Plating of Metacarpal Fractures: Unicortical or Bicortical Screws?

Abstract

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.

Angular stable lateral plating is a valid alternative to conventional plate fixation in the proximal phalanx. A biomechanical study

“…Arrows indicate the direction of loading. Our findings suggest that there is no essential biomechanical advantage of bicortical over unicortical screw fixation in a phalangeal locking plate system, which is in line with the results of previous studies performed by other research groups (Dona et al, 2004;Freeland and Lindley, 2006;Freeland et al, 2003). Bicortical fixation is known to provide higher pullout strength compared to monocortical screw fixation (Khalid et al, 2008;Windolf and Perren, 2012), but does not necessarily imply a higher construct rigidity.…”

“…Hence, this advantage of bicortical screw placement does not come into play in the investigated fracture model. Different results may be obtained using a different loading protocol as for example under torsional loading, which however might not be relevant for the early postoperative rehabilitation of plated phalanx (Dona et al, 2004). Therefore, this is an important statement since in clinical practice the use of unicortical screws minimizes the risk of irritation of the far cortex anatomic structures.…”

Comparison Between Locking and Non-Locking Plates for Fixation of Metacarpal Fractures in an Animal Model

“…Several authors note that the predominant force seen at the metacarpal is apex dorsal bending, because the flexor tendons are stronger than the extensor tendons. 21,28 Additionally, in vitro biomechanical testing has limitations because of the absence of soft tissue, ligament, and tendon interaction with the rigidity of the construct.…”

Comparison of Metacarpal Plating Methods

“…10 However, cadaveric bone is often weak and osteopenic because of the advanced age of the donor. Because most metacarpal fractures occur in the 15-to 24-year-old age group, 20 results from cadaveric testing may not apply directly to most of these fractures.…”