A Tendoncy for Inaccuracy: No New Body Part Was Discovered!

If, like me, you’re one of the 8.4 million people who ‘like’ the ‘I F**king Love Science’ Facebook page, then you would have been stunned by the news article posted last Wednesday that a new human body part was discovered. As a medical student, I became greatly concerned about extra ligaments (connective bits of tissue that bind bones together at a joint) that we may have to learn.

The post reads, “As impossible as it may seem, two surgeons at University Hospitals Leuven have discovered an entirely new part of the human body. It is a ligament in the knee and it appears to play a role in patients suffering from a tear in their anterior cruciate ligament (ACL), a common sports injury.”

Too good to be true, I thought, and a little extra reading confirmed my suspicions. Had Elise Andrew, the owner of the lighthearted Facebook page, read the first sentence of the work by the Belgian surgeons, she would never have made such a bold statement.

It is true that the ‘newly discovered’ ligament had been largely uncharacterised before. None of my textbooks discusses it. Gray’s Anatomy (the book, not the TV series) doesn’t mention it at all, nor is it illustrated in any diagram. However, this is not to say that people had never encountered the ligament previous to the orthopaedic surgeons’ meticulous and clear anatomical and functional description.

In 1879, 21 years after Henry Gray published his authoritative text book, Paul Segond, a French surgeon, described the ligament’s existence in a paper called ‘Recherches cliniques et expérimentales sur les épanchements sanguins du genou par entorse,’ which translates to ‘Clinical and experimental research on blood effusion following knee sprains.’

In his paper, published in the journal Publications du Progrès Médical, Segond described the ligament for the very first time in human history:

“Les fibres nacrées et résistantes qui forment la partie antéro-externe du surtout fibreux articulaire et dont nous avons signalé plus haut le degré de tension extrême, lorsque la jambe est tordue en dedans, exercent une traction violent sur leur point d’insertion et l’arrachent.”

which roughly translates to,

“Pearly and resistant fibres that form the anterolateral part of the fibrous joint, in which we especially noted a high level of extreme tension when the leg is rotated internally, exert a strong pull on their point of insertion.”

Since then, medical literature has not discussed the poor ligament in detail. The Belgians who published their clinical description this year in the Journal of Anatomy state, “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.’” For the record, the ligament is not even part of the iliotibial band, so whoever came up with that name needs to return to the bare bones of the matter. No pun intended.

So what exactly is this ligament then?

The surgeons, headed by Dr. Claes and Professor Bellemans, have decided to christen the ligament by using its anatomical description, the anterolateral ligament, or the ALL for short. Anterolateral means that it is found towards the front (anterior) and towards the side (lateral) of the joint, in this case, the knee joint. This naming, though somewhat pedagogic, prevents the ligament from any other misnomers. Its placement (also known as an insertion) begins from the lateral epicondyle of the femur, the thighbone, and ends at the anterolateral portion of the tibia, the shinbone.

To study the ALL, the surgeons dissected the knees of 41 different cadavers and found the ligament in all but one of the knees. It averaged 4.15cm in length when the knee is bent at 90°.

What does it do?

All ligaments act as connecting, supporting or stabilising structures. They usually prevent dislocation and restrict the movement of a joint to avoid damage due to excess movement. Just as Paul Segond said in his paper, when the leg is rotated internally, the ALL becomes taut, helping to stop the rotation, as excessive rotation would cause the joint to dislocate.

If that didn’t make sense to you, take your right leg and hold your lower leg with both hands. Gently attempt to twist your lower leg anti-clockwise. The ALL is one of the connective structures that prevents you from being able to twist it any more than 10°.

Why do we care about it?

To some, it may hardly seem a breakthrough, given that medical science has apparently been unhindered by its dearth of knowledge on the ALL since it was first described 134 years ago. However, Dr. Claes and Professor Bellemans speculate that the ALL may in fact play a part in the most common ligament injury in the knee – a torn anterior cruciate ligament (ACL).

Most commonly observed in high impact sports like skiing, football and rugby, a torn ACL usually occurs if the knee and lower leg are twisted or if the lower leg extends forwards too much. Reconstructive ACL surgery is often used to treat this kind of injury, but it is unsuccessful in about 10% of cases. It may be that the ALL is also injured in these unsuccessful cases and that the instability due to a torn ALL may hinder healing from an ACL injury.

The surgeons suggest that more studies need to be done to see how the ALL contributes to ACL injuries as well as another injury known as a Segond fracture, where parts of the tibia, close to the insertion site of the ALL, are ripped away from it. It is possible that the ALL pulls on the tibia, causing it to fracture. The anterolateral ligament may in fact be the missing piece of the puzzle, explaining why over three-quarters of ACL tears are also associated with Segond fractures.

Greater knowledge surrounding this seemingly insignificant ligament may allow surgeons to successfully treat the 2,000 people each year in the UK who do not respond to reconstructive surgery following a torn ACL.

Despite the ‘discovery’ not exactly being a discovery after all, this paper provides a firm anatomical basis to understand the lesser-known ligament of the body, the anterolateral ligament. Before you burn your copy of Gray’s Anatomy and save up for the next edition of the Oxford Textbook of Functional Anatomy, however, it is important to remember the clinical applications of this discovery.

Dr Claes said, “We surgeons may need to rethink what we know about common ACL injuries. Though we have shed light on the purpose of this ligament and its role in common injuries, we now need to find out for certain when it is best to intervene surgically. Long-term studies will give us that answer and hopefully allow us to perfect minimally invasive techniques to give our patients a better recovery.”

What an exciting age for an orthopaedic surgeon tibia in! And this is no humerus matter. Puns intended.