A single-bundle ACL graft is a reconstruction of the anterior cruciate ligament using a 'single-bundle' of graft material as opposed to a 'double-bundle'.
Two endobuttons constrain the ends of the graft.
The ACL anatomy
The anterior cruciate ligament itself is comprised of two bundles. Most knee surgeons still reconstruct it with a single graft, but there are many who are convinced that the double bundle better reproduces the anatomy.
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