Large, prospective study begins to look at this important question

What factors account for the different success rates for primary and revision anterior cruciate ligament (ACL) reconstructions? Why do revision ACL reconstructions have worse outcomes? What is the most appropriate graft choice for revision ACL reconstruction?

Finding the answers to these and other questions is the goal of the Multi-Center ACL Revision Study (MARS), and Rick W. Wright, MD, presented the progress to date at the annual meeting of the American Orthopaedic Society for Sports Medicine (AOSSM).

Multisurgeon, multicenter study
Improving outcomes for revision ACL reconstruction (RevACLR) depends, in part, on identifying predictors for the worse outcomes. Dr. Wright and his colleagues determined that a multivariable analysis to identify these predictors would require up to 750 patients in a prospective, longitudinal cohort.

Because RevACLR is a “relatively infrequent procedure—even in a sports medicine practice,” according to Dr. Wright, “this study would need multiple surgeons at multiple sites to gather the number of revision reconstructions for analysis in a reasonable amount of time.

“Such a large, multicenter cohort could be used to identify independent predictors of RevACLR outcomes and potentially improve RevACLR outcomes in the future. We have initially focused on the mechanism of injury, mode of failure, and graft choice,” he said.

“With these issues in mind, we formed the ‘MARS Group’—a prospective cohort study of patients undergoing RevACLR. Currently, 71 surgeons at 31 sites are participating; half of them are in private practices and half are in academic settings,” he continued.

All surgeons completed training sessions and received institutional review board approval to participate. Surgeons document mode of failure, mechanism of injury, method of RevACLR, and all intra-articular injuries and treatment.

Patient enrollment began in May 2007; each patient completed a series of validated patient-oriented questionnaires including the Knee Injury Osteoarthritis Outcome Score, Marx Activity Level, Inter­national Knee Documentation Committee, Short Form-36, and Western Ontario and McMaster Osteoarthritis Index.

By May 2008, 159 patients were enrolled in the study. The median age of the patients was 26 years old (range: 12 to 54 years). Men comprise of 53 percent of the cohort. Nearly 9 out of 10 patients (87 percent) were undergoing their first revision; half of those patients had their primary surgery at least 2 years prior to the revision reconstruction.

Initial findings are traumatic—and technical
Results of the first phase of the study indicate that trauma is the primary mechanism of reinjury, identified in 70 percent of the patients. Among these patients, more than half (55 percent) sustained a noncontact traumatic reinjury.

Approximately one third of all failures (32 percent) were believed to be due to purely traumatic reinjuries, 7 percent of failures were biologic, and 31 percent were a combination of factors. (Multiple responses were possible.)

“Technical issues were the sole cause of failure in 27 percent of the patients,” said Dr. Wright, but were potentially related to two thirds of all failures. Tunnel malposition was the primary “technical contributor to failure”; researchers identified femoral tunnel malposition in 65 percent of patients, and tibial tunnel malposition was present in 31 percent of patients.

“The most common autograft used was bone-patellar tendon-bone,” he explained, “which was also the most common allograft used. Approximately one in four allografts used were anterior or posterior tibialis, and 10 percent were Achilles tendon.”

Looking to the future
Although this study is descriptive in nature and not practice-changing at this point, it does demonstrate the ability of the MARS group to rapidly and prospectively accumulate a high number of revision reconstructions. The multisurgeon series also found that traumatic reinjury is more common than noted in previously published studies.

“The planned 2-year follow-up, which will begin in 2009, will determine which of these potentially modifiable factors can predict outcomes. Obviously this cohort has many future questions to ask and answer,” Dr. Wright concluded.

Grant support for this research was provided by the AOSSM and the Musculoskeletal Tissue Foundation. The authors of “Revision ACL reconstruction: Reinjury mechanism, failure mode and graft choice from the Multi-Center ACL Revision Study (MARS)” are Rick W. Wright, MD; Laurie J. Huston, MS; Amanda J. Haas, MA; Barton Mann, PhD, and Kurt P. Spindler, MD. The authors have no other disclosures pertaining to this study.

Annie Hayashi is the senior science writer for AAOS Now. She can be reached at hayashi@aaos.org