Double Bundle ACL Reconstruction

Double-bundle ACL reconstruction addresses stability concerns for both ACL bundles at the time of surgery.  Like a door with two hinges, the ACL is likewise more durable and moves more smoothly over time with two surgically strengthened bundles rather than only one. In select patients, a “Double Bundle” ACL reconstruction has potential advantages over traditional single bundle reconstruction.

Patient Profile:

  • Torn anteromedial and posterolateral bundles of the ACL (very common to tear both at the same time)
  • Failed prior ACL reconstruction surgery
  • Increased ligament laxity
  • Hyperextension or mild limb malalignment
  • Chronic or longstanding ACL injuries with increased knee laxity

The ACL consists of two functional bundles of tissue, the anteromedial (AM) which primarily controls forward range of motion, and the posterolateral (PL) which controls rotational stability.  When the knee is straight the AM and PL bundles are parallel.  When the knee is flexed, the two bundles cross each other.  Most patients who tear their ACL damage both bundles at the same time. Some patients complain of knee pain and residual instability following single-bundle ACL reconstruction and arthritis has been observed in long-term follow-up exams.  In recent years Dr. Karas has begun performing anatomic “double-bundle” ACL reconstruction.  The goal here is to improve the stability of the knee and restore native knee kinematics by reconstructing both the AM and the PL bundles at the same time.  The most common analogy drawn to describe the benefit of double vs. single bundle ACL reconstruction is that of the door hinge.  A door with one hinge will open and close, but that one hinge is required to do all the work. Over years of use it will loosen and become unstable. In comparison, a door with both its hinges disperses the workload more evenly, allowing the door to open and close smoothly for long periods of time.

Double bundle ACL reconstruction surgery aims to:

  • reproduce the individual anatomy of the patient’s ACL by reconstructing both the AM and PL bundles
  • reproduce the insertion sites of the ACL by identifying and measuring their exact locations
  • drill the bone tunnels of both bundles precisely where they belong.
  • Control not only anterior stability, but also the rotational stability of the knee

Dr. Karas will also endeavor to reproduce the tension pattern of each bundle of the ACL by fixing them at their respective angles and individualizing all aspects of the surgery to unique anatomical aspects of the patient’s knee.  After double-bundle ACL reconstruction, patients should expect to have excellent range-of-motion and stability, typically equal to the other knee.