Apparent Proximal Ulna Dorsal Angulation Variation Due to Ulnar Rotation

Area of Science:

• Orthopedic surgery
• Radiology
• Anatomy

Background:

• Proximal ulna dorsal angulation (PUDA) is a key measurement in assessing ulna anatomy.
• Understanding factors influencing PUDA, such as ulna rotation, is vital for accurate diagnosis and treatment planning.

Purpose of the Study:

• To investigate the impact of varying degrees of ulna rotation on the apparent proximal ulna dorsal angulation (PUDA).

Main Methods:

• Computed tomography (CT) scans of 59 ulnas were used to create 3D models.
• Ulnas were rotated in 5-degree increments (internal and external rotation) from a neutral position.
• Measurements of PUDA, PUDA apex, varus angulation, and varus apex were recorded at each rotation increment.

Main Results:

• Neutral rotation showed a mean PUDA of 3.7 degrees and a mean varus angle of 10.5 degrees.
• External rotation increased PUDA, while internal rotation decreased PUDA, with changes being statistically significant.
• The magnitude of change in PUDA due to rotation was relatively small.

Conclusions:

• Small degrees of ulna rotation cause statistically significant changes in apparent PUDA.
• These changes may not be clinically significant, highlighting the importance of consistent imaging.
• Contralateral imaging or 3D planning is recommended for accurate PUDA assessment in complex cases due to anatomical variations.