VIENNA — Nearly one third of anterior cruciate ligament (ACL) injuries appear to heal without surgery, according to an analysis of three-dimensional MRI data taken from the NACOX study, presented as a late-breaking poster at the OARSI 2024 World Congress.
At 2 years after injury, three-dimensional MRI showed that 13 of 43 (30%) knees had evidence of normal, continuous ACL fibers. Moreover, a further 14 (33%) knees had a continuous ACL fiber structure following rehabilitation alone. ACL fibers were partly (16%) or completely (21%) ruptured in the remainder of cases.
Sara Freeman/Medscape Medical News
Dr. Stephanie Filbay
“If you think of the ACL like a rope, when there is continuity, it means those fibers have rejoined,” study coauthor Stephanie Filbay, PhD, an associate professor at the University of Melbourne in Australia, told this news organization.
“Within that, there’s a few variations of healing that we’re seeing. Some look like they’ve never been injured, while some have rejoined but appear thinner or longer than a normal ACL,” Dr. Filbay said.
She added: “What all this research is showing is that it’s happening at a much higher rate than we thought possible. And in some of the studies, it looks like ACL healing is associated with very favorable outcomes.”
At OARSI 2024, Dr. Filbay presented additional data from her and others’ research on the relationships between ACL healing and long-term functional outcomes and osteoarthritis (OA) incidence in comparisons between patients’ treatment pathways: Early ACL surgery, rehabilitation followed by delayed surgery, or rehabilitation only.
Healing Without Surgery
The idea that the ACL can heal without surgery is relatively recent and perhaps still not widely accepted as a concept, as Dr. Filbay explained during a plenary lecture at the congress.
Dr. Filbay explained that the ideal management of ACL injury depends on the severity of knee injury and whether someone’s knee is stable after trying nonsurgical management. Results of the ACL SNNAP trial, for example, have suggested that surgical reconstruction is superior to a rehabilitation strategy for managing non-acute ACL injuries where there are persistent symptoms of instability.
However, there have been two trials — COMPARE performed in the Netherlands and KANON performed in Sweden — that found that early surgery was no better than a strategy of initial rehabilitation with the option of having a delayed ACL surgery if needed.
What Happens Long Term?
Posttraumatic OA is a well-known long-term consequence of ACL injury. According to a recent meta-analysis, there is a sevenfold increased risk for OA comparing people who have and have not had an ACL injury.
ACL injury also results in OA occurring at an earlier age than in people with OA who have not had an ACL injury. This has been shown to progress at a faster rate and be associated with a longer period of disability, Dr. Filbay said at the congress, sponsored by the Osteoarthritis Research Society International.
But does the ACL really heal? Dr. Filbay thinks that it does and has been involved in several studies that have used MRI to look at how the ACL may do so.
In a recently published paper, Dr. Filbay and colleagues reported the findings from a secondary analysis of the KANON trial and found that nearly one in three (30%) of the participants who had been randomized to optional delayed surgery had MRI evidence of healing at 2 years. But when they excluded people who had delayed surgery, 53% of people managed by rehabilitation alone had evidence of healing.
The evaluation also found that those who had a healed vs non-healed ligament had better results using the Knee Injury and Osteoarthritis Outcome Score (KOOS), and that there were better outcomes at 2 years among those with ACL healing vs those who had early or delayed ACL surgery.