General info on ACL
The knee joint is the largest and most complex joint in the human body. In addition to bending and stretching, other movements are possible in the joint, such as rotation and sliding. The natural knee consists of three bones: the thighbone (femur), the shinbone (tibia), and the kneecap (patella). The knee is reinforced with ligaments made up of collagen fibers and embedded in connective tissue called tendons. On the sides of the knee, the joint is reinforced by the medial and lateral collateral ligaments. In addition, there are ligaments that lie in the center of the knee and are called the anterior and posterior cruciate ligaments due to their crossed course.
How does an ACL injury occur ?
The anterior cruciate ligament primarily functions as a stabilizer of the knee in both the anterior-posterior direction and during rotation. Typical injuries occur during sudden turning maneuvers, such as pivot movements or torsions during sports activities. The patient typically reports feeling or hearing a ‘crack’. In most cases, at that moment, you cannot continue exercising and the knee swells. Afterwards, one often experiences a sensation of giving way with short rotational movements. Sometimes, however, the symptoms are much more subtle, with only mild pain and swelling.
Diagnosis
The diagnosis of a torn anterior cruciate ligament can usually be made based on the account of a ‘twisting injury with a cracking sound’. During the clinical examination, the Lachman, drawer, and pivot shift tests should be performed. In most cases, an MRI scan of the knee is recommended to detect any additional cartilage and meniscus injuries (up to 40%). Treatment options
Anterior cruciate ligament injuries can rarely be treated conservatively. Surgery can only be avoided if there are no significant complaints of instability. In most cases, sports involving rotational movements should also be avoided. For most patients, based on their complaints of instability, age, presence of additional meniscus or cartilage injuries, and activity level, a decision will be made to undergo cruciate ligament reconstruction surgery. The timing of the reconstruction primarily takes into account the knee’s stiffness (which should be minimized). Therefore, the procedure can usually be performed within 6 weeks after the trauma. Ideally, the procedure should be conducted before 9 months, as additional stretching of other ligaments often occurs afterwards, significantly increasing the risks of additional meniscal tears.
ACL Reconstruction
The torn anterior cruciate ligament is replaced with a new one. The hamstring tendons, quadriceps tendon, or patellar tendon from your knee can be used for this. The choice of tendon will be discussed with you in advance. In exceptional cases, a donor tendon or artificial tendon may be used.
During the arthroscopy, the remnants of the damaged cruciate ligament are removed, and two tunnels are drilled into the bone: one in the upper leg and one in the lower leg, both ending in the knee at the exact location of your anterior cruciate ligament. The ends of the tunnels in the knee correspond to the place where the original cruciate ligament attaches to the upper and lower leg.
The tendon material is introduced into the knee through the tunnels at the location of the original cruciate ligament (anatomical anterior cruciate ligament reconstruction). The tendon is secured with a special fixation system. This system is crucial as it must provide stability until the graft has fully healed and integrated into the bone, which typically takes three to six months after the procedure.
In selected cases, the anterolateral complex may also be repaired through a MONOLOOP reconstruction. The rest of the knee is also examined, and any damage to the cartilage and meniscus is repaired. Some meniscal tears can even be stitched.
Anterolateral instability (ALI)
Recent research has shown that anterior cruciate ligament injuries often involve tearing not only of the anterior cruciate ligament, but also of the anterolateral capsule. The anterolateral capsule is an important stabilizer during pivot movements! The MONOLOOP procedure (performed by our group for over 20 years!) on the outside of the knee repairs this ligament and enhances resistance to rotational movements.
ACL Repair instead of reconstruction ? Is it possible ?
Recently, there has been significant scientific interest in repairing the cruciate ligament using sutures and augmentation, as an alternative to the traditional reconstruction where the ligament is replaced with a tendon graft. In this scenario, the torn anterior cruciate ligament is not substituted with a tendon, but rather it is stitched together and reinforced (augmented). Only 10% of all cruciate ligament tears, specifically those where the anterior cruciate ligament ruptures at the femoral origin, might be eligible for this approach. Ongoing scientific research aims to refine this technique, as prior studies have clearly indicated that a satisfactory recovery is not achievable through simple suturing or augmentation alone. Based on the latest scientific findings for athletes, we recommend against repair and strongly advocate for reconstruction.
Revision ACL Surgery
Anterior cruciate ligament revision surgery is typically a more complex procedure. In addition to revising the anterior cruciate ligament, specific attention must also be given to the position of the previous tunnels, the condition of the menisci, as well as any additional instability of the medial and lateral ligaments. Various options will be discussed with you, including choices for tendon grafts and the potential need for additional surgery.