Solving the Mystery of the Anterolateral Ligament

    Dr. Johan Bellemans and his colleagues in Belgium have finally described the elusive “pearly band” in the knee first mentioned by Dr. Paul Segond in the 19th century.

    French surgeon Dr. Paul Segond is best known for describing an avulsion fracture of the lateral tibial condyle of the knee, immediately beyond the surface which articulates with the femur, that bears his name: the Segond fracture. It is present in most anterior cruciate ligament (ACL) tears.

    But what about the “pearly, resistant, fibrous band which invariably showed extreme amounts of tension during forced internal rotation (of the knee)” that he also described? What is it, and what is its role in knee function and stability?

    In the more than 130 years since Dr. Segond’s findings, this “pearly band” has proved to be elusive. There are occasional mentions of it in the orthopaedic surgery literature, [1-8] but these descriptions are inconsistent and vague.

    Describing the Anterolateral Ligament

    About 4 years ago, Johan Bellemans, MD, and his colleagues in Belgium began a study to find and definitively describe Dr. Segond’s “pearly band.” In October, their findings were published in the Journal of Anatomy. [9]

    Dr. Segond’s “pearly band’’ now has a name: the anterolateral ligament (ALL). In their paper, Dr. Bellemans and his colleagues confirm that the ALL “can be identified as a distinct ligamentous structure of the anterolateral aspect of the human knee” [9] and indicate that it originates “proximal and posterior to the popliteus tendon insertion, on the lateral femoral epicondyle.” [9]

    They further describe the anatomy of the structure:

    “The origin of the ALL was situated at the prominence of the lateral femoral epicondyle, slightly anterior to the origin of the lateral collateral ligament, although connecting fibers between the two structures were observed. The ALL showed an oblique course to the anterolateral aspect of the proximal tibia, with firm attachments to the lateral meniscus, thus enveloping the inferior lateral geniculate artery and vein. Its insertion on the anterolateral tibia was grossly located midway between Gerdy’s tubercle and the tip of the fibular head, definitely separate from the iliotibial band (ITB).” [9]

    It is important to note that a paper published in 2012 [8] also describes what the authors of that paper believed to be the ALL. Their description was based on observations from total knee arthroplasty procedures. Dr. Bellemans and his colleagues do not agree with the findings.

    “Vincent et al vaguely describe the location (which we believe is incorrect and very different from the ligament we describe), and they do not report the anatomic dimension – neither its exact origin nor its insertion,” Dr. Bellemans said. “They have not attributed a specific function or clinical relevance, contrary to our work on the structure we have described.”

    Questions Seeking Answers

    Dr. Bellemans and his colleagues were prompted to find and describe the ALL by questions they had about a possible role for this anatomic structure in pain, instability, and functional issues following some ACL tears and reconstruction.

    “We wondered why, after successful ACL reconstruction and rehab, 10-20% of patients have persistent, mild to severe instability,” Dr. Bellemans said. “We also wondered why many patients seen in the first hours after ACL surgery have pain on the anterolateral aspect of the joint line and proximal tibia – the region where we now know the anterolateral ligament is located.”

    Dr. Bellemans noted that patients with an untreated ACL tear typically develop a progressively increasing pivot shift, despite the fact that their ACL was completely torn. He and his colleagues wanted to know if this is “indicative that another secondary restraint would be present and play a role.”

    Finally, “we wondered why one in two high-level athletes do not reach their initial competitive level after successful ACL repair and still continue to experience some feeling of instability,” Dr. Bellemans said.

    Consistent and Accurate Description

    For the study reported in the Journal of Anatomy, [9] 41 unpaired human cadaveric knees were dissected by Steven Claes, MD, under the direction of Dr. Bellemans. All dissections were done the Institute for Orthopaedic Research and Training, the research lab at the University of Leuven Belgium.

    To ensure that he and his colleagues would be able to consistently and accurately describe the anatomy of the ALL, Dr. Claes measured and described for each dissected knee the:

    • Origin
    • Insertion
    • Interconnecting fibers with the lateral collateral ligament
    • Lateral intermuscular septum and lateral meniscus
    • Ligamentous tension in different flexion
    • Rotation angle [9]

    “We found the structure straight from the first pilot case,” Dr. Bellemans said. “We did about three more cases to fine-tune our dissection technique so we were sure that we could isolate and visualize the ligament in toto.”

    Dr. Bellemans said that other investigators have replicated their findings, notably Adrian Wilson in the United Kingdom, Alan Getgood in Canada, and Robert LaPrade in the United States.

    Clinical Implications

    Dr. Bellemans and his colleagues have continued their research and have subsequently determined the biomechanical effect of the ALL on controlling rotation of the knee. They are currently working on a surgical technique to optimally restore its function in case of injury.

    “Today we now know that in 80% of ACL ruptures, some damage – ranging from mild to severe – occurs to the ALL,” Dr. Bellemans said. “So far, this injury has remained untreated, even though it occurs in the majority of ACL patients. We believe that treating this injury could have a significant positive effect on outcomes after ACL surgery.”

    In his own surgical practice, Dr. Bellemans now repairs the ALL in acute cases when it is severely damaged, as observed on MRI. In chronic cases, he augments the ALL with an anatomic bypass. “Both procedures still need clinical validation,” he said.


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