Seattle Sports Medicine
The anterior cruciate ligament, or ACL, is one of the main ligaments stabilizing the knee. ACL injuries are common sports injuries, and many of these occur without contact. These injuries are commonly seen in sports such as football, soccer, basketball, skiing, and volleyball. Once the ACL is torn, it does not heal on its own. Treatment options include nonoperative treatment with physical therapy and bracing or surgical treatment with ACL reconstruction. Often, there are associated injuries such as meniscus tears, other ligament injuries, or injuries to the joint surface cartilage. In general, for those patients who want to remain active in sports or whose knee gives way in daily activities, ACL reconstruction is recommended.
Signs and Symptoms of an ACL Tear
The most common mechanism for tearing the ACL is when an athlete has his or her foot planted and twists the knee or is hit on the outer aspect of the knee causing the knee to buckle. A pop may be felt and/or heard. There is usually immediate swelling and difficulty bearing weight. The knee may feel unstable or may buckle.
Diagnosis and Evaluation
Initial management of this type of injury should include discontinuing play, protected weightbearing, ice, compression, and elevation.
Evaluation by an orthopedic surgeon specializing in sports medicine is recommended. The examination can reveal laxity (looseness) of the ACL and may also reveal other injuries. X-rays and an MRI are also recommended to confirm the diagnosis and evaluate for additional injuries.
MRI of torn ACL (white arrows)
For sedentary or older patients without additional injuries, nonoperative treatment may be attempted and may be successful.
ACL Reconstruction is recommended for active patients. Surgical treatment consists of reconstructing the torn ACL, which involves replacing it with a graft. A graft is a tendon that is placed in tunnels drilled in the tibia (bottom bone of the knee) and the femur (top bone of the knee) recreating the path the normal ACL takes through the knee. There are different graft options and there is controversy about which graft is the best. ACL reconstruction is a very predictable operation with an approximately 90% success rate when performed by qualified surgeons.
ACL reconstruction is performed arthroscopically with small incisions. A slightly larger incision is used to obtain the graft and drill the tunnel in the tibia. Arthroscopy is performed to evaluate and treat other injuries such as meniscus tears as well as reconstructing the ACL.
Arthroscopic Surgery of the Knee
Incision used for hamstring graft harvest and drilling tibial tunnel
Tunnel drilled in femur for ACL graft
The graft is typically fixed in the tunnels with screws. I prefer to use absorbable screws to avoid any problems after surgery with MRIs. Also, metal screws may be in the way during repeat surgery if someone re-tears their ACL.
Absorbable screw being placed in femoral tunnel next to ACL graft
The surgery is performed as an outpatient procedure allowing patients to go home the same day. A nerve block is typically used to help with the pain afterwards along with either a spinal or general anesthetic.
ACL Graft Options
Patellar Tendon Graft
A patellar tendon graft is the most common graft used for ACL reconstructions. This graft involves using the middle third of the patellar tendon with bone from the patella and bone from the tibia. The pros of this graft are that it has been time-tested and provides excellent knee stability. Healing of the graft in the bone tunnels occurs faster with bone-to-bone healing versus tendon-to-bone healing. The cons of this graft are that rehabilitation is more painful compared to a hamstring graft or an allograft (donor graft), up to approximately 30% of patients may have persistent pain in the kneecap area or pain with kneeling, there may be a higher rate of arthritis later on, and there may be a higher rate of complications.
Patellar Tendon Graft
The next most common graft is a hamstring graft. There are 5 hamstring muscles and tendons. Two of the tendons, the Semitendinosus and Gracilis, are doubled to create a 4-stranded hamstring graft. The pros of this graft are that rehabilitation is typically much less painful than a patellar tendon graft, it is approximately 50% stronger than a patellar tendon graft, the incidence of kneecap pain or pain on kneeling is extremely low, and return to sport may occur at a higher rate and earlier than with a patellar tendon graft. The cons of this graft are that it does not have bone-to-bone healing in the tunnels, and this graft healing may be delayed versus a patellar tendon graft. Regardless of this biologic difference, studies in general have not shown that knee stability, or return to sport, are compromised by this.
Four Stranded Hamstring Graft
An allograft is yet another option and involves using donor tissue. I typically use an Achilles tendon allograft. The advantages of this graft are that it involves no donor site morbidity (pain or functional deficit from using one’s own tissues for a graft), it may be done with a smaller incision, and rehabilitation is typically easier than using an autograft (one’s own tissue). The cons of this graft are there is a small risk of disease transmission with bacteria or viruses such as hepatitis or HIV, there is slower incorporation of an allograft versus an autograft (meaning that the body transforms the graft into a ligament slower when allograft is used), and there may be a low-level immune response leading to higher failure rates with allografts.
Achilles Tendon Allograft
It is my opinion that the scientific literature has proven that good results can be obtained with any of these grafts. Other grafts may be used as well with good results. My approach is to evaluate an individual person’s activities and demands and make a recommendation for a graft based on these considerations. For example, an athlete such as a catcher who spends much of their time in a squatting position may do well with a patellar tendon graft, but I think they would do much better with a hamstring graft to avoid any potential kneecap issues. Conversely, I think an athlete such as a sprinter and most football players (especially running back, defensive back, and wide receiver) would do better with a patellar tendon graft avoiding any potential issues with hamstring weakness or tightness. Although hamstring tendons have been shown to regenerate following their use as graft and the incidence of hamstring problems following hamstring grafts is very low, it is probably a risk not worth taking in these individuals.
My ACL rehabilitation protocol includes using crutches for 7-10 days with partial weightbearing. Following this, patients may progress to weightbearing as tolerated unless other procedures dictate that we change this protocol. A postoperative brace is used for 6 weeks to protect the graft from injury. Physical therapy is started several days after the surgery to decrease swelling and improve range of motion. A strengthening program emphasizing core and lower extremity strength is started. If patients have met their goals, they typically start a jogging program at 12 weeks after the surgery. Return to some sports may occur at 6 months after surgery, but many patients require 9-12 months to achieve satisfactory strength and endurance to return to full, unrestricted activities. Rehabilitation from injury or surgery is flexible and not based only on time but also on how one progresses through the phases of rehabilitation. Some patients will work very hard and can shorten their recovery time to some extent.
Dr. Khalfayan’s Tip: It is very important to ice the knee or use a cooling pad frequently after surgery to decrease the swelling and pain. As the swelling decreases, range of motion and pain improve, allowing rehabilitation to progress. It is also important not to place pillows under the knee and to obtain full extension of the knee as soon as possible.