ACL (anterior cruciate ligament) injuries are an all too common problem. Over the winter, we blogged about Lindsay Vonn and her troubles with her ACL surgery and subsequent reinjury. Lindsay is not alone. Over 200,000 patients suffer an ACL tear every year and more than half of them end up having at least one surgery. Throughout the 1990s and into the early years of the 21st century, the orthopaedic scientific community poured much of its research efforts into figuring out the strongest, stiffest, and technically best way to put a new ACL into a damaged knee. Recently, researchers have taken a long hard look at the outcomes after surgery and the factors that lead to reinjury. Some of the new data has surprised us and its not all good news.
The MOON study group looked at 2, 695 patients between 2002 and 2008, and found that age, activity level, and graft type can influence reinjury. The overall retear rates were 4.3 percent, but more concerning was the 3.6 percent chance of tearing the OPPOSITE ACL during the study period. Adding to that sobering fact is that our youngest patients are affected the most. For each year of increased age, the odds of retearing the same ACL decreased by 9 percent. Conversely, the risk of tearing the opposite ACL reduced by 4 percent for every gained year of age.
The authors pointed our that that younger age, higher activity levels at time of injury and what type of graft used may increase risk of same side ACL injury within two years. They suggested the high incidence of opposite leg ACL tears presents a difficult problem for patients and therapists during the rehabilitation period.
Another study evaluated the type of graft used for reconstruction and its effects on retear rates. Grafts tend to fall into 2 categories: autograft (tissue taken from the patient’s own body) or allograft (tissue from a cadaver donor). Allografts have become popular because they help limit the pain and disability that comes from removing a tendon to use somewhere else and they are fast and easy to prepare. Researchers evaluated ACL reconstructions on active duty military personnel for 10 years and found that 8.3% of autografts failed and retore but 26.5% of allograft ligament reconstructions tore again. And while the absolute numbers are small, that is still a 3 times greater chance that a cadaver donor graft will retear.
These studies, and more like them, will be critically important in improving patient outcomes after ACL reconstruction surgery. More importantly, it shows us that we have a long way to go and alot of room for improvement.