Simple assessment for rotation of the forearm using three-dimensional bone models

Area of Science:

• Biomechanics
• Medical Imaging
• Anatomy

Background:

• Dynamic medical imaging aids in diagnosing forearm rotational impairment but has limitations like radiation exposure and intensive analysis.
• Current methods for determining the forearm's rotation axis are often resource-intensive.

Purpose of the Study:

• To investigate if a static axis based on bony landmarks is comparable to axes derived from dynamic imaging for forearm rotation.
• To establish a simpler, more efficient method for calculating the forearm rotation axis.

Main Methods:

• Computed tomography (CT) scans of eight post-mortem human forearms were performed across seven rotational positions.
• Three distinct rotation axes were calculated: landmark-based, average helical, and circle fit.
• Differences between axes (angle, distance) and orientation errors in pose modeling were analyzed.

Main Results:

• The landmark-based axis showed minimal differences (mean 0.38-0.40 degrees, 0.51 mm) compared to average helical and circle fit axes.
• Modeling forearm radius pose using these axes resulted in errors below 2 mm and 1 degree.
• The landmark-based axis provides a highly accurate representation of forearm rotation.

Conclusions:

• The forearm rotation axis can be precisely calculated using automatically identified bony landmarks.
• This method negates the need for dynamic imaging or multiple static scans for accurate axis determination.
• Further clinical application of this landmark-based approach is recommended to validate its practical utility.