Lateral Extraarticular Tenodesis (LET)
Lateral Extrarticular Tenodesis (LET) 
The history of Lateral Extraarticular Tenodesis (LET)
  • In the 1960s ACL reconstructions were limited to open techniques as this was before key hole surgery (arthroscopy) and they involved rerouting the patella tendon to provide stability
  • However, this resulted in such poor outcomes that alternative techniques were sought
  • In 1967 Dr Marcel Lemaire was the first to describe an isolated LET to help reduce rotational instability 
  • This involved an 18 x 1cm wide strip of iliotibial band and rerouting it around the outside part of the knee 
  • With the advent of arthroscopic ACL reconstruction techniques, the benefit of smaller scars and less pain, LET was thought to be unnecessary
  • Increasing medical evidence though has shown that whilst isolated ACL reconstruction may be adequate for lower demand athletes, new modified LET procedures help to significantly improve rotational stability to an arthroscopic ACL reconstruction
What is the Anterolateral Ligament (ALL)
  • The anterolateral ligament is a thickening of the joint capsule that runs from the lateral femoral epicondyle of the knee to the anterolateral edge of the tibia
  • It forms part of the anterolateral complex which are the tissues at the front outer aspect of the knee: 
    • The other key and more important structure is the Iliotibial Band (ITB)
  • When the ACL is injured there is a rotational force in the knee and the anterolateral structures are stretched
  • A pathognomonic finding on knee X-rays is a Segond fracture:
    • a small bone pulled off the anterolateral (front outer) aspect of the tibia and when it is seen on X-rays it almost invariably means there is an ACL injury
  • The anterolateral ligament is thought to cause the Segond fracture as it attaches there
  • There has been renewed interest in the anterolateral ligament following more accurate anatomic description of it by a group of surgeons in Belgium in 2013
  • However, it has been known to exist since it was first described in 1879 by Dr Paul Segond
ALL reconstruction vs Lateral Extraarticular Tenodesis
  • Since the 2013 publication about the ALL there has been a big drive to perform ALL reconstructions without first carrying out appropriate analysis and biomechanical testing to confirm if it is appropriate
  • ALL reconstruction involves attempting to reconstruct the ALL along the tract it is thought to exist
  • Biomechanical testing though has repeatedly shown that the ALL is far less important in controlling femoral rotation than the ITB
  • The ITB has numerous attachment points on the lateral (outside) aspect of the knee:
    • Attaches on the tibia at Gerdy’s tubercle
    • Has a deep capsulo-osseous portion attaching to the outside part of the distal (lower end) femur:
      • This is a deep layer attaching directly to the bone of the femur
      • Is now considered to be the key part in controlling knee instability
      • Lies in a plane that would better control rotation than ALL
      • LET most closely approximates in function this ITB attachment to the which explains its effectiveness in improving rotational stability and therefore reduce ACL injuries
What does a Lateral Extraarticular Tenodesis (LET) involve?
  • There are various techniques used to perform a lateral extraarticular tenodesis
  • The preferred technique is the modified Lemaire
  • After the arthroscopic ACL reconstruction has been performed a small lateral incision is made over the lateral side of the lateral femoral condyle
  • An 10cm long by 1cm wide strip of iliotibial band is rerouted under the lateral collateral ligament (LCL) and secured on the lateral femoral condyle proximal to the attachment of the LCL
  • The iliotibial band strip remains attached to the tibia at Gerdy’s tubercle
Does an isolated ACL reconstruction help provide rotational stability to the knee?
  • One of the key functions of an ACL is to help provide rotational stability to the knee
  • Studies have shown that up to 25% of ACL reconstructions have residual rotational instability despite an intact ACL graft
  • This instability is termed anterolateral rotational instability and it occurs at the front outer aspect of the knee 
  • The reason being that the ACL is located in the centre of the knee very close to the axis of rotation 
  • Rotation about a fixed point is controlled easier further away from the axis of rotation due to the longer lever arm
  • This means that even a small amount of support further away from the axis of rotation can have a significant impact on rotational instability
 What is the benefit of a Lateral Extraarticular Tenodesis?
  • Cadaveric studies have shown that the addition of a lateral extraarticular tenodesis to an ACL reconstruction reduces the stress on the ACL graft by 43%
  • This means that it has a protective effect on the ACL graft:
    • Minimises risk of graft stretching during its healing phase
    • Protect graft rupture when knee is pushed through the rehabilitation phase 
  • The addition of lateral extraarticular tenodesis in patients at higher risk of ACL rupture
    • Reduces the risk of ACL graft rupture by 40%
Patients that would benefit most from Lateral Extraarticular Tenodesis
  • Patients younger than 25 years old returning to pivoting sports
  • High demand athletes
  • Revision ACL reconstruction
  • Marked anterolateral rotatory instability on examination as shown by an explosive pivot shift
  • Generalised ligamentous laxity
 Complications of Lateral Extraarticular Tenodesis
  • In experienced hands most people do very well and it makes a significant difference to their sense of rotational stability and reduces risk of ACL graft failure
  • Numerous studies have shown no increased complication rates when combining ACL reconstruction with lateral extraarticular tenodesis
  • However, with poor surgical technique complications can arise:
    • Reduced internal rotation of tibia and feeling of a stiff knee:
      • This is due to incorrect tightness or positioning of foot when the iliotibial band is secured on the femur
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