Evaluation of a simulated pivot shift test: a biomechanical study

Area of Science:

• Orthopedic biomechanics
• Sports medicine research
• Anterior cruciate ligament (ACL) injury assessment

Background:

• Double-bundle ACL reconstructions have increased the need to quantify anterolateral rotatory stability.
• The pivot shift test is a clinical examination used to assess ACL integrity.
• In vitro biomechanical testing is crucial for understanding knee joint mechanics.

Purpose of the Study:

• To compare the effectiveness of two different loading methods in recreating anterolateral subluxation in vitro.
• To determine which loading condition best simulates the subluxation observed during the pivot shift test.
• To establish a laboratory test for assessing ACL integrity.

Main Methods:

• Biomechanical testing of twelve cadaveric knees with intact and sectioned ACLs.
• Application of two simulated pivot shift loads: internal rotation with valgus torque, and internal rotation with anterior tibial load.
• Measurement of six-degree-of-freedom positional data at various knee flexion angles (0°, 20°, 30°, 60°, 90°).

Main Results:

• Coupled internal rotation and valgus torques significantly increased anterolateral subluxation at most tested angles (except 90°).
• Coupled internal rotation and anterior tibial load also significantly increased anterolateral subluxation at most tested angles (except 30°).
• Valgus torque combined with internal rotation more closely replicated the subluxation seen in the pivot shift test.

Conclusions:

• Combined internal rotation and valgus torques are superior in recreating in vitro anterolateral subluxation compared to anterior tibial loads.
• This study presents a validated laboratory method for assessing ACL integrity through anterolateral subluxation.
• The findings support the use of this biomechanical model for further research into knee stability.