When a torn anterior cruciate ligament (ACL) is repaired for the first time, it's called a primary ACL reconstruction. If the reconstruction ruptures or fails, then a second operation called a revision or revision ACL reconstruction may be needed.
Reinjury and failures occur most often in athletes who return to their former level of sports activity. With more and more people participating in sports, revisions are on the rise. A study from Australia reports the number of revision ACL reconstructions has doubled in the last 10 years.
There are many possible reasons for this to happen. Technical errors during the operation are common. The tendon graft used to replace the ACL may not be put in the best place or with the right amount of tension.
Sometimes the patient's body just doesn't heal well. The graft may not "take." An overactive immune reaction or lack of blood supply may result in biologic failure. In other cases the athlete reinjures the leg while playing.
Most often there isn't one single cause of primary ACL repair failure. Usually, it's a combination of two or more factors. And, if there are other damaged ligament structures in the knee that aren't repaired, then the joint can become unstable. Joint instability puts more load and stress on the healing tendon repair.