Three-dimensional assessment of lower limb alignment: Accuracy and reliability.

Area of Science:

• Orthopedic surgery
• Medical imaging
• Biomechanical analysis

Background:

• Three-dimensional (3D) surgical planning and patient-specific implants are gaining traction in orthopedics.
• Lack of standardized protocols for 3D lower limb bone model analysis hinders pre-operative planning.
• Established 2D long standing radiographs (LSRs) offer standardized alignment assessment.

Purpose of the Study:

• To develop a prerequisite for pre-operative planning by establishing a standardized 3D alignment assessment protocol for the lower limb.
• To define landmarks and evaluate their reliability for analyzing 3D bone models.
• To address the need for validated methods in 3D orthopedic analysis.

Main Methods:

• Defined 24 landmarks on 3D bone models from computed axial tomography (CT) scans for 3D alignment assessment.
• Three observers with varying experience levels tested the landmarks across three specimens.
• Evaluated intraobserver and interobserver variability and calculated the intraclass correlation coefficient (ICC) for resulting axes and joint angles.

Main Results:

• Low intraobserver and interobserver variability observed, with mean deviation <5 mm for all landmarks.
• High ICC values (>0.8) for most joint angles and axis deviations, indicating good reliability.
• Excellent ICC (>0.95) for all knee joint angles, demonstrating high consistency.

Conclusions:

• The defined landmarks enable a standardized 3D lower limb alignment assessment with low variability and high reliability, irrespective of examiner experience.
• This method provides a reliable protocol for 3D malalignment testing.
• 3D pre-operative analysis can improve understanding of deformities and influence surgical planning.