The Transverse Sigmoid Notch Morphology Unravelled

Area of Science:

• Orthopedics
• Radiology
• Anatomy

Background:

• Pathology is often linked to transverse sigmoid notch morphology using the Tolat classification.
• The Tolat classification assumes a consistent sigmoid notch shape across different anatomical views.

Purpose of the Study:

• To investigate if sigmoid notch shape (SNS) determination is influenced by the transverse computed tomography (CT) plane level on the distal radius's axial axis.
• To compare transverse SNS at different axial CT levels within the same wrist.

Main Methods:

• The transverse SNS of 53 participants were classified by two researchers using Tolat's four morphologies.
• SNS was assessed at two distinct axial CT levels: Lister tubercle and the smallest distance between the ulnar head and sigmoid notch (SDUS).

Main Results:

• Forty-seven percent of wrists exhibited different SNS types based on the CT scan's axial level.
• Excellent interobserver agreement was achieved (87% at Lister tubercle, 85% at SDUS).

Conclusions:

• Significant variability (47%) in transverse sigmoid notch types was observed within the same wrist across different CT levels.
• The Tolat transverse sigmoid classification may have limited utility for describing pathology related to sigmoid notch morphology due to this variability.