital, 4-2-78 Fukushima, Fukushima-ku, Osaka-City, Osaka 553-0003, Japan; +81-6-6441-5451; e-mail: ta-mae@unim.ac.jp. He has no financial conflicts to disclose.
• Mae T. Optimization of graft fixation at the time of ACL reconstruction.
• Mae T, Shino K, Matsumoto N, et al. Biomechanical effects of knee flexion angle at the time of graft fixation in ACL reconstruction. E-Poster #91. Both presented at the 2007 International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine Congress. May 27-31, 2007. Florence.