Tearing or rupturing the anterior cruciate ligament (ACL) is a common knee injury, especially in people who participate in certain sports. And, as more people become active, surgeons are performing more ACL rupture repairs than ever before. Surgeons usually repair the ACL using a graft to hold the ligament together. Unfortunately, the graft doesn't always hold and the repair fails. This means the patient needs revision surgery for another attempt at repairing the injury. Up to now, doctors haven't agreed on what they classify as a failure after ACL surgery, but there are four main categories of failure: arthritis and pain, loss of motion, inability to stretch the knee out, and the knee becoming loose (lax) again.

It's difficult to determine what exactly the failure rate is of ACL surgery, although the numbers 10 percent to 20 percent have been mentioned. However, many failures aren't reported, so this may really affect the true number. The authors of this article wanted to study the clinical and stability results between initial ACL surgery and revision ACL surgery, and to compare revision surgery and the different types of graft materials used by the surgeons.

Researchers recruited 55 patients, who had 56 surgeries total who were between 21 and 55 years old at the time of surgery. Other surgeons had done 52 of the surgeries in which the grafts came from various sources, from both the patient and from donors. The types of grafts chosen (Achilles tendon, knee area, patient or donor) depended on the patient's situation, which included their age, activity level, economic status, if there were any earlier surgeries, and the surgeons' preference.

To assess the patients and their knee function, the researchers used the Lysholm score and International Knee Documentation Committee (IKDC) measurement criteria. To assess if the patients' knee was stable, a arthrometer was used. Other tests and x-rays were also used to get a better impression of what was going on with the knee. As a result of the assessments, the patients were placed in to one of two groups: mild (grades 0 and 1) and severe (grades 2, 3, and 4).

All patients were operated on while they were under general anesthetic. Immediately after surgery, some patients were permitted to begin exercising their quadriceps, the muscle at the front of the thigh. By day three after surgery, they were allowed to do partial weight bearing. A brace was applied to the knee on day four after surgery and range of motion exercises were increased by 15 degrees every week. After four weeks, the patients were encouraged to 90 degrees bending of the knee, by six weeks it was 135 degrees, and by six months, they were allowed to straighten their knee completely.

After looking at the data, the researchers found that according to the results of the Lysholm score, which is on a scale of one to 100, was on average 72.6 before surgery and improved to 93.7 after surgery. When looking at results of the IKDC, the results showed that 64.1 percent of the knees were normal after surgery, 30.8 percent were near normal, only 5.1 percent were abnormal, and none were severely abnormal. When looking at revision surgery, done if the first one failed, the Lysholm score changed from 63.3 before surgery to 84.6 after. As for normalcy, after revision surgery, it was found that only 23.2 percent were classified as normal, 62.5 percent were nearly normal, 10.7 percent were abnormal, and 3.6 percent were severely abnormal. The researchers were also interested in how stable the knees were after surgery, compared with before the repair. They found that there was a significant improvement in the stability of side-to-side motion after the first surgery, but it wasn't as good following revision surgery.

Failures of knee repairs were most often due to technical errors during surgery. For example, the knee wasn't always positioned ideally, not allowing proper healing.

The authors wrote that there are many factors that are involved in ACL surgery failures, but they aren't as clear in revision surgery failures. The researchers looked at the technical aspects and the materials used for grafting, but there weren't many differences found with the graft successes or failures among revision surgeries. The authors then concluded that if revision of ACL repair is needed, it could provide stability and improvement in knee movement, but revision surgery was usually not as successful as initial repair surgery.

Jin Hwan Ahn, MD, et al. Comparison of Revision Surgery with Primary Anterior Cruciate Ligament Reconstruction and Outcome of Revision Surgery Between Different Graft Materials. In American Journal of Sports Medicine. October 2008. Vol. 36. No. 10. Pp. 1888-1896.