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The anterior cruciate ligament, or ACL, is the most important ligament of the knee to prevent the knee from sliding forward or rotating anterolaterally. Patients who sustain an ACL tear often have problems with twisting and turning activities, such as in playing football, soccer, or skiing, and will often require an ACL reconstruction to provide stability to their knee.
In addition to its stability role in the knee, the ACL also provides protection for the menisci of the knee. When the knee continues to have instability episodes, it is not uncommon to have either the medial or lateral meniscus tear. However, when menisci tear there is much higher risk of the development of osteoarthritis. Because of this, Dr. LaPrade usually recommends ACL surgery and that an ACL reconstruction be performed in young or otherwise active patients and in almost all patients who report instability with twisting or turning activities.
• Grade I: a partial ACL tear
• Grade II: near complete ACL tear
• Grade III: a complete ACL tear – the ligament is non-functional
Depending on the patient’s age, activity level and grade of tear will determine the correct treatment option.
An ACL surgery requires precise knowledge of the anatomy of the knee, attachment sites of the ACL and knowledge on the other ligaments and structures of the knee. If one fails to replace an anterior cruciate ligament at its correct attachment sites or if other concurrent injuries are not treated, there is a much higher risk of failure of the ACL graft.
While there are two bundles of the ACL, the anteromedial and posterolateral bundles, there is still controversy as to whether both should be reconstructed as a single ligament or as two separate ligament grafts. While the double-bundle ACL reconstruction technique appeared very promising initially, many research groups, including ours, have significantly narrowed the indications for double-bundle ACL surgery and found there is very little difference between a single and double-bundle ACL reconstruction for the vast majority of patients.
The most important technical issue is to have the ACL reconstruction graft placed in the correct position. On the tibia (shinbone), the tunnels should be in line with the posterior margin of the anterior horn of the lateral meniscus. On the femur (thigh bone), the reconstruction tunnel should be placed at the midpoint of the attachment bundles of the anteromedial and posterolateral bundles, with the main portion of the reconstruction tunnel being posterior to the lateral intercondylar ridge (resident’s ridge).
A large number of ACL reconstruction graft failures are in those patients who have the graft placed too posterior (central) on the tibia with an inability to control rotation of the knee or too anterior on the femur (anterior to resident’s ridge) or too central on the femur (effectively only reconstructing the anteromedial bundle), which leads to either stretching of the reconstruction graft or failure to control knee rotational laxity.
ACL Graft Placed Too Central On The Tibia
Sagittal MRI scan demonstrating an anterior cruciate ligament graft placed in a nonanatomic position on the tibia. The central position on the tibia does not allow for rotational control, so these patients may have problems with instability with twisting, turning and pivoting.
ACL Tunnel Too Central
Lateral knee x-ray demonstrating a central position of the ACL reconstruction graft on the femur. In this position, the fixation device is located above Blumensaat’s line, which indicates that the graft is placed centrally. These grafts often have a negative Lachman’s test but patients often will have a positive pivot shift and have instability with twisting, turning, or pivoting activities.
Lateral Knee X-ray of ACL Reconstruction Tunnels
CLICK IMAGE TO ENLARGE
The technique of ACL reconstructions has changed dramatically over the last decade in orthopaedics. ACL reconstruction grafts performed prior to 5-10 years ago were usually placed more centrally on both the tibia and femur and many of these patients have continued problems with rotation instability. This problem became recognized through extensive clinical and biomechanical research and the surgical technique has currently changed dramatically to where the reconstruction tunnels are now placed more anatomically to provide better stability to the knee.
Dr. LaPrade’s primary surgical reconstruction technique involves using a patellar tendon autograft (from the patient’s own tissues) during ACL surgery. The reconstruction tunnel is drilled at the anatomic attachment site of the ACL on the tibia and a closed socket tunnel is drilled at the ACL attachment site on the femur. The patellar tendon graft is pulled into the joint and fixed in place with titanium interference screws. Dr. LaPrade utilizes one incision for this surgical technique, as well as an autograft to place it in the correct position. The utilization of fewer incisions results in less pain post-operatively for the patient, while the use of the autograft allows the patient to return to activities sooner with a lesser risk of reconstruction graft failure.
Patellar tendon allografts (donor grafts) or soft tissue graft material may be required in patients with open growth plates or in older patients (women greater than 40 years, men greater than 45-50 years) due to the desire not to have any bone across an open growth plate and for older patients to have a strong enough graft. Cadaver grafts can be larger than ones harvested from one’s own knee and it is well known the patellar tendon and the other grafts around the knee are approximately three times weaker in someone who is 60 years of age compared to someone who is 20 years of age.
It is absolutely essential for a physical therapist to be consulted and to work with one’s surgeon post-operatively following ACL surgery. Reactivation of the quadriceps mechanism, edema control, patella mobilization, maintenance of full knee extension and regaining knee motion are absolutely essential to obtaining optimal post-operative outcomes.
In our practice, we strongly suggest and require patients remain in Vail to work with our physical therapists at Howard Head Sports Medicine for a minimum of 5-7 days post-operatively to make sure they are having appropriate care post-operatively and also so that their rehabilitation will advance to higher levels sooner.