Don't Braid Your Hamstring Graft--YetBraiding. We've seen it in hair, rope, and yarn. Now doctors are using it in tendon grafts. If you tear the anterior cruciate ligament (ACL) in your knee, it might be replaced by a piece of tendon from your hamstring muscle. In the past doctors have folded the tendon in half to make a stronger graft. This makes the hamstring graft shorter, but stronger. Braiding the tendon graft was the next step.
Braiding changes the shape of the tissue, but does this actually increase the strength of the graft? Researchers from Harvard Medical School say no. Braiding may actually put the tendon fibers in a position that weakens the tendon's strength. They don't recommend braiding tendon grafts at all.
How did they come to this conclusion? They took hamstring tendons from human cadavers. Half of the grafts were braided. The other half weren't. A special machine was used to test the strength of the grafts. Stiffness was measured. Maximum load handled by the graft was also recorded.
The authors report a 35 percent reduction in strength in braided tendons. Stiffness was decreased by as much as 45 percent. The use of braiding was first based on the thought that braiding ropes and cables increased their strength. In fact, braiding materials improves flexibility, not strength.
Braiding hamstring tendon grafts decreases stiffness and the amount of force the graft can handle. Researchers are going to keep testing the braided method of grafting. The next step is to try different types of braiding. Testing in live tissue may also make a difference.
Peter J. Millett, MD, MSc, et al. Effects of Braiding on Tensile Properties of Four-Strand Human Hamstring Tendon Grafts. In The American Journal of Sports Medicine. September/October 2003. Vol. 31. No. 5. Pp. 714-717.
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