Unicortical fixation of metacarpal fractures: is it strong enough?

Unicortical fixation has some practical and theoretical advantages over bicortical fixation. Questions have been raised to its adequacy for post-operative mobilization. We hypothesized that fixation using a plate and eight unicortical screws would be as strong as using a plate and four bicortical screws. A total of 40 unicortical and 40 bicortical fixations were compared using a cadaveric metacarpal model. Unicortical fixation was performed using an eight-hole parallel plate and bicortical fixation with a four-hole straight plate. Fixations were tested to failure using four-point bending load. The mean load to failure was 414 N SD 38(SE) for the unicortical group and 296 N SD 29(SE) for the bicortical group. Significant differences between these two constructs were observed. The mean stiffness of the fixation was higher for the bicortical group than the unicortical, although this difference did not reach significance. Unicortical fixation alone is sufficient to enable early post-operative mobilization in a live model.