Development and Testing of a Novel Locking Pin Cap to Create a Fixed-Angle K-Wire Plate Construct

Purpose: To test the effectiveness of a novel locking pin cap to attach a K-wire rigidly to a volar locking plate and resist fracture displacement compared with commercially available alternatives.

Methods: Two different methods of fracture fixation were tested on a total of 12 Sawbones models with volar shear distal radius fracture (6/group). The fragments were fixed with either 2 commercially available pin plates (industry standard) or a volar plate with 2 locking screws fixing the scaphoid facet and 2 pins locked to the plate with a novel locking pin cap in the lunate facet. Axial load conditioning was performed followed by sinusoidal loading to 250 N at 50 mm/s. A motion capture system was used to assess the relative movement of the fracture fragments relative to the intact shaft. The strength of the fixation construct was quantified by (1) the force required to achieve a 2-mm gap between the shaft and fracture fragments and (2) ultimate load to failure.

Results: One industry standard pin plate demonstrated disassociation of the pin from the plate after fatigue conditioning. This did not occur in the locking pin cap group. The locking pin cap construct group was able to sustain a significantly higher load compared with the industry standard when the construct was displaced to the 2-mm gap. The locking pin cap also significantly increased the ultimate load to failure compared with the industry standard.

Conclusions: The novel locking pin cap creates a fixed-angle attachment of a K-wire to an existing locking screw hole in a plate. This fixed-angle K-wire is significantly stronger in preventing gap formation and resisting ultimate failure than commercially available plates that use bent K-wires.

Clinical relevance: The development of novel techniques to secure small articular fragments may ultimately improve clinical outcomes.