Does axial limb rotation affect the alignment measurements in deformed limbs?

Area of Science:

• Orthopedic surgery
• Biomechanical analysis

Background:

• Achieving precise alignment is critical for successful total knee arthroplasty and osteotomy outcomes.
• Preoperative planning relies on accurate measurements of lower limb alignment.

Purpose of the Study:

• To investigate the impact of axial limb rotation on tibiofemoral angles.
• To assess the effect of axial rotation on the angle between the femur's anatomic and mechanical axes.
• To compare these effects in lower extremities with valgus and varus deformities versus normal alignment.

Main Methods:

• Utilized lower extremity models with varying degrees of valgus and varus deformities.
• Measured tibiofemoral angles under different degrees of internal and external axial rotation.
• Measured the angle between the femur's anatomic and mechanical axes across a range of rotation.

Main Results:

• Tibiofemoral angles showed statistically significant changes with 10-degree rotation in severe valgus/varus deformities.
• The angle between the femur's anatomic and mechanical axes varied by less than 1 degree, even with 40 degrees of rotation.
• Tibiofemoral angle measurements are more susceptible to axial rotation in deformed limbs compared to normally aligned limbs.

Conclusions:

• Tibiofemoral angle measurements are significantly affected by axial limb rotation in valgus and varus deformities.
• The angle between the femur's anatomic and mechanical axes is a more rotationally stable measurement for preoperative planning.
• This finding is important for improving the accuracy of preoperative planning in total knee arthroplasty and osteotomy procedures.