Anterior Lateral Ligament

When “new” knee anatomy makes headlines not only in an academic journal, but also in Time magazine and is an answer on Jeopardy, it must be a spectacular discovery. The reality is that the ligament, the anterior lateral ligament or ALL, was first observed by a French surgeon, Segund, in 1876. Recently, French researchers, Vincent et al, in the KSSTA 2012 journal (http://www.ncbi.nlm.nih.gov/pubmed/21717216) reported finding the ligament in 30 consecutive patients undergoing total knee arthrplasty and in 10 cadaveric knee dissections.  It was also detailed by Belgium surgeon, Dr. Claes, in his doctorate thesis with his findings later published with co-authors Vereecke, Maes, Victor, Verdonk and Bellemans in the Journal of Anatomy 2013 (http://www.ncbi.nlm.nih.gov/pubmed/23906341).  The initial cadaveric dissections were followed by biomechanical studies to evaluate the ALL effect in limiting abnormal lateral knee rotation--a key topic of interest to senior author, Dr. Belleman. The importance of this small band of tissue is its association with the ACL (anterior cruciate ligament) and ACL injuries. ACL injuries are so frequent in sports that anyone who follows sports, even casually, is familiar with an athlete who has suffered an ACL tear. To return to high level sport without fear of instability, athletes often undergo ACL reconstruction, which is a very reliable and reproducible surgery. However, in a small subset of athletes, although the surgery “goes well”, they still have the sensation of instability when attempting to pivot on that extremity. The biomechanical work of Claes et al would suggest the problem may be in residual looseness of the ALL. That is, while the ACL is the predominate ligament in limiting direct anterior movement of the tibia and rotation, the ALL may play a key role specifically in limiting abnormal rotation.

If the ALL is a key for an optimal result in a subgroup of athletes with ACL reconstructions, the challenge now is to identify those athletes with ACL injuries who might benefit with repair or reconstruction of the ALL at the time of their ACL reconstruction. That is, in those athletes with recent tears, which ones should have the ALL repaired. A second group is athletes with longstanding ACL tears being considered for reconstruction. Finally, a third group might be more readily identified as needing an ALL reconstruction: those patients with instability pivoting after an otherwise well performed ACL reconstruction (strong graft oriented and attached correctly). With the currently available information, it appears part of the decision making process may be based on the physical examination for those who have instability after ACL reconstruction (with the graft and placement excellent). That is, during the knee exam, the surgeon demonstrates excessive looseness during a knee rotation stress maneuver termed a “pivot shift” (http://medical-dictionary.thefreedictionary.com/lateral+pivot+shift+test). 

In the acute setting, it is currently difficult to predict, which patients should have the ALL repaired noting that current patient satisfaction with stability after standard ACL reconstruction is very high. Possibly a first step in the acute setting, would be to repair the ligament when is has pulled off a small piece of bone from the tibia—the small fleck of bone observed on the lateral aspect of the tibia that is associated with ACL tears and has the name “Segund fracture” in honor of the surgeon who originally described it. The rationale in this situation is that the majority of the injury to the bone-ligament-bone construct is probably at the site of the ligament pulling the small fleck of bone off the tibia. Left alone, it will heal in this displaced position: causing “no harm”, but probably meaning the ALL has healed “looser” than normal. The treatment would be to anchor the ligament back at its original attachment site. Close clinical follow up and comparative studies will be important in fine tuning the application  and indications of ALL repairs and reconstructions.

Jack Farr, MD