Ask a Sports Doc: Rebuilding ACL techniques, skiing’s common knee injury
February 3, 2014
Question: I tore my ACL skiing and I am hearing that not all doctors perform an ACL reconstruction the same way. Can you explain your philosophy?
Answer: Techniques for surgical reconstruction of a torn anterior cruciate ligament (ACL) have advanced considerably in the past decade. I perform a large number of ACL reconstructions each year and believe that the key to a good ACL reconstruction is to restore the patient's anatomy as close to the original as possible. In other words, the goal is to surgical place an ACL tendon graft in the exact same place in the knee as was the original ACL. This may sound obvious, but honestly some ACL reconstruction techniques have not achieved this.
Many surgeons who do ACL reconstruction use what is called a trans-tibial technique. With this, a small bone tunnel is created in the tibia and then through this tibial tunnel, a small drill is advanced to create a corresponding tunnel in the femur. The ACL tendon graft is then threaded up through these tunnels and fixed in place to serve as the new ACL. I have found that this trans-tibial technique does not allow for precise, anatomic positioning of the ACL graft. Instead, this technique leads to a tibial tunnel and femoral tunnel that are not perfectly positioned, and thus the ACL graft will not be located exactly where the original ACL was in the knee.
Instead of a trans-tibial technique, I drill the femoral and tibial tunnels independent of one another so that I can better reproduce these two different attachment sites of the ACL in the knee. Everyone's knee is different and therefore it is important to individually assess and identify each person's unique ACL attachment sites in the knee. I mark these original attachment sites of a patient's ACL on both the femur and tibia and then drill tunnels in the femur and tibia at these exact attachment sites. To accomplish this, the tibial and femoral tunnels have to be drilled independent of one another. Seldom can these attachment sites be reproduced using a trans-tibial drilling technique. By placing the ACL graft exactly where the original ACL once lived in the knee, the knee can be made as stable as it was prior to the injury. If the graft is positioned using a trans-tibial technique, the position of the ACL is not perfect and the knee may never feel as stable as it was before the injury.
Another factor that can negatively impact a patient's result after ACL surgery is the failure to address and correct any other ligament tears that occurred at the time of the ACL injury. For example, it is very common for a person to tear their medial collateral ligament (MCL) when they tear their ACL. In the past, most orthopedic surgeons assumed that any associated MCL tear would heal on its own. Fortunately, most associated MCL tears do heal in a knee brace, but not all. Failure to surgically repair MCL tears that have not completely healed and just fixing the ACL will cause the patient to continue to feel somewhat unstable when that person gets back to cutting and pivoting sports such as skiing. Moreover, if the MCL remains somewhat lax and just the ACL is repaired, the knee is at greater risk for reinjury and possibly re-tearing the ACL graft. Therefore, in a patient with a severe ACL and MCL tear, I recommend that these patients wait several weeks before going forward with ACL reconstruction surgery. During this time, the knee is placed in a knee brace to protect the MCL, the patient does several weeks of physical therapy to decrease their swelling and improve their range of motion. Finally, I re-examine the knee after several weeks to determine if the MCL is going to heal on its own or whether it will require surgical repair at the time the ACL is reconstructed.
Another variable in ACL reconstruction surgery is what type of tendon graft to use for your ACL reconstruction. The first choice is whether to utilize an autograft (your own tendons) or allograft (tendons from a donor). For young, active patients who do a lot of cutting and pivoting sports, I recommend using an autograft. There is better incorporation of your own tendons than a donor tendon. In other words, your own tendons grow very well into the bone tunnels that were drilled and with time small blood vessels grow into the autograft making it a healthier tissue. We see less of this ingrowth and vascularity with an allograft and this is one of the reasons why allografts re-tear at a higher rate than autograft tendons. In fact, some recent scientific papers show that allografts re-tear three to four times as often as an autograft. In an older person who is not doing a lot of cutting or pivoting sports, I would consider an allograft, but I strongly encourage anyone under the age of 40 to have an autograft for ACL reconstruction. As for autografts, using two of the patients hamstring tendons has proven to be a great graft. Using the central third of the patellar tendon is also a good, strong graft but with this graft the patient has a higher incidence of pain along the front of the knee with kneeling.
Dr. Rick Cunningham is a knee and shoulder sports medicine specialist with Vail-Summit Orthopaedics. He is also a physician for the US Ski Team and Chief of Surgery at Vail Valley Medical Center. Do you have a sports medicine question you'd like him to answer in this column? Visit his website at http://www.vailknee.com to submit your topic idea. For more information about Vail-Summit Orthopaedics, visit http://www.vsortho.com.