Biomechanics of Subcutaneous Locked Plating Versus Burke Plate and External Fixator for Comminuted Distal Radius Fractures

Abstract

Background External fixators that span the wrist have been the historical norm in treating distal radius fractures. We have modified a dorsal distraction approach by using a subcutaneously applied locked bridge plate through two small incisions superficial to the extensor tendons and outside the extensor compartment. The purpose of this study was to biomechanically evaluate this modified method of fixation for comminuted distal radius fractures in comparison with two established constructs. Methods Matched cadaver specimens were used to model an AO Type 23-C3 distal radius fracture. Biochemical testing for stiffness during axial compressive loading was done on three constructs: a conventional Burke distraction plate, the subcutaneous internal fixation plating technique, and an external fixator. All specimens were cyclically loaded for 3000 cycles and then retested. Results The modified construct was found to be stiffer than the external fixator (p=0.013). When compared to the Burke plate, the modified construct was significantly less stiff before axial cycling (p=0.025). However, the difference was not maintained after cycling, and the post-axial loading stiffness difference was non-significant (p=0.456). Conclusion Our data demonstrate the biomechanical integrity of the subcutaneous plating technique for the fixation of comminuted distal radius fractures. It is stiffer than an external fixator and has the theoretical advantage of avoiding pin-tract infections. In addition, it is subcutaneous and not a cumbersome external construct. Our construct is minimally invasive, and it does not violate the dorsal extensor compartments. This allows for finger movement even while the construct is in place.

Keywords: burke plate; external fixator; fracture; internal fixation; radius; subcutaneous.

Figure 1. Testing positions and point of loading of the specimens within the materials testing machine for A) axial loading, B) torsional loading, C) radial-to-ulnar loading, and D) dorsal-to-volar loading.

Figure 2. Photograph of fixation demonstrating A) incision placements for subcutaneous in-fix plate fixation along the dorsal aspect of the forearm and B) a close-up of the proximal incision demonstrating its subcutaneous placement and suspension superficial to the fascia and extensor compartments.