Information on ACL surgery and rehabilitation based on the Multicenter Orthopaedic Outcomes Network (MOON)



The Multicenter Orthopaedic Outcomes Network (MOON) was created in 2002 to begin collecting information on a large group of anterior cruciate ligament (ACL) reconstructions in order to improve research and treatment. Since then this group has included over 4,400 participants from many surgical centers, and more than 40 publications have used this data. A lot of good information has come from this group which has helped guide surgeons and patients in decisions about their surgery. This article went into detail about many of the findings, but here are a few of the more interesting.

ACL injuries are a common injury to the knee which often occurs in young active individuals and limits their ability to continue to participate in high-level competitive sports. Most people with this injury have a reconstruction of the ACL with surgery. The repair is to done to restore ability for high level sports and to decrease the risk of further wear and tear in the knee. It is estimated that between 175,000 and 200,000 ACL reconstructions are performed every year in the United States and with such a high number of injuries it is important to have high-quality research guiding the treatment decisions.

Of particular interest to this young athletic group is how will they get back to their previous level of sport. The break down for individual sports is as follows: For high school and college football the rate of return to play was in the mid to high sixties, forty-three per cent reported that they returned to the same level of play, the rest either at a lower level or did not return at all. For soccer players, the return to play was seventy two per cent, and of this more than three quarters returned to the same or higher level of play. It appears that a major factor in not returning to play is fear of re-injury.

One of the most important things to consider when having an ACL reconstruction is what to use as the graft. The choice of graft and the patients age were the most predictive variables to success. Use of an allograft (donor, someone else’s, tissue) had a four times greater risk of re-rupture than when an autograft (patients own tissue) was used. Tearing the recently repaired ACL is most likely in the age group 10 to nineteen year olds and then every 10 years the risk decreased slightly. The take home message is that for younger patents the best choice is autograft, with the least chance for re-tear.

For rehabilitation the take home information is that you don’t need a continuous passive motion machine following surgery, but that early knee range of motion was important to prevent stiffness in the knee. Immediate weight bearing is also helpful to decrease pain. Bracing right after the surgery did not offer any benefit. It works fine to rehab at home. Closed chain exercises, like squats, were found to be good in the first six weeks. High-intensity neuromuscular electrical stimulation is safe and believed to improve quadriceps strength, but is not necessary for a successful rehabilitation.

The biggest complication to ACL reconstruction is the risk of re-injury, both of the same operated knee and the other “good” knee. Wright et al, in a study of 460 patients who had to have a revision surgery, found that the most common reason for re-tear was traumatic injury (thirty-two per cent) and then technical error from the initial surgery (twenty-four per cent). This same author discovered that in the first two years after the initial ACL surgery there is a 5.8 per cent chance of tearing the other ACL and an 11.8 per cent chance of re-tearing the repaired ACL.

Another interesting finding made by Mather et al through the MOON group is that in the long term, there is a lifetime cost to society based on whether a person chooses surgery or just rehabilitation following an ACL injury. Looking at the MOON participants and comparing the costs associated with reconstruction, including the medical costs and other things such as lost wages from time off work, and even disability payments, it was shown that the cost to society for an ACL reconstruction was $38,121 compared with $88,538 for rehabilitation only and no surgery. So, it appears that it may be better to have surgery both in terms of knee health, overall cost and quality of life.

The MOON has provided a lot of data for researchers looking into important factors of ACL surgery, and is already helping to guide decisions. There are many more future plans to continue using this as well as other similar large subsets of data to continually improve outcomes from ACL surgery.