Plating of metacarpal fractures: unicortical or bicortical screws?

Mid-shaft transverse osteotomies were performed in 18 cadaveric metacarpals and randomly divided into two groups. Using dorsally applied plates for repair, one group was secured using 6mm unicortical screws, while bicortical screws were used in the second group. The metacarpals were tested to failure with a four-point bending protocol using a servo-hydraulic testing machine and a 1kN load cell. The mean load to failure was 596N (SD=142) for the unicortical and 541N (SD=171) for the bicortical group. The stiffness was 333N/mm (SD=116) for the unicortical and 458N/mm (SD=158) for the bicortical group. Both load to failure and stiffness were not statistically significant between the two groups. Failure occurred by fracture at the screw-bone interface in all specimens: no screw pull-out was observed. No biomechanical advantage was found when using bicortical screws in metacarpal fracture plating.