Researchers have identified key associations between graft choice and clinical outcomes of anterior cruciate ligament (ACL) revision surgery in the largest study ever performed on the topic.
Results from 1,234 surgeries across 52 U.S. study sites show conclusively that autografts are less likely to rerupture than allografts, now up to six years post-placement.
The monumental Multicenter ACL Revision Study (MARS) is led by Rick W. Wright, M.D., the Dan Spengler, M.D. Professor and Chair of orthopaedic surgery at Vanderbilt University Medical Center.
“Graft choice is a major issue in these surgeries,” Wright said. “While a patient’s previous graft might limit options, surgeons haven’t had a lot of data to inform this critical choice. We now know graft choice is a modifiable risk factor that directly affects reoperation rates and quality of life.”
Essential Prospective Design
The recent finding, published in the American Journal of Sports Medicine, is one of many reported by the MARS Group since the study began in 2007.
The study’s prospective, longitudinal cohort design has allowed surgeons to identify several key factors that contribute to long-term ACL revision surgery failure rates, which Wright has found can reach nearly 12 percent.
“We now know graft choice is a modifiable risk factor that directly affects reoperation rates and quality of life.”
“As we designed the study, we were uncertain of the critical factors leading to the worse outcome observed following revision ACL reconstructions. Thus, we felt a randomized controlled trial of one or two variables might be misguided and inappropriate,” the authors wrote in a recent summary of their findings.
Incorporating Private Practice
The massive study eclipses all others, Wright said. More than 80 surgeons are participating, and uniquely, half are in private practice.
“The multiple sites and the mix of private and academic surgeons using a variety of surgical techniques and grafts makes our findings generalizable to the broader sports medicine-trained community,” Wright said.
So far, the researchers have successfully followed up with 949 patients six years post-surgery. An analysis by Wright of all studies previously available found follow ups at the five-year mark for only 121 patients.
Graft Choice and Reruptures
The MARS Group’s latest results center on graft choice, comparing outcomes between patients who received a bone-patellar tendon-bone (BTB) autograft (26 percent), soft tissue autograft (20 percent), BTB allograft (23 percent), soft tissue allograft (25 percent) or other graft (5 percent).
Wright noted the unintentional but relatively equal distribution of graft types across the study cohort further emphasizes the lack of standardization in the field.
“The multiple sites and the mix of private and academic surgeons using a variety of surgical techniques and grafts makes our findings generalizable to the broader sports medicine-trained community.”
By six years post-surgery, graft rerupture had occurred in 55 of 949 reachable patients.
While the researchers hypothesized rerupture rate differences between graft types might level out over time, this was not the case. More than twice as many patients who received an allograft (8.4 percent) experienced a rerupture as compared to those who received an autograft (3.5 percent). Specific rerupture rates for each patient cohort were:
- BTB autograft, 3.8 percent
- Soft tissue autograft, 3.1 percent
- BTB allograft, 10.6 percent
- Soft tissue allograft, 6.2 percent
- Other graft, 3.8 percent
The researchers further calculated that patients who received a BTB autograft for revision surgery were 4.2 times less likely to rerupture than those who received a BTB allograft. Use of an allograft was a significant predictor of additional surgeries.
The results help validate the MARS Group’s two-year outcomes that also showed lower rerupture and reoperation rates when an autograft was chosen instead of an allograft.
Other Modifiable Risk Factors
The risk of rerupture was not affected by age, sex, or baseline activity level, which often influences graft choice, Wright explained. The median age in the study was 26 years.
“The allograft had been used in people who were less active and, on average, four years older,” Wright said. “These allografts were failing in an older, less active population. Here we found they also commonly fail in younger, more active patients in the revision setting.”
The study is ongoing, and a 10-year follow up is planned that will focus on early osteoarthritis and further measure surgical outcomes.
Approximately 200,000 primary ACL reconstruction surgeries are performed annually in the U.S., yet an individual surgeon may perform only a few revisions each per year, Wright said. The MARS Group was created to help pool data and better power studies to effectively analyze risk factors associated with revision surgery.
For their many contributions, the American Academy of Orthopaedic Surgeons recognized Wright and the MARS Group with the 2019 Kappa Delta Ann Doner Vaughn Award.
“It’s the highest research award in orthopaedics. I don’t get too wound up usually, but this was quite the honor,” Wright said.
