Do small changes in rotation affect measurements of lower extremity limb alignment?

Area of Science:

• Orthopedics
• Biomechanics
• Radiology

Background:

• Lower extremity alignment is crucial for knee arthritis development.
• The impact of limb rotation on alignment parameters remains understudied.

Purpose of the Study:

• To establish standardized neutral position measurements for lower extremity alignment.
• To investigate how axial rotations affect common lower extremity alignment parameters.

Main Methods:

• Utilized CT angiography data from 87 patients (49 male, 38 female, average age 66).
• Created 3D models and performed rotations in 3° intervals around the longitudinal axis on 30 randomly selected scans.

Main Results:

• Established neutral position values: mLDFA (85.6°), MPTA (86.1°), mTFA (-0.7°).
• Observed differences in mTFA between sexes (females: 0.5°, males: -1.7°).
• Axial rotations caused statistically significant changes in all measured alignment parameters.

Conclusions:

• Provides novel data on standardized lower extremity alignment measures.
• Highlights the relationship between axial limb rotation and alignment parameters, with clinical relevance yet to be determined.