Summary

An in-vitro study to assess the role of anterolateral structures with an automated pivot shift simulator under biplanar radiography, that concludes that the iliotibial band contributes more to rotatory stability than the ALL

Abstract

The role and contributions of the anterior cruciate ligament (ACL) and anterolateral structures to rotatory stability are still debated 1–3. Pivot-shift simulation is a reliable and clinically relevant rotatory instability measuring technique4,5. Biplanar radiography with three-dimensional reconstruction (BR-3DR) can provide reliable femorotibial positional tracking6. The objective of this study is to determine the role of the ACL, capsulo-osseous layer of the Iliotibial band (c-ITB) and anterolateral ligament (ALL) in simulated pivot-shift conditions on an automated test bench using BR-3DR.
MM: 7 cadaveric knees from four subjects aged 90 to 99 were examined in four ligamentous configurations (intact, ACL sectioned, added c-ITB section, added ALL section) and four flexion angles (0°, 15°, 30° and 45°). An automated testing rig was designed to simulate pivot-shift with 5Nm internal torque and 10Nm valgus force. Static BR-3DR was used to track anterior tibial translation and internal rotation in each examined state

Results

anterior translation and internal rotation linked to ACL section were maximal at 30°, they increased with increasing knee flexion after sectioning the c-ITB and the ALL. Tibial translation linked to c-ITB section was superior but not statistically different to ALL section (3.5±1.8mm vs 2.0±1.8mm at 15°, 4.0±1.6mm vs 2.8±1.5mm at 30°, 5.6±2.8mm vs 3.4±2.7mm at 45°). Internal rotation linked to c-ITB section was statistically higher than that linked to ALL section at 30° and 45° knee flexion (7.1±2.6° vs 3.6±2.7° at 30° (p=0.002), 8.5±3.1° vs 3.5±1.8° at 45° (p=0.004) )

Conclusion

The c-ITB seems to contribute more than the ALL in combined stability as measured by the pivot shift.