ACL Reconstruction Graft Configuration
Structure of the ACL
The ACL is made up of 2 distinct functional bundles, the anteromedial (AM) bundle and the posterolateral (PL) bundle. The figure on the right shows the knee with these 2 bundles in place. The red bundle is the AM bundle and the blue one is the PL bundle. Each of these bundles functions separately to maintain the stability and function of the knee. However, the AM bundle is larger and appears to play a slightly greater role in creating a stable knee. The angles and attachment points of the bundles are slightly different from each other.
Anatomic vs Non-Anatomic Reconstruction
When an ACL is torn and is reconstructed, the new graft can be placed in a variety of different locations and angles. Over the years, many placements have been studied. Many studies have concluded that an anatomic placement of the graft results in the greatest stability of the knee after surgery. An anatomic placement is one which most closely mimics the locations that the original ACL attached to the bones.
Single Bundle Reconstruction
In traditional, single bundle reconstruction, a single bundle of tendon is used to replace the torn ACL. One tunnel is drilled in the femur and one in the tibia. The graft is drawn into these tunnels and fastened in place. The healing of the bone around the new tendon anchors the graft firmly in place.
Usually, the tunnels are located and angled to replicate the position of the central attachment points of the original ACL.
Traditional single bundle reconstruction has several advantages.
- The techniques to do this type of surgery are well established, so surgeons have experience performing this type of surgery.
- Since only one tunnel is drilled in each bone, the surgery takes less time to perform.
- Many studies have been published showing excellent anterior stability. Anterior stability is the type of stability measured by performing a Lachman test, or using a KT 1000 device.
Double Bundle Reconstruction
Double bundle reconstruction is a newer surgery that is designed to try to replicate more closely the actual anatomic structure of the original ACL. In this surgery, the graft is divided into two bundles and they are attached in place separately to mimic the AM and PL bundles of the ACL. There are a variety of techniques being used. All techniques require 2 tunnels to be drilled into the femur. Some use one tunnel in the tibia and some use 2 tunnels.
The main advantage of a double bundle reconstruction is improved stability. Studies have shown that anterior stability is about the same or slightly better in double bundle than in single bundle techniques. However, there is a second type of stability called rotational stability. This is measured by twisting the knee in a test called the pivot test. Unlike anterior stability, there is currently no device (like the KT 1000) for accurately measuring the rotational stability. However, numerous studies have suggested that rotational stability is better after double bundle reconstruction.
Because of this improved stability, double bundle reconstruction may be especially beneficial for younger, more athletic individuals who place more extreme demands on their knee.
See These Published Papers for Additional Information:
Prospective Randomized Clinical Evaluation of Conventional Single-Bundle, Anatomic Single-Bundle, and Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction: 281 Cases with 3- to 5-Year Follow-Up. Hussein, et al. 2012Other ACL related papers