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 6 mm 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 1 kN load cell. The mean load to failure was 596 N (SD=142) for the unicortical and 541 N (SD=171) for the bicortical group. The stiffness was 333 N/mm (SD=116) for the unicortical and 458 N/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.