Pin Configurations for the Treatment of Scaphoid Nonunion: A Biomechanical Study

Area of Science:

• Orthopedic surgery
• Biomechanics
• Skeletal trauma research

Background:

• Scaphoid fractures are common, with nonunion posing significant challenges.
• Kirschner wire (K-wire) fixation is a standard treatment, but optimal configuration for nonunion with defects remains debated.

Purpose of the Study:

• To compare the biomechanical strength and stiffness of convergent versus parallel K-wire configurations.
• To evaluate fixation stability in a cadaveric scaphoid nonunion model with a simulated 6-mm defect.

Main Methods:

• Eight pairs of cadaveric scaphoids underwent simulated nonunion with a 6-mm defect.
• Fixation was performed using either parallel or convergent K-wire configurations.
• Biomechanical testing assessed interfragmentary motion and construct stiffness under cyclic loading.

Main Results:

• Convergent K-wire fixation exhibited significantly higher maximum force (median 36.5 N) and stiffness (median 81.6 N/mm) compared to parallel fixation (16.6 N and 54.1 N/mm, respectively).
• Scaphoid morphology showed minor variations between contralateral hands.

Conclusions:

• Convergent K-wire configuration provides greater biomechanical stability than parallel configuration for scaphoid nonunion with a bony defect.
• This finding suggests a potential clinical advantage for convergent fixation in complex scaphoid nonunion cases.