Sparing the anterior cruciate ligament remnant: is it worth the hassle?

INTRODUCTION: Anterior cruciate ligament (ACL) rupture is the most common surgically treated ligament injury. Many efforts have been taken to reconstruct it as anatomically as possible to restore knee stability and, possibly, prevent knee osteoarthritis. SOURCES OF DATA: A literature search was performed using the isolated or combined keywords 'ACL augmentation remnant', 'ACL reconstruction and remnant and stump', 'ACL reconstruction and remnant and stump preserving and stability' and 'ACL remnant complete tear' with no limit regarding the year of publication. We identified seven published studies. AREAS OF AGREEMENT: The ACL remnant might accelerate the vascularization and the ligamentization of the graft and contribute to faster graft innervation leading to a better proprioception. AREAS OF CONTROVERSY: The role of the ACL remnant is debated, because, although it may increase the risk of impingement and the formation of cyclops lesion, its preservation can improve proprioception, biomechanical functions and vascularity. However, the current assessment methods to assess proprioception, vascularization and the ligamentization do not lead to hard evidence that preservation of the remnant confers clinically relevant advantages over its excision. GROWING POINTS: The ACL remnant has been demonstrated in experimental studies to have a role in improving revascularization, ligamentization and reinnervation of the graft, but these findings are still not supported by clinical findings. A more direct way to assess proprioceptive function after ACL reconstruction and appropriately conducted powered and rigorously prospective randomized double-blind studies comparing the clinical outcomes of excising the remnant to leaving it in situ are necessary.