Biomechanical Comparison of Dorsal Nail Plate Versus Screw and K-Wire Construct for Extra-Articular Distal Radius Fractures in a Cadaver Bone Model

Purpose

The purpose of the study was to compare the biomechanical stability of distal radius fracture fixation with 2 new implants, the DNP (Hand Innovations LLC, Miami, FL), a dorsal locked hybrid of nail and plate, and the XSCREW (Zimmer, Freiburg, Germany), an implant combining a cannulated screw and K-wires, in a cadaver bone distal radius fracture model.

Methods

Eight pairs of fresh-frozen cadaver radii were used. To simulate an extra-articular distal radius fracture, a 5-mm volar open wedge osteotomy was made. Axial loads of 10 to 100 N and torque loads of −1.5 to 1.5 Nm were applied by a testing machine to the intact radii and to the radii after each device was fixed as recommended by the manufacturer. One thousand cycles in torque and failure tests were performed.

Results

With a median of 136.0 N/mm, the axial stiffness of XSCREW-fixed specimens was higher than that of DNP-fixed specimens, with a median of 69.5 N/mm, but differences were not statistically significant. With a median of 0.163 Nm/°, the torque stiffness of XSCREW-fixed specimens was significantly higher than that of DNP-fixed specimens, with a median of 0.068 Nm/°. The XSCREW-group reached 33% of the axial stiffness and 49% of the torque stiffness of the intact radii, and the DNP-group reached 14% of the axial stiffness and 20% of the torque stiffness of the intact radii.

Conclusions

In this human cadaver bone biomechanical study, the XSCREW provided more stability than the DNP in torque stiffness but not in axial stiffness.

Key words: Biomechanics, distal radius, fracture, internal fixation, intramedullary