RESPONSE OF METACARPAL FRACTURE FIXATION CONSTRUCTS TO PHYSIOLOGICAL LOADINGS

This study compares the functional capabilities of different metacarpal fixation constructs under physiological loadings in an attempt to identify the optimal construct rather than the strongest one. One hundred and twenty-six preserved human metacarpals were mechanically tested after oblique osteotomies and internal fixation. Maximum load to failure, average structural rigidity, and energy absorbed were determined. All the fixations, except the intramedullary rods, tolerated the assigned physiological loadings below their failure limits in tension and torsion. The safety factor for K-wire tension band in bendings was only 1.4, which is very low compared to those of dorsal plate fixation (4.3) and the two interfragmentary lag screw fixation (4.0). Both torsional and axial rigidity of the K-wire tension band fixation were significantly less than the two interfragmentary lag screw fixation. Fixation by two interfragmentary lag screws was the optimal method, providing adequate strength and stability while requiring less soft tissue dissection than dorsal plate fixation.