Anterior cruciate ligament (ACL) injuries are one of the most common sports injuries in the United States. The ACL is one of the most important ligaments in the body, and is crucial to providing stability of the knee joint. Unfortunately, the ACL has poor healing potential, and ACL surgery is by a fellowship trained ACL surgeon is usually required to reconstruct the torn ligament in most cases. In some cases, however, the ACL can be repaired in a way that it will heal.
Most of the time, repair is not possible and a reconstruction is needed. ACL reconstruction surgery is done by taking a tendon from somewhere else in the body (or from a donor) and using it to replace the torn ACL.
Individualized, Anatomic ACL Surgery
In the past, the ACL was reconstructed in a non-anatomic fashion. In other words, the reconstructed ACL was not placed exactly where the patient’s own ACL had been located. This was done for many reasons, partially because technology and understanding of knee anatomy was limited.
However, newer imaging techniques have helped us to better understand the native ACL anatomy, and newer surgical technology and techniques have allowed us to place the reconstructed ACL in the exact place that the old one was located. This provides better knee stability and decreases the risk of future injury and arthritis.
In addition to anatomic placement, we take several measurements of the knee on the MRI and during surgery to make sure that the ACL graft is exactly the size that is needed – not too small and not too big.
ACL Reconstruction Graft Options
There are several options for grafts in ACL reconstruction, each with its own set of advantages and disadvantages. Autograft is tendon that is harvested from your own body, and allograft is tissue harvested from a donor (cadaver).
Bone-Patellar Tendon-Bone (BTB) Graft
This has historically been considered the gold standard, especially in competitive athletes. The two bone blocks kept on each end improve the healing of the graft within the bone tunnels, and the tendon itself is very strong.
However, it has been associated with increased incidence of pain in the front of the knee and difficulty kneeling. Also, there is a risk of patellar fracture during harvesting, and then tendon is not as thick as some other options. However, it has been used in millions of patients, many of them highly competitive athletes, with good success.
Quadriceps Tendon (QT) Autograft
The quadriceps tendon is more recently being recognized as an excellent graft choice for ACL reconstruction. The tendon is harvested just above the knee cap and provides a very thick and strong graft. In many cases, it is stronger than the hamstrings and has a greater cross sectional area (20% more) and density than the patellar tendon. In addition, there are no worries about pain in the front of the knee, difficulty kneeling, or the need to augment with donor tissue.
Research has shown that there may be some early quadriceps muscle weakness that resolves soon after returning to full activity. The quadriceps tendon graft can be harvested with or without a bone block. The most common way to use it is without a bone block.
The hamstring tendon graft is perhaps the most popular graft in use today. One or two of the three hamstring tendons on the inside of your knee are harvested through a small incision on the front of your knee, and they are doubled or tripled over to make a graft. The hamstring tendons are very versatile and well proven in ACL reconstruction. They can be harvested through a smaller incision than the BTB graft and don’t add much time to the procedure. Patients tend to have less anterior knee pain after surgery as well.
However, some studies have suggested that they might fail at a higher rate than BTB and quadriceps tendon grafts, and that it hamstring graft may not restore rotational stability as well as BTB and quadriceps tendon; the results are not conclusive at this point. It can also be difficult to judge the size of the tendons before surgery, and allograft (donor tissue) is sometimes added to make the graft more robust.
Allograft (Donor or Cadaver Tendons)
Allografts have the benefit of being very flexible, and grafts can be chosen with or without bone blocks, and in multiple sizes and configurations. It also makes the surgery quicker since there is no time spent harvesting autograft, and there is no harvest site pain after surgery.
However, strong research has demonstrated that using allograft in young patients (teens and 20’s) can result in a significantly higher graft failure rate than using autograft. For this reason, we typically don’t use allograft in young patients, except in specific situations, such as revision cases or where there is not a good autograft option. In slightly older or less active patients it is still a reasonable option.
ACL Surgery Facts
- Timing of Common ACL Postoperative Milestones
- ACL Functional Progression
- ACL Rehabilitation and Non-operative Protocols