Comparison of the effects of two screw insertion patterns on bone fragment translocation in a 3.5 mm dynamic compression plate and a 3.5 mm limited-contact dynamic compression plate.

Objective: To compare the effects of screw insertion pattern, plate type, application of bone reduction forceps, and additional load screw insertion in an 8-hole 3.5 mm dynamic compression plate (DCP) and limited-contact dynamic compression plate (LC-DCP) on bone fragment translocation (BFT) in a fracture gap model.

Study Design: In vitro mechanical study.

Methods: Two screw insertion patterns were tested in the DCP and newly redesigned LC-DCP using gap model synthetic bone constructs. In Pattern 1, screws were first inserted into the holes at each end of the plate, then screws were inserted into the holes adjacent to the fracture gap. In Pattern 2, screws were only inserted into the holes adjacent to the fracture gap. The effects of tight or loose bone forceps securing the plate, loosening a neutral screw in Pattern 1, and inserting up to 4 additional load screws with each pattern were tested. Changes in the fracture gap were measured after insertion of all neutral screws and after each load screw.

Results: Pattern 2 BFT was significantly greater than Pattern 1 BFT when bone forceps were loose with both plates (P < .001). In the DCP, the BFT was significantly increased by loosening the bone forceps with Pattern 2 (P < .001) and by loosening 1 neutral screw in Pattern 1 (P < .001). The BFT for each additional load screw inserted was significantly less than 1.0 mm.

Conclusions: A tight neutral screw in the same bone fragment as the load screw or bone clamps that tightly secure the plate to the bone can limit BFT.