Anterolateral Rotatory Instability

Discussion

• defined as excessive forward rotation of tibial plateau w/ excessive lateral opening of the joint;
• there is excessive internal rotation of tibia on femur in flexion;
  • as knee extends, subluxation is reduced by the bony stability, and a jerk is  noted which is basis for the pivot shift test;

disrupted structures

• disruption of ACL
• disruption of lateral supporting structures;
  • LCL
  • arcuate complex;

 

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Exam

• anterior drawer:
  • lateral tibial plateua rotates forward in relation to femur at 90 deg of flexion with excessive lateral opening of the joint;
  • there is then excessive internal rotation of tibia on femur with the knee in flexion;
  • positive anterior drawer test in neutral tibial rotation, that is accentuated when the test is repeated in 30 deg of external rotation and reduced when performed with the tibia in 15 deg of internal rotation indicates anteromedial rotary instability;
  • when anterior drawer test w/ tibia in neutral rotation demonstrates equal displacment of both condyles & this displacment is elminated by internal rotation of the tibia, then both anteromedial and anterolateral rotary instability may be present;
• pivot shift;
  • as knee comes into extension while wt bearing anterior subluxation of the lateral tibial plateua is dramatic;

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Radiographs

• there may be a chip like fracture of the lateral tibial plateau that is suggestive of this type of ligament injury;
• references:
  • Lateral capsular sign: x-ray clue to a significant knee instability.

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• Distal iliotibial-band transfer for anterolateral rotatory instability of the knee.
• Anterolateral rotatory instability of the knee joint. An early analysis of the Ellison procedure.
• Lachman test evaluated. Quantification of a clinical observation.
• Injury to the anterior cruciate ligament producing the pivot-shift sign.
• Long-term functional results in patients with anterolateral rotatory instability treated by iliotibial band transfer.
• The role of incompetence of anterior cruciate and lateral ligaments in anterolateral and anteromedial instability. A biomechanical study of cadaver knees.
• Combined anterolateral-anteromedial rotatory instability of the knee.
• Classification of knee ligament instabilities. Part II. The lateral compartment.
• Clinical test for anterolateral rotary instability of the knee.
• Anterolateral rotational knee instability: role of posterolateral structures. Winner of the AGA-DonJoy Award 2006