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Unwinding the Facts about Twisting or Braiding ACL Tendon Grafts

Surgeons generally use tendon grafts to reconstruct a damaged anterior cruciate ligament (ACL) in the knee. The tendon graft is usually taken from tissues near the patient's own knee. In this study, the grafts were taken from the hamstring muscle along the inside of the knee. The "new" ACL is never as strong as the original one. ACL grafts sometimes tear or become loose and weak. Surgeons are always looking for ways to make the tendon grafts stronger.

Some doctors feel that strength could be increased by twisting or braiding the graft tendons before stitching them in. Not many studies have been done on this. Past studies usually involved animal tendons. This study used cadavers (human bodies preserved for research) to test tendon grafts. The authors put twisted tendon grafts in the knees of one group of cadavers. A second group got braided tendon grafts. A third group got the usual tendon grafts.

The authors then used a special machine to test the strength and stiffness of the grafts. The usual tendon grafts were the strongest and stiffest. Twisting the tendon grafts decreased strength by 26 percent and stiffness by 43 percent.

More study is needed before doctors will know for sure if braiding and twisting tendon grafts is bad in all cases. However, these authors worked hard to make the tests realistic. This means that the loads put on the cadaver knees were much like the loads put on real knees after ACL surgery. This study makes a strong case against twisting or braiding the hamstring tendon to reconstruct a damaged ACL.

References: David H. Kim, MD, et al. Twisting and Braiding Reduces the Tensile Strength and Stiffness of Human Hamstring Tendon Grafts Used for Anterior Cruciate Ligament Reconstruction. In The American Journal of Sports Medicine. November/December 2003. Vol. 31. No. 6. Pp. 861-867.

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