Editorial Commentary: Remnant-Preserving Anterior Cruciate Ligament Reconstruction Shows Long-Term Advantages, but Patient Selection, Characterization of Remnant Tissue, and Efficacy in Patients at Risk of Postoperative Knee Instability Are Areas for Future Investigation.

Remnant preservation is one specific anterior cruciate ligament (ACL) reconstruction technique that has been explored to improve outcomes and involves retaining, as opposed to debriding, the "remnant" or native ACL tibial stump at the time of reconstruction. The ACL remnant tissue contains important mechanoreceptors and nerve endings, and preservation of this tissue is thought to enhance biological healing within the bone tunnels, graft ligamentization, maturation, synovialization, and proprioception, as well as reduce the risk of tunnel enlargement. Remnant preservation may also offer several technical advantages such as creation of a biological sleeve for the graft and improved anatomic graft placement. The indications for remnant preservation remain unclear, but greater than 50% thickness of remaining remnant tissue is our recommended threshold for preservation. Although long-term clinical studies are currently lacking, multiple short- and mid-term follow-up studies have suggested that remnant-preserving techniques can offer significantly superior pivot-shift outcomes and anterior knee stability, in addition to lower graft rerupture rates. Ultimately, remnant-preserving ACL reconstructions are exciting techniques that appear to offer a variety of benefits, but patient selection and indications, standardized characterization of the remnant tissue, and assessment of the long-term efficacy in patients at risk of residual postoperative rotational knee instability are still areas for future investigation.