Fracture Fixation Strength in Metacarpal Plating Versus Intramedullary Nailing Using a 3-Point Bending Model: A Cadaveric, Biomechanical Study.

PURPOSE: The purpose of our study was to evaluate the ultimate load to failure for 2 metacarpal fracture fixation strategies, plating versus intramedullary nailing, and then compare them to the native metacarpal. Our hypothesis was that the intramedullary nail after fracture fixation would more closely restore the native strength of the metacarpal when compared to plate fixation.

METHODS

Matched pairs of cadaveric hands (age range, 19-49; 5 men and 6 women) were dissected to produce 88 intact and equally distributed metacarpals (little, ring, middle, and index fingers). The metacarpals were then randomly selected to undergo either plate fixation or intramedullary nail fixation. A 3-point bending model was used to test the native metacarpal strength to the point of fracture and, subsequently, the fracture fixation construct. The data were then compared against the native metacarpal for normalized load to failure, normalized displacement, and stiffness.

RESULTS

The normalized maximum force (ratio of fixation:native) for the intramedullary nail specimens was significantly closer to normal than for the plated specimens for the little, middle, and index fingers, as well as for all metacarpals combined. We did not detect a difference in maximum force for the ring finger.

CONCLUSIONS

When compared to plate fixation, metacarpal intramedullary nailing more closely restores the ultimate load to failure of the native metacarpal after midshaft fracture.

CLINICAL RELEVANCE: For metacarpal fracture patterns amenable to intramedullary screw fixation, an intramedullary nail has biomechanical properties that are superior to a plate and screws in a 3-point bending model.