Ulnar shaft diameter as it relates to plate osteosynthesis: A cadaveric study

Area of Science:

• Orthopedic surgery
• Anatomy
• Biomechanics

Background:

• Ulnar shaft fractures are common orthopedic injuries.
• Current standard treatment involves 3.5 mm plating.

Purpose of the Study:

• To measure ulna diameters along its length.
• To inform screw length selection and assess 3.5 mm screw appropriateness.
• To guide optimal plate placement for ulnar shaft fractures.

Main Methods:

• Dissection of ten embalmed cadaveric ulnas.
• Measurement of ulna length and division into four segments.
• Transverse osteotomies at 1/4, 1/2, and 3/4 lengths.
• Measurement of ulna diameters in radio-ulnar and volar-dorsal directions.

Main Results:

• Smallest diameters observed in the distal ¾ shaft, particularly in the volar-dorsal direction (average 9.1 mm for females, 12 mm for males).
• Volar-dorsal diameters were consistently smaller than radio-ulnar diameters across all measured locations.
• Ulna diameters increased proximally along the bone.

Conclusions:

• Results provide critical data for selecting appropriate screw width and length for ulnar shaft fixation.
• The use of 3.5 mm screws in the distal and midshaft ulnar diaphysis of females is questioned due to potential for creating stress risers.
• Removal of 3.5 mm screws from female ulnar shafts could leave significant voids (23-27%), potentially compromising bone integrity.