ACL rupture affects an estimated 35 people per 100,000 and can increase based on gender and activity. Female athletes face a two to eight times increase in risk of ACL rupture compared to their male counterparts. With numbers like this, it is not wonder that the annual estimated health care cost for ACL repair is three billion dollars just in the United States. The most common treatment for ACL rupture is surgical repair, though non surgical rehabilitation is also an option. The decision to repair a ruptured ACL depends on many factors, including age, desired level of activity, episodes of instability and general health.
Before reviewing the surgical options for ACL reconstruction, it is important to understand the basic anatomy of the ACL, or anterior cruciate ligament. It is composed of two functional bundles of ligaments, the anteromedial and posterolateral bundle, which are so named due to their insertion sites on the tibia. Both bundles work together to stabilize the knee into flexion. The anteromedial bundle length remains constant throughout flexion and extension of the knee but is most taut at 45 to 60 degrees flexion. The posterolateral bundle is tight with extension but loosens with flexion in order to allow some rotation to take place at the knee joint.
Once the the decision to have surgery has been made, there are several factors to consider including timing of the surgery, technique used by the surgeon, and the graft site from which to build the new ACL. When making these decisions one must look at preoperative range of motion, swelling and strength as well as individual anatomy, post-operative activities and goals.
Timing of the knee surgery is one of the first factors to consider. There is evidence supporting early surgery, as it may lead to improved functional outcomes and decreased rate of future meniscal damage. However, delayed surgery can allow for potential avoidance of surgery all together if the individual is satisfied with their knee function. Allowing more time before surgery can definitely help an individual improve preoperative strength and range of motion.
Preoperative strength of at least 90 per cent of the quadriceps, is correlated with improved long term functional outcomes. Preoperative swelling and limitations in range of motion are correlated with increased arthrofibrosis after surgery. Thus, a preoperative rehabilitation program focusing on decreased swelling, improved range of motion and quadriceps strength is beneficial.
There are two main surgical techniques utilized in ACL reconstruction, single or double bundle. Though the single bundle technique is far more common, with the double bundle technique being used primarily in Europe and Asia, the rupture pattern of the ACL in that individual and their unique anatomy should be considered by the surgeon when making the ultimate decision on which technique to use. Variations in the tibial notch, arthritic changes, multiligament injuries and bone bruising are all taken into consideration by the surgeon with the aid of a detailed flow chart. Outcomes measures detect no difference in long term functional outcomes between the two techniques, with the exception of fewer reported meniscal injuries with double bundle repair. Regardless, it is important that the surgery match anatomical placement of the ligament in order to help restore optimal biomechanics.
After the technique has been selected, the graft site is the next major decision. Typical graft options include bone-patellar-bone autograft, hamstring tendon autograft, quadriceps tendon autograft, and allograft. If a double bundle repair has been selected the bone-patellar-bone graft cannot be utilized. MRI scans can be helpful in allowing the surgeon to determine which tendon may be most useful based on graft size. The long term goals of the patient are also important in selecting the graft site. For example, an athlete that relies heavily on hamstring strength will not want to use the hamstring autograft. Similarly an individual who has to do a lot of kneeling will not want to choose the bone-patellar-bone autograft.
Once the surgery has been performed, several questions arise, including when one can return to sport, what is the chance of re-injury and/or developing osteoarthritis in the future. Return to sport is dependent on many factors including the healing of the graft, the individuals anatomy and the desired sporting level. For those who do not return to high level of sport, fear of re-injury is a common reason. Graft failure rate is about 11 per cent and does not seem to be dependent of the choice of graft site. Several authors have actually reported a higher rate of ACL injury in the opposite leg compared to a re-injury of the repaired ACL. In general, those who do re-injury a repaired ACL are younger and returning to a higher level of activity. Arthritic changes and the development of osteoarthritis after ACL rupture is more common in those who have sustained some meniscal damage or lose range of motion in the knee joint.