Stability of volar locking plate systems for AO type C3 fractures of the distal radius: biomechanical study in a cadaveric model

The purpose of the present study was to compare the relative stability of fi ve volar locking plates (all of which are available for the treatment of intraarticular fractures of the distal radius) under loading conditions simulating the physiological forces that occur during early active mobilization. Five plating techniques were applied to surgically simulated AO type C3.2 distal radius fractures in formalinfixed cadavers. The specimens were tested with a servohydraulic materials testing machine with 250N of axial compression load for 3000 cycles. After cyclic loading, the specimens were loaded until they demonstrated failure in axial compression. The fi ve fi xation systems studied included a DRV locking plate (group 1), a Stellar plate (group 2), an Acu-Loc plate (group 3), AO Locking Distal Radius System 2.4 (group 4); and a Matrix SmartLock plate (group 5). None of the plate fixations tested failed during the cyclic loading. Group 2 had a higher elastic limit than groups 4 and 5. There were no signifi cant differences among the five groups for the failure load. Failure occurred at the distal portion of the fi xation system, at the ulnar side locking pin, or the locking screw was bent (groups 1, 2, 3); the ulnar side locking screw was broken (groups 3, 4); the locking screw became loose (group 4); and the ulnar side locking screw was uncoupled from the screw hole (group 5). All of the fi ve volar plate fi xation systems provided suffi cient stability to permit 3000 repeated motions of the digits after surgery for AO type C3 distal radius fractures.