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November 14, 2013

BehindTheMedspeak: A new knee ligament

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Just when you thought our knowledge of knee anatomy was pretty much a done deal, now come surgeons from University Hospitals Leuven in Belgium with the surprising news that after years of painstaking anatomical dissections and research, they have identified a previously overlooked ligament in the knee, which they have named the Anterolateral Ligament (above and below).

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Their remarkable discovery may explain why so many people whose damaged knees have been repaired surgically continue to have postoperative instablity: failure to account for this previously unknown structure and its subsequent under-the-radar loss may result in permanent weakness and subpar function of the joint.

Below, the abstract of the Journal of Anatomy paper describing the newly characterized structure.

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Anatomy of the anterolateral ligament of the knee

In 1879, the French surgeon Segond described the existence of a "pearly, resistant, fibrous band" at the anterolateral aspect of the human knee, attached to the eponymous Segond fracture. To date, the enigma surrounding this anatomical structure is reflected in confusing names such as "(mid-third) lateral capsular ligament," "capsulo-osseous layer of the iliotibial band," or "anterolateral ligament," and no clear anatomical description has yet been provided. In this study, the presence and characteristics of Segond's "pearly band," hereafter termed anterolateral ligament (ALL), was investigated in 41 unpaired, human cadaveric knees. The femoral and tibial attachment of the ALL, its course, and its relationship with nearby anatomical structures were studied both qualitatively and quantitatively. In all but one of 41 cadaveric knees (97%), the ALL was found as a well-defined ligamentous structure, clearly distinguishable from the anterolateral joint capsule. 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). The ALL was found to be a distinct ligamentous structure at the anterolateral aspect of the human knee with consistent origin and insertion site features. By providing a detailed anatomical characterization of the ALL, this study clarifies the long-standing enigma surrounding the existence of a ligamentous structure connecting the femur with the anterolateral tibia. Given its structure and anatomic location, the ALL is hypothesized to control internal tibial rotation and thus to affect the pivot shift phenomenon, although further studies are needed to investigate its biomechanical function.

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[via the New York Times]

November 14, 2013 at 08:01 PM | Permalink


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Comments

It's still fascinating - the difference between what people see and what they observe.

Posted by: 6.02*10^23 | Nov 15, 2013 5:15:14 PM

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