Intramedullary Screw Fixation of Distal Metacarpal Fractures: A Biomechanical Study

Area of Science:

• Orthopedic surgery
• Biomechanical analysis
• Hand surgery

Background:

• Intramedullary headless compression screw (IHCS) fixation is a common treatment for metacarpal (MC) fractures.
• A key concern is hardware stability, especially for distal fractures, and potential intra-articular hardware placement.

Purpose of the Study:

• To evaluate the biomechanical stability of IHCS fixation in progressively distal metacarpal osteotomies.
• To assess stability using a cadaveric simulated active motion model.

Main Methods:

• 12 matched-pair cadaveric hands underwent osteotomies at 15, 10, and 5 mm proximal to the MC head cartilage.
• Osteotomies were stabilized with retrograde IHCS and subjected to 2,000 cycles of simulated active finger motion.
• Displacement was measured, with failure defined as >1 mm displacement.

Main Results:

• Significant differences in failure rates and displacement were observed between the 15 mm vs. 5 mm and 10 mm vs. 5 mm osteotomy groups.
• IHCS fixation demonstrated reduced biomechanical stability as the osteotomy approached the metacarpal head.

Conclusions:

• IHCS fixation of distal metacarpal osteotomies is significantly less stable when placed 5 mm proximal to the articular margin.
• Clinical recommendations for immediate full active range of motion should consider fracture location and fixation stability.