The anterior cruciate ligament, or ACL, is one of four major knee ligaments. The ACL is critical to knee stability, and people who injure their ACL often complain of symptoms of their knee giving-out from under them. Therefore, many patients who sustain an ACL tear opt to have surgical treatment of this injury.
Surgical treatment of an ACL tear involves the placement of a new ligament, followed by several months of rehabilitation. One of the potential problems that can occur at the time of ACL surgery is an infection of the ACL graft.
Infection after ACL reconstruction surgery is a rare complication. Studies estimate the chance of developing a joint infection, called a septic joint, after an ACL reconstruction surgery are less than 1% (0.3% in the largest study).
Causes of Infection
Infections occur when bacteria are able to grow inside your body. Your immune system can fight infections when they are small, but some infections may be too severe for your immune system to adequately eradicate.
Infections are a concern after ACL surgery for two reasons:
Joints are susceptible to infection
Joints are spaces occupied by fluid that has little immune defenses. Therefore, when infections get inside a joint, the body has a limited defense against the infection. Surgery is necessary to clean out the joint for treatment of the infection.
ACL grafts have no blood supply
The graft used for ACL surgery has its normal blood supply disrupted; this is true for both grafts harvested from your own body, or grafts donated from a cadaver. The graft has no blood supply, and thus antibiotics have no way to get to the graft tissue.
Treatment of Infections After ACL Surgery
Joint infections after ACL surgery are treated with surgery and antibiotics. Surgical treatment is necessary to clean the joint of bacteria, and antibiotics are intended to prevent a recurrence of the infection.
When the infection is found early in its onset, a surgical procedure to clean the joint may be sufficient for treatment. However, when the infection has been present longer, the entire ACL graft may need to be removed in order to cleanse the infection. When this more aggressive step is necessary, the ACL graft is removed, the infection is eradicated, and several months later, a new ACL reconstruction surgery is performed. Deciding when the graft can be retained depends on the appearance of the ACL graft at the time of surgery, and the response to treatment. If multiple surgeries are performed without improvement in the infection, the graft will likely need to be removed.
Avoid ACL Infections
Yes and no. We know there are steps that can be taken to minimize the risk of infection, but we have not found a way to make the risk of infection 0%. Steps that can be taken include ensuring sterile procedure in the hospital operating room, giving antibiotics at the time of surgery, and appropriate sterilization of the affected knee. Ask your doctor about steps you can take to ensure you have the lowest chance of developing an infection.
Burks RT, et al. "Treatment of Postoperative Anterior Cruciate Ligament Infections with Graft Removal and Early Reimplantation" Am. J. Sports Med., May 2003; 31: 414 - 418.
Schulz AP, et al. "Septic Arthritis of the Knee After Anterior Cruciate Ligament Surgery: A Stage-Adapted Treatment Regimen" Am. J. Sports Med., Jul 2007; 35: 1064 - 1069.
Williams RJ, et al. "Septic Arthritis After Arthroscopic Anterior Cruciate Ligament Reconstruction: Diagnosis and Management" Am. J. Sports Med., Mar 1997; 25: 261 - 267.