A biomechanical comparison of two volar locked plates in a dorsally unstable distal radius fracture model.

BACKGROUND

This study compares the biomechanical stability of two volar locked plate systems for fixation of unstable, extra-articular distal radius fractures.

METHODS

In six matched pairs of fresh frozen cadaveric specimens, a simulated unstable, extra-articular distal radius fracture was created. The fractures were stabilized with one of two types of volar locked plates. Specimens were axially loaded at five different positions: central, volar, dorsal, radial, and ulnar. Initial (precyclic loading) stiffness of each locked plate system was calculated. Each specimen was then loaded for 5,000 cycles with an 80 N central load. Finally, specimens were axially loaded at the same five positions to calculate the postcyclic loading stiffness of each volar locked plate system. Main outcome measurements were precyclic loading stiffness, postcyclic loading stiffness, maintenance of stiffness after cyclic loading, and amount of fracture displacement between the two volar locked plate systems.

RESULTS

There were no differences in maintenance of stiffness and fracture displacement following cyclical loading between the two volar plate systems. After cyclic loading, the distal volar radius (DVR) locked plate was significantly stiffer than the Synthes volar locked plate in volar loading only (p < 0.01).

CONCLUSION

Materials properties and design differences between these systems did not provide enough biomechanical difference to support use of either implant over the other. With this in vitro model, both implants provided adequate stability to resist physiologic loads expected during therapy in the initial postoperative period.