A Comparison of Plate Versus Screw Fixation for Segmental Scaphoid Fractures: A Biomechanical Study

Abstract

Background: Volar locking plate fixation may offer several advantages over headless screw fixation for scaphoid nonunion, or segmental or comminuted fractures: (1) increased surface area for bony healing; (2) preserved vascularity; and (3) maintenance of a gap for graft insertion. The purpose of this study is to compare headless screw and locking plate fixation of segmental scaphoid fractures and to determine whether either fixation provides a greater mechanical advantage in osteoporotic versus nonosteoporotic bone.

Methods: Sixteen matched-pair cadaver scaphoids were dissected from a range of osteoporotic and nonosteoporotic specimens. Scaphoids from each matched pair were randomly assigned to either volar locking plate or compression screw fixation. A 3-mm segment of bone was circumferentially excised from each scaphoid waist to simulate a segmental defect. Implants were applied, and each specimen was then loaded in axial compression. Load to failure was defined as the load required to achieve gap closure. Mechanism of failure, load to failure, and percent gap recovery were recorded for each trial.

Results: Gap closure occurred in all trials. Difference in load to failure was not statistically significant between plate and screw fixation in either nonosteoporotic or osteoporotic cadaver specimens. However, percent gap recovery was significantly higher for plate fixation than for screw fixation.

Conclusions: In scaphoid fractures with segmental defect, plate and screw fixation demonstrate similar loads to failure, but plate fixation performs superiorly to screw fixation for gap recovery after an applied load to failure.

Keywords: biomechanical; nonunion; plate; scaphoid.

Figure 1.

Scaphoid cadaver with plate fixation mounted on load frame.

Figure 2.

Scaphoid cadavers with plate fixation (a, preloading, and b, postloading) and screw fixation (c, preloading, and d, postloading) representing typical mechanism of failure and gap recovery. Note. Percent gap recovery is represented by the space remaining between the scaphoid poles after a load to failure and is represented by the distance Y/X. This gap represents the space in a scaphoid nonunion model that is without structural support after bone grafting.