Validation of the contralateral side as reference for selecting radial head implant sizes

Area of Science:

• Orthopedic Surgery
• Radiology
• Anatomy

Background:

• Radial head arthroplasty requires accurate implant sizing.
• Contralateral radial head diameter is often used as a reference.
• Bilateral asymmetry may lead to implant mismatch.

Purpose of the Study:

• Evaluate anatomical right-to-left differences in radial head diameters.
• Compare three-dimensional (3D) measurements with conventional two-dimensional (2D) measurements.

Main Methods:

• Utilized bilateral CT scans from 25 healthy adult radius pairs.
• Generated 50 3D radial head models for analysis.
• Calculated diameters using a 3D automated circle-fit method and compared with 2D measurements from axial slices.

Main Results:

• The average 3D radial head diameter was 23.0 ± 1.7 mm.
• The dominant right radial head was significantly wider (0.2 ± 0.4 mm difference, max 0.9 mm).
• 2D measurements were slightly smaller than 3D measurements (0.1 ± 0.3 mm difference).

Conclusions:

• Right-to-left radial head diameter differences are typically less than 1 mm in healthy individuals.
• This asymmetry is not clinically significant for implant selection, as increments are usually 2 mm.
• The contralateral radial head is a suitable reference, and standard axial CT slices can provide adequate estimations.